Siglent SDS800X HD Review & Demonstration Thread - Page 1
Forum section: electronics / testgear

author: Performa01
author_rank: Super Contributor
timestamp: January 23, 2024, 08:33:24 am
content: A revised summary of this thread together with some new content in a PDF can be found here:SDS800X HD Review Part 1SDS800X HD Review Part 2----------I have decided to evaluate the SDS824X HD and will post the results here.Why the 800 and not the 1000X HD?Well, I suppose the SDS800X HD to be the most popular offer for hobbyists and small businesses in Siglent’s lineup, eventually replacing the successful SDS1000X-E series.Even though there are some differences, most of that are comfort features (except for the 50 ohm inputs), hence the SDS800X HD test results should be largely valid for the SDS1000X HD as well.I’ve once listed the obvious differences between SDS800X HD and SDS1000X HD here (reply #45):https://www.eevblog.com/forum/testgear/siglent-just-drop-its-mic-new-sds800hd-12bit-scope-crazy-price-leaked/msg5212773/#msg5212773In the meantime I have a confirmed list of differences:-SDS800X HD has no external trigger input.-Only the 200 MHz SDS800X HD have 100 Mpts memory, the lower models have only 50 Mpts.-SDS800X HD has no 50 ohm inputs.-SDS800X HD doesn’t have the higher quality encoders with indents-SDS800X HD has less serial protocols: CAN-FD and FlexRay are missing.-SDS800X HD has only 2 USB host ports.-SDS800X HD has only 7” capacitive touch screen, but at the same resolution 1024 x 600.-SDS800X HD doesn’t support probe factor detection.-SDS800X HD doesn’t support Tektronix Mode.-SDS800X HD doesn’t support Advanced Measurements Display Mode M2.-SDS800X HD doesn’t support Measurement Histograms Secondary Zoom.-SDS800X HD has no RTC.+SDS800X HD supports NTP.The first impression was very positive. The instrument feels solid, the display appears a bit small, especially for someone used to the 10.1” screens of the 2000 series, yet the resolution is the same and it’s bright and crisp.Operation feels snappy, it appears to be (at least) on par with the SDS2000X Plus/HD series in this regard.The fan noise is about the same as in the SDS1104X-E, thus it can be slightly annoying and users will have something to optimize 😉Boot time is less than 40 seconds.And sorry, no, I haven’t tried to install a web browser or PDF reader or play doom on it, even though I know that these might be the most important features for some 😉Now that these trivialities are out of the way, let’s have a look at the performance – and I have to state in advance that there is a lot of progress when compared to the trusty 1000X-E series – it’s almost a completely different world.Table of ContentThis postinghttps://www.eevblog.com/forum/testgear/sds800x-hd-review-demonstration-thread/1. Bandwidth2. Pulse ResponseReply #1https://www.eevblog.com/forum/testgear/sds800x-hd-review-demonstration-thread/msg5293744/#msg52937441. Noise & Spurs2. Vertical Zoom DemoReply #2https://www.eevblog.com/forum/testgear/sds800x-hd-review-demonstration-thread/msg5293747/#msg52937471. History & Sequence Mode2. Counting Pulses3. Trigger JitterReply #3https://www.eevblog.com/forum/testgear/sds800x-hd-review-demonstration-thread/msg5293750/#msg52937501. Measurements2. Measurement Histograms3. Vertical Axis Labels4. DC Check5. CounterReply #4https://www.eevblog.com/forum/testgear/sds800x-hd-review-demonstration-thread/msg5293753/#msg52937531. AC Trigger Coupling2. Triggering noisy signalsReply #5https://www.eevblog.com/forum/testgear/sds800x-hd-review-demonstration-thread/msg5293756/#msg52937561. Deep Measurements2. Probe BandwidthReply #6https://www.eevblog.com/forum/testgear/sds800x-hd-review-demonstration-thread/msg5293759/#msg52937591. Poor Men’s Differential Probing2. Distortion measurementsReply #7https://www.eevblog.com/forum/testgear/sds800x-hd-review-demonstration-thread/msg5293762/#msg52937621. Digital ChannelsReply #8https://www.eevblog.com/forum/testgear/sds800x-hd-review-demonstration-thread/msg5293765/#msg52937651. Measurements 2 (Trend/Track)2. FFT Dynamic rangeReply #9https://www.eevblog.com/forum/testgear/sds800x-hd-review-demonstration-thread/msg5293771/#msg52937711. True Vertical Sensitivity2. Peak Detect3. Bode Plot at a glanceReply #58https://www.eevblog.com/forum/testgear/sds800x-hd-review-demonstration-thread/msg5332358/#msg53323581. Bode Plot ExampleReply #63https://www.eevblog.com/forum/testgear/sds800x-hd-review-demonstration-thread/msg5335604/#msg53356041. SPI Speed TestReply #65https://www.eevblog.com/forum/testgear/sds800x-hd-review-demonstration-thread/msg5335802/#msg53358021. The 200 Mbps SPI challengeReply #67https://www.eevblog.com/forum/testgear/sds800x-hd-review-demonstration-thread/msg5338655/#msg53386551. Mask TestReply #68https://www.eevblog.com/forum/testgear/sds800x-hd-review-demonstration-thread/msg5341157/#msg53411571. Zoom ExpectationsReply #72https://www.eevblog.com/forum/testgear/sds800x-hd-review-demonstration-thread/msg5343827/#msg53438271. Serial DecodersReply #73https://www.eevblog.com/forum/testgear/sds800x-hd-review-demonstration-thread/msg5346977/#msg53469771. CursorsReply #74https://www.eevblog.com/forum/testgear/sds800x-hd-review-demonstration-thread/msg5351024/#msg53510241. System Performance with SP5050A ProbeReply #80https://www.eevblog.com/forum/testgear/sds800x-hd-review-demonstration-thread/msg5354024/#msg53540241. Custom Probe FactorsReply #82https://www.eevblog.com/forum/testgear/sds800x-hd-review-demonstration-thread/msg5357321/#msg53573211. Dots ModeReply #90https://www.eevblog.com/forum/testgear/sds800x-hd-review-demonstration-thread/msg5360858/#msg53608581. X-YReply #150https://www.eevblog.com/forum/testgear/sds800x-hd-review-demonstration-thread/msg5373095/#msg53730951. IdentityReply #155https://www.eevblog.com/forum/testgear/sds800x-hd-review-demonstration-thread/msg5373974/#msg53739741. Noise DensityReply #160https://www.eevblog.com/forum/testgear/sds800x-hd-review-demonstration-thread/msg5377403/#msg53774031. Noise density 2Reply #167https://www.eevblog.com/forum/testgear/sds800x-hd-review-demonstration-thread/msg5380811/#msg53808111. Granular NoiseReply #180https://www.eevblog.com/forum/testgear/sds800x-hd-review-demonstration-thread/msg5384846/#msg53848461. HAM TestReply #199https://www.eevblog.com/forum/testgear/sds800x-hd-review-demonstration-thread/msg5389646/#msg53896461. Fun with Square WavesReply #214https://www.eevblog.com/forum/testgear/sds800x-hd-review-demonstration-thread/msg5392730/#msg53927301. Zoom ChallengeReply #234https://www.eevblog.com/forum/testgear/sds800x-hd-review-demonstration-thread/msg5396741/#msg53967411. FFT-Setup2. FFT Window FunctionsBandwidthLet’s start with the bandwidth. We would like to get the specified bandwidth even with all channels active, yet we do not want to deal with excessive aliasing.At first, one single channel at 2 GSa/s:SDS824X_HD_FR_2GSa_logAmplitude drop at 200 MHz is less than 2 dB and actual -3 dB bandwidth is 244 MHz. Frequency response is even a tad better when two channels are in use at 1 GSa/s:SDS824X_HD_FR_1GSa_logAmplitude drop at 200 MHz is <1.8 dB and actual -3 dB bandwidth is 245 MHz. Finally we look at all four channels in use at only 500 MSa/s:SDS824X_HD_FR_500MSa_logNow the bandwidth is actually limited to the advertised 200 MHz.Pulse ResponseFor all these tests, a 10 MHz square wave with 1 ns rise time has been fed into cannel 4.Lets start with single channel mode and 2 GSa/s:SDS824X_HD_PR_2GSa_Zoom_StopIn stop mode, we get a clear picture of the imperfections of the pulse top even when zoomed in 20x (main window: 100 mV/div, zoom: 5 mV/div). The rise time measurements yield the expected result of ~1.8 ns, which corresponds to 1.5 ns rise time for the SDS824X HD. This is well below the specified 1.8 ns for the 200 MHz model.In Run mode we can see some modulation because of noise, yet nothing that could not be cured by averaging using a math trace:SDS824X_HD_PR_2GSa_Zoom_Avg16In case you wonder why the imperfections of the pulse top are so pronounced in the previous screenshot, this is simply the price we pay for less than perfect impedance matching when using a scope that lacks 50 ohm inputs. External termination is always a compromise working reasonably well up to 70 MHz at best. Fast edges like the 1 ns rise time in this example occupy 600 MHz bandwidth. The output impedance of the pulse generator isn’t perfect 50 ohms either, and both phenomena combined lead to reflections showing up in the first ~16 ns of the pulse.Of course it can be demonstrated, how better impedance matching improves things. For this I’ve used a quality 18 GHz cable with two 10 dB 18 GHz Narda in-line attenuators (one at each end) to ensure sufficient attenuation for any reflections between generator and DSO. Because of the 20 dB attenuation in total, I had to increase the generator output level by 20 dB as well. This would have been 6 V amplitude, but at that level, it’s rise time is limited to min. 1.2 ns, hence I made do with just 3 V and increased the DSO sensitivity to 50 mV/div, in order to still get the 1 ns rise time:SDS824X_HD_PR_2GSa_Zoom_Avg16_MatchWith two active channels, the sample rate drops to 1 GSa/s:SDS824X_HD_PR_1GSaThe overshoot is more pronounced now (probably because of additional AA-filtering), yet rise time measurements haven’t changed.With four active channels, the sample rate drops to only 500 MSa/s:SDS824X_HD_PR_500MSaWe can see hints on slight reconstruction errors together with rather pronounced Gibbs ears. Rise time measurement is off by hefty 27%, so we can safely state that this configuration is not fit for characterizing pulses with <2 ns rise time.With a signal rise time of 2ns we can measure 2.6 ns: assuming 1.5 ns rise time for the SDS824X HD, this measurement now is only ~5% off and should be acceptable already. Furthermore, we can use Dots mode to get rid of any reconstruction errors:SDS824X_HD_PR_500MSa_2ns_Dots

author: Performa01
author_rank: Super Contributor
timestamp: January 23, 2024, 08:34:33 am
content: Noise & SpursThis is a demonstration of the noise with all channels active, where the bandwidth is limited to true 200 MHz.The noise is shown for various conditions:Ch.1: input open, 200 MHz bandwidth;Ch.2: input open, 20 MHz bandwidth;Ch.3: input 50 ohm terminated, 200 MHz bandwidth;Ch.4: input 50 ohm terminated, 20 MHz bandwidth;Because of the pronounced 1/f characteristic of the frontend noise below about 300 kHz, the results strongly depend on the lower bandwidth limit. Let’s start with 100 kHz:SDS824X_HD_Noise_100kHz-200MHz_4ChCompare this with 10 kHz lower bandwidth limit:SDS824X_HD_Noise_10kHz-200MHz_4Ch1 kHz lower bandwidth limit:SDS824X_HD_Noise_1kHz-200MHz_4ChFinally 200 Hz lower bandwidth limit:SDS824X_HD_Noise_200Hz-200MHz_4ChHere you can see the noise characteristic up to 25 MHz at a RBW of ~90 Hz. In order to prevent aliasing taking effect, the noise measurement has been done of a 20 MHz bandwidth limited input channel. Since this bandwidth limiter is only first order, a digital 30 MHz lowpass filter has been added.SDS824X_HD_Noise_20Hz-25MHz_4Ch_F30MThe Noise characteristic is a combination of the 1/f noise of the MOSFET input buffer in the HF path and the FET OpAmp in the LF path, which is fed with a heavily attenuated signal that has to be amplified again before the recombination of both paths.We can clearly see this in the previous screenshot:At 300 kHz, the measured noise level is -150.894 dBV, this corresponds to a noise density of just 3 nV/√Hz at a RBW of 89 Hz. The following table shows the complete measurements:300 kHz: -150.894 dBV 3.0 nV/√Hz100 kHz: -144.227 dBV 6.5 nV/√Hz30 kHz: -135.927 dBV 16.9 nV/√Hz10 kHz: -125.303 dBV 57.5 nV/√Hz3 kHz: -116.034 dBV 167.2 nV/√Hz1 kHz: -111.083 dBV 295.6 nV/√Hz300 Hz: -111.665 dBV 276.5 nV/√Hz100 Hz: -108.281 dBV 408.2 nV/√HzAt 10 MHz, the noise density has dropped to about 2.4 nV/√Hz.Finally let’s have a look at the spurious signals (CH.4, 50 ohm termination, 20 MHz bandwidth limit):SDS824X_HD_Spurs_200Hz-200MHz_4ChThe Peaks List shows the 10 strongest spurious signals, where all are at or below 1 µVrms, except for a single spur at 1.14155 MHz, which is 3.85 µVrms. This is exceptionally good, especially in this class.Vertical Zoom DemoVertical zoom can suffer from noise, if high zoom factors are used. Some demonstrations use bandwidth limits to reduce noise when zooming in. It is in the responsibility of the user then to make sure that no relevant high frequency detail gets lost by this.In general, the question remains: what if we need to look at higher frequencies? A 200 MHz 12-bit DSO should be able to demonstrate a resolution advantage with 200 MHz bandwidth signals just as well…Here is the signal mix: a 1 MHz 600 mVpp sine with a 200 MHz 10 mVpp sine riding on it:SDS824X_HD_VZ10x_RunI’ve chosen straight 10 mV/div for the zoom window, i.e. a ten times magnification. The superimposed waveform is a little noisy, yet clearly visible.This is run mode. In stop mode, we can see that all the noise is just modulation and lowering the bandwidth wouldn’t help anyway:SDS824X_HD_VZ10x_StopIn stop mode we basically get a clean waveform with some distortion. Yet this is just 12 bits without any additional tricks.We can use the average math function to get rid of the modulation:SDS824X_HD_VZ10x_Avg1616 times average (Math trace F1) is enough to get the waveform pretty clean even in run mode. The implicit resolution enhancement of this measure is 4 bits, so that the DSO is effectively working with 16 bit data now.

author: Performa01
author_rank: Super Contributor
timestamp: January 23, 2024, 08:35:34 am
content: History & Sequence ModeInspired by the complaint here:https://www.eevblog.com/forum/testgear/rigol-hdo1000-and-hdo4000-12bit-oscilloscopes-launched-in-china/msg5269170/#msg5269170I’ve tried to replicate the test scenario described by forum member Egonotto, which is a fairly moderate one. For this, the SDS800X HD doesn’t need any special mode; the always active background history can handle that:SDS824X_HD_5ms_HistThe test signal is a burst packet, 20 µs long, consisting of 100 pulses. The repetition interval (burst period) was 5 ms for this test.At 5 µs/div, the SDS824X HD takes an average of 650 µs/frame and a maximum of <2 ms/frame. The screenshot shows the History List displaying the time delta between the packets. It is 5 ms throughout, with the occasional 4.999 ms because of the not so accurate timebase of the SDS800 (25 ppm vs. 1 ppm in the SDS2000X Plus/HD series).For event recording, we’d rather use the dedicated Sequence mode. This provides a constant 52 µs/trigger @ 5 µs/div, hence can capture a burst period of 100 µs without a single missing frame:SDS824X_HD_100us_SeqThe screenshot shows the History List displaying the time delta between the packets. It is 100 µs throughout, with the occasional 99 µs because of the not so accurate timebase of the SDS800.For complete information, here are my measurements for the trigger rates during normal use with vector and dots display mode as well as sequence recording from the fastest timebase of 1 ns/div up to 100 µs/div.SDS824X HD Trigger rateCounting PulsesThis is a demonstration of the pulse count function. As further refinement, gated measurements can be used in order to ignore unwanted portions of the record.First the basic pulse measurement without any bells and whistles; a 100 MHz pulse packet with 1 ns rise time and 1000000 pulses is fed into Ch.4SDS824X_HD_PulsecountThe scope registers the correct number of one million positive pulses. The negative pulse count naturally delivers the same number minus one. Together with the peak to peak deviation of zero over >100 acquisitions it is obvious that the pulse count is spot on.Let’s add a measurement gate. We define it to start 1.0 ms after the trigger point and to be 5 ms wide:SDS824X_HD_Pulsecnt_GateWe now get a count of ~500k (100 MHz x 0.005 sec.) as expected. The count is a little higher because of the limited accuracy of the timebase in the SDS800.We can engage the zoom view for a closer inspection of the waveform:SDS824X_HD_Pulsecnt_Gate_ZoomWe can still see the gating cursors in the main window, but the detailed view with time data is in the zoom window now. Since the “B” cursor exceeds the size of the zoom window, it is drawn at the right border and the time specification of 6.00 ms is another hint that it is outside the zoom window, which is only 100 ns wide.The gating cursors are fully independent, consequently we can still add regular cursors (manual/tracking/measurement):SDS824X_HD_Pulsecnt_Gate_Zoom_CursorsWith all these information, screen gets a bit busy, but we could also use the traditional info block for the regular cursors and place it at the least disturbing spot:SDS824X_HD_Pulsecnt_Gate_Zoom_Cursors2Trigger JitterThe datasheet specifies the trigger jitter as <100 ps. This doesn’t sound great, considering the SDS2000X HD, where the specification is <10 ps RMS (and it has been measured as 2.02 ps actually).Now let’s measure this using a 200 MHz sine signal from an OCXO-driven AWG (SDG7102A), fed into channels 2 and 4 of the SDS824X HD via a 12.4 GHz resistive power splitter. This way we can observe the jitter in the trigger channel as well as a not triggered channel.The high quality 200 MHz sine signal has been chosen for its fast edges and low inherent jitter – after all we want to characterize the DSO and not the signal source.We need to utilize a measurement gate, because for some unknown reason the T@M measurement considers all rising edges in the record, whereas we only want to measure the first one.SDS824X_HD_Trigger JitterAt a timebase of 1 ns/div, we cannot see any jitter in the triggered as well as the non-triggered channel after more than 10 minutes at infinite persistence.The jitter measurements are as follows:Triggered channel: 28.6 ps pk-pk, 4.852 ps rms;Un-triggered channel: 28.9 ps pk-pk, 4.652 ps rms;Skew Ch.2-Ch.4: 20.9 ps pk-pk, 3.39 ps rms;While this is about twice as much as the SDS2000X HD, it is still very respectable and miles ahead of older designs with analog trigger system (none of Siglent’s X and A series).

author: Performa01
author_rank: Super Contributor
timestamp: January 23, 2024, 08:36:11 am
content: MeasurementsThere are the simple measurements, where we can define an arbitrary set of up to all 52 measurements that are related to a single channel. This set can subsequently be applied to any Input-, Zoom-, Math- or Reference-Channel. That’s also one disadvantage of the simple measurements – it’s restricted to a single channel. The other drawback is the total lack of statistics in this mode.SDS824X_HD_Measure_Simple_EmbeddedA high number of measurements might be desirable at times, yet it takes up a lot of screen space. Siglent has now introduced a new display option for measurements; “Floating”:SDS824X_HD_Measure_Simple_FloatingThis is a transparent overlay which might help to better utilize the screen space in certain situations.We also got the Advanced Measurements., but unfortunately only mode A; mode B is available only in its bigger (and more expensive) siblings:SDS824X_HD_Measure_Advanced_EmbeddedWe can have statistics and also enable the little Histicons (History Icons) as in the screenshot above, we can also mix various channels, yet we are restricted to only 5 measurements at a time.We can have floating measurements in this mode as well, yet it might be a good idea to turn the axis labels off to avoid text collisions:SDS824X_HD_Measure_Advanced_FloatingMeasurement HistogramsThe small Histicons in the advanced measurements statistics can be enlarged by simply clicking or tapping on them. This opens a separate window with a more detailed version of the histogram. The last measurement result is marked by a small red dot in the histogram, so one can watch the build up of the histogram even when there is already a lot of data collected and histogram bars don’t visibly change anymore.SDS824X_HD_Measure_Advanced_HistogramVertical axis labelsThe new kids in town like the SDS800X HD also bring new features: apart from the logarithmic frequency axis for the FFT, as demonstrated in the noise measurements, we also got a selectable vertical label position.SDS824X_HD_VLabel_leftSDS824X_HD_VLabel_rightSDS824X_HD_VLabel_centerDC CheckOne of the advantages of a 12 bit DSO should be not only high resolution, but also good accuracy. The SDS800X HD has a typical error of 0.5% at vertical gain settings from 5 mV/div up to 10 V/div, thus entering 3.5 digit DMM territory.Here is a quick check with a 300 mV DC “signal”:SDS824X_HD_DC_300mVThe error in this measurement is <0.13%. Mean and RMS measurements show pretty much the same result, as expected.CounterThe SDS800X HD does not provide a DMM, but it has at least the Counter application. It can be used as a frequency counter or totalizer. I don’t see much use in the frequency counting function, chiefly because the automatic measurements can do exactly the same – and even on more than one channel at a time – and then we have the always visible 7 digit trigger frequency counter on top of that (I wouldn’t ever want a scope without that feature!).But the Counter is still not totally useless, as it can also be configured as gated totalizer:SDS824X_HD_Totalizer_GatedChannel 3 is fed with a 1 ms wide pulse as a gating signal, channel 4 is connected to a 10 MHz sine source. Consequently, a single shot acquisition results in 10000 hits = 10 khits. This is deadly accurate because both signals come from the same AWG, hence both signals are derived from the same OCXO (whose accuracy is irrelevant in this application, yet is specified <100 ppb)Other than the pulse counts in the measurements, the counting process can be controlled by an external signal.EDIT: Section "Measurement Histograms" added.

author: Performa01
author_rank: Super Contributor
timestamp: January 23, 2024, 08:36:51 am
content: AC Trigger CouplingMost of us use DC coupling for the trigger almost all the time, and there is not much to talk about it, other than that it works just as it should. We rather want to examine AC trigger coupling now.Why and when would we need AC coupling for the trigger at all? Usually, we make that choice for the channel input and if we select AC coupling there, the trigger will inevitably be AC coupled as well. So there we already have the answer – we have the opportunity to force the trigger into AC coupling, even when the corresponding input channel is DC coupled. This can be useful for AC signals that have a DC offset that we want to watch on the screen. The offset might change with time and we still don’t want to lose triggering.AC trigger coupling does not display a trigger level indicator, simply because it would need to closely follow even a fast-changing signal offset, thus might be rather distracting instead of beneficial.The following test uses a 200 mVpp 100 ns wide pulse at 1 MHz repetition frequency that is superimposed on a 600mVpp sine wave at 100mHz, which acts as a variable DC offset here. As if this weren’t enough, this signal has a fixed DC offset of -6V on top of that, which needs to be removed by means of the vertical position control and the trigger level adjusted accordingly. Infinite persistence is used to give a hint what is going on.With DC trigger coupling, triggering would only occur about 1/3 of the total time in this scenario and even then, the horizontal position would only be reasonably stable because of the short 1 ns rise time of the pulse edges. A signal with slower edges would move horizontally as well, because of the permanently changing trigger level (relative to the AC portion of the input signal).SDS824X_HD_Trigger_DC_VarOffsetIt’s totally different if we use AC trigger coupling. When using Auto-Set by pushing the trigger level control, the trigger level is set to 50% of the signal amplitude. With this, triggering occurs always at the same point on the X-axis, no matter what the DC offset or low frequency instantaneous signal level is. The waveform constantly changes its vertical position on the screen, but remains stable on the time axis – and even more important, the signal is triggered continuously.SDS824X_HD_Trigger_AC_VarOffsetWe’ve heard complaints about DSOs that prove unable to maintain an AC- or LFRJ-trigger without some additional jitter. So here’s a test with AC trigger coupling and a 6 ns wide pulse with 1 MHz repetition frequency. The screenshot has been taken after several minutes with infinite persistence.SDS824X_HD_Trigger_AC_JitterJitter can be measured as 36.0 ps peak to peak and 6.84 ps RMS; not quite as good as the former test with the 200 MHz sine signal, yet certainly not bad either – and also reveals that my pulse generator (SDG7102A) produces quite stable signals, even when fast edges are involved.Triggering noisy signalsOf course, for serious measurements our goal should be to find a reliable, stable and noise-free trigger source with sufficient amplitude. Sometimes this is not available and we need to try the next best thing by getting a stable triggering also from less ideal sources.Let’s assume a low frequency signal with high frequency spikes (maybe from fast logic cicuits nearby) superimposed. To simulate this, a 600 mVpp 1 kHz sine wave has a 10 mVpp 3.254 MHz pulse train (10 ns wide pulses) riding on it. Standard DC trigger doesn’t work with such a signal, but HF-reject coupling does:SDS824X_HD_Trig_Spikes_HFRJJust for fun, we can do the opposite thing and use LF-reject trigger coupling. This triggers stably on the pulses, yet because of the high waveform update rate the screen is full of traces from the 1 kHz sine.SDS824X_HD_Trig_Spikes_LFRJAfter stopping the acquisition, we can closely inspect the last record. Even better, we can look up all the previous acquisitions in the history:SDS824X_HD_Trig_Spikes_LFRJ_Hist1SDS824X_HD_Trig_Spikes_LFRJ_Hist2Another common situation is just a noisy signal like this:SDS824X_HD_Trig_Noise_DCInfinite persistence has been used to visualize the unstable signal phase.We can still trigger on such a signal by simply lowering the trigger bandwidth, i.e. using HFRJ:SDS824X_HD_Trig_Noise_HFRJAlternatively, the Noise Reject switch in the trigger settings will increase the trigger hysteresis, thus making it immune to noise (within reason).SDS824X_HD_Trig_Noise_DC_NRJ

author: Performa01
author_rank: Super Contributor
timestamp: January 23, 2024, 08:37:25 am
content: Deep MeasurementsHere's some demonstration of a common exercise which cannot be solved without deep measurements.Imagine a 16 bit PWM based on 20 MHz clock frequency. This results in a rather slow 304 Hz PWM signal that can resolve 65536 different levels of duty cycle. To analyze this, we should be able to have accurate time measurements with at least 0.001525878 % (15 ppm) resolutionA very similar demonstration has been published for the 8-bit SDS2354X Plus a while ago already (reply #4336):https://www.eevblog.com/forum/testgear/siglent-sds2000x-plus-coming/msg5183499/#msg5183499Let’s see how the SDS800X HD fares.Timebase is set to 500 µs/div, so that we can capture at least one full PWM period.At 2 GSa/s, this results in 10 Mpts record length.The PWM signal for this test has 1 ns rise time and 0.001% resolution for the duty cycle.First the lowest at 0.001 %:SDS824X_HD_Duty_0.001Near full scale at 99.999 %:SDS824X_HD_Duty_99.999Half scale at 50.000 %:SDS824X_HD_Duty_50.000Finally, one step higher at 50.001 %:SDS824X_HD_Duty_50.001The duty cycle measurement is spot on and stable, even though not quite as impressive as the SDS2000X Plus (look at the peak-peak and standard deviation).The period measurement is fairly stable too, with a standard deviation of only 9.2 ps. Peak deviation can only be measured in 100 ps steps, which is ten times more than the SDS2000X Plus. Quite obviously the peak deviation was well below 100 ps, hence gets reported as 0 s.The Cycle Mean measurements gives an approximation of the resulting voltage level. It is far less precise than the duty cycle measurement though. No wonder – an even 12 bit DSO is still no precision bench DMM, hence measurement resolutions of ~15 µV are not going to be stable – this also shows in the standard deviation of ~324 µV – which is about ten times as much as with the SDS2000X Plus, but that’s only because the amplitude was ten times lower for the test back then (and the required resolution there would have been ~1.5 µV).Finally, the rise and fall times are about as (in)accurate as can be realistically expected at 2 GSa/s. The rather high peak deviation of ~1.4 ns already hints on the averaging of many individual measurements to get the final result. Once again, we see an advantage of the SDS2000X Plus, even though the sample rate is the same. Yet this is not only about the physical sample rate, but also interpolation strategies, which require massive HW support and might be a bit simpler in the SDS800X HD. The higher bandwidth of the SDS2000X plus is helpful in this case as well.Of course we can always get full accuracy for one local detail like the rise time by using zoom trace measurements:SDS824X_HD_Duty_50.001_RiseNow the rise time measurement result is much closer to the truth. The key for this is to use a timebase faster than 50 ns/div in the zoom window. Now the Sinc reconstruction generates additional data points, thus increasing time resolution and reducing the standard deviation of the measurement to just ~6 ps, which is in turn even better than the SDS2000X Plus.Probe BandwidthThe frequency response plots in the “Bandwidth” section have been made with a properly terminated coax connection. A proper review should also test the associated probes – unfortunately, I don’t have one, as my test unit didn’t include any accessories. I suspect that the standard probes delivered with the SDS824X HD will be the well known PP215. Even though I do have some very old PP215 (which probably aren’t quite the same as the current ones), I don’t have access to them right at the moment, hence make do with the only slightly younger 100 MHz PP510, just to give you an idea.First the frequency response up to 500 MHz:SDS824X_HD_Probe_PP510_FRIt can be seen, that even Siglent’s cheapest 100 MHz probe extends the system bandwidth to ~274 MHz (244 MHz with direct coax connection). So much for the practical relevance of probe ratings and textbook formulas, which are way to simplistic as to actually model the real world.Of course, the probe has been properly LF-compensated prior to the measurements:SDS824X_HD_Probe_PP510_PR_1kHzThe transition times are about 2 ns, which is slightly slower than with the direct coax connection. This is another occasion, where we can see the (ir)relevance of textbook formulas when it comes to real-world performance. The bandwidth was wider, yet the rise time is slower – how can that be?Of course it’s in the frequency response, which is a far cry from the first order low pass, that is assumed in a textbook. The sudden drop of ~1.5 dB at about 120 MHz is most likely responsible for the slower rise time.The ultimate test for proper HF-compensation is done with a fast (1 ns) risetime 1 MHz square wave.SDS824X_HD_Probe_PP510_PR_1MHz_ZoomIt can be seen, that the PP510 isn’t an ideal match for this scope because of an overdamped edge. In other words, the HF-compensation, which is not user adjustable, is not perfect for this probe-scope combination.The screenshot above is also another demonstration how such details can be observed on a 12 bit DSO with proper zoom implementation, without the need to take a chance by overdriving the inputs.

author: Performa01
author_rank: Super Contributor
timestamp: January 23, 2024, 08:38:00 am
content: Poor Men’s Differential ProbingWith analog scopes, we were able to combine two regular (single ended, ground referenced) channels into one differential channel. This was done by adding both channels with the 2nd channel inverted, whose gain had to be fine-tuned in order to get the maximum common mode rejection. Of course, this solution was far from ideal and sensitivity as well as common mode rejection were rather limited, especially at higher frequencies, which made it hard to get meaningful results when common mode voltages were high compared to the differential signal.We can’t do the same on a modern DSO, for a number of reasons:• The fine adjust of the vertical gain has only ~2% resolution, so it is not suitable to balance the channels for a CMMR >34 dB.• The difference has to be computed by a math channel, which always takes the vertical gain setting into account and scales to the true value, thus ignoring any gain adjustments.• Finally, with only 8 bits the math result doesn’t have enough resolution to properly analyze the differential signal. It is the same problem as with having vertical zoom on an strict 8-bit DSO.The screenshot below demonstrates the result of two identical 10 MHz signals fed into channels 3 and 4 at 100 mV/div and a difference math channel is set to a 100 times higher gain at 1 mV/div:SDS824X_HD_PMDiff_10MHzCommon mode rejection can be estimated from the amplitude measurements and would be 606.7/2.44 = 248.6 ~ 47.9dB, which is not bad at all – but we can do even better...Of course, the balance is not perfect out of the box. Input channels and probes will both have gain tolerances, which compromise the common mode rejection. With a fairly precise instrument like the SDS800X HD we can just measure that:SDS824X_HD_PMDiff_10MHz_corr1As expected, there are slight differences. In this particular case, we get 516.955 mVpp for Ch.3 and 519.555 mVpp for Ch.4, so we can calculate the correction factor as 516.955/519.555 = 0.995. Consequenty, we just replace C4 in the formula by the expression C4*0.995.The common mode rejection can be estimated from the amplitude measurements and would be 519.555/1.613 = 322.1 ~ 50.16 dB, just 2.25 dB better than before. But the correction would certainly make a much more significant difference when the initial imbalance is more pronounced.For best accuracy, (especially external) 50 ohms termination cannot be used at the scope input, as their tolerances could be up to 2%. Without termination, a direct coax connection of 1 meter length can work reasonably well up to a couple MHz, but at higher frequencies, amplitude accuracy and common mode rejection degrade considerably. Even at only 10 MHz, the 600 mVpp signal was measured ~14 % low. The next screenshot demonstrates the same test at 100 MHz:SDS824X_HD_PMDiff_100MHz_corr1Peak amplitude is totally off now and common mode rejection is degraded to 173.2/3.82 = 45.34 = 33.13dB, which could still be acceptable for some tasks, yet is clearly degraded compared with the 10 MHz test. Even more importantly, the amplitude ratio has significantly changed now. This means, that the correction factor is not valid over the entire DSO bandwidth.Just for fun, we could try to alter the correction factor; now we get 173.236 mVpp for Ch.3 and 170.833 mVpp for Ch.4, so we can calculate the correction factor as 173.236/170.833 = 1.014.SDS824X_HD_PMDiff_100MHz_corr2Common mode rejection would now be respectable 173.25/1.288 =134.5 ~ 42.5 dB.In most practical scenarios, we’ll use probes; this is problematic because of their complex impedance and transmission characteristics, so that the tolerances cannot be eliminated by applying a simple correction factor. I’ll demonstrate the use of probes for a low frequency like 1 MHz. I only have a set of SP5050A probes here, yet I’m pretty confident my test results are still representative for any suitable 10x probe:SDS824X_HD_PMDiff_SP5050A_1MHz_corrWe get 3.0097 Vpp for Ch.3 and 3.0633 Vpp for Ch.4, so we can calculate the correction factor as 3.0097/3.0633 = 0.9825.With this, common mode rejection is 3.0633/0.02541 = 120.55 ~ 41.6 dB. This degrades quickly at higher frequencies.As a conclusion, thanks to 12 bit resolution, 16 bit data processing and high accuracy of 0.5%, poor men’s differential probing can be an option at low frequencies with this scope, whereas it didn’t work at all with the older 8-bit SDS1000X-E series.Distortion measurementsGeneral purpose oscilloscopes cannot have ultra low distortion frontends, especially nowadays, where even entry level instruments start at 70 or 100 MHz bandwidth. And even a low end device like the SDS800 goes up to 200 MHz for the top model within the line, and I’d bet the integrated PGA (Programmable Gain Amplifier) in these devices has more than 0.5 GHz bandwidth.To cut a long story short: the usual techniques to keep distortions down in audio devices, particularly global feedback, cannot be applied to wideband amplifiers. Taking this into account, it’s still amazing what can be achieved with modern integrated circuits, yet it’s the main reason why 12-bit DSOs fail to come even close to 12 bit ENOB.Let’s start with the harmonic spectrum of a low distortion 10 MHz sine wave:SDS824X_HD_FFT_THD_10MHzStrongest harmonic is the 2nd at -66 dBc. Since all other harmonics have considerably lower amplitude, we can safely state that THD is about 0.05%, which isn’t bad at all.Yet such results cannot be guaranteed; the individual gain stages within the PGA can have differences in linearity, so we need to know our instrument and take note of the weak as well as sweet spots within the vertical gain range. My particular sample of the SDS824X HD has a weak spot at exactly 100 mV/div, whereas all the settings >100 mV/div up to (at least) 110 mV/div yield results like the one shown above.Whenever we do distortion measurements of the DSO frontend, we need to be confident that the distortion products actually come from the DSO and not the signal source. It can be tricky to verify this, hence a different approach might be more precise: the dual tone intermodulation test.SDS824X_HD_FFT_IMD_10MHz_95FSTwo independent +6 dBm signals at 9.5 and 10.5 MHz are fed into a resistive wideband power combiner. To ensure proper isolation between the two signal sources and avoid intermodulation distortion at their output stages, a 10 dB inline attenuator has been added to each generator output. Together with the 6 dB attenuation of the splitter, we’d expect two -10 dBm input signals.Quite obviously, the external termination of the DSO input, which cannot compensate for the ~17 pF input capacitance, is responsible for the higher-than-expected losses, hence inaccurate input level. Since we use relative measurements anyway (delta amplitude in the markers list), this doesn’t matter though.A vertical gain of 50 mV/div doesn’t appear to be a weak spot in this instrument, so we get respectable -69 dBc for the third order intermodulation products.SDS824X_HD_FFT_IMD_140MHz_95FSTwo independent signals at 140 and 141 MHz are fed into the power splitter. At these higher frequencies, the problems with the external termination get even more obvious and instead of the nominal level of -10 dBm we get up to 2.2 dB less. Once again we don’t care because we’re only interested in relative levels.The vertical gain of 50 mV/div from the last test is used again and we get respectable -67 dBc for the third order intermodulation products. Other than an OpAmp with global feedback, distortion performance does not necessarily get much worse at higher frequencies.

author: Performa01
author_rank: Super Contributor
timestamp: January 23, 2024, 08:38:36 am
content: Digital ChannelsAll contemporary Siglent DSOs can be upgraded to MSOs. The cheaper low end devices like the SDS800/1000X HD don’t have the required hardware built in, but communicate with a completely autonomous subsystem: it’s the SLA1016, which has already been introduced back in early 2018 to add MSO capabilities to the SDS1004X-E and later 2000X-E series.Reply #64 in my review from that time shows the hardware, which is nowhere near as sexy as the fully integrated SPL2016 solution:https://www.eevblog.com/forum/testgear/siglent-sds1104x-e-in-depth-review/msg1449168/#msg1449168In order to work with the SDS800/1000X HD, the firmware in the SLA1016 needs to be upgraded. Unfortunately, the current beta version 8.2.3 provides no backward compatibility; once upgraded, the SLA1016 no longer works with SDS1004/2000X-E. If a single SLA1016 shall be shared between older SDS1004/2000X-E and new SDS800/1000X HD, the FW would have to be up- and downgraded accordingly.The external subsystem approach has a few disadvantages:• Since it incorporates a complete SOC and local memory, it cannot be cheap even though the probe head and the grabbers leave a cheap impression.• Mixed analog / digital pattern trigger is not possible.• Zoom mode cannot be used as soon as digital channels are enabled.• History doesn’t work either when digital channels are activated.If you wonder where these limitations come from, it’s simply because this is a separate subsystem connected via a (probably only moderately fast) serial interface. Because of the long memory, the DSO cannot have instant access to the full sample data through the SBUS interface (about 200 Mbit/s transfer speed needed for even only a single frame per second). Consequently, the SLA1016 only transfers the decimated screen data during normal operation.I’ve already demonstrated its performance here in Reply #1068:https://www.eevblog.com/forum/testgear/siglent-sds1204x-e-released-for-domestic-markets-in-china/msg2007983/#msg2007983Now let’s add some more content. First, it might be important to know that the SDS800X HD doesn’t collapse when its advertised capabilities are actually called up.SDS824X_HD_Digital_4Ch_P16_DeskewIn the above screenshot we can see 16 digital channels at 1 GSa/s sample rate together with 4 active analog channels at 500 MSa/s each.We can further see one digital parallel bus decoder placed right under the digital traces, showing hexadecimal values.The Deskew parameter is there to compensate for runtime differences between analog and digital probes; it can be adjusted in 10 ps steps.There is a digital Edge trigger set on channel D0.We can enable just 8 bits if we want to show e.g. the activity of a 7-bit counter:SDS824X_HD_Digital_4Ch_P8_CounterNow let’s check a fast clock signal (on 7 channels):SDS824X_HD_Digital_4Ch_P8_200MHz_1msIn order to see the details. We need to stop the acquisition and then zoom in using a faster time base:SDS824X_HD_Digital_4Ch_P8_200MHz_Stop_Zoom_5nsWho said we cannot have a perfect 200 MHz square wave on a 200 MHz bandwidth oscilloscope 😉Here’s another challenge: a 2 ns wide pulse with 500 ps rise time, captured analog and digital at the same time:SDS824X_HD_Digital_1Ch_p4_Pulse_2nsA digital Deskew value of 6.52 ns was required to get both domains reasonably aligned; as expected, the digital channel shows a simplified representation of the pulse, which can be characterized by the measurements of the analog channel. Of course, 200 (or even 245) MHz bandwidth is not nearly enough to even remotely reproduce such a pulse; for this, at least 1 GHz bandwidth would be required. Yet it looks clean and good within the capabilities of a low bandwidth DSO and the transition time measurement results of 1.4 and 1.25 ns suggest an unexpected good oscilloscope risetime.Probably the most popular use case nowadays would be serial decoding. I’ll just demonstrate I2C, even though this protocol only requires two channels.SDS824X_HD_Digital_1Ch_I2C_RunWe can see some I2C messages in the decoder table at the bottom and two digital channels together with an analog trace in the upper half of the screen. Right in the middle, there is still the parallel bus decoder line, which is of course unreadable at this time base. The I2C decoder line right under the digital channels is readable, yet messages are truncated, as indicated by the red dots.In stop mode, we can choose a faster time base and show the complete I2C messages in the decoder line.SDS824X_HD_Digital_1Ch_I2C_Stop_Zoom_200usThere’s finally the question: what if we want some advanced measurements (with statistics and Histicons) on top of that all?SDS824X_HD_Digital_1Ch_FullHouseWell, this looks a bit cramped, yet still not so bad if only we’d disable that useless parallel bus decoder line. Maybe we could make do with simple measurements, then we’d get a bigger signal display again.

author: Performa01
author_rank: Super Contributor
timestamp: January 23, 2024, 08:39:11 am
content: Measurements 2 (Trend/Track)Even the entry level DSOs like the SDS800X HD provide advanced features like Trend and Track Plots for measurements. They can be a bit fiddly at times, but the results are definitely worth it.Trend PlotsLet’s start with the more familiar (to most) Trend charts. As the name suggests, they plot a measurement value over time. For this, the record length of the raw acquisition can be short – a single full signal period would already be enough. Shorter records have the advantage of faster processing and less memory consumption.SDS824X_HD_Measure_Trend_AM_IntervalOf course, even a 12-bit DSO is not a metrology-grade instrument, hence we cannot use Trend Plot to observe the stability of a voltage standard; yet there are still plenty of applications where 0.5% accuracy is sufficient.For the example above, we have used a 1 s time interval Trend Plot, measuring the peak to peak amplitude of a 10 MHz sine wave, 100% amplitude modulated by a 10 mHz ramp signal. The minimum time interval for Trend Plot would be 0.5 s.SDS824X_HD_Measure_Trend_AM_enlargedIt can be seen that the Trend Plot has a separate statistic, as it is significantly slower than the regular measurements, hence works on a decimated subset of the original measurement data. Consequentially, since the time interval of the Trend Plot is one second, the measurement rate of the PK-Pk measurement can be calculated as ~19.4 per second, while at the same time we get 174 frequency measurements per second.Instead of a fixed time interval, we can alternatively use sequence record mode. Now the trend plot window behaves like a scope in roll mode, i.e. the update rate is faster, but the time axis shows measurement samples instead of time units now.SDS824X_HD_Measure_Trend_AM_SequenceTrack PlotsTrack plots also show the developing of a measurement value, but not over time but within a single record. As opposed to trend plots, this works best with long record lengths and only with certain measurements – the ones that are computed for the entire record, i.e. all the time related measurements.Consider a 10 MHz carrier frequency modulated with a 20 kHz sine wave and a frequency deviation of +/-1 MHz. Other than e.g. AM, we cannot really see this in the regular y-t display. This is where the Track Plots come in handy; they let us “demodulate” frequency and phase modulated signals – and such modulations could also come from noise, drift and jitter.SDS824X_HD_Measure_Track_FMTake a closer look at the above screenshot: the record length is 5 Mpts and there are 1000 times more frequency measurement samples than Pk-Pk amplitude measurement samples. Experienced people could tell from the histogram that the modulation signal would very likely be a sine wave, but they would not be able to determine the deviation and modulation frequency.From the Track Plot we can see that the modulation signal is a sine wave with exactly 50 µs period (=20 kHz) and it alters the carrier frequency between 9 and 11 MHz.FFT Dynamic rangeSince the introduction of the SDS1004X-E in early 2018, FFT has always been a strong point of Siglent DSOs. The SDS800X HD is no exception and numerous examples have been published already in this review, as the FFT is an incredibly universal tool to demonstrate fundamental features like frequency response, noise distribution and signal spectra in general, as well as measure distortion products, spurious signals and weak signals, deeply buried under the noise floor.One of the concerns with the FFT in DSOs is the dynamic range. For 8-bit acquisition systems, this is only about 49 dB according to the textbook, as it is some 73 dB for 12 bits. And indeed we need to be careful when acting outside these “guaranteed” dynamic ranges. Yet the wonders of process gain in an FFT and other resolution enhancement techniques can extend the usable dynamic range quite a bit, and this shall be demonstrated for the SDS800X HD in some best case scenario.What is the “best case” scenario? It is a frequency at or above 1 MHz in order to escape the 1/f noise, but at the same time the frequency should be low enough so we can get rid of all the high frequency noise by using the 20 MHz bandwidth limiter plus an additional steep 20 MHz lowpass filter. Consequently, we practice math on math (the SDS800X HD could also have combined it in one formula instead) and calculate the FFT on the filter output instead directly on the Ch.4 data.Two signals from an AWG at 9.9 and 10.1 MHz are fed into a wideband signal combiner, where the second signal goes through a fixed 20 dB attenuator together with a 1 GHz step attenuator before it hits the combiner, whose output is connected to the SDS824X HD Channel 4 input via another 10 dB inline attenuator and a 50 ohm through terminator. Of course, the tolerances of these various components sum up, so I have calibrated the whole setup for a 0 dB setting of the step attenuator first by means of the AWG output levels, but left them untouched for all subsequent measurements. As a consequence, any tolerances of the step attenuator settings will affect the results. The step attenuator is a Wavetek 5080.1 with a specified tolerance of +/-1 dB up to 400 MHz. After using it many decades, I can tell from experience that it thankfully is clearly more accurate than that.In order to get a low RBW (Resolution Bandwidth), hence also a low noise floor, we don’t want an excessively high sample rate; 100 MSa/s and a Nyquist frequency of 50 MHz is plenty to deal with a 10 MHz signal and also a 20 MHz FIR filter.Here's the calibration result:SDS824X_HD_FFT_DR_500kpts_10MHz_40dBThe error is <0.05 dB. Going from there, here’s the measurement for 80 dB level difference:SDS824X_HD_FFT_DR_500kpts_10MHz_80dBThe error is < 0.25 dB, which could well be attributed to the step attenuator.Now let’s try 100 dB with the same setting:SDS824X_HD_FFT_DR_500kpts_10MHz_100dBThe measurement error is still <0.7 dB, yet the 2nd signal is almost down in the noise.Up to now, we’ve only computed a 512 kpts FFT, so let’s try 1 Mpts now, thus cutting the RBW in half.SDS824X_HD_FFT_DR_1Mpts_10MHz_100dBNow the 2nd signal is clearly above the noise floor and the total error is less than 0.15 dB!Even if we assume the step attenuator would have no tolerances at all, this still is a remarkable result.

author: Performa01
author_rank: Super Contributor
timestamp: January 23, 2024, 08:39:43 am
content: True Vertical SensitivityThe SDS800X HD has a specified vertical gain range from 500 µs/div up to 10 V/div. Many contemporary DSOs have similar specs, yet only a small minority of them can provide true 500 µV/div as the real highest sensitivity at full resolution. The real sensitivity of many instruments is lower, sometimes significantly so (up to 5 mV/div). As a consequence, anything above the true highest sensitivity is just software zoom and won’t provide full resolution anymore. This might be not that much of a problem for a 12 bit DSO, but 8 bit instruments degraded to 6 bits at 1 mV/div could get problematic. On the other hand, most of those instruments also exhibit high noise levels, so the ENOB (Effective Number of Bits) drops below 6 bits at these higher sensitivities anyway.For the SDS800X HD, I stumbled across the unexpected property of nearly equal noise levels for all vertical sensitivities from 500 µV/div to 5 mV/div:SDS824X HD_NDThese numbers are not totally accurate because it proves very difficult to place the markers close to the intended frequency without hitting a minor spur. Consequently, I would think that the noise level is fairly uniform across all the higher sensitivities from 500 µV/div to 5 mV/div and the minima across all measurements would be the best representation of the truth:Noise 500 µV/div – 5 mV/div :1 kHz : 232.9 nV/√Hz3 kHz : 174.2 nV/√Hz10 kHz : 62.5 nV/√Hz30 kHz : 16.0 nV/√Hz100 kHz : 5.7 nV/√Hz300 kHz : 2.7 nV/√Hz1 MHz : 2.4 nV/√Hz10 MHz : 2.5 nV/√HzThis made me suspicious: does Siglent cheat after all? Are all vertical gain settings below 5 mV/div just fake? First, I’ve checked the raw acquisition data for 500 µV/div vertical gain and found the lowest voltage step to be 1.042 µV.Time  Value  Delta -4.0000000000E-08 -4,166667E-05 5,208E-6-3.9500000000E-08 -4,166667E-05 000,000E+0-3.9000000000E-08 -4,270833E-051,042E-6The SDS800X HD has 480 LSB per vertical division (just like the SDS2000X HD), thus 3840 LSB on the visible part of the screen. Since a 12 bit acquisition system provides a total 0f 4096 LSB, there is very little headroom outside the visible screen area.The interesting part is when we multiply the 1.042 µV resolution with the 480 LSB of one division: 1.042 * 480 ~ 500 µV/div; -> Bingo!A less accurate, but quicker and simpler method to verify the resolution of the SDS800X HD is using vertical zoom; we can zoom into the noise in dots display mode, thus getting horizontal lines vertically spaced according to the true resolution of the instrument.At a vertical gain of 500 µV/div and a vertical zoom window at 2 µV/div, we get the following picture:SDS824X_HD_Resolution_DemoSince we still have 8 vertical divisions also in the zoom window, the total visible screen height covers 16 µV at 2 µV/div. We can count 15 horizontal lines, hence 16 steps and can conclude that each step has to be close to one microvolt.Verdict: Siglent don’t cheat. The uniform noise level at and below 5 mV/div is just a property of the integrated PGA (Programmable Gain Amplifier) used in this instrument.Peak DetectThe peak detection capability of the SDS800X HD is specified as 2 ns. Let’s have a closer look at that.First a 2 ns wide pulse with 300 mV amplitude and 500 ps rise time in normal acquisition mode at sufficient sample rate (2 GSa/s):SDS824X_HD_Pulse_W2ns_RT500ps_2GSa_Norm_ZoomIt can be seen that such a narrow pulse is already a bit too much for a 200 (244) MHz oscilloscope; the amplitude has already dropped a bit and pulse width measurement isn’t quite accurate either. As expected, the rise time measurement approaches the scope’s own rise time.With all these shortcomings, we still get a fairly stable picture – look at the main window and the peak and standard deviations in the measurements statistics.In the screenshot above, the time base was at 5 ms/div and the sample memory was already at its maximum of 100 Mpts; slowing down the time base any further will inevitably lower the sample rate:SDS824X_HD_Pulse_W2ns_RT500ps_100MSa_Norm_ZoomAt 100 ms/div and 100 Mpts record length the sample rate has to be decimated to just 100 MSa/s – far too slow for capturing a 2 ns wide pulse. As a consequence, many pulses get lost. In the main window we would expect to see about 1000 pulses at a pulse repetition rate of 1 kHz, but there are actually much less and the amplitudes vary wildly.This isn’t a very realistic scenario; not many engineers would try to watch 2 ns wide pulses at a time base of 100 ms/div and have to use 2 million times zoom to watch the pulse details. Yet this is where Peak Detect acquisition mode comes into play:SDS824X_HD_Pulse_W2ns_RT500ps_100MSa_Peak_ZoomThe main window now shows all the pulses; the amplitudes still vary a bit, but at least we don’t miss any pulses anymore. Pulse shape has nothing to do with reality anymore and measurements yield just house numbers. This should be a clear warning to not use Peak Detect for anything serious, as any math and measurements on such waveforms are of artistical value at best.All that Peak Detect really can do is to hint on any pulses within the record.Of course peak detection works for even narrower pulses just as well. This is not because the specification is not correct, but the simple fact that a 244 MHz DSO like the SDS824X HD simply cannot process even faster pulses:SDS824X_HD_Pulse_W1ns_RT500ps_2GSa_Norm_ZoomThis is now a 1 ns wide pulse at maximum sample rate of 2 GSa/s. The amplitude is still 300 mV, yet the SDS824X HD cannot cope with it anymore and the amplitude measurement result has dropped to just 173 mV. The pulse width is still measured as 1.8 ns, so the relative slowness of the frontend widens shorter pulses at the expense of amplitude, hence makes an even faster peak detection unnecessary.Bode Plot at a glanceInstead of showing an inexpressive first order RC-lowpass filter demonstrating less than 40 dB dynamic in the audio range, I’d rather check the most important characteristics of a Bode Plot: frequency- & dynamic range and accuracy.For this, I’ve refrained from using inline terminators at the scope inputs but fed them from 50 ohms sources directly via ~25 cm long coaxial cables. The source resistance of 50 ohms, together with the cable and scope input capacitances, forms a first order lowpass filter at ~10 MHz. This can also serve as a warning how even very short cables can introduce significant amplitude errors at relatively low frequencies, as long as a transmission line is not properly terminated.We can see this characteristic when using the “Vout” mode of the Bode Plot, where we get the absolute amplitude of the DUT output (where the DSO itself represents the DUT).SDS824X HD_Bode_1M_VoutThe amplitude drops quite significantly above 10 MHz. It is not the 20 dB/decade like a classic first order lowpass – and this is for a number of reasons that I won’t discuss in this article. Bottom line is, that even with very short cables, accuracy of the absolute signal level is gone already at moderate frequencies of a couple MHz.The phase plot does not resemble this, as it stays within +/-1° up to 120 MHz quite easily. It almost looks like this would not be a minimal phase system, yet it’s just the nature of a multi-channel oscilloscope, where the input signals are always phase aligned.When using the relative (Vout/Vin) mode (as we usually do), things look completely different:SDS824X HD_Bode_1M_S21Bode Plot now shows the difference between reference channel 1 and the other channels. It is indicative of the quality of the SDS800X HD that the differences between channels are really negligible: less than 0.3 dB amplitude error as well as less than 1° phase error up to 120 MHz, and almost no differences between channels 2-4, speaks for itself.Let’s check the accuracy and dynamic range now. Two signals are used to visualize a 60 dB amplitude difference. This time, 50 ohm inline termination has been used.SDS824X HD_Bode_50_S21_60dBThere is a significant phase difference, and this comes from the additional 3-stage step attenuator + Inline attenuator + some 50 cm additional coaxial cable for channel 4.As a final experiment, here is a 100 dB amplitude difference (phase has been adjusted by means of the channel skew parameter):SDS824X HD_Bode_50_S21_100dBNoise is getting a major problem, yet amplitude measurements can still yield useable results in the range 100 kHz to ~20 MHz.The reference level is low (~570 mVrms), hence channel 4 input sees only 5.7 µVrms!I’ve not nearly exploited the dynamic range of the SDS800X HD, which could handle up to 28 Vrms (but then with beefy external >16 W terminators) if the need should be.

author: Martin72
author_rank: Super Contributor
timestamp: January 23, 2024, 09:23:12 am
content: QuoteAbsolutely, no contest.

author: Wintel
author_rank: Regular Contributor
timestamp: January 23, 2024, 02:32:02 pm
content: Is this a real or a "hack" SDS824X HD?

author: 2N3055
author_rank: Super Contributor
timestamp: January 23, 2024, 02:35:17 pm
content: Quote from: Wintel on January 23, 2024, 02:32:02 pmI presume real one...What would be the difference anyways?

author: chillidog
author_rank: Newbie
timestamp: January 23, 2024, 02:36:08 pm
content: Thanks for the elaborate testing! Looks like a very capable scope indeed. Is this still a pre-release/China version or the real deal?

author: Performa01
author_rank: Super Contributor
timestamp: January 23, 2024, 03:14:11 pm
content: This is a genuine SDS824X HD, an early production unit ment for the international market. I've got this unit for beta tests and now that the official introduction comes nearer, I had asked Siglent product management for permission to publish the most relevant details, so you can know what you might be waiting forI most definitely don't know it, but from the datasheet I would not rule out that the SDS822/4X HD might have slightly different hardware compared to the SDS802/4 and 812/4X HD, because SDS822/4X HD provide slightly higher waveform update rates.

author: Wintel
author_rank: Regular Contributor
timestamp: January 23, 2024, 06:44:54 pm
content: Quote from: Performa01 on January 23, 2024, 03:14:11 pmHi,Could you please do 2 tests?1. Set the coupling of channel 1 to GND, Timebase to 1ms and 500uV/div to test the noise floor.2. Set the coupling of channel 1 to GND, Timebase to 20ms and 1mV/div to test the noise floor.

author: rf-loop
author_rank: Super Contributor
timestamp: January 24, 2024, 05:10:57 am
content: Quote from: Wintel on January 23, 2024, 06:44:54 pmHere with input coupling GND as you askZoom window: Zoomed in vertically to max and horizontally so that every single real ADC sample dots are visible. Without interpolations.In this oscilloscope, GND coupling is not done in start of analog input pathway. But it is also not after ADC zero binary data.But it nicely tell what are ADC real steps...coupling of channel 1 to GND, Timebase to 1ms and 500uV/div (and Zoom window (Z1) 10ns/div and 2uV/div)coupling of channel 1 to GND, Timebase to 20ms and 1mV/div (and Zoom window (Z1) 50ns/div and 2uV/div)With 1mV/div ADC F.S. is ~8.5mV and display full scale is 8mV

author: ebastler
author_rank: Super Contributor
timestamp: January 25, 2024, 01:08:12 pm
content: Subscribing, and giving this thread a little bump -- updates to the reserved posts don't move it up the "recent posts" list, I think. Many thanks for the in-depth review, Performa01, I am looking forward to the sequel!

author: Veteran68
author_rank: Frequent Contributor
timestamp: January 25, 2024, 01:50:44 pm
content: I'd love to see someone do a side-by-side with the Rigol DHO1000 line (not the DHO800 line). I know I could do a datasheet comparison but that doesn't tell the whole UX and real-world performance story.I have the DHO1074 (upgraded to 200Mhz + 50Mpts memory) since the BF deal was too good to pass up, but I'd been holding out for Siglent's new HD scopes to arrive. I have a suspicion that the SDS1000 isn't going to be nearly as affordable as the DHO1000 series -- especially considering the BF discount -- but I'm wondering if the SDS800 series might be close enough and have some compelling improvements over even the "next-tier" DHO1000.I realize it's not really fair to try and compare scopes from different tiers, but I wouldn't be surprised if Siglent's bottom-tier 800HD offering was as good or better in some ways than Rigol's next-tier 1000HD line.Obviously the screen will be the major downgrade going from the DHO1000, and I do love the big, sharp Rigol screen. To give that up for the smaller Siglent would require some substantial improvements in other features.Now if the SDS1000 comes to NA within the ballpark of Rigol's DHO1000 pricing, that's where I'll be looking, but I'm still curious where this 800 series fits in the comparison.

author: 2N3055
author_rank: Super Contributor
timestamp: January 25, 2024, 02:19:39 pm
content: Quote from: Veteran68 on January 25, 2024, 01:50:44 pmMaybe SDS1000 will have better pricing ?I guess we will see soon...Biggest differences between 1000XHD and 800XHD are:Screen size (same resolution though, so same screen content)No 50Ω inputs. Only 1MΩDecodes: 1000XHD (I2C, SPI, UART, CAN, LIN, CAN FD, FlexRay) vs 800XHD(2C, SPI, UART, CAN, LIN)Simpler I/O: one less USB port and no External Trigger INSome differences in measurement display options.As for comparisons, truth is, SDS800XHD as a scope compares very favourably to DHO1000. I do understand the screen size is important (I'm nearsighted) though.But, mind you, class numbers are not arbitrary. I expect for Siglent 1000XHD to be in a ballpark price wise compared to Rigol DHO1000 (list prices, not fire sale prices) and more capable. And 800XHD should be less than that, in it's class.. They might not try to undercut Rigol in prices, but should be in the same class, maybe bit more.

author: Performa01
author_rank: Super Contributor
timestamp: January 25, 2024, 05:02:43 pm
content: I have updated the opening posting with a confirmed list of differences between SDS800X HD and SDS1000X HD and have added a contents overview.The following content has been added:Reply #3: Measurements, Vertical Axis Labels, DC Check, CounterReply #4: AC Trigger Coupling, Triggering noisy signals

author: ebastler
author_rank: Super Contributor
timestamp: January 25, 2024, 05:09:38 pm
content: Quote from: Performa01 on January 23, 2024, 08:33:24 amThank you, that's a helpful summary.Regarding bandwidth and memory depth, is it fair to assume that the basic model will be upgradable? Also, as the SDS1000X HD does not support NTP, I assume it has an on-board real-time clock with battery backup (while the 800X HD does not)?

author: Performa01
author_rank: Super Contributor
timestamp: January 25, 2024, 05:27:46 pm
content: Quote from: ebastler on January 25, 2024, 05:09:38 pmI honestly don't know, but the ugrade from 70 to 100 MHz goes without saying. Hackers will also find a way to upgrade to 200 MHz, even though there is a small chance that the memory depth and waveform update rate might not be upgradable. Who knows, maybe Siglent management holds the view that this product is such a great price/performance ratio that they actually want to optimize the BOM for the lower bandwidth models. Time (and the Hackers) will tell.I think that this scope will become popular among amateurs on a budget, even if the memory depth would stay at 50 Mpts and the max. waveform update rate is 20% slower.I don't have an SDS1000X HD, but rf-loop owns the previous version of it, so he should be able to answer that question. Yet it's a safe bet that it has a RTC - the missing NTP support is a dead giveaway.

author: tautech
author_rank: Super Contributor
timestamp: January 25, 2024, 06:35:04 pm
content: Quote from: Performa01 on January 25, 2024, 05:27:46 pmI do, the early white version and indeed it has a RTC.

author: rf-loop
author_rank: Super Contributor
timestamp: January 25, 2024, 09:25:59 pm
content: Quote from: tautech on January 25, 2024, 06:35:04 pmYes I can also confirm, SDS1000X HD (1G version) sure have internal HW RTC with battery backup (and I "believe" that 2G version also have hardware RTC).SDS800X HD do not have.Of course it have date/time of day clock function where user can set date and time manually or configure it for get real time from NTP when it is connectd to network where NTP is available. Naturally if one have own NTP server it do not need connect to internet.It keep time as long as it is ON. After shut down it loose time and it need get time manually or from NTP again after booted up. If user do not need real time at all. Time display can also shut off so that it do not start display date and time from year 1970Also in my previous image can see there is clock displayed and all times when I turn it on (if cable is connected), it get right time from network NTP server (when configure it, user need know suitable NTP server IP, instead of name)

author: Martin72
author_rank: Super Contributor
timestamp: January 25, 2024, 09:48:20 pm
content: Hi,QuoteIt seems so (pic taken from the 1000X HD(2ndG) unboxing thread)...

author: ebastler
author_rank: Super Contributor
timestamp: January 25, 2024, 09:50:25 pm
content: Duh, right, thank you! I had not remembered that post. Alright, so the lack of NTP is a non-issue for the larger model, as expected.Maybe the RTC could be added to the list of SDS800X HD vs 1000 differences in the top post?

author: orzel
author_rank: Regular Contributor
timestamp: January 25, 2024, 10:31:36 pm
content: Quote from: rf-loop on January 25, 2024, 09:25:59 pmThat seems scary. Most of the time, the dhcp server will provide a NTP server as well... Can the scope use this ?

author: tautech
author_rank: Super Contributor
timestamp: January 25, 2024, 10:41:09 pm
content: Quote from: orzel on January 25, 2024, 10:31:36 pmNTP server URL's can be found in seconds, here's yours for France:https://www.ntppool.org/en/zone/frFor large countries with multiple time zones you also need specify your location in the scopes NTP menu.

author: orzel
author_rank: Regular Contributor
timestamp: January 25, 2024, 11:01:21 pm
content: Quote from: tautech on January 25, 2024, 10:41:09 pmThat's not what i meant. I know where to find a ntp server. I even have one here.The question was : do you really need to manually enter an IP ?Most networks use DHCP for hosts to get an IP. And this same DHCP server that answers, can also provides some more information. And typically, it can provide a NTP server.Here at least, this is the way almost all networks do.

author: tautech
author_rank: Super Contributor
timestamp: January 25, 2024, 11:15:46 pm
content: Quote from: orzel on January 25, 2024, 11:01:21 pmFor the older SDS1*04X-E, yes.800X HD is a continuation of this NTP functionality but with a different and updated touch UI where entering a URL via the virtual or an external keyboard is quicker and simpler.For X-E, we setup the NTP for NZ in every unit we sell and we will be doing the same when 800X HD arrives.Edit to addPerforma01 might like to show us use of the virtual keyboard.

author: rf-loop
author_rank: Super Contributor
timestamp: January 26, 2024, 05:17:59 am
content: Currently, for now, System Settings/Time is like this. The IP address of the NTP server is entered there. What could be easier. One could get by with even less if you could enter it in hex but it accept it only decimal form.Personally I would have left out those time zone name lists entirely. Instead, one parameter field where one can enter time difference +/- hh.mm relative to UTC. Every engineer or who have attended elementary school know how many hours the clocks in their area are in relation to UTC. If one don't know - back to school. However, now there is that list and we live with it... How can someone, who doesn't know the offset to UTC, find the right one if their own city or state is not found there... (...censored...).In images below can see menu for configure System / Time

author: chillidog
author_rank: Newbie
timestamp: January 26, 2024, 10:53:03 am
content: Quote from: rf-loop on January 26, 2024, 05:17:59 amWell... even easier would be not having to enter it at all, i.e., relying on DHCP. Of course, when no NTP option is presented, manual entry should still be possible. I suppose it's the same way with the IP address? If there's no DHCP on the network, one could still manually enter an IP address, right?

author: rf-loop
author_rank: Super Contributor
timestamp: January 26, 2024, 11:25:55 am
content: Quote from: chillidog on January 26, 2024, 10:53:03 amYes.

author: orzel
author_rank: Regular Contributor
timestamp: January 26, 2024, 05:29:24 pm
content: Quote from: chillidog on January 26, 2024, 10:53:03 amThat's even very easy. Those scope use linux, and very probably a common package for dhcpd, all of them defaulting to handle ntp... At worse, it's a one liner in some config file. I can do some "pro bono" consulting to help Siglent if they can't manage that !

author: empeka
author_rank: Contributor
timestamp: January 26, 2024, 05:58:57 pm
content: I'm not an android expert, but I think that dhcpcd in android was deprecated many years ago in favor of... more android nativejava library, that does not seem to handle option 42.

author: baldurn
author_rank: Regular Contributor
timestamp: January 26, 2024, 06:32:35 pm
content: Quote from: rf-loop on January 26, 2024, 05:17:59 amIt is for automatic daylight saving. The rules for that varies all of the world. So you need to know the country or state.Of course it happens that the politicians change the rules and your software gets outdated.

author: orzel
author_rank: Regular Contributor
timestamp: January 26, 2024, 07:19:17 pm
content: Quote from: empeka on January 26, 2024, 05:58:57 pmHopefully those new siglent scopes wont be android, but linux as usual. That's not Rigol !

author: tautech
author_rank: Super Contributor
timestamp: January 26, 2024, 07:29:20 pm
content: Quote from: orzel on January 26, 2024, 07:19:17 pmYep, Linux all the way to even the PC based SDS7000A.

author: empeka
author_rank: Contributor
timestamp: January 26, 2024, 07:49:25 pm
content: Oh... I've sunk in hacking dho800 so deep in the last few days, that I almost forgot that there are other OSesWell, it's good to be wrong sometimes;)

author: Performa01
author_rank: Super Contributor
timestamp: January 29, 2024, 09:04:04 am
content: The following content has been added:Reply #51. Deep Measurements2. Probe BandwidthThe opening posting has been updated accordingly.

author: Martin72
author_rank: Super Contributor
timestamp: January 29, 2024, 09:10:38 am
content: Thank you for the enormous effort you are putting in here - THIS is a review...

author: Performa01
author_rank: Super Contributor
timestamp: February 01, 2024, 03:40:01 pm
content: The following content has been added:Reply #3https://www.eevblog.com/forum/testgear/sds800x-hd-review-demonstration-thread/msg5293750/#msg52937502. Measurement HistogramsReply #6https://www.eevblog.com/forum/testgear/sds800x-hd-review-demonstration-thread/msg5293759/#msg52937591. Poor Men’s Differential Probing2. Distortion measurementsThe opening posting has been updated accordingly.

author: Orange
author_rank: Frequent Contributor
timestamp: February 01, 2024, 06:25:08 pm
content: Performa01I'm not impressed by the HF response step size the first 15ns; there is much undefined over and undershoot. The same behavior can also be seen on the SDS1000HD. Almost as if they use the same front-end design.Can you also make a test on a 100Hz square wave input signal ? Some recent Siglent scopes also have problems with this (not showing a real square)Thank you

author: Martin72
author_rank: Super Contributor
timestamp: February 01, 2024, 11:08:15 pm
content: QuoteWhich screenshot are you referring to?

author: rf-loop
author_rank: Super Contributor
timestamp: February 02, 2024, 07:33:18 am
content: Quote from: Orange on February 01, 2024, 06:25:08 pmSDS824X HD, 100Hz sqr from SDG1032X with normal 10x probe.average for better see top and bottom line shape

author: 2N3055
author_rank: Super Contributor
timestamp: February 02, 2024, 07:58:04 am
content: Quote from: Orange on February 01, 2024, 06:25:08 pmWhy would they not share input design, when their specifications for inputs are pretty much the same...? Of course, they would only share 1MΩ input path design.Are you referring to images with top part of signal zoomed in 20X ?(Which by the way is something not many scopes can do, not to mention in this class.)Your definition of recent is very different from mine. Problems with compensation were in scopes from 2017.. that is going on to 7 years now... there were 3 generations of new products released. Just saying...

author: Orange
author_rank: Frequent Contributor
timestamp: February 02, 2024, 08:18:59 am
content: Quote from: 2N3055 on February 02, 2024, 07:58:04 amPicture SDS824X_HD_PR_1GSa is NOT zoomed in, and clearly shows strange strange aberrations, almost there is a reflected wave interfering with one of the internals...A TDR or VNA would shed some light on this to see what is going on. (at least on a SDS1000X HD this is possible, but outside the scope of this thread)There is nothing wrong with sharing a good design, I did not imply this is a bad thing, just an observation, so no defense from your side is needed here.As for the LF compensation in the front-end, Siglent does not have a good track record for this, specially on the low end scopes. I consider the SDS800 as a low end scope give the fact it has only a 7'' screen hence my curiosity for the LF distortion on this model.Thanks Performa01 and RF-loop for the tests

author: Performa01
author_rank: Super Contributor
timestamp: February 02, 2024, 08:57:36 am
content: Quote from: Orange on February 01, 2024, 06:25:08 pmI’ve demonstrated how the details of a pulse flat can be closely inspected without overloading the scope input by means of a proper zoom implementation and additional math to deal with noise. Yes, neither pulse generators nor oscilloscope frontends are 100% ideal, especially in terms of impedance matching. Because what we see in my screenshots are clearly reflections stemming from less than perfect impedance matching. On the other hand, small aberrations in the realm of 2.5 % (as in this case) are usually well accepted in the industry.I’ve added a paragraph and a screenshot to the “Pulse Response” section in the opening posting to demonstrate a modified test setup for the occasions where we really need highest possible signal fidelity up to the fine details.Quote from: Orange on February 01, 2024, 06:25:08 pmAbsolutely no problem with a 100 Hz square when using the SDS800X HD (or any other contemporary Siglent DSO):SDS824X_HD_PR_100Hz_ZoomAlso the claims about serious problems with the SDS1000X-E (at 10 Hz this time) could not be confirmed:https://www.eevblog.com/forum/testgear/siglent-sds1104x-e-in-depth-review/msg5278090/#msg5278090

author: Orange
author_rank: Frequent Contributor
timestamp: February 02, 2024, 09:16:01 am
content: Much better HF pulse response now in the added testLF distortion is also absent ;GOOD !Thanks Performa01

author: 2N3055
author_rank: Super Contributor
timestamp: February 02, 2024, 11:07:29 am
content: Quote from: Orange on February 02, 2024, 08:18:59 amThank you for explaining. I wasn't defending, just wanted to know what exactly you mean.But I think "As for the LF compensation in the front-end, Siglent does not have a good track record for this, specially on the low end scopes" is a bit over the top.There were 2 entry level scopes, 7 years ago, then new, sharing input design that had error in manufacturing on one batch.Shall I start with all the major problems Keysight, Tek, R&S had in their equipment over the years.From outright bad designs to major manufacturing problems. Does that makes them "they don't have good reputation making T&M equipment"Of course not.He who works makes mistakes... that is just a fact.In a perfect world there would be none.In real world, as long as problem is recognized and taken care off, it is all we can ask for.

author: Performa01
author_rank: Super Contributor
timestamp: February 02, 2024, 11:51:33 am
content: Quote from: 2N3055 on February 02, 2024, 11:07:29 amEven that statement is not correct.The SDS1202X-E, introduced to the public in Autumn 2016, had missing compensation capacitors in the frontend in the very first production batch.Somewhere I've read claims that the SDS1104/1204X-E, introduced in early 2018, also was affected - but this is Chinese Whispers at best. I got my SDS1104X-E several months before its market start and it did not have any issues. You'll also not be able to find any complaints from users about such issues.

author: 2N3055
author_rank: Super Contributor
timestamp: February 02, 2024, 12:39:34 pm
content: Quote from: Performa01 on February 02, 2024, 11:51:33 amI stand corrected then. Thank you for clarification.

author: Performa01
author_rank: Super Contributor
timestamp: February 04, 2024, 05:01:32 pm
content: The following content has been added:Reply #7https://www.eevblog.com/forum/testgear/sds800x-hd-review-demonstration-thread/msg5293762/#msg52937621. Digital ChannelsThe opening posting has been updated accordingly.

author: ebastler
author_rank: Super Contributor
timestamp: February 04, 2024, 05:19:37 pm
content: Many thanks for being very clear on the capabilities as well as limitations! I also appreciate the older photos of the probes (in the 1104X-E thread, had not come across these yet) -- they give a good impression what to expect.I am pleasantly surprised that in your screenshot, the digital channels hardly ever show the +- 1 ns skew stated in the datasheet. The DHO900 logic analyser is specified for +- 5 ns skew between digital channels, typical (!). Although I don't know whether it actually exhibits these rather large deviations.

author: Performa01
author_rank: Super Contributor
timestamp: February 09, 2024, 12:32:07 pm
content: The following content has been added:Reply #7https://www.eevblog.com/forum/testgear/sds800x-hd-review-demonstration-thread/msg5293762/#msg52937621. Digital Channels: fast pulse measurement addedReply #8https://www.eevblog.com/forum/testgear/sds800x-hd-review-demonstration-thread/msg5293765/#msg52937651. Measurements 2 (Trend/Track)2. FFT Dynamic rangeThe opening posting has been updated accordingly.

author: Performa01
author_rank: Super Contributor
timestamp: February 13, 2024, 09:58:44 am
content: The following content has been added:Reply #9https://www.eevblog.com/forum/testgear/sds800x-hd-review-demonstration-thread/msg5293771/#msg52937711. True Vertical Sensitivity2. Peak Detect3. Bode Plot at a glanceThe opening posting has been updated accordingly.

author: Martin72
author_rank: Super Contributor
timestamp: February 13, 2024, 11:08:01 am
content: Thank you for your incredible efforts....

author: Performa01
author_rank: Super Contributor
timestamp: February 13, 2024, 05:50:44 pm
content: Bode Plot ExampleHere is my standard test for Bode Plot: a simple 455kHz IF filter, consisting of a Kyocera KBF-455R-20A ceramic 6 element filter with two resonant 2nd order L-matching networks for the 50/1500 ohm impedance transformation at both the input and output.SDS824X HD_Bode_50_S21_IF455kHzA complex structure like this has a somewhat chaotic phase response, especially in the passband and the transitions into the stopband. The amplitude shows nice steep transitions into the stopband, yet there are some unwanted resonances as is typical for this type of filters. The important fact is that we need high frequency resolution to capture all the fine details. Furthermore, this test demonstrates at least 90 dB dynamic range.The data table has been adjusted to the nominal center frequency of the filter, which should be 455 kHz. A vertical cursor marks the selected frequency in the plot and from the table we can see that insertion loss of this filter is some 3.66 dB. The frequency with the lowest attenuation of 3.57 dB is 458 kHz though. This “data cursor” is independent of the manual cursors that are available in the Display menu.I’ve set up some specific measurements: UF (Upper Frequency), LF (Lower Frequency) and BW (Band Width) to characterize the most important properties of the filter. We can see at a glance that the bandwidth is precisely 21.4 kHz.For those bothered by the complex phase plot, there is always the option to disable any trace we like:SDS824X HD_Bode_50_S21_IF455kHz_NP

author: tszaboo
author_rank: Super Contributor
timestamp: February 13, 2024, 09:58:36 pm
content: Few questions: Is that 500 steps to measure the Bode plot? What did you use to make the signal, USB to a desktop AWG or the S-BUS AWG?

author: Performa01
author_rank: Super Contributor
timestamp: February 14, 2024, 09:25:59 am
content: Quote from: tszaboo on February 13, 2024, 09:58:36 pmIt is 501 points Bode Plot with an external SDG6052X connected via USB.For better dynamic I've used the SDG6052X in Tracking mode, so I could connct the reference channel and the DUT directly to the AWG and didn't need a power splitter, which would have caused 6 dB signal loss.

author: mawyatt
author_rank: Super Contributor
timestamp: February 14, 2024, 06:08:35 pm
content: Quote from: Performa01 on February 14, 2024, 09:25:59 amGood idea using the AWG tracking mode instead of a splitter when you have a 50 ohm systemBest,

author: rf-loop
author_rank: Super Contributor
timestamp: February 15, 2024, 04:56:10 am
content: BodePlot. It is also good to look for performance limits. So what can't be done with it. Here are a couple of examples of where performance becomes a limiting factor. In one, the dynamics of the measurement is limiting, and in the other, the frequency resolution.First, an IF filter built using the "Bob Peace" style. (there is cascaded 2 very cheap Murata filters and some "this and that" for reduce cross over etc.)In addition to the form factor of the filter, the stopband is extremely important. This doesn't even come close to see it. Here it is necessary to reach at least somewhere -120----130dB below the passband and this can not at all.The steepness of the edge is also such that it would be good to have more frequency resolution. Of course, the edges could be run separately with a narrower Span if need go more deep.455kHz IF filter wide sweepGreen trace is BP noise level. (just empty channel) There can see jump in noise levelperhapsdue to overlapping between two different RBW when RBW change, just there is one point where BodePlot "receiver" bandwidth (RBW) is changing.Same filter, BP Span now 50kHzIt is here clear that this BodePlot can not at all see this filter stop band charasteristics. For this, there need be lot of more dynamic range down from 0dBm level.Steep edges can analyze separately if need more frequency resolution. (50kHz Span minimun step is 100Hz what is not enough for very steep and narrow filters, but this filter is not so steep)Then two xtal resonators. The frequency resolution ends in both. That approximately 84kHz resonator should be driven with perhaps a 0.1Hz step sweep. Because the minimum Span is 500Hz and the maximum number of samples 501 limit in this case limit is 1Hz.Here bit over 84kHz resonator.Now Span is 500Hz and 1Hz steps. (501 pts). It is clear that this 1Hz step is far too big for this if need carefully look series and parrel resonances.It need least 10 times more resolution.Notice that the phase information in the table is just random noise. It's a pity that in scalar measurements that part cannot be closed. So user have to ignore them only in his own head. (In this case there is not reference signal at all.)And same here in next.Cheap around 2.4MHz resonator. Sweep resolution is not well enough but here (if any reason) if need look series and/or parallel resonances mode more detailed, here can do it running these separately using more narrow span. Limit is 500Hz Span and 501pts what give 1Hz resolution.In the ad, of course, a real careless salesman could write that the resolution is up to 275204396 pts/decade, which is not false if we are precise. On the other hand, it is in all cases at least 70/decade when full sweep 10Hz - 120MHz.Finally, a picture of what it can do quite easily.This is very simple cascaded HiPass CRCR (green trace) and LoPass RCRC filter for get BandPass (yellow trace). Traces are BandPass, HighPass and one trace (pink) is after first CR in HiPass.As can see there is visible also this capacitor resonace.Green trace signal use 1x probe. (this is reason for higher freq attenuating)But overall it still amazing how much this can do.It's good to know what can do. It's also good to know what can not.

author: Performa01
author_rank: Super Contributor
timestamp: February 15, 2024, 09:21:00 am
content: SPI Speed TestWe could ask the question: how fast an SPI data stream can we decode with a 200 MHz DSO? Huch much oversampling do we need?For some DSOs it is said that they need a fair bit of oversampling for proper decoding. Yet the answer is, a proper implementation doesn’t require much in this regard, hence it should be perfectly adequate to have a bandwidth three times the SPI clock frequency. The sample rate on the other hand should be irrelevant, as long as the Nyquist criterion for the required bandwidth is fulfilled. That makes for more than 6 times the SPI clock frequency.The SDS824X HD true bandwidth is limited to 200 MHz in full channel mode and its sample rate is 500 MSa/s. According to the hypothesis stated above, this bandwidth would allow a max. SPI clock of 66 MHz and the sample rate is sufficient for that. The only way to know how good this works is to try it out…I felt adventurous, hence didn’t bother with 66 MHz, but tried 100 MHz right away:SDS824X_HD_SPI_100MbpsThe above screenshot shows a bidirectional (full duplex) 100 Mbps SPI data stream with a message length of 11 bytes. No special trigger has been used, just falling edge trigger on the /CS line.The decoding works without issues, but how can we prove that the results are correct? Here’s a simple test: I’ve replaced the MOSI signal with a phase synchronized copy of the 100 MHz clock signal, phase shifted 90° such that it is always sampled at its low state and then shifted by another 180° so that it is always sampled at its high state. This way we’re putting the maximum stress on the acquisition chain, whereas it would be an easy task if we had just static signals for MISO/MOSI.SDS824X_HD_SPI_100Mbps_0SDS824X_HD_SPI_100Mbps_1The expected results of all 0x00 for the first test and all 0xFF for the second one has been achieved, proving that there is a good chance to decode a 100 Mbps SPI data stream correctly with only twice the bandwidth and five times the sample rate.If we trigger on the rising edge of the clock, we can produce an eye diagram which clearly shows that there is plenty of margin for correct decoding. Even the MISO signal, while slightly delayed, causes no problem in this scenario.SDS824X_HD_SPI_100Mbps_EyeThe fast pulses look very soft on the 200 MHz scope and the clock signal is a pure sine now, since we can only capture the 2nd harmonic, but not the 3rd.Compare this to the same clock and MOSI signals displayed at ten times the bandwidth of the SDS6204X HD:SDS6204_Pro_H12_SPI_100Mbps_EyeSo, could we go up to even 200 Mbps maybe?SDS824X_HD_SPI_200Mbps_EyeThis is quite revealing. There might be a small chance to get it working with a fair share of luck, yet this certainly isn’t a robust solution. The transitions are way too slow to give any reasonable error margin for the decoder.

author: gf
author_rank: Super Contributor
timestamp: February 15, 2024, 10:25:37 am
content: Quote from: Performa01 on February 15, 2024, 09:21:00 amThe eye diagram is still very nice and has fully open eyes. If MISO/MOSI are sampled at the zero-crossing of the clock, there is still plenty of error margin, although there is a small time offset between the 4 signals. I think the potential problem is rather that the decoder is possibly working directly with the original (asynchronous) 500MSa/s samples. With prior interpolation/upsampling, I think decoding should still work fine. Can the decoder run on an interpolated math trace?

author: Performa01
author_rank: Super Contributor
timestamp: February 15, 2024, 11:59:01 am
content: Quote from: gf on February 15, 2024, 10:25:37 amYes, the eye is wide open, but timing is extremely critical. The slightest phase shift throws off the decoder and during my tests, I could never get it completely stable.I do not know whether the decoders work on the raw sample data, butI guess noton the other hand I do know that there is no reconstruction/interpolation for slower time bases, where the record length approaches or exceeds the screen width. It mightratheralso have to do with the digital 200 MHz bandwidth limiter, that is activated whenever more than two channels are active and helps to suppress aliasing artifacts in the region from 250 to ~290 MHz.Decoders cannot work on anything other than true input channels. Depending on the operation, Math traces might get too slow to act as reliable source for the decoders, and even more importantly they are not suitable as a trigger source. The serial triggers are implemented in hardware and operate on a separate trigger data stream, which is never decimated butalwayseither sin(x)/x reconstructed or linearly interpolated, according to the user settings.The 200 Mbps SPI challengeWhile we cannot decode a SPI data stream in 4-channel mode, it appears to be no problem if we stick to just two channels (I’ve switched to 32 bit words by now):SDS824X_HD_SPI_200Mbps_2ChHere’s the obligate 0 and 1 test:SDS824X_HD_SPI_200Mbps_2Ch_0SDS824X_HD_SPI_200Mbps_2Ch_1… and the eye diagram:SDS824X_HD_SPI_200Mbps_2Ch_EyeThe eye-diagram looks way better now, as the bandwidth is 245 MHz in this configuration and there is no digital filter. The sample rate is twice as high, so your guess is as good as mine as to which of these factors actually makes all the difference.EDIT: my guess now is that it's actually the sample rate.

author: mawyatt
author_rank: Super Contributor
timestamp: February 15, 2024, 06:22:02 pm
content: Quote from: rf-loop on February 15, 2024, 04:56:10 amMy god man, it's just a DSO after allEvidently (we don't have one.....yet!!), a pretty damn good one at thatBest,

author: Performa01
author_rank: Super Contributor
timestamp: February 16, 2024, 09:26:03 pm
content: Mask TestConsistent with the previous SPI speed test, I want to demonstrate the usefulness of the full speed mask test, as it’s a perfect tool for automatic eye diagram monitoring.Let’s get back to the 100 Mbps eye diagram of the previous test and set up a mask for it. For this, there is an integrated mask editor; we cannot just use the automatic mask creation here, because we don’t want to define a particular waveform with certain tolerances, but rather some forbidden area, so that the “eye” stays wide open.SDS824X HD_Mask_EditorI didn’t spend much time creating a perfect mask; this one has just been cobbled together quite quickly. Furthermore, the eye most likely doesn’t need to be that wide open in practical applications, yet this is just for demonstration’s sake.Now we let the mask test run. With the clean signals produced in a near ideal lab environment, we could have run that test for days without any failure, so I’ve added 224 mVrms noise with 500 MHz bandwidth to the data signal, hoping that I’ll get a mask violation eventually:SDS824X HD_Mask_Test_runThe mask test is implemented in hardware, so we are getting a high number of passes within a short time. The screenshot has been taken a few seconds after the test started and up to this point, no mask violation has occurred. Yet it only takes a little while longer and a total of 411262 test runs until the first violation occurs.SDS824X HD_Mask_Test_failAs can be seen, the mask test was set up in a way that it would beep and stop on the first violation. Alternatively, we can also get an automatic screenshot every time the violation occurs.This is another small difference to the SDS2000X HD: there we can also have the option “Failure to History”, which means that all mask violations (and only these) are stored in the history, so we can have the mask test run overnight and then analyze all the mask violations in peace later.The info block in the display tells us that the failure rate in this test scenario was less than 0.001%. Of course, it can be seen quite clearly that this violation wouldn’t have prevented the SPI decoder to deliver correct results. It’s all a matter of setting up the mask appropriately…

author: Performa01
author_rank: Super Contributor
timestamp: February 18, 2024, 11:18:18 am
content: Zoom ExpectationsWhen using a 12-bit DSO, some people tend to get enthusiastic and expect miracles. Maybe we all should come back to earth and ask ourselves what we can realistically expect.There’s the zoom, where the SDS1000X HD has been shown to exhibit some Sinc artefacts at extreme zoom settings. But shouldn’t we first of all get a feeling what a realistic zoom factor is?Consider a signal that has to be viewed at a vertical gain of 1 V/div in order to fit on the screen:SDS824X HD_PR_H50ns_StopNow we want to zoom in, e.g. 5x:SDS824X HD_PR_H50ns_Stop_Zoom5We already see a bit of noise creeping in. Apart from that, we should determine how much zoom is feasible, before we try to zoom in any further:Just like the SDS800X HD, an SDS1000X HD will have 480 LSB (aka codes) per division. Consequently, 20x zoom is about the sensible limit, because then we get 24 LSB per division – and with this, there would still be a chance to see something meaningful. 20x zoom means 1 V / 20 = 50 mV/div:SDS824X HD_PR_H50ns_Stop_Zoom20Now the noise is stronger and it already gets hard to spot any details. Yet we can take it to the extreme and try 100x zoom:SDS824X HD_PR_H50ns_Stop_Zoom100We are now at 4.8 codes per division and what we see is just (mostly granular) noise – all this has nothing to do with the real signal anymore. Most obvious when viewing it in Dots mode.SDS824X HD_PR_H50ns_Stop_Zoom100_DotsWe can take it one step further and zoom in horizontally as well (while still in Vectors mode), so that it becomes less obvious that we’re actually looking at pure noise:SDS824X HD_PR_H2ns_Stop_Zoom100As can be seen, the SDS800X HD doesn’t show any Sinc artifacts, yet the much more important insight should be that it is completely irrelevant what a DSO shows at such extreme zoom levels, where we see nothing but noise anyway.Of course, we could also do it the correct way. Whenever we need to use some extreme zoom, then we also need a means toa) Increase the vertical resolutionb) Reduce the noiseThe tool of choice for repetitive signals is Averaging, because it increases the vertical resolution, suppresses any modulation (hence also noise) and doesn’t affect the bandwidth.Even at the extreme 100x zoom setting we can get the following:SDS824X HD_PR_H50ns_Stop_Zoom100_AVg1024We leave the input channel at its original gain of 1 V/div, but set the final time base while still in Run mode and set up a math trace with averaging, which can be displayed at any vertical scale, i.e. also 10 mV/div for a 100x zoom. When the desired number of averages has been processed, we can stop the acquisition, yet this is not required, as the input channel is left unchanged anyway. In this example it is 1024 averages shown at 10 mV/div, hence a 100x zoom again.Now compare this with the previous screenshots. This one now has much less curves and kinks than even the pointless capture at 2 ns/div before, proving that it’s just nonsense (=noise) what we get at such zoom levels without proper averaging.Of course, 1024 averages are quite a lot. In theory, it would enhance the resolution by 10 bits, making for a total of 22 bits. The current platform doesn’t support sample data and digital signal processing results at a higher resolution than 16 bits, so this is what we get as soon as we use 16x or higher averaging. The ENOB on the other hand benefits a lot more from this, even though it’s limited to 16 bits as well. But it starts at just 8.4 bit according to the data sheet, and 1024x averaging will increase this by 5 bits for a total of ~13.4 bits.

author: ebastler
author_rank: Super Contributor
timestamp: February 18, 2024, 11:34:07 am
content: Quote from: Performa01 on February 18, 2024, 11:18:18 amThank you for following up on the discussion in the SDS1000/3000X HD thread. But I think you missed a key point of that discussion.Even without any zoom (in your first screenshot), the effective vertical resolution of the trace display is cut in half! There are always pairs of identical pixels in the vertical direction, resulting in a trace that is fatter than necessary and has lower resolution -- despite the fact that there must be plenty of vertical resolution to spare in the actual sample data. See the magnified view below.Why does the scope do that? The Math trace in your final screenshot shows proper resolution of individual pixels.

author: Performa01
author_rank: Super Contributor
timestamp: February 18, 2024, 12:22:26 pm
content: Quote from: ebastler on February 18, 2024, 11:34:07 amJust because I didn't address that point yet, it doesn't mean that I "missed the point".Regarding the pixel rendering, I've already looked into this and prepared a posting, until it occured to me that this product is not even released yet and I should rather report any issues, rather than publishing them. Because that's my personal approach for public reviews prior to a product release: I publish the content as I've planned it and minor bugs that I notice along the way will be reported, but not explicitely published. In case of severe bugs that prevent me from doing what I have planned, I would refuse to publish anything at all and just say the product is not yet ready for review.To cut a long story short, the "point that I missed" has long been reported when I posted the "Zoom Expectations" article.Of course the Sinc artifacts in the SDS1000X HD are a bug, and this has been reported quite a while ago (not by me, as I don't have an SDS1000X HD), but there has been Chinese New Year silence in the past two weeks and then again, just like the SDS800X HD, the SDS1000X HD is not even released outside of China yet.

author: ebastler
author_rank: Super Contributor
timestamp: February 18, 2024, 12:33:08 pm
content: Quote from: Performa01 on February 18, 2024, 12:22:26 pmApologies if I caused offense, I did not mean to. It just appeared to me that you had posted this in direct response to the current discussion in the SDS1000/3000X HD thread, and I wanted to point out that the vertical screen resolution issue discussed there is in fact not related to the Zoom function.I think Siglent would be doing themselves a big favor if they can change the trace rendering to make use of the full vertical screen resolution. In the SDS1000/3000X HD thread, this started as a complaint about the "poor screen" used in the Siglents, in comparison with the Rigol DHOs -- but it turns out that the slightly lower physical resolution only plays a very minor role in this.Edit: Thanks for the explanation in the other thread. So this is not going to be improved, due to hardware (FPGA block RAM) constraints in the budget HD scopes. Which is not a big deal for the SDS800X HD with its smaller screen, but a pity for the SDS1000X HD, in my opinion.

author: Performa01
author_rank: Super Contributor
timestamp: February 19, 2024, 04:52:56 pm
content: Serial DecodersThis is just a quick test to demonstrate some serial decoders. For convenience sake (simple connections to the test board without having to bother with probes), I’ve used the digital channels of the SLA1016.The I2C decoder has already been used in the course of the Digital Channels test in Reply #7, so I’ll not show it again here:https://www.eevblog.com/forum/testgear/sds800x-hd-review-demonstration-thread/msg5293762/#msg5293762Here’s some SPI data stream with simple edge trigger on /CS:SDS824X HD_Digital_SPIThis is some UART data stream in 8N1 format with serial UART trigger on the start condition of a byte:SDS824X HD_Digital_UARTFinally, a CAN telegram with serial CAN trigger on the start condition.SDS824X HD_Digital_CAN

author: Performa01
author_rank: Super Contributor
timestamp: February 21, 2024, 09:18:29 am
content: CursorsCursorsNot everyone might be familiar with the various concepts of cursor measurements, so here comes a brief explanation together with some examples.There are three kinds of cursors: Manual, Tracking and Measure.InManualmode, the x and y cursor pairs can be moved freely and used like calipers to measure distances in both axes, even at the same time if so desired.SDS824X HD_Cursors_ManualInTrackmode, the x-cursor pair can be moved freely, whereas the y-cursor pair will always track the selected signal trace. Of course, this makes most kind of cursor measurements much easier and also more precise.SDS824X HD_Cursors_TrackFinally, inMeasuremode the cursors are fully automatic and just visualize the points of the signal trace that are used by a certain automatic measurement. Here are some examples:Rise TimeSDS824X HD_Cursors_Measure_RiseFor the 10-90% rise time measurement, the measure cursors show the corresponding positions for the 10% and 90% threshold on the time axis.Rising Edge OvershootSDS824X HD_Cursors_Measure_ROVFor the rising edge overshoot, the measure cursors show the amplitude difference between top and positive peak.Positive Pulse WidthSDS824X HD_Cursors_Measure_WidthFor the pulse width (according to the thresholds configured in the Measurement Config, default is 50-50%), the measure cursors show the corresponding positions on the time axis.

author: Performa01
author_rank: Super Contributor
timestamp: February 23, 2024, 08:59:01 am
content: System Performance with SP5050A ProbeMany folks worry about the adequacy of the supplied probes.There are few situations where it would be appropriate to use passive 10x high impedance probes at a test node within a circuit carrying >100 MHz signals. With a tip capacitance of 10 pF the impedance at 100 MHz is just 160 ohms and forms a low-pass filter together with all not extremely low source resistances. This might still be okay for low impedance nodes like the outputs of line drivers, but certainly not anywhere else.Apart from the fact, that at higher frequencies alternative probing solutions are required, the previous test of the good old 100 MHz PP510 has shown that they do not limit the system bandwidth, but even extend it to ~274 MHz and the rise time is quite adequate at 2 ns, see section “Probe Bandwidth” in Reply #5:https://www.eevblog.com/forum/testgear/sds800x-hd-review-demonstration-thread/msg5293756/#msg5293756If you wonder what you could gain with a much better (and much more expensive) probe – here’s a test with Siglent’s top model, the 500 MHz SP5050A.Just to give you an idea, I’ve once tested the quite similar SP3050A, which is also rated 500 MHz, as always using the industry standard test with 25 ohm source impedance (2nd screenshot in Reply #90):https://www.eevblog.com/forum/testgear/at-last-siglent_s-sds5054x-touchscreen/msg2165488/#msg2165488On a 1 GHz SDS5104X, the system bandwidth was 1.096 GHz with this “500 MHz” probe. Of course, this is useless in practice as it would only work on a terminated 50 ohm port with the supplied coax-adapter – and in that case we could dispend with the probe and just use a direct coax connection instead.Now here’s the system frequency response with SP5050A up to 500 MHz:SDS824X_HD_Probe_PP5050A_FRIt can be seen, that this 500 MHz probe extends the system bandwidth to ~291 MHz (274 MHz with PP510 and 244 MHz with direct coax connection).Of course, the probe has been properly LF-compensated prior to the measurements:SDS824X_HD_Probe_PP5050A_PR_1kHzThe transition times are now in the 1.7-1.8 ns ballpark, hence very similar to the direct coax connection.The ultimate test for proper HF-compensation is done with a fast (1 ns) risetime 1 MHz square wave.SDS824X_HD_Probe_PP5050A_PR_1MHz_ZoomIt can be seen, that the SP5050A is a pretty good match for this scope because the initial overshoot is about the same level as the top of the pulse.Verdict: yes, the SP5050A outperforms a PP510 in just about every regard. It’s a very nice probe overall and it sure demonstrates the bounds of possibilities with the SDS824X HD. There still isn’t a huge difference after all.

author: Mortymore
author_rank: Frequent Contributor
timestamp: February 24, 2024, 01:04:44 pm
content: Hi!I have a couple of questions that address the probe settings, namely, about "custom" in the "Probe attenuation" setting, and if it's possible to set the probe for current.The datasheet for the SDS800X-HD (pg.10) and for the SDS1000X-HD (pg.9), states for Probe attenuation the options: 1X, 10X, 100X andcustom. The flexibility of this last option is very important to me to set proper values on the oscilloscope, when monitoring IV from an SDL1000. The IV output ranges up to 10v, independently of the voltage or current scale set in the SDL.So, for a current scale of 5A, the scope should be set for an attenuation of 0.5X, that is, when measuring 5A, the SLD is outputting through I.monitor 10V. If one can set a multiplier of 0.5X and Current instead of voltage, the scope will "translate" de correct interpretation of what's being measured.My IDS2000E, can do this partially. I can set the channel to display Amps, instead of Volts, but the probe attenuation is only available in multiple steps of 1X, 2X and 5X.Since the SDL has a scale of 36V;150V, to display the correct voltage the scope would need an attenuation factor of 3.6X;15X, and for Amps 30A;5A a factor of 3X;0.5X. I only have available the latest on my scope.Hope I manage to transmit the idea.I would appreciate if someone could clarify about the options available to the probe settings for the SDS800X-HD/SDS1000X-HD.Sorry if there's a picture were that was already shown, or talked about, that I have missed.I'll take the opportunity to thank Performa01 for is initiative and gigantic work on this thread.Thanks

author: Martin72
author_rank: Super Contributor
timestamp: February 24, 2024, 02:15:14 pm
content: QuoteMe too, and I suggest you move this question to the other, more general SDS800 thread.https://www.eevblog.com/forum/testgear/siglent-sds800x-hd-12-bit-dsos-coming/

author: Mortymore
author_rank: Frequent Contributor
timestamp: February 24, 2024, 02:58:28 pm
content: Quote from: Martin72 on February 24, 2024, 02:15:14 pmThanks for the suggestion but I'd prefer to get the answer here, were the 800-HD functionality is being address, than mix it up with the colour opinions chatIf that's OK for the OP and moderators, naturally.If my questions were answered, it will serve us all I expect. Besides the intention is to know if it will be able to match the Siglent scopes functionality with the Siglent Loads potential.If not, I hope it will be considered by Siglent in the future the ability to set the inputs of the scope as a current probe, and get to show Amps, not only Volts, since I expect the ratio option thing is doable with the existing "custom" option.Regards

author: Martin72
author_rank: Super Contributor
timestamp: February 24, 2024, 03:40:04 pm
content: Hi,Usermanual, chapter 11.2, channel setup...https://www.batronix.com/files/Siglent/Oszilloskope/SDS2000X-HD/Datasheets/SDS2000X_HD_UserManual_EN01A.pdfIt´s from the 2k HD, but should be the same.

author: 2N3055
author_rank: Super Contributor
timestamp: February 24, 2024, 04:15:31 pm
content: Quote from: Mortymore on February 24, 2024, 02:58:28 pmI don't think Siglent even hasanyscope they are making now that does not support choice if channel shows V or A...And then you have custom probe scaling factor, fractional... 2 of them per channel.And not only that, but if you make one channel V and other A and in math multiply them it show in watts..

author: Performa01
author_rank: Super Contributor
timestamp: February 24, 2024, 06:23:58 pm
content: Custom Probe FactorsThis is a demonstration how to use custom probe factors for current measurement.Consider we want to measure current using channel 4 and this should be set up for a rather weird conversion factor of 0.1234567 amperes per volt. First thing to do would be changing the Channel units from Volts to Amperes:SDS824X HD_Ch_Current_1V_ANow we have set channel 4 to measure current at a conversion factor of 1 V/A (one volt per ampere), as it is displayed in the channel tab now. But in our example, we need a different conversion factor. Consequently, we enter the Probe menu:SDS824X HD_Ch_Current_ProbesThere is currently 1.0 V/A selected, and we can also get some more predefined probe factors, but not the one we want to use. Thankfully, there are also two permanent user settings. We can preset them to our most used custom probes and can use them just like the predefined ones from now on. Tapping on the user setting, we get the input keypad for the custom V/A setting:SDS824X HD_Ch_Current_Probe_InputHere we can enter any desired conversion factor from 1 µA/V up to 1 MA/V with at least 6 digits resolution. For example, here is 0.1234567 V/A:SDS824X HD_Ch_Current_Probe_0.1234567Here’s a measurement example: channel 1 is set to 1x voltage probe at 500 mV/div, whereas channel 4 is set to a custom probe at 4.05 A/div.SDS824X HD_Ch_0.1234567_PowerDuring normal use, channel 4 would be set to 500 mV/div with a 1x voltage probe. The custom probe factor of 0.1234567 V/A is equivalent to 8.1000059 A/V. This multiplied by 500 mV/div results in 4.050003 A/div, just as it is displayed in the corresponding channel tabJust for fun, I’ve set up a math operation, simply multiplying the two channels to get the power. Trace F1 shows a scaling of 8.1 W/div and a vertical offset of 0.0 W.The measurements show the standard deviation (=AC-RMS) for channels 1 in volts and for channel 4 in amperes. Formula trace F1 shows the AC-RMS power in watts.

author: Mortymore
author_rank: Frequent Contributor
timestamp: February 24, 2024, 08:08:29 pm
content: Thank you Martin72 and 2N3055 for your replies, and a special appreciation to Performa01 for taking the time to make such a detailed exposition of the probe settings.Best regards

author: Performa01
author_rank: Super Contributor
timestamp: February 26, 2024, 10:08:45 am
content: Dots ModeNot every DSO has it, but Dots display mode is essential whenever the DSO gets near the limits of the sample theorem, hence signal reconstruction – or even acquisition itself – appears flawed.As an example, consider a 12 MHz square wave with quite moderate 3 ns rise time, hence a perfectly adequate signal to a 200 MHz oscilloscope like the SDS824X HD.SDS824X HD_Square_12MHz_3ns_1GSa_VectThe screenshot above shows the standard use case: Auto memory with at least 10 Mpts max. record length, Sin(x)/x reconstruction, Vector display mode, no Color grading, Persistence off.In 2 channel mode, where we get a sample rate of 1 GSa/s without aggressive AA-filter, the waveform looks pretty good. With these settings, it would be pretty hard to provoke major reconstruction errors or even aliasing on a deep memory DSO like the SDS824X HD. Yet there might still be situations where we can’t get a sufficient real time sample rate. To demonstrate this, we can use the Constant Sample Rate setting instead of Auto Memory.As a first step, let’s reduce the sample rate to 250 MSa/s, which many would consider still adequate for a 12 MHz signal:SDS824X HD_Square_12MHz_3ns_250MSa_VectEven though the fundamental frequency of the signal is just 12 MHz and the Nyquist frequency (125 MHz) is more than ten times higher, we still get to see massive reconstruction artefacts and aliasing already. So much for the sometimes mentioned “rule of thumb” which suggests that a bandwidth five times the repetition frequency of a square wave would be adequate…Let’s take this one step further and set the sample rate to 100 MSa/s:SDS824X HD_Square_12MHz_3ns_100MSa_VectWith the previous settings, we still got something remotely similar to a square wave. We go one step further and reduce the sample rate to 50 MSa/s:SDS824X HD_Square_12MHz_3ns_50MSa_VectNow we finally got a pure sine wave with lots of amplitude modulation and jitter – certainly not a very good representation of the original waveform anymore. We still want to take it to the extreme and reduce the sample rate even further to 20 MSa/s, thus violating Nyquist even for the fundamental frequency:SDS824X HD_Square_12MHz_3ns_20MSa_VectThis last screenshot needs not be commented, as it speaks for itself – except for the fact, that the SDS824X HD won’t let us use the original time base of 20 ns/div with such a low sample rate anymore. As a consequence, the DSO has automatically switched to 50 ns/div.Anyway, this is not the end – after all we’ve got the Dots display mode up our sleeves:SDS824X HD_Square_12MHz_3ns_20MSa_DotsYes, with only 1 point per division (10 points for the whole record!), there is no contiguous trace and the rendering is a bit dim. Yet nothing that could not be improved by a little Persistence time:SDS824X HD_Square_12MHz_3ns_20MSa_Dots_P1What we get now is a perfect visual representation of the original signal – within the bounds of the 244 MHz bandwidth, that is – despite the effective sample rate of only 20 MSa/s.

author: ebastler
author_rank: Super Contributor
timestamp: February 26, 2024, 10:16:53 am
content: Thank you, Performa01 -- that was an impressive demonstration case for dot mode!But I am intrigued: How can triggering work so well in the under-sampled acquisition modes, to allow the scope to precisely overlay the multiple captures?

author: gf
author_rank: Super Contributor
timestamp: February 26, 2024, 10:34:06 am
content: Quote from: ebastler on February 26, 2024, 10:16:53 amThe ADC and the trigger engine still run at the full sample rate. The down-sampling to the acquisition sample rate happens thereafter.

author: ebastler
author_rank: Super Contributor
timestamp: February 26, 2024, 10:38:06 am
content: Ah, ok -- so dot mode can't work any magic if one really pushes the scope to the limits of its sampling rate. That makes sense, thank you!

author: gf
author_rank: Super Contributor
timestamp: February 26, 2024, 10:46:15 am
content: Quote from: ebastler on February 26, 2024, 10:38:06 amThe trigger engine also interpolates, i.e. it can determine the trigger point with sub-nanosecond resolution @1Gsa/s ADC sample rate.

author: ebastler
author_rank: Super Contributor
timestamp: February 26, 2024, 12:17:50 pm
content: Quote from: gf on February 26, 2024, 10:46:15 amBut that would be the same interpolation algorithm which is used for sin(x)/x interpolation of the traces in line mode, right? Hence would suffer from the same aliasing problems if the scope is pushed beyond its sampling rate limits?

author: gf
author_rank: Super Contributor
timestamp: February 26, 2024, 01:24:28 pm
content: Quote from: ebastler on February 26, 2024, 12:17:50 pmGood question what kind of interpolation it uses.Sure, as long as the front-end provides sufficient alias rejection for the ADC sample rate (i.e. for frequencies >= fs/2), it is not surprising that a sinc trigger interpolation works well.Some time ago I was indeed curios what happens if this is not granted, and did a simulation. For the attached plots I'm assuming a "maximally flat" 4th order Butterworth frequency response with -3dB cut-off at 250MHz. This gives sufficient alias rejection for 1Gsa/s, but clearly not for 500MSa/s. As expected, with sinc interpolation, the 1GSa/s traces line up cleanly in figure1, but the sinc-interpolated 500MSa/s traces in figure2 suffer from aliasing and and don't line up. The simulated dots plot with trigger interpolation in figure 3 is still nice at 500MSa/s,despite violation of the sampling theorem, but the shape is no longer perfectly correct. All three plots use sinc interpolation for the simulated trigger (i.e. for the horizontal alignment of the overlaid traces or dots). The trigger level is 0.9, trailing edge.So interestingly, trigger interpolation + dots mode still seems works to some extent (not in general, of course) if the sampling theorem is violated.[ Btw, ignore the horizontal line at y=0 in figure3. ]

author: Performa01
author_rank: Super Contributor
timestamp: February 26, 2024, 04:00:08 pm
content: Quote from: gf on February 26, 2024, 01:24:28 pmA while ago, Siglent have changed that strategy and the trigger interpolation seems now to be the same as for the waveform display/processing.I other words, even in Dots display mode where there should be no difference for the display waveform, the choice of linear (x) interpolation vs. Sin(x)/x reconstruction still matters for the trigger. Yet I don't think this will make a huge difference as soon as Nyquist is violated in the trigger path.

author: Performa01
author_rank: Super Contributor
timestamp: February 28, 2024, 08:22:14 am
content: X-YAs usual, X-Y mode is hardware accelerated with high waveform update rates and intensity or color grading.An important property is the waveform update rate in X-Y acquisition mode and it shows that at faster time bases (≤2 µs/div) the trigger rate is even higher in X-Y mode than the corresponding 2-channel Y-t mode. The table below shows the trigger rates for various time base settings from 100 ns/div up to 1 ms/div and compares the trigger rates in regular dual channel Y-t mode to the X-Y mode:SDS824X HD_XY_UpdateRateThe maximum speed at 100 ns/div was more than 63000 updates per second and X-Y mode limits the time base so that it cannot get any faster than that. Up to 1 µs/div, the update speed is always greater than 10000 per second and from there it scales as expected, i.e. the trigger speed is proportional to the record length.The figures stated above are valid for the full sample rate of 1 GSa/s, which also means record lengths of e.g. 10 Mpts at 1 ms/div. In other words, these numbers represent the worst case and X-Y operation could be accelerated by limiting the record length (thus also reducing the sample rate).I want to show some examples, which also demonstrate the intensity and color grading. First a familiar Lissajous figure, and then some I/Q waveform patterns at 1 Mbps, which can serve as a speed demonstration because of their complexity.SDS824X HD_Sine_1MHz_5MHz_45deg_IGSDS824X HD_QPSK_1Mbps_CGSDS824X HD_8PSK_1MbpsSDS824X HD_D8PSK_1Mbps_CGSDS824X HD_16QAM_1Mbps_CG

author: ebastler
author_rank: Super Contributor
timestamp: February 28, 2024, 08:29:53 am
content: Thank you for demonstrating XY mode. The waveform update rates are quite impressive for this scope class, and the color grading is a nice touch!I guess it was to be expected that the limited trace resolution (grouping 2 pixels together) now applies to the X axis as well, due to the limitations of the block RAM capacity in the FPGA.But why did Siglent choose to render this differently in the X direction? On the Y axis, pairs of pixels showing the same brightness are displayed. On the X axis, every other line is simply left black, resulting in rather pronounced scan lines and a dim display overall. Are there technical reasons for this, or was it a UI design choice? Or is it a user-changeable setting maybe?

author: Anthocyanina
author_rank: Frequent Contributor
timestamp: February 28, 2024, 08:57:45 am
content: do these scopes have fine timebase adjustment? i've been wondering about this feature in modern scopes for a while. so far the only one i know for sure has this is the keysight 1000 series.Thank you!

author: mwb1100
author_rank: Frequent Contributor
timestamp: February 28, 2024, 09:48:52 am
content: Quote from: Anthocyanina on February 28, 2024, 08:57:45 amThe SDS800X-HD manual doesn't mention it (it does for the vertical adjustment), so it looks like not. As far as other modern scopes that have it, the Rigol MSO5000 does.

author: ebastler
author_rank: Super Contributor
timestamp: February 28, 2024, 09:59:07 am
content: Quote from: mwb1100 on February 28, 2024, 09:48:52 amRigol's DHO series supports it too. Although a bit inconvenient on the small DHO800/900, since they have a single shared button for Zoom or Vernier; the user needs to configure what it does and can reach the other function only via touch menus. The larger DHO1000/4000 have two separate buttons.

author: Performa01
author_rank: Super Contributor
timestamp: February 28, 2024, 10:49:14 am
content: Quote from: ebastler on February 28, 2024, 08:29:53 amI don’t know – in any case there are no user settings about this. Quite honestly, for me this is pure cosmetics, hence clearly one of the less important things. All the more so as the X-Y mode is rarely used nowadays. Eventually I might inquire about any possible improvements.A high-resolution scope is not meant for inspecting traces with a magnifier glass, but getting suitable data for vertical zoom and precise measurements.Quote from: Anthocyanina on February 28, 2024, 08:57:45 amNo. What would be the use case for this?All contemporary Siglent DSOs have huge secondary buffers for measurements and math, and support gated measurements with separate gating cursors.

author: ebastler
author_rank: Super Contributor
timestamp: February 28, 2024, 11:06:35 am
content: Quote from: Performa01 on February 28, 2024, 10:49:14 amI certainly agree that X-Y mode is a somewhat exotic use case, and not a forte of any digital scope. I'm keeping a CRT scope around for those rare occasions anyway... So certainly not a critical limitation.I don't really agree on the "it's not meant for looking at traces" argument. It's anoscilloscope, after all. If the user were not meant to look at the trace in detail, why bother with intensity or color grading?Maybe Siglent can improve the visual quality of the display with limited effort -- actually not only in X-Y mode, but also for the Y dimension in regular Y-T mode. If the doubled-up pixels were not simply rendered black or at the same intensity as the respective "real" pixel from block RAM, but could be shown as anintensity average of the two neighboring "real" pixels, that should produce much smoother traces.

author: 2N3055
author_rank: Super Contributor
timestamp: February 28, 2024, 11:38:51 am
content: SDS800xHD and vertical pixels......Can those claiming this scope always renders waveform with double vertical pixels please explain attached images:On this capture it is clearly visible that portions of the waveform are rendered with exactly ONE vertical pixels....Download images to your PC and zoom in....

author: ebastler
author_rank: Super Contributor
timestamp: February 28, 2024, 11:57:26 am
content: Quote from: 2N3055 on February 28, 2024, 11:38:51 amThat would be great news! This might convince me to get an SDS1000X HD with the larger screen after all.What exact scope type did you use, and what did you do differently? I have zoomed into many of Performa01's screenshots in this thread, and they all show the doubled-up pixels. And Performa01 has also explained why this limitation exists (see below). So what is different now?Quote from: Performa01 on February 18, 2024, 12:45:07 pm

author: baldurn
author_rank: Regular Contributor
timestamp: February 28, 2024, 11:57:52 am
content: Quote from: 2N3055 on February 28, 2024, 11:38:51 amLooks to me like there are certain lines that are 1 pixel and the rest are two? Like it is reducing from a resolution that is not a whole fraction of the screen resolution.

author: Performa01
author_rank: Super Contributor
timestamp: February 28, 2024, 11:58:21 am
content: Quote from: ebastler on February 28, 2024, 11:06:35 amDid you leave out the bold part of my message on purpose?We do not need to look at traces at a pixel level, just to take advantage on intensity or color grading.If ~0.5% resolution is not enough to inspect some tiny (and usually insignificant) signal details, then vertical zoom is the right tool for it.

author: ebastler
author_rank: Super Contributor
timestamp: February 28, 2024, 12:00:49 pm
content: Sorry, I did not mean to mis-quote you. But I find that the slightly jagged traces in Y-T mode are quite visible on a 10" screen without magnification, and even more so the black "scan lines" in X-Y mode.

author: DaneLaw
author_rank: Frequent Contributor
timestamp: February 28, 2024, 12:14:20 pm
content: Quote from: ebastler on February 28, 2024, 12:00:49 pmWas unsure what you meant, but I reckon it's this stepping in the vertical axis. (pic from #90 zoomed on two graticules)

author: ebastler
author_rank: Super Contributor
timestamp: February 28, 2024, 12:18:39 pm
content: Quote from: DaneLaw on February 28, 2024, 12:14:20 pmYes, it's alway double-pixels at the same intensity in the vertical direction, both in X-Y and Y-T mode. (Unless under some conditions, as shown by 2N3055 -- hope he can shed some more light onto that.) And in X-Y mode, the fact that every other column remains black.

author: 2N3055
author_rank: Super Contributor
timestamp: February 28, 2024, 12:22:20 pm
content: Quote from: baldurn on February 28, 2024, 11:57:52 amThat is direct dump of screen from a scope with Web control.1024x600 pixel for pixel.

author: baldurn
author_rank: Regular Contributor
timestamp: February 28, 2024, 12:47:01 pm
content: Quote from: 2N3055 on February 28, 2024, 12:22:20 pmYes what I am saying is that appears like it is upscaling from a lower resolution in a primitive way. Say the original data is 200 pixels and the screen is 300 pixels. You could do that by mapping even source pixels to two screen pixels and odd source pixels to just one screen pixel. That way 2 pixels becomes 3 on the screen. Looks to me something like that is going on. You have some horizontal lines one pixel and other horizontal lines are two pixels.

author: 2N3055
author_rank: Super Contributor
timestamp: February 28, 2024, 01:55:40 pm
content: Quote from: baldurn on February 28, 2024, 12:47:01 pmYou mean inside the scope?Why would they do that?You do realize that problem with the scope is that they have TOO MANY data points/values to map to one pixel.Vertical res of ADC is 4000 points.Even worse, internal representation is 16 bit, so 65536 vertical values.So unless you have that much EXACTLY on the screen, you have to map..How do you plot it when you have 600 vertical pixels?You need to map 6.6 data values vertically to one pixel for one ADC data point.And cca 109 from internal 16 bit value.And then you have fact that one pixel horizontally must map hundreds of thousand of data points to one pixel.When your buffer has 10 Mpts and screen is 1024 pixels wide, that is 10000 sample points to single pixel, horizontally. And they will all have different values...How do you map that to screen?You create data cloud.As I said, those "double" pixels are simply accurate representation of in-between values. It is nor pixel above nor pixel below, but somewhere in the middle or both...I you were to upsample by pixel doubling (or tripling) , you would never have any combination of pixels different form integer multiplier of upsampling: for x2 it would be always 2, 4 ,6 8.. or for 3x 3, 6, 9 ...You couldn't have 1, 2 and 3 at the same time on the screen. Ever.

author: baldurn
author_rank: Regular Contributor
timestamp: February 28, 2024, 02:07:19 pm
content: Quote from: 2N3055 on February 28, 2024, 01:55:40 pmThis is just speculation, but it appears they downsample the 12 bit raw data to 8 bits before processing it in the UI chain. It would halve the amount of data they need to work assuming the CPU would otherwise have to work with 12 bit stored in a 16 bit data structure. Then the final step to display the data is to upscale from 256 values to maybe 400 lines on the screen.We may find the reason if we compare the SDS2000X HD. Does it have a slower CPU or maybe the memory bandwidth is worse? So they had to do something to make the UI quicker on the cheaper platform.

author: ebastler
author_rank: Super Contributor
timestamp: February 28, 2024, 02:08:15 pm
content: Quote from: 2N3055 on February 28, 2024, 01:55:40 pmI am still puzzled by your screenshots. I have scrutinized quite a few other screenshots published here, copying them to a bitmap editor and zooming in. I always strictly saw doubled pixels in the Y dimension. It's even more striking in Performa01's recent X-Y screenshots, with the alternating black columns along the X dimension.And Performa01's explanation made sense to me: When there is limited fast memory to create the "digital phosphor" overlay of traces in the FPGA, lumping two screen pixels together seems like a technically efficient way of getting by.Hence I am wondering what you did differently. Is it maybe that a single capture gets rendered differently -- plotted directly from the full-resolution data buffer? Did you capture these traces in the screenshot in Single mode; or did you stop the acquisition and then shifted the displayed time window so the screen got redrawn from the buffer?(Edit: Typos)

author: 2N3055
author_rank: Super Contributor
timestamp: February 28, 2024, 02:16:00 pm
content: Quote from: ebastler on February 28, 2024, 02:08:15 pmRead my post above.You all ignore that if you have 10000 horizontal data point to squeeze into one pixel, there are hard decisions to be made...I made a capture with 1000 data points. So data is not crowded horizontally.

author: ebastler
author_rank: Super Contributor
timestamp: February 28, 2024, 02:24:03 pm
content: Quote from: 2N3055 on February 28, 2024, 02:16:00 pmI don't see how "horizontal crowding" explains the strict double-pixel patterns seen in all those other screenshots. There should be some single pixels, and many double-pixels which are vertically shifted vs. the others by 1 pixel.I still like my hypothesis about the screen being redrawn from the full-resolution data buffer under certain cirumstances, resulting in a full-resolution display. (While it is always half-resolution when drawn from the "digital phosphor" buffer in the FPGA.) Could you comment on the questions I asked? Thanks!Quote from: ebastler on February 28, 2024, 02:08:15 pm

author: 2N3055
author_rank: Super Contributor
timestamp: February 28, 2024, 02:35:31 pm
content: Quote from: ebastler on February 28, 2024, 02:24:03 pmNo, sorry.I cannot comment to all wild speculations here. I have no internal knowledge of exact algorithm used, and if I had, nobody in their right mind would tell me something like that without signing NDA, in which case I would not be able to share it....I'm afraid that all that like to speculate here will have to be happy with that status quo.What I can, and am saying is how I think it could have been done.All I know that Occams razor is king, and it is probably simply done in simplest way it could be, for reasons of speed and resource size.....

author: ebastler
author_rank: Super Contributor
timestamp: February 28, 2024, 02:47:26 pm
content: Quote from: 2N3055 on February 28, 2024, 02:35:31 pmI am baffled. Why don't you want to answer two simple questions on how you acquired those two screenshots?Look -- I am not criticizing either you or Siglent with these questions. I just want to understand what's going on, out of technical curiosity. It's my favorite type of puzzle, where you have to deduce the internal mechanism based on observations of the external behaviour.I have tried to explain why I don't think your assumption (horizontal crowding) explains the observed pattern. I have proposed another assumption, and those two data points on how you acquired the screenshots would help to support or falsify that. Please indulge me and tell me how you acquired them.

author: 2N3055
author_rank: Super Contributor
timestamp: February 28, 2024, 03:03:50 pm
content: Quote from: ebastler on February 28, 2024, 02:47:26 pmWhat do you mean how I acquired them? What do you mean I don't want to answer?They are acquired with a scope. By using settings in plain view on the screen (which is one of great things on this scopes, it is all there on the scope screen).They are directly from the scope by using screenshot button in Web view.It is as plain as it can be...What are you implying? Some tricks or manipulations on my side? Are you questioning my integrity?As I said, there is not only horizontal crowding (nice term for this by the way) but also vertical. If you use 2 pixels and pixel brightness you can achieve more visual states that single pixels. Think of it as using dithering instead of AA...Combine all of that and you get this...In the end, apart from intellectual curiosity it does not matter.It works quite well the way it is.

author: baldurn
author_rank: Regular Contributor
timestamp: February 28, 2024, 03:13:18 pm
content: I have marked some lines in this cutout of a screen shot:The numbers corresponds to the "y" line number. The line y=2 is a single line and no other lines are partial into the screen line occupied by y=2. In my opinion this fact rules out the theory that we are seeing 4096 values (12 bit) being mapped to approximately 400 screen lines. In that case it is very unlikely that we will see this set of steps where no value gets partially mapped to the line with y=2. We should see some double pixels a half step up from y=1 and we should see some double pixels a half step down from y=3. But we are not seeing that.My theory is that we are seeing 8 bit data (256 values) mapped to 400 screen lines. Some of the values do indeed end up being in between and are rendered as two pixels. A few values do end up being close to exact and are rendered as one pixel.I know this is supposed to be a 12 bit scope and we want to see 12 bit data. But I think we are seeing evidence that the 12 bits are downsampled to 8 bit before being processed by the UI. They can still use the full 12 bits raw data in other contexts. I assume the FPGA is working with 12 bit data but the CPU might be working with 8 bit to speed things up.

author: Veteran68
author_rank: Frequent Contributor
timestamp: February 28, 2024, 03:15:29 pm
content: Quote from: 2N3055 on February 28, 2024, 01:55:40 pmI think (hope?) everyone here understands that with any scope you're going to have more data than pixels. Nobody argues that point. What does matter to those of us who care more than others about the visualization, is how that mapping is done. Saying "it does not matter" is simply dismissive of those to whom it DOES matter.It shouldn't be necessary to point out that the criticisms/disappointments with Siglent here compared to Rigol's approach with the DHO line is the physical resolution of the display. Rigol supports MORE data at 1280x800 than the more limited 1024x600 resolution in the Siglent scope. You have 67% more pixels on the screen to work with. That's not a trivial difference. While I'd say the 1024x600 resolution is more tolerable, if not ideal, in the smaller 800 series, with the 1000 series and their 10.1" screens it's more of an egregious design decision. That's a very limited resolution which just makes display quality noticeably worse, especially on the bigger screen which just magnifies scaling artifacts.I get that some people care more about the data than the visualization of it, but to ebastler's earlier points, at the end of the day an oscilloscope is all about displaying a waveform. Expecting it to be displayed as cleanly and accurately as possible is not a baseless "nitpick," it's a legitimate concern. Especially given the relatively low cost of a higher resolution LCD panel (or else Rigol wouldn't have done it at their lower pricepoint). While it may not sway everyone away from the other clear benefits of the Siglent design, dismissing these concerns out of hand is not productive to the discussion either. Those of us on the fence due to the downgrade in visual quality want to be convinced of the reasons to buy something that -- in this specific technical case -- is inferior to what we have. So please, indulge our concerns and help us understand what Siglent was thinking, and what might be done to improve things that we may not be aware of.I really want another Siglent scope as I prefer the brand, but I'm not yet to the point of giving up my DHO for one, even if it is inferior in other ways.

author: ebastler
author_rank: Super Contributor
timestamp: February 28, 2024, 03:19:40 pm
content: Quote from: 2N3055 on February 28, 2024, 03:03:50 pmNo second thoughts, and no cause to get defensive -- just the two questions mentioned earlier. Please take them at face value.As I tried to explain before, it would make sense to me that the scope can draw traces on the screen at full resolution (only) if it gets the data to be plotted directly from the 12-bit capture buffer, under the circumstances described in my questions. So I would like to understand whether that is the reason for the different appearance of your screenshots vs. others I have seen.I can obviously try this myself once I have an SDS HD scope. But the thing is that my decision whether to get an 800 or 1000 series scope will depend on what I can expect to see on the screen. So I would much prefer to understand this upfront, rather than create extra hassle for myself and Batronix by buying one model, then potentially having to exchange it.I don't think the answer to those questions can be gleaned from the screenshots themselves. And unless I overlooked something, I don't think you have answered them yet. Pretty please?Quote from: ebastler on February 28, 2024, 02:08:15 pm

author: 2N3055
author_rank: Super Contributor
timestamp: February 28, 2024, 03:31:25 pm
content: Quote from: Veteran68 on February 28, 2024, 03:15:29 pmI'm not being dismissive of anybody. If such a detail is important to you that is your prerogative.You do realize that in image Baldurn is showing up here pixels are being artificially magnified almost 10 times from their physical size on the screen?That nobody even noticed that and did even understand what are they talking about until they started (they, few people that complained about it) showing these highly magnified images?In real life I literally had to pick up a magnifying glass to be able to see it.This is how big deal it is in real life.If you object to it on principle, that is fine with me.I don't deny effect is there.I simply state it is pretty much invisible for all practical purposes.You alone decide what are your priorities.Take care.

author: KungFuJosh
author_rank: Super Contributor
timestamp: February 28, 2024, 03:35:06 pm
content: Here's an idea. Grab a CSV file from the scope and plot it out in Excel and see how it looks.

author: 2N3055
author_rank: Super Contributor
timestamp: February 28, 2024, 03:52:43 pm
content: Quote from: ebastler on February 28, 2024, 03:19:40 pmI'm not being defensive but wanted a clarification. We are both conversing in what is, to us, a second language. Better verify than presume...All I did was start the scope, attached 1MHz squarewave into it, chose that timebase at random and you see results.Plain as that.I tried in both Stopped and Single. Made no difference.I do not know why their images are different. Maybe they (them) cherry picked images to illustrate point they wanted to prove?Or maybe simply, as I did, chose some random settings that resulted in those images. I don't know what they did.You will have to ask them. I didn't answer that question , because it is not addressed to me.I told you what I did, which is all I can answer. Sorry.I'm not disputing their images.I simply wanted to investigate statement that kept being repeated that 1000xHD draws 2 vertical pixels ALWAYS, and that 800xHD will probably too.Well, now we know 800xHD for sure does not draw 2 vertical pixels ALWAYS.That is all.That is my data point. I leave further speculations about rendering implementations to others.I personally didn't notice it until this discussion broke out. I had to use loupe to actually see it. That is how "big" problem this is in real life (pun intended).I find implementation fine in normal work and will prefer not to waste more time on it.There are many more interesting things (for me..) on the scope to investigate.You guys have fun with this, if you like.Best,

author: ebastler
author_rank: Super Contributor
timestamp: February 28, 2024, 04:51:47 pm
content: Quote from: 2N3055 on February 28, 2024, 03:52:43 pmYou can look at any of Performa01's screenshots in this thread, typically captured in "Run" mode. I don't think he hand-picked them to make the scope look bad.It's all consistent with the assumption that traces rendered from the FPGA "digital phosphor" buffer show the coarser pixilation, due to size constraints of that buffer.QuoteI agree that it is not obvious at all on the smaller SDS800X HD screen, which is why I am leaning towards an 824. I have said several times, in this and other threads, that I find it a disappointing design choice in the SDS1000X HD in particular, given its larger screen and the markup you pay for that.As stated and shown in theother thread, I do find that traces look noticeably more jagged on the SDS1000X HD than on the DHO1000; no magnifying glass required. But -- as witnessed by the fact that I have returned my DHO1074 -- I fully agree that there are more important aspects to a DSO.

author: Anthocyanina
author_rank: Frequent Contributor
timestamp: February 29, 2024, 01:52:42 am
content: Quote from: Performa01 on February 28, 2024, 10:49:14 amI find this feature to be useful all the time. Sometimes a waveform of interest won't fit nicely on the screen with the 1-2-5 steps, it either fits more than one period, or less, or the portion of interest either is too visually narrow on the horizontal axis, or goes beyond the screen at the next step.For example, look at these waveforms of the switching node of a flyback converter:using a timebase between 200 and 500ns/ let me fill more of the screen with the relevant portion of the waveform. using 500ns/ would have scrunched the high frequency ringing enough that you wouldn't distinguish it well enough, and using 200ns/ would have cut out the moment when the MOSFET turns on again.

author: KungFuJosh
author_rank: Super Contributor
timestamp: February 29, 2024, 02:21:08 am
content: It's a little weird that we can't do it since there's the manual entry option. It automatically rounds to either 200 or 500 in that space. I would think this feature could be implemented at any point if enough people want it.

author: ebastler
author_rank: Super Contributor
timestamp: February 29, 2024, 10:32:21 am
content: Quote from: KungFuJosh on February 29, 2024, 02:21:08 amHow does the scope handle "pinch and zoom" gestures on the touch screen? Does the horizontal scale also snap to the 10-20-50 grid, or is a continouos vernier control available in that way?

author: ebastler
author_rank: Super Contributor
timestamp: February 29, 2024, 10:50:56 am
content: Oh, one more question: Has anyone explored the maximum waveform update rates, for the 824 and/or its smaller siblings? There are some data in the recent post on X-Y mode; but I think Performa01 did not aim to hit the maximum rates there, but rather looked for a good balance of speed and data points per frame.The datasheet specifies a higher update rate in normal mode for the 824. So this would also be a good check to see whether an "upgraded" 804 or 814 performs at the full 824 spec, or whether there is different hardware in the 824 which enables the higher waveform rate. I'm asking for a friend...

author: rf-loop
author_rank: Super Contributor
timestamp: February 29, 2024, 12:26:18 pm
content: Quote from: ebastler on February 29, 2024, 10:32:21 amHorizontal scale "pinch and zoom" 1-2-5 steps. No vernier.

author: rf-loop
author_rank: Super Contributor
timestamp: February 29, 2024, 12:35:55 pm
content: Quote from: ebastler on February 29, 2024, 10:50:56 amDue to very busy times I have not made yet detailed speed tables with different settings etc.But naturally I have inspected that said value in data sheet is true. SDS824X HD, measured ETA:tiny bit over 120kwfm/s.average around 118.5kwfm/s and peak around 127kwfm/s. (FW 1.1.3.2: 1Ch on, display Dots, 50ns/div, input 10MHz)

author: ebastler
author_rank: Super Contributor
timestamp: February 29, 2024, 12:42:18 pm
content: Quote from: rf-loop on February 29, 2024, 12:35:55 pmThanks! If you still have it in your notes, could you indicate the settings where the maximum rate is achieved? (Time base, memory points, presumably dot mode?) Then others could easily compare with the 804/814 in off-the-shelf and "upgraded" condition.

author: Performa01
author_rank: Super Contributor
timestamp: February 29, 2024, 02:18:54 pm
content: Quote from: ebastler on February 29, 2024, 12:42:18 pmWe are right there in the review thread, aren't we?Why not look up the regular content? The table in the third picture of the linked posting shows everything relevant. I did not optimize the input signal for best performance though, hence I could only attest 118690 waveforms per second in dots display mode at 50 ns/div.https://www.eevblog.com/forum/testgear/sds800x-hd-review-demonstration-thread/msg5293747/#msg5293747There is even a table of contents in the opening posting, so it all can be found quite easily.

author: ebastler
author_rank: Super Contributor
timestamp: February 29, 2024, 03:37:10 pm
content: Quote from: Performa01 on February 29, 2024, 02:18:54 pmPerfect information (what else?), thank you!I thought I had seen these data in the thread, then could not find them, and concluded that I must have mixed things up with your work on some earlier scope. In my defense, I did check the table of contents carefully before posting the question -- but it lists the relevant post as "History & Sequence Mode, Counting Pulses, Trigger Jitter", which did not click.

author: capslock
author_rank: Contributor
timestamp: March 04, 2024, 11:02:30 am
content: For the Bode plot, which function generator did you use and did you need special software modules for it?The 800x series seems to be compatible with the SAG1021I, which ist just a glorified USB dongle for € 139 + tax. The much more expensive scopes need a costly software(In addition the function generator software option (SDS1000X-E-FG) or (SDS-5000X-AWG) or (SDS6000Pro-FG) is required.) So do we need this with the SDS800X, too?

author: 2N3055
author_rank: Super Contributor
timestamp: March 04, 2024, 11:35:11 am
content: Quote from: capslock on March 04, 2024, 11:02:30 amYou can use any of Siglent AWGs, including SAG1021I you mentioned. For bode plot there is no need for any special license. Just AWG.But if you want to use AWG as AWG then you need AWG license. But for Bode plot no. Just AWG hardware.

author: capslock
author_rank: Contributor
timestamp: March 04, 2024, 12:26:24 pm
content: Thanks. I found the software option for the 800 series, it's another 95 € + tax.Sounds like the SDG810 for € 169 is a better deal then, since it is standalone and includes the AWG functionally. Any downsides, i.e. is there a need to control the AWG functionally from the scope or can the scope even talk to the SDG?Or for that matter, do I need a Siglent function generator at all to do Bode plots, i.e. could I set my Owon generator to do a sweep and let the Siglent trigger on the start of the sweep?Bonus question: is there any good reason to by a 4-channel scope when all I do is analog (including Class D) audio? So far, I have never felt the need for more than two channels.

author: 2N3055
author_rank: Super Contributor
timestamp: March 04, 2024, 12:30:48 pm
content: Quote from: capslock on March 04, 2024, 12:26:24 pm4 channels is something you have to decide. I would not buy 2ch anymore. It is something you find ways to use when you have it. For instance, you can do Bode with 3 channels and one reference.Usage? A 3 way xover that you can plot at the same time. You can make plot with overlapping all 3 bands...If you have only 2 ch, you will have to do it 3 times, and merge data manually.I personally like external AWG better because you can operate it independent to the scope. No need to do it from the scope.You cannot use external AWG that way. It has to be controlled by scope, step by step... I know there was an effort to make piece of software that would act as a gateway to other AWGs. I don't know how far that went and what is supported...

author: capslock
author_rank: Contributor
timestamp: March 04, 2024, 12:34:31 pm
content: Thanks. So the SDG810 is controlled by the scope and can do all the things the SAG + software does at a lower price?

author: 2N3055
author_rank: Super Contributor
timestamp: March 04, 2024, 12:42:02 pm
content: Quote from: capslock on March 04, 2024, 12:34:31 pmHeeeh, kinda mixed bag.SDS810 will have lower max frequency. Signal quality will be mostly the same. AWG core is the same basically.It will have modulation.Honestly, SDS810 is older generation.My recomendation is to get SDG1032x if you can afford it..It is new generation, very good signal quality, especially pulse and squarewave and it is 2 independent channels.

author: capslock
author_rank: Contributor
timestamp: March 04, 2024, 12:48:18 pm
content: Thanks. First of all: in order to do Bode plots, I need SAG or any of the SDG, i.e. the scope will talk to the external device?Secondly, what do you mean by modulation? That the older SDG is spec'ed only at 10 MHz bandwidth (which I suspect is the highes frequency it can output, not the analog bandwith)?

author: 2N3055
author_rank: Super Contributor
timestamp: March 04, 2024, 01:10:28 pm
content: Quote from: capslock on March 04, 2024, 12:48:18 pmYou really need to download datasheets for SAG1021I, SDG810 and SD1032x and set the side by side..SAG is simplest in capabilites, 1ch, but goes to 25MHzSDG810 is also 1 channel, only up to 10MHz sine but more functions: modulation etc.SDG1032X is new generation, 2 independent channels, up to 30MHz (60 actually for platform), and very good pulse capability.

author: capslock
author_rank: Contributor
timestamp: March 04, 2024, 01:22:54 pm
content: Yes, thank, I understand the differences. I am just not sure I need better signal quality that I cannot use without using 50 Ohms T-pieces on the inputs.Sorry for asking again: the SDS will talk to any of the SAG, SDG, SD to generate a Bode plot?

author: 2N3055
author_rank: Super Contributor
timestamp: March 04, 2024, 01:24:39 pm
content: Quote from: capslock on March 04, 2024, 01:22:54 pmYes. I thought I was clear. Sorry.

author: KungFuJosh
author_rank: Super Contributor
timestamp: March 04, 2024, 01:33:18 pm
content: That depends on how you want to communicate. The newer AWGs with an X at the end generally have ethernet ports. The SDG810 does not have an ethernet port, so if it does work with BODE plots, you're limited on how you can set it up.

author: capslock
author_rank: Contributor
timestamp: March 04, 2024, 03:33:45 pm
content: Yet the SAG also only has a USB port and this is how the SDS800x talks to it.

author: adam4521
author_rank: Regular Contributor
timestamp: March 04, 2024, 05:00:59 pm
content: The difference in price between a SAG1021I with signal generator license and SDG1032X in the uk is just £21+VAT. With the latter you get 2 channels that can work separately or synchronised, modulation, more amplitude range, plus the convenience and flexibility of a dedicated instrument with its own screen. I get that the ‘I’ means that the signal output is isolated, but overall the SAG1021I feels poor value compared to the rest of the offer within the brand.

author: KungFuJosh
author_rank: Super Contributor
timestamp: March 04, 2024, 05:02:40 pm
content: Quote from: capslock on March 04, 2024, 03:33:45 pmSure, but that's not a standalone unit. I use ethernet for communication between my Siglent devices. The point is to be aware of what the options and limitations are.

author: orzel
author_rank: Regular Contributor
timestamp: March 04, 2024, 05:04:14 pm
content: Quote from: capslock on March 04, 2024, 12:48:18 pmYes, the scope will drive the SDG. It's very simple: connect them using usb (typically), or ethernet (if available on both), then a simple setting on the scope establishes the communication and confirms it's ok. Then you can do bode plot. It only works with signal generator and scope of the same brand, there doesn't seem to be any established standard on how to do that.

author: capslock
author_rank: Contributor
timestamp: March 04, 2024, 07:05:16 pm
content: Quote from: adam4521 on March 04, 2024, 05:00:59 pmHere it is € 67 including tax. The software is € 113 (with tax), i.e. about as much as my standalone Owon was. I am still toying with the idea of buying the SAG without the software if that is all that is needed for Bode plots.How useful is this feature anyway for testing discrete audio amps? I'd have to run them open loop and feed them a much attenuated signal from the generator. Wonder if this means noise or phase issues?

author: 2N3055
author_rank: Super Contributor
timestamp: March 04, 2024, 07:57:55 pm
content: Quote from: adam4521 on March 04, 2024, 05:00:59 pmMy personal recommendation is SDG1032X because for very little more money you get the device that is superior in every respect.

author: tautech
author_rank: Super Contributor
timestamp: March 04, 2024, 08:02:10 pm
content: Quote from: 2N3055 on March 04, 2024, 07:57:55 pmFTFY.The usefulness of an isolated AWG should never be overlooked.YMMV.Otherwise I agree, SDG1032X is the superior choice for the functionality it offers.

author: KungFuJosh
author_rank: Super Contributor
timestamp: March 04, 2024, 08:09:27 pm
content: Quote from: capslock on March 04, 2024, 07:05:16 pmI haven't tried it yet, but I recently built this project for testing DOAs:https://www.fivefishstudios.com/diy/opamptestjig/

author: orzel
author_rank: Regular Contributor
timestamp: March 04, 2024, 11:37:02 pm
content: Quote from: 2N3055 on March 04, 2024, 07:57:55 pmYeps. I got one and i'm very happy with it. Never cared for 'options' or 'integrated' awg in scopes.

author: Performa01
author_rank: Super Contributor
timestamp: March 05, 2024, 07:32:31 am
content: IdentitySince the SDS800X HD is an extremely affordable package, some corners had to be cut, one of them being the signal samples rendered as clusters of two vertical pixels (because of the limited amount of block RAM in the Xilinx Zynq FPGA).While this hardly poses constraints to our everyday tasks, there might still be situations where we want to get the maximum visual resolution for certain measurements. This is where the math channels come into play.The Identity function returns the original acquisition data, whereas the Average function is the preferred choice for repetitive signals, because it reduces (also) the 1/f-noise and increases the resolution, hence enables us to produce clean traces even from very noisy signals.SDS824X HD_Math_Zoom_Identity_Avg16The screenshot shows a 12 MHz square wave with 1 ns rise time. Zoom mode has been engaged to take a closer look at the rising edge overshot details.The channel 4 trace is always 2 pixels high, so it appears thicker than the math traces.Math trace F2 plots the Identity function, which is basically the same as channel 4, but uses the full screen resolution, hence looks nicer.Math trace F3 plots the a 16x Average of the signal in channel 4. It reduces the noise and increases the vertical resolution to 16 bits.If we want to show the math trace(s) exclusively, e.g. for documentation purposes, we can hide the original signal trace in the corresponding channel menu.EDIT: added the reason for this restriction to the 1st paragraph.

author: tautech
author_rank: Super Contributor
timestamp: March 05, 2024, 08:15:19 am
content: Played with something similar today while testing some current probes of which one when set to highest sensitivity was very noisy.Averaging ( Math) had to be engaged to get readings close to actual.

author: ebastler
author_rank: Super Contributor
timestamp: March 05, 2024, 09:23:36 am
content: Thank you for demonstrating the full-resolution display via Math function, Performa01!I think Siglent could make the Math traces look even smoother if they rendered a change in value not via a "stair step", but via a proper diagonal step. See the lazy ASCII "illustration" below -- stair step on the left, diagonal on the right.The hardware channels are actually rendered (by the FPGA?) with diagonal steps. The Math traces are rendered (by the CPU?) with full vertical resolution, but with the stair steps -- which emphasizes the discrete steps, makes them appear a bit brighter, and makes the curves look more jagged than necessary in my opinion. Assuming the rendering is done on the CPU side, this should be easily changed -- maybe worth a try to make the screen look its best?Code:XXXXXX XXXXXXXXXX XXXXXXX XXXEdit: Hmm, that ASCII art looks less than convincing. Here's a more realistic example: In Performa01's screenshot, I removed the "stair steps" from the red Math trace. It does look smoother than the blue one, and certainly better than the original red trace a few posts above -- not a huge effect, but worthwhile in my opinion.

author: capslock
author_rank: Contributor
timestamp: March 05, 2024, 09:48:10 am
content: Is there any idea why they implemented it this way? It is hard to imagine this is dictated my hardware, and hence necessary from a cost saving point of view. It sound more like an oversight in programming to me.

author: ebastler
author_rank: Super Contributor
timestamp: March 05, 2024, 10:12:33 am
content: Quote from: capslock on March 05, 2024, 09:48:10 amThe double-pixels in the traces for physical channels are due to a hardware limitation, as mentioned by Performa01 above and explained in a bit more detail here:https://www.eevblog.com/forum/testgear/siglent-sds3000x-hd-and-upgraded-sds1000x-hd/msg5341286/#msg5341286For the stair-step rendering of the math traces, I can't imagine a hard constraint which would force Siglent to do it that way. It might just have been the "first draft" implementation of the curve rendering, and then never got questioned?

author: Performa01
author_rank: Super Contributor
timestamp: March 05, 2024, 05:57:41 pm
content: Noise DensityIn my previous testhttps://www.eevblog.com/forum/testgear/sds800x-hd-review-demonstration-thread/msg5293744/#msg5293744I used a constant sample rate of 100 MSa/s, which allowed a 2 Mpts FFT with an effective FFT-sample rate of 50 MSa/s and Δf = 23.84 Hz. This was required, since the FFT in the SDS800X HD is limited to 2 Mpts max. and I wanted to measure the 1/f noise down to at least 100 Hz. As a consequence, I had to set up the FFT in a way that I get a frequency step (Δf) well below that.Of course, if we want any accuracy in the spectrum plot, the Flattop window has to be used, and the RBW is Δf * 3.73 in case of Siglent’s version of the Flattop Window.Because of the low sample rate of just 100 MSa/s for the acquisition, there will inevitably be aliasing, folding back all the noise above 50 MHz to the first Nyquist zone. Then there will be even more aliasing because the FFT introduces one more decimation step, from 100 to 50 MSa/s. The latter could be countered by a digital filter, but it doesn't make that much of a difference anymore.All this does not matter much as long as we are mainly interested in the 1/f noise below about 300 kHz, because it is much stronger than the high frequency noise anyway.Now we want to see the real noise density up to 10 MHz without any aliasing spoiling our measurements. For this we can activate all channels, thus reducing the input bandwidth to a well defined 200 MHz and engage the 20 MHz bandwidth limiter on top of that, so that we can be absolutely sure that there will be no aliasing products of any significance affecting the measurement at 10 MHz.SDS824X HD_ND_1mV_20MHz_500MSaCalculation for 10 MHz: -144.58 dBV = 59 nVrms.The noise density at this point is 59 nV / √889.3 Hz = 59 nV / 29.8 = 1.98 nV/√Hz;Here is the complete table:10 MHz: -144.58 dBV 2.0 nV/√Hz3 MHz: -142.48 dBV 2.5 nV/√Hz1 MHz: -141.88 dBV 2.7 nV/√Hz300 kHz: -141.55 dBV 2.8 nV/√Hz100 kHz: -131.63 dBV 8.8 nV/√Hz30 kHz: -125.49 dBV 17.8 nV/√Hz10 kHz: -113.34 dBV 72.2 nV/√Hz1 kHz: -101.97 dBV 267.2 nV/√HzWith a noise density below 2 nV/√Hz, the Siglent SDS824 X HD beats most of the competition at higher frequencies, whereas the 1/f noise is nothing to write home about, but that has to do with the special split path input buffer design with its enormous offset compensation capability (±8 V starting at only 10.2 mV/div!).Attached is the binary data file for this measurement.SDS824X_HD_Binary_C4_2.7zChannel 4, 1 mV/div, 50 ohms terminated;500 µs/div, 2.5 Mpts, 500 MSa/s;Bandwidth limit = ~20 MHz to get rid of any remaining aliasing from >250 MHz;EDIT:Of course, the above measurement was flawed, because the 20 MHz bandwidth limiter affects the 10 MHz measurement. The actual noise density, measured without bandwidth limit at 10 MHz is 2.4 nV/√Hz, just as it was stated in the first test.SDS824X HD_ND_1mV_200MHz_500MSaHere is the updated noise density table:10 MHz: -144.58 dBV 2.4 nV/√Hz3 MHz: -142.48 dBV 2.5 nV/√Hz1 MHz: -141.88 dBV 2.6 nV/√Hz300 kHz: -141.55 dBV 2.9 nV/√Hz100 kHz: -131.63 dBV 6.0 nV/√Hz30 kHz: -125.49 dBV 16.0 nV/√Hz10 kHz: -113.34 dBV 68.8 nV/√Hz1 kHz: -101.97 dBV 247.0 nV/√HzA noise density of <2.4 nV/√Hz is still one of the best in the industry.Attached is the binary data file for this measurement.SDS824X_HD_Binary_C4_3.7zChannel 4, 1 mV/div, 50 ohms terminated;500 µs/div, 2.5 Mpts, 500 MSa/s;Full Bandwidth;

author: gf
author_rank: Super Contributor
timestamp: March 06, 2024, 09:46:25 pm
content: Quote from: Performa01 on March 05, 2024, 05:57:41 pmActually it is not the RBW (-3dB bandwidth), but the ENBW, which matters for noise denity. For Octave's flattop window, RBW=3.73*Δf, and ENBW=3.77*Δf. The Matlab variant it is almost the same. Don't know the factors for the Siglent variant of the window. The Siglent window must be different, though, since the SDS800X handbook specifies a main lobe width of 23*PI/N (-> 11.5*Δf), while it is 10*Δf for the Matlab/Octave variant. The exact coeffients are unfortunately not documented.[ Fortunately, for a flattop window, the difference between RBW and ENBW happens to be small, so it does not make a big difference if the wrong one is used. ]QuoteIs the 200 MHz limiter an analog or a digital filter?[ If it is digital, then it cannot remove noise that has already been folded by the sampling process from 490-500 Mhz, 500-510 MHz and from 990-1000 MHz down to 0-10 MHz (at 500MSa/s). Then it might be better to use 2GSa/s in order to avoid this folding. ]

author: pdenisowski
author_rank: Super Contributor
timestamp: March 06, 2024, 10:07:38 pm
content: First, thank you for doing all this - really excellent analysis.One small question: is it possible to configure the FFT parameters independently of the time domain settings? Or does changing the parameters in one domain change the settings in the other domain?

author: Performa01
author_rank: Super Contributor
timestamp: March 06, 2024, 11:49:18 pm
content: Quote from: pdenisowski on March 06, 2024, 10:07:38 pmNo - there is no dedicated SA-application. The FFT is just a math operation.We can select the FFT length (as long as it does not exceed the total record length).We have vertical and horizontal settigs, but these define the view parameters and do not affect the signal acquisition. Consequently, they are primarily used for zooming and navigating within the total FFT result.We always need to set the correct acquisition mode (normal in most cases, ERES only in special situations, no Average and certainly no Peak Detect at all), input coupling, vertical gain & offset and time base to ensure sufficient record length.

author: Performa01
author_rank: Super Contributor
timestamp: March 07, 2024, 12:12:22 am
content: Quote from: gf on March 06, 2024, 09:46:25 pmThat’s what I am relying on. The “RBW-filter” defined by the flattop window has steep transitions into the stop band, hence the noise bandwidth is assumed to be approximately the same as the resolution bandwidth.Furthermore, if the actual noise bandwidth is a little wider than the RBW, what would the result be? The resulting noise density would be even ~0.5% lower, so it’s totally safe to specify the noise density by using the RBW of the Flattop window.Quote from: gf on March 06, 2024, 09:46:25 pmIt is a combination of both. Yes, at 500 MSa/s we cannot guarantee there will be no high frequency noise components folded back to the first Nyquist zone, this is why I used the 20 MHz (analog) bandwidth limiter at first. Unfortunately, this already affects the noise floor at 10 MHz a little. But you can see that there is no significant difference between 20 MHz and 200 MHz at 3 MHz (2.5 nV/√Hz), which I take as prove that the aliasing components can be neglected in the 200 MHz test scenario.

author: Performa01
author_rank: Super Contributor
timestamp: March 07, 2024, 11:07:41 am
content: Noise Density 2This time I’ve decided to put not so much weight on the 1/f noise at really low frequencies, but do a flawless measurement where we can rule out any aliasing artefacts affecting the numbers.I used only a single channel (Ch. 4), hence a sample rate of 2 GSa/s, which permits a 2 Mpts FFT with an effective FFT-sample rate of 2 GSa/s and Δf = 953.67 Hz, resulting in 3.56 kHz RBW with the Flattop window. This allows us to measure the 1/f noise down to at least 10 kHz and guarantees full accuracy up to 1 GHz.Now we want to measure the real noise density up to 100 MHz without any aliasing spoiling our results.SDS824X_HD_ND_2GSa_1mVCalculation for 10 MHz (I’ve used 9.9 MHz to escape a micro-spur): -137.35 dBV = 135.68 nVrms.The noise density at this point is 135.68 nV / √3560 Hz = 135.68 nV / 59.66 = 2.27 nV/√Hz;Here is the complete table:100 MHz: -137.73 dBV 2.18 nV/√Hz10 MHz: -137.35 dBV 2.27 nV/√Hz3 MHz: -136.64 dBV 2.47 nV/√Hz1 MHz: -136.54 dBV 2.50 nV/√Hz300 kHz: -135.01 dBV 2.98 nV/√Hz100 kHz: -128.72 dBV 6.14 nV/√Hz30 kHz: -120.57 dBV 15.70 nV/√Hz10 kHz: -104.51 dBV 99.67 nV/√HzWe are getting pretty close to 2 nV/√Hz at frequencies of 10 MHz and higher.

author: hpw
author_rank: Frequent Contributor
timestamp: March 08, 2024, 07:28:37 am
content: @Noise Density 2: Any chance to save 100x AVG by 2M as one 200M BIN file size to save?

author: Performa01
author_rank: Super Contributor
timestamp: March 08, 2024, 09:04:43 am
content: Quote from: hpw on March 08, 2024, 07:28:37 amThat’s not easy:The record length is 4 Mpts with these settings, which means there are 400 Mpts in total used with 100x averaging – and the settings are as they are for a reason. At slower time bases, it would not be possible to retain the 2 GSa/s FFT-sample rate. A faster time base setting (e.g. one that leads to 2 Mpts) would not be sufficient for a 2097152-point FFT.Of course, I could just capture a long record so that you can play with it – but that I’ve done already and since the total sample memory in the SDS824X HD is just 100 Mpts, I can’t provide anything longer than that.A different approach would be to save the complete history, but this feature is not implemented yet and then the entire history is limited by the max. 100 Mpts sample memory just as well.Only way would be to save 100 individual records, each 4 Mpts = 8 MB long. But that’s a bit too much asked 😉

author: gf
author_rank: Super Contributor
timestamp: March 08, 2024, 09:19:43 am
content: EDIT: Moved my answer to hpw's "A call for Bin-Files as for new Siglent HD-Models" thread - I think it fits better there.https://www.eevblog.com/forum/testgear/a-call-for-bin-files-as-for-new-siglent-hd-models/msg5379377/#msg5379377

author: hpw
author_rank: Frequent Contributor
timestamp: March 08, 2024, 03:39:38 pm
content: Quote from: Performa01 on March 08, 2024, 09:04:43 amLook, I like(d) simple getting the equal results as you using equal samples.The given BIN files shows on the first 5..10 FFT's anyway a higher noise as the flowing once. Even on SDS3000 HD.This is may a thermal or stability issue, as the gear to heat up (1h or more) before any 1/f & noise to measure.The calculations of the dBrtHz could be easier done, as the ENBW value in dB to subtract of the dBV. But works only with equal used FFT Window for dBV to dBVrtHz graphs.

author: gf
author_rank: Super Contributor
timestamp: March 08, 2024, 11:18:32 pm
content: Quote from: hpw on March 08, 2024, 03:39:38 pmIf you lower your expectations and are also satisfied with averysimilarresult, you can obtain it from the .bin file posted by Performa01.

author: maxwell3e10
author_rank: Frequent Contributor
timestamp: March 09, 2024, 06:17:35 am
content: Thanks for these measurements, 2 nV/sqrt(Hz) at 1mV/div is indeed quite impressive, among the very best noise for front end amplifier.https://www.eevblog.com/forum/testgear/oscilloscope-input-noise-comparison/The 1/f noise is not as good, a bit worse than Rigol HDO.Did you make measurements at 1V/div scale? That would be a test of the ADC and a direct measure of HD performance.

author: Performa01
author_rank: Super Contributor
timestamp: March 09, 2024, 07:58:00 am
content: Granular NoiseThis time we shall have a look at the granular noise of the 12-bit SDS800X HD. At high sensitivities like 1 mV/div, we cannot expect much of an advantage from the 12 bits, but at low sensitivities like 50 mV/div and higher, the 12 bits should clearly give us a benefit.I used only a single channel (Ch. 4), hence a sample rate of 2 GSa/s, which permits a 2 Mpts FFT with an effective FFT-sample rate of 2 GSa/s and Δf = 953.67 Hz, resulting in 3.56 kHz RBW with the Flattop window. This allows us to measure the noise down to at least 10 kHz and guarantees full accuracy up to 1 GHz.SDS824X_HD_ND_2GSa_1VThere’s little point in calculating a noise density (which would have to be specified in hundreds of nanovolts or even single digit microvolts per square-root Hertz), but we should consider the full-scale value of +9 dBV in this test scenario.We get a SNR of >110 dB at 100 MHz with a RBW of 3.56 kHz.You can download a 100 Mpts binary file for this test scenario:SDS824X HDChannel 4, 1V/div, 50 ohms terminated;5 ms/div, 100 Mpts, 2 GSa/s;Full bandwidth = 254 MHz;https://mega.nz/file/XD5UVL7a#KQhhly2Zo7U2D5wumdrSVm2psvrTVdZtO8pwSQV34wA

author: Bad_Driver
author_rank: Frequent Contributor
timestamp: March 09, 2024, 11:03:38 am
content: Performa01, a dumb question.Is there a special reason for always using channel 4 for your tests?

author: RAPo
author_rank: Super Contributor
timestamp: March 09, 2024, 11:19:17 am
content: Maybe the green color trace, it looks more like an analog scope and the rigol (sadly) doesn't have it? 🤔

author: Martin72
author_rank: Super Contributor
timestamp: March 09, 2024, 11:56:49 am
content: Quote from: Bad_Driver on March 09, 2024, 11:03:38 amI usually use the first channel - because the short cables don't get any further and my measuring equipment is to the left of the scope.Edit:QuoteIs canceled for me with the reference to a (possible) virus (Win10,Edge)

author: Performa01
author_rank: Super Contributor
timestamp: March 09, 2024, 11:58:39 am
content: Quote from: Bad_Driver on March 09, 2024, 11:03:38 amIt's actually the green color trace that I prefer, also because of fond memories of analog CROs, so I decided to use Ch.4 as the default choice back when I got my first Siglent MSO (SDS2304) about 10 years ago.Back then I've even found a bug that was specific tonotusing channel 1 - so one more reason to stick to Ch.4 ever since

author: gf
author_rank: Super Contributor
timestamp: March 09, 2024, 01:54:13 pm
content: Quote from: Performa01 on March 09, 2024, 07:58:00 amIf you relate it to a specific bandwidth, then it is still a density.Maybe dBFS/Hz would be an appropriate (bandwidth-independent) metric?Then it would be about -145 dBFS/Hz at 100MHz.However, the full bandwidth noise floor is ~4.3 mVRMS, which corresponds to a total SNR (or better say SINAD?) of ~56 dBFS, or ~9.1 ENOB (not yet including harmonic spurs and mixing products of the measured signal, since no signal is present).What I also noticed, by the way, is that roughly 1/3 of the noise floor's total power is contributed by the two (interleaving?) spurs at 500MHz and 1GHz! I wonder if it would not be possible to calibrate them out? Or is it already the best possible calibration?

author: rf-loop
author_rank: Super Contributor
timestamp: March 09, 2024, 02:05:52 pm
content: Here some example where are bottom and top of voltage band I and IINow here is also other individual SDS824X HDAnd as can see very close with @Performa01Below images, all inputs terminated with 50 ohm terminator (HP11593A).Voltage band IIF1 1V/divF2 102mV/divVoltage band IF3 100mV/divF4 1mV/divFFT window FlatTopbtw, I do not know this Siglent used FlatTop window real ENBW (EquivalentNoiseBand Width) so here below is same using Rectangle aka "Boxcar" window.FFT window Rectangle, Input 1mV/div, Full BWCalculation for 9,85 MHz -142.8 dBV = 72.1nVrmsNoise density in this point 72.1nVrms / √953.7 Hz = 2.33 nV/√Hz;

author: Performa01
author_rank: Super Contributor
timestamp: March 09, 2024, 03:50:41 pm
content: Quote from: gf on March 09, 2024, 01:54:13 pmRight. I should have said: “there’s not much point in calculating the classic noise density expressed in nV/√Hz.Since the vertical axis is dBV (and not dBm) in this example, I guess dBFS/√Hz would be more appropriate.Since the SDS800X HD lacks 50 ohm inputs, it feels more natural to work with voltages instead of power levels.Quote from: gf on March 09, 2024, 01:54:13 pmSince there is no distortion component, SNR would be the better term in my book. Static spurs can be looked at as some sort of noise, and dynamic ones (that depend on input signal) could rather be classified as some complex form of non-harmonic distortion.Since distortion products can easily be lower than -54 dBc, actually up to -70 dBc as also demonstrated in this thread, the 9.1 ENOB should be actually achievable in many practical scenarios.Quote from: gf on March 09, 2024, 01:54:13 pmThe self-calibration takes quite a long time, so it’s actually been a while since I’ve last performed one.Now I’ve tried again, even though I didn’t expect much from it – in my experience the calibration in this instrument seems pretty stable anyway. Yet there is a little difference indeed:SDS824X_HD_ND_2GSa_1V_cal

author: BRZ.tech
author_rank: Regular Contributor
timestamp: March 10, 2024, 01:15:00 pm
content: Dear @Performa01Regarding this topic, I consider it like Star Trek episodes, in terms of content and depth. I can't imagine the next episode...The SDS800X HD really put SIGLENT at the forefront and in the minds of hobbyists compared to other manufacturers. Soon we will have 1,000,000 views on the set of related topics.Competing manufacturers will have to greatly improve their hardware and free firmware to compete with the SDS800X HD in entry-level DSO/MSO. For beginners and hobbyists, it can deliver much more quantity and quality of information, for an affordable price, compared to competitor models, in addition to 12 bits of vertical resolution.As for the 8-digit frequency meter, it is spectacular, achieving displays with single-digit resolution, frequencies up to 99.999999 MHz. Competitive models provide a maximum of 6 digits, with single-digit resolution of 999.999 KHz.I am currently a user of a RIGOL MSO5000, which serves my hobby. But I intend to soon buy one the SDS800X HD, perhaps the SDS804X HD, even for the challenge of reproducing your tests, and learning many things. Very soon, with regular deliveries from SIGLENT, as here for me the best value for money is to buy on Aliexpress.As for my doubts and questions, let me know @Performa01 if you have a YouTube channel that shows step by step how to carry out these brilliant tests. And if you accept it here on the list, let “beginners” ask you “obvious things” questions.In the HAM – Amateur Radio universe, in which I am, which is a potential client for the SDS800X HD, we measure many very low amplitude signals, below 1mVrms, in the time domain, and in the FFT, it can be in dBm or dBV . It looks like the SDS800X HD can present both possibilities.Any colleague on the topic can also answer my questions, they will be welcome.Maybe it's already on your rehearsal schedule:I suggest you do a test to measure a signal, which we use in HAM, a VHF sinusoidal signal f=146MHz, without modulation, Amplitude = 1mVrms, at 50 Ohm, to start, and Decreasing the Amplitude up to 10uVrms, and if possible even lower, up to the sensitivity limit of the SDS800X HD. And present the images in the Time domain, and also in the Frequency domain, using the FFT with the Table, it can be in dBm or dBV.And present your conclusions to the HAM universe.Afterwards, perform FM Modulation, with a sinusoidal signal of f=1KHz, with a 5KHz deviation. Present the same images, in the Time and FFT domains.And present your conclusions to the HAM universe.Afterwards, perform AM Modulation, with a sinusoidal signal of f=1KHz, with Modulation Index = 80%. Present the same images, in the Time and FFT domains.And present your conclusions to the HAM universe.Translation with Google translator.TKS.73.

author: rf-loop
author_rank: Super Contributor
timestamp: March 10, 2024, 05:21:03 pm
content: You ask from @Performa01But here is some quick demo from me.carrier bit over 145MHz, AM 1kHz 80% ( sidebands are ~-8dBc )Yes when I did it I forget you ask 146... my head "best berore" day was far away in previous millenium...For 2m band there need use 500MSa/s so even with 2M FFT we can not get more resolution - this is simple direct FFT.( and I have not tested if internal down conversion (Nyquist "trick") can use so that result give any even somehow acceptable result)(note, I have used Hamming window so levels accuracy is poor. (FlatTop is better but around 890Hz RBW with this setup is so borderline for detect sidebands so I use here Hamming... when carrier and sidebands freq do not match with FFT bins there is some amounf scallop error in amplitude. With -107dBm it can clearly see also that noise start affect lot (it can see when look carrier and sidebands persistence traces... I have usede 30 sec persistence)There is Tektronix 50ohm feedthru termination in scope input.image a: -87dBm carrier is ~10uVrmsimage b: -107dBm carrier is ~1uVrmsSignal come from HP 8642B "boat anchor"Very limited time so only these examples.

author: BRZ.tech
author_rank: Regular Contributor
timestamp: March 10, 2024, 06:53:00 pm
content: Quote from: rf-loop on March 10, 2024, 05:21:03 pmDear @rf-loop,I am very grateful for providing your input.I modified my previous post to add:"Any colleague on the topic can also answer my questions, they will be welcome."As for the wavelength frequency in 2m, f=145MHz, there is no problem. I indicated f=146MHz because it is the center of the 2m band here in my country. But calculating at 145MHz will not change the practical effect of the test. TKS.In image "a", at the Carrier frequency, with 10uVrms of input Amplitude, in the AM signal, it was great to see the exact Amplitudes and Frequencies, and clearly, of the Carrier and LSB and USB lanes.In image "b", it was even better to see the same information, and well defined, with an AM signal input amplitude of 1uVrms...In my opinion, the SDS824X HD passed the AM test...As for the CW and FM Modulation test, it is not possible to know yet.@rf-loop, a question, because I don't know how to use SIGLENT's UI: in your table you present "MARKER: 1, 2 and 4", but you did not present "Marker: 3". Can you explain why?TKS73.

author: Martin72
author_rank: Super Contributor
timestamp: March 10, 2024, 07:07:06 pm
content: Hi,QuoteYou can set and activate/deactivate the markers individually.Example:In my bandwidth measurement yesterday, I first measured the 70Mhz variant and distributed markers 1-5 accordingly.With the 200Mhz variant, for example, markers 2 (which I had set to 25Mhz) and 3 (set to 50Mhz) no longer made sense, so I no longer activated them.

author: BRZ.tech
author_rank: Regular Contributor
timestamp: March 10, 2024, 07:17:19 pm
content: Hi,Martin72.Thank you for your response.Understood, regarding disabling the marker individually. This is very practical when you have many weak signals around a signal of measurement interest.I will see your Bandwidth measurement in the other topic.I inform you that I always watch the videos on your YouTube channel...TKS73.

author: Performa01
author_rank: Super Contributor
timestamp: March 11, 2024, 08:37:24 am
content: Ham TestHere come some tests that could be of interest for HAM operators.First, I should ensure that expectations don’t get unrealistic. A general-purpose oscilloscope like the SDS800X HD is neither a spectrum analyzer nor a test receiver, even when its noise figure drops below 10 dB at frequencies above 300 kHz. Yet it just works on the full input signal bandwidth, there is no pre-selector, no mixer to shift small portions of the upper spectrum down to a lower intermediate frequency and no filter that could isolate the IF signal.In the time domain, 400 µVrms is pretty much the limit for reliable triggering, indicated by a correct trigger frequency counter display; for even lower levels, triggering gets increasingly sporadic and at 100 µVrms, the trigger frequency counter drops below 1 MHz. Only if we have a strong copy of the signal of interest, such as measuring the stop band of a filter, we could trigger on the input signal and use the Average math function to make even very weak output signals visible and measurable, even those way below the noisefloor, as has been demonstrated already in this thread.For all the following tests, a Siglent SDG7102A AWG with OCXO option has been directly connected with coaxial Hyperflex 5 cables, a step-attenuator Wavetek 5080.1 and an inline terminator “hp10100C” at the scope input.CW TestFor the 1 mVrms demo I had to bring quite a lot of information onto a single screen:SDS824X HD_SA_CW_146MHz_1mVThe main window at the top is showing the 146 MHz signal at a timebase of 500 µs/div. We need that slower timebase to get sufficient data for a 2 Mpts FFT. Of course we can’t see any details there, hence there is the zoom window below, where the signal is displayed at a timebase of 10 ns/div. We can see that the vertical position is not constant across the screen width, which hints on the noise that gets very noticeable at such low signal levels.The zoom window also contains the FFT which reveals some weak modulation due to noise and we can see the corresponding sidebands indicated by markers 1, 2, 4 and 5, whereas marker 3 corresponds to the main signal.Below we have two windows nested: the advanced measurements together with the Peaks List, for which I’ve freed up some space by removing measurements 2 and 3. We can see that the amplitude measurements in the time domain still work reasonably well, at least Stdev (= AC-RMS), whereas the peak-to-peak amplitude cannot be accurate – once again because of the noise.The signal frequency measurement is not accurate as well and all automatic measurements have a high variance, as can be seen in the measurement statistics and histograms, yet the 7-digit trigger frequency counter is still rock stable and pretty accurate. Of course, it is 2 kHz off, which is equivalent to 13.7 ppm, but that’s because the time base of the SDS800X HD has 25 ppm tolerance, which is pretty much standard, while Siglent’s higher end DSOs starting at the SDS2000X plus provide class leading 1 ppm timebase accuracy.The peak table shows the various signal amplitudes, but we are mainly interested in Peak #3, which is indicated as -47.146 dBm at 146.00205 MHz. Surprisingly, the frequency is exactly the same as the trigger frequency counter, hence absolutely correct relative to the SDS800X HD timebase, also the amplitude is pretty much spot on (should ideally be -47.0 dBm).At this point I should mention that the Peak table is automatic and we only set the search parameters, i.e. threshold and excursion. This is in contrast to the Markers, which can be preset on peaks or harmonics, yet each marker can be set individually to any desired frequency by the user. For the measurements here, Peak tables have been used exclusively.There is no point to further look at the time domain for weaker signals, because they will get heavily distorted and eventually buried in the noise anyway. Yet I don’t change the arrangement and only move the zoom trace out of view.Next, we try 100 µVrms:SDS824X HD_SA_CW_146MHz_100uVThe main window at the top shows mainly noise for the 100 µVrms signal at 245 MHz bandwidth. The zoom window with the FFT displays a clean spectral line, hence we only get a single peak marker.The advanced measurements below just try to measure the noise, even though the Stdev measurement still isn’t too far off – just a coincidence?Since such a weak signal cannot be properly triggered anymore anyway, I’ve used AC-line trigger instead and the trigger frequency counter just shows a constant 50 Hz now. FFT doesn’t need a triggered signal.The peak table shows the signal amplitude as -67.316 dBm at 146.00205 MHz. The amplitude is still pretty accurate (should ideally be -67.0 dBm).Now let’s try 10 µVrms:SDS824X HD_SA_CW_146MHz_10uVOnce again, we get a clean spectral line with a single peak marker.The advanced measurements below are totally meaningless, but the peak table shows the signal amplitude extremely accurate as -87.073 dBm at 146.00205 MHz.Another attempt with 1 µVrms:SDS824X HD_SA_CW_146MHz_1uVOne more time, we get a clean spectral line with a single peak marker.The advanced measurements below are totally meaningless, but the peak table shows the signal amplitude pretty accurately as -107.291 dBm at 146.00205 MHz.A final attempt with 100 nVrms:SDS824X HD_SA_CW_146MHz_100nVWe even get a tiny spectral line, but have to tweak the search parameters to get the peak marker. Its amplitude is now way off: -123.737 dBm at 146.00182 MHz (should be -127.0 dBm). The signal is just too close to the noise floor now.This test is quite revealing. Even a 100 nVrms signal could be detected, and even though the signal amplitude was off by 3.26 dB, the frequency could still be measured with just ~200 Hz error (relative to the DSO’s timebase that is)!FM TestFor the modulation tests, I did not feel like trying many different levels again, so 1 mV and 10 µV RMS shall be sufficient for FM.First I need to repeat what I’ve already stated initially: An oscilloscope is a baseband instrument, not a spectrum analyzer. There is only so much frequency resolution we can get from a 2 Mpts FFT. As a consequence, the expectations shouldn’t be very high when looking at one kilohertz frequency spacing in signals from the 2 meter band.Modulation: 1 kHz modulation frequency and 5 kHz frequency deviation.1 mVrms at 146 MHz first:SDS824X HD_SA_FM_146MHz_1mVWell, that’s not very convincing. I was forced to use the Blackman window, which is still usable for spectrum analysis with a max. amplitude error of 1 dB. Its resolution bandwidth is not that much better than Flattop hence the picture isn’t very useful and we only get a vague idea of the FM spectrum.It should be clear that a general-purpose oscilloscope isn’t a test receiver. If we look at bandwidth limited signals, like filtered IF, where we need not worry about aliasing from unrelated signals in the neighborhood, we could just use the “frequency conversion by undersampling” method.Any ADC acts as a mixer, thus producing a spectrum of ±n*fi±m*fs, wherefiis the input frequency andfsis the sample clock, whilenandmare just integers running from 0 to (theoretically) infinity. During normal operation, we don’t want to see any mixer products, which is perfectly possible as long as the input signal and all its harmonics don’t exceedfs/2 and the output of the ADC has a brick-wall filter (then in the digital domain of course, aka Sinc filter or sin(x)/x reconstruction) that removes everything abovefs/2.Yet in some circumstances, we can make use of a certain high-order mixer product, just as in this example, where the effective FFT sample rate is only 5 MSa/s, which is quite obviously way too low for a 146 MHz input signal.According to the formula given above, we are aiming at the mixer product for 1 *fi- 29 *fs, which is1 * 146 MHz – 29 x 5 MHz = 146 MHz – 145 MHz = 1 MHz;Now if we set the center frequency to 1 MHz, we get the carrier at 146 MHz and a resolution bandwidth of only 35.57 Hz, even with just 512 kpts FFT, hence can also clearly see the sidebands and their 1 kHz spacing. 16x averaging has been used in order to get a clean and stable display:SDS824X HD_SA_FM_146MHz_1mV_5MSaBe aware that the true center frequency is Peak #6 at 1.00197 MHz because of the SDS824X HD timebase tolerance of 25 ppm.The following table compares the measured sidebands with the expected ones in dBm:Ord. Meas. Expected0 -62.052 -62.0831 -56.750 -56.7632 -73.700 -73.7133 -55.823 -55.8334 -55.200 -55.223Now for the 10 µVrms test:SDS824X HD_SA_FM_146MHz_10uV_5MSaThere is a spurious signal at marker 5 exceeding the signal spectrum – we just have to ignore it.The following table compares the measured sidebands with the expected ones in dBm:Ord. Meas. Expected0 -102.07 -102.0831 -96.700 -96.7632 -113.70 -113.7133 -95.700 -95.8334 -95.100 -95.2235 -98.500 -98.733All in all the down-mixing via the ADC can save our day as long as we have an isolated signal and the signal levels don’t get too low.There are several caveats though:• We need to make sure thatnis always positive, otherwise we’d get the result in reverse frequency position, i.e. the upper sideband appears below the carrier and vice versa.• Mixing with the 29th harmonic of the sample clock introduces also 29 times more phase noise and jitter and this might get visible the FFT plot.• Amplitude accuracy might suffer, as a harmonic mixing process is not guaranteed to be as efficient as the fundamental one, hence we might see some attenuation.AM TestModulation: 1 kHz modulation frequency and 80% modulation depth.SDS824X HD_SA_AM_146MHz_1mVWell, that looks familiar. Once again, the picture isn’t great and we only get a vague idea of the AM spectrum. The sidebands should be -8 dBc = -61.6 dBm. The deviations come from the insufficient resolution bandwidth and the amplitude error of the Blackman window.We are looking at the mixer product for 1 *fi- 29 *fsagain, which is1 * 146 MHz – 29 x 5 MHz = 146 MHz – 145 MHz = 1 MHz;Now if we set the center frequency to 1 MHz, we get the carrier at 146 MHz and a resolution bandwidth of only 35.57 Hz, hence can also clearly see the sidebands and their 1 kHz spacing. 16x averaging has been used in order to get a clean and stable display:SDS824X HD_SA_FM_146MHz_1mV_5MSaBe aware that the true center frequency is Peak #3 at 1.00197 MHz because of the SDS824X HD timebase tolerance.The sidebands should be -8 dBc = -55 dBm. The accuracy is very high despite the harmonic mixing process.General Remark:I don’t maintain a YouTube channel and my time is limited. Since I’ve already published most of the intended content, and I made sure the relevant information can easily be found by means of the table of contents in the opening posting, I don’t mind people asking questions here, even newbie questions 😉EDIT: Corrected the statement for the 10 µV FM-test and added a comparison of measured vs. expected results.

author: Martin72
author_rank: Super Contributor
timestamp: March 11, 2024, 08:47:57 am
content: So much useful and worth knowing information and basics in a single thread - that's why I will keep the link to it "forever" in my signature.

author: hpw
author_rank: Frequent Contributor
timestamp: March 11, 2024, 08:58:54 am
content: @CW Test:could be enhanced as 1/f PN and Jitter test. Using a -3dB signal at fs/xxx, where xxx is exact 2^n and then ZOOM-In or use simple a 10MHz OXCO sine signal.This is mostly done on Audio as using fs/4 as looking for 1/f & symmetric jitter or modulation spurs.I did similar tests already on a Siglent SSA and the internal reference synthesizer is as

author: Muttley Snickers
author_rank: Unknown
timestamp: March 11, 2024, 09:58:47 am
content: Quote from: Performa01 on March 11, 2024, 08:37:24 amYou sir are to be thoroughly commended, an inspirational piece of work if ever there was.Quote from: Martin72 on March 11, 2024, 08:47:57 amJust to add to Martin72's post.As the thread is currently 8 pages and still under 20 people have the ability to select "All" at the top of the page to open all of the existing pages and then print as a hard copy or save as a pdf for reference, don't forget the images though. You won't find this level of information in any user manual that's for damn sure.

author: Mortymore
author_rank: Frequent Contributor
timestamp: March 11, 2024, 10:18:20 am
content: Quote from: Martin72 on March 11, 2024, 08:47:57 amGreat idea! I've added a signature with the link to this thread also.Quote from: Muttley Snickers on March 11, 2024, 09:58:47 amI've been compiling in a doc the posts from Performa1, according to the list of links provided in the 1st.It's not in a PDF format because I suspect that Performa1's work is not done yetsince he keeps open to suggestions and extremely supportive answering them.PS: By the way... This weekend I made the same "mistake" as Martin72 and bought an SDS804X-HD. It was shipped 10 minutes ago, wile I was reading this thread updates

author: pdenisowski
author_rank: Super Contributor
timestamp: March 11, 2024, 10:24:36 am
content: Quote from: Performa01 on March 11, 2024, 08:37:24 amAgain, many thanks for the detailed analysis - if you don't already work for a T&M manufacturer, you really ought to consider itQuick question: which window types does the Siglent support?I'm not sure I would have used a Blackman(-Harris) window here, although I presume this is the default (at least it's the default on a lot of scopes). Since you're going to have to trade between frequency selectivity and amplitude accuracy, a window type with better selectivity might be better for generic spectrum analysis (i.e. what's where in spectrum).

author: RAPo
author_rank: Super Contributor
timestamp: March 11, 2024, 12:01:02 pm
content: Quote from: Performa01 on March 11, 2024, 08:37:24 amThanks for your knowledge and insights. They're really appreciated. This thread convinced a Rigol-fan boy to order a Siglent!

author: gf
author_rank: Super Contributor
timestamp: March 11, 2024, 12:13:10 pm
content: Quote from: Performa01 on March 11, 2024, 08:37:24 amTheoretically, a bandpass filter could help to reduce noise in the time domain display. The handbook sais that 200 FIR taps are supported. With 200 taps @2Gsa/s you can design filters with ENBW down to 10 MHz (see attachment). For the provided 500µV/div noise floor data, this would improve the 0..1GHz SNR by ~16dB. Is it actually possible to specify/upload arbitrary custom filter taps, or are only the predefined filters supported? The latter seem to be a bit limited (e.g. bandpass passband >= 0.02 * sample_rate).

author: mawyatt
author_rank: Super Contributor
timestamp: March 11, 2024, 02:26:03 pm
content: @Performa01Superb work, well doneYou nicely show the inherent built-in capability of this new highly affordable Analytical Instrument wedisrespectfullycall a "Scope"!!Also like the use of the "Trick", reminiscent of our 80s multi-tier DTCA CCD based RTSA, this technique seemed lostintime!!We thought/hoped Siglent might "answer" Rigol's excellent DHO800 introduction, they've certainly answered that "call"Edit: AddedinBest,

author: Performa01
author_rank: Super Contributor
timestamp: March 11, 2024, 02:32:03 pm
content: Quote from: pdenisowski on March 11, 2024, 10:24:36 amNo, Blackman is not default, I think it's Hanning (correctly: "von Hann"), and unfortunately so, because many folks not really understanding how to properly setup a FFT stick to the default and - quite frankly - everything but Flattop is pretty useless for spectrum analysis. I thought I made it clear that I have used Blackman because it is the only other acceptable window with max. 1 dB amplitude error, which has at least a little bit narrower bandwidth.The reason for this hard assessment together with the answers to your questions can be found here:https://www.eevblog.com/forum/testgear/siglent-sds2000x-plus-coming/msg4318822/#msg4318822

author: pdenisowski
author_rank: Super Contributor
timestamp: March 11, 2024, 02:49:28 pm
content: Quote from: Performa01 on March 11, 2024, 02:32:03 pmThanks for the link. Perhaps I'm misunderstanding you (or you're speaking tongue-in-cheek), but I would however rather strongly disagree that "everything but Flattop is pretty useless for spectrum analysis" It very much depends on the application (i.e. what kinds of signals you're looking at). Even if amplitude accuracy is your primary concern, there are still multiple window types that provide "acceptable" amplitude accuracy in many applications.The fact that various window types exist (and all modern T&M FFT implementations support multiple window types) speaks to the need for different windowsI'm working on my own presentation / video covering this, but in the meantime there is an excellent (and accessible) coverage of FFT windowing in this paperhttps://www.egr.msu.edu/classes/me451/me451_labs/Fall_2013/Understanding_FFT_Windows.pdf(see page 4)Or a little more technical:https://www.ti.com/content/dam/videos/external-videos/2/3816841626001/5834902778001.mp4/subassets/adcs-fast-fourier-transforms-and-windowing-presentation-quiz.pdf(see slide 10)

author: mawyatt
author_rank: Super Contributor
timestamp: March 11, 2024, 04:03:43 pm
content: Good elementary FFT Windowing referencesA priori signal type and post measurement intent certainly helps with proper Window selection, sort of a "Matched Filter" type representation!!Best,

author: pdenisowski
author_rank: Super Contributor
timestamp: March 11, 2024, 04:44:48 pm
content: Quote from: mawyatt on March 11, 2024, 04:03:43 pmThat's a great way of putting it. In my experience, customers often don't (necessarily) know the frequency domain characteristics of their signal in advance, so choosing an FFT window is still sometimes a trial-and-error process.I'mguessing(because I haven't read it ... mea culpa) that the Siglent documentation is much like most other documentation in that it lists the FFT window types but provides very littlepracticalguidance about when to use one window type instead of another (and/or guidance about how to recognize when you're using the wrong window type for the signal you are measuring).

author: ebastler
author_rank: Super Contributor
timestamp: March 11, 2024, 04:53:15 pm
content: It's actually a tad better than that, and describes the frequency resolution vs. amplitude "resolution" properties of the various window functions. See the relevant table from the SDS800X HD manual attached.

author: Performa01
author_rank: Super Contributor
timestamp: March 12, 2024, 11:59:40 am
content: Filter DemoThere was the suggestion for cleaning up high frequency narrowband signals by means of a bandpass filter. In this case we are talking about the 146 MHz signal from the HAM Test demo.The narrowest bandwidth achievable at 146 MHz is 40 MHz (126-166 MHz). This appears very wide, but is pretty effective nevertheless. Just look at the noise floor:SDS824X HD_Math_FFT_BP_126-166MHz_NoiseThe screenshot above shows two math channels with FFT plots; F4 is the original signal (which is just the frontend noise for now), whereas F1 shows the result of the filter operation performed in math channel F2. It should be immediately obvious that getting rid of the strong 1/f-noise below 300 kHz alone would help a lot. With the BP-filter, only at 1 kHz the 1/f-noise approaches the level of the original HF-noise (~-120 dBm).We cannot expect a major improvement for FFT measurements, because the resolution bandwidth there is much narrower than our bandpass-filter anyway. Here is the FFT with the 1 mVrms signal at 146 MHz applied:SDS824X HD_Math_FFT_BP_126-166MHz_1mVYes, there actually is a difference. The original signal is measured ~0.43 dB too high because of the noise, resulting in -46.57 dBm, see F4 Markers List. On the other hand, the filtered version of that signal measures -47 dBm almost spot-on, as can be seen from F1 Markers List. So yes, even the FFT measurements can benefit from a cleanly filtered signal.Now let’s have a look at the time-domain, where the improvement because of the filter should be even more obvious:SDS824X HD_Math_BP_126-166MHz_1mVAdvanced automatic measurements have been set up for the amplitudes of both the original signal and its filtered version. The visual difference is quite striking already, and the measurements confirm the improvement: just like with the FFT, automatic measurements are more accurate with filter than without.We already know that reliable triggering is only possible down to about 400 µVrms, yet it still works with 100 µVrms signals, if we can accept a high failure-rate (look at the trigger frequency counter):SDS824X HD_Math_BP_126-166MHz_100uVOnce again, the visual difference is quite striking, and even though the automatic measurements for both signal variants aren’t entirely accurate, there is still a major improvement with the filtered version.

author: Veteran68
author_rank: Frequent Contributor
timestamp: March 12, 2024, 03:35:42 pm
content: Quote from: Muttley Snickers on March 11, 2024, 09:58:47 amI agree this is a level and quality of documentation that deserves to be immortalized in a document format like PDF. To that end, I spent some time this morning using a browser extension I'm fond of that lets you "clean" a web page to make it more suitable to printing and/or saving as PDF. I stripped out all of the forum decorations/controls and as much of the back and forth dialog, Q&A, and other noise as I could to keep it limited to the documentation type posts and screenshots provided by Performa01, rf-loop, and others. Of course where a question resulted in further exposition and educational presentation, I kept that. I may have scrubbed (inadvertently or intentionally) some useful details or interactions here and there, as it turned out to be a larger chore than I expected and had to drop and come back to it multiple times in between work stuff (yes, I did this while at work, lol).If/when more such content is added to the thread, it won't be hard to edit the PDF to append the new info. It's not perfect, and it's not paginated, but it is searchable and it's cleaner than a raw forum dump.I was going to host it somewhere, then realized that if I zipped it, it came to just under the 8000KB attachment limit for the forum. So I've attached it here ZIP'ed for now. If it grows much larger, we can find a host for it later. I have Google Drive, OneDrive, Box, Dropbox, as well as some personal web hosting space that I could use. Not to mention the free file hosting services.

author: BRZ.tech
author_rank: Regular Contributor
timestamp: March 12, 2024, 09:45:56 pm
content: Quote from: Performa01 on March 11, 2024, 08:37:24 amHi,@Performa01I am very grateful about your amazing analysis of CW-AM-FM for the HAM universe. TKS.I have another question that I consider relevant to the HAM universe, which is the Frequency Response of the SDS800X HD for Square Wave Excitation.It is very interesting for HAMs when it comes to making RX-TX in Digital Modes, in various RF bands, where HAMs DIY artisanal new low power RF radios, called QRP, for the frequencies authorized by legislation, on each country or region.And the analysis of Digital Signals in the time regime and frequency regime is very welcome for HAM users. And I'm sure the SDS800X HD will literally be able to supply the most important measurements.In this topic, I looked in the index, in the first post, and I didn't find the Frequency Response for Square Wave Excitation."Any colleague on the topic can also answer my questions, they will be welcome."I suggest you do a test to measure a signal, which we can use in HAM, a SQUARE WAVE signal f=50.000MHz, without modulation, Amplitude = 0 to 1Vpp, at 50 Ohm, to start, and increase the frequency, to have the minimum number of tracks that you think are necessary in the FFT of the SDS800X HD, for the cutoff frequency that you consider sufficient for the BW.On the FFT screen where you found BW, in the “FFT Table”, locate the Frequencies and Amplitudes of the Fundamental and Harmonics, and set up an equation in time of f(t), with the coefficients and sines and cosines, of the sum Fourier Series: A0, An, Bn. (I put them in UPPERCASE characters for emphasis, but they are lowercase characters).I have read many “Theoretical Articles” and I have seen many “Videos” on Youtube, which theoretically calculate the “Fourier Series Coefficients”, but without the practical part, of collecting the coefficients from the FFT Table, and inserting them into f(t).Next, a video that I thought was excellent, about the calculation of the “Fourier Series Coefficients” presented by “Professor Michel van Biezen”:At the end of the video, he presented the conclusion, with f(t) with (DC Value = A0), the Fundamental and the Third and Fifth Harmonics.At the end of the test, the “Fourier Series Coefficients” collected from the “FFT Table” of the SDS800X should be very close to those presented by “Professor Michel van Biezen”.There is the question that how the “Fourier Series Coefficients” in their Amplitude values should be presented in the f(t) equation: Vpp, Vrms, Vp, or other??You can present the images in the Time domain, and also in the Frequency domain, using the FFT with the Table, it can be in dBm.And present your conclusions to the HAM universe.TKS.73.

author: maxwell3e10
author_rank: Frequent Contributor
timestamp: March 12, 2024, 10:58:29 pm
content: Thank you for providing so many detailed measurements. I am wondering if you can test the averaging and ERES math features, which are not described in detail in the manual. Basic questions are what is the maximum number of averages, does it allow finite and running average, how much does averaging or ERES slow down update rate?

author: tautech
author_rank: Super Contributor
timestamp: March 12, 2024, 11:54:25 pm
content: Some screenshots from SDS814X HD via PC for your study.Probe comp output.

author: Performa01
author_rank: Super Contributor
timestamp: March 13, 2024, 06:30:14 pm
content: Fun with Square WavesQuote from: BRZ.tech on March 12, 2024, 09:45:56 pmThe frequency as well as pulse response of the SDS800X HD have been presented in some detail in the opening posting (sections “Bandwidth” and “Pulse Response”). Why do you think you need a special frequency response for square waves?You’re talking about Fourier and point to a video showing how to derive the well-known Fourier coefficients for a square wave. Maybe these all too theoretical approaches still don’t convey the fundamental insight that the fidelity of a square wave reproduction on the oscilloscope screen depends on the rise time of the square wave and the bandwidth of the scope. The scope bandwidth is known, whereas our task now is to find the rise time a 200 MHz DSO can handle smoothly.Okay, let’s recap some fundamentals.Even with moderate 3.5 ns rise time, the pulse spectrum extends up to >800 MHz – look at the spectrum in the screenshot below (for this I pulled out a heavier gun with 2 GHz bandwidth):Ref-Spec_Square_3.5ns_10MHzOf course, a fast scope like this reproduces a comparatively slow rise-time like this flawlessly. We can see that with 210 MHz bandwidth we could expect a decent reproduction of this signal with no more than ~1% aberrations, because all harmonics down to -40 dBc would be included. With 250 MHz bandwidth (which the SDS824X HD nearly has with up to 2 channels in use), the expected aberrations would be even lower at about 0.3%, as all the harmonics down to -50 dBc would be included.Quote from: BRZ.tech on March 12, 2024, 09:45:56 pmWell, let’s see what a 50 MHz square wave would look like if we stick to a rise-time of 3.5 ns, which would be adequate for the SDS824X HD:SDS824X HD_Square_3.5ns_50MHzYes, this is a perfectly flawless rendering of the square wave with 3.5 ns rise time, as also quite accurately measured by the SDS824X HD. A Look at that picture enables us to predict how an even faster square wave would look; here’s an example for 80 MHz:SDS824X HD_Square_3.5ns_80MHzRight, there’s almost a pure sine left. With just 3.5 ns rise time, we cannot expect anything better.Of course, we can use a faster rise time, like 1 ns, which clearly is a bit fast for a 200 MHz DSO:SDS824X HD_Square_1ns_80MHzOverall, the result doesn’t look bad – it just can’t properly characterize the original signal as the rise time measurement is totally off and approaches that of the DSO itself. The signal shape is just what to expect from a bandwidth limited square wave signal. The amplitude measurement is still pretty accurate though.I hope it is now clear that it’s not the frequency of a square wave, but its rise time, which makes all the difference.Quote from: BRZ.tech on March 12, 2024, 09:45:56 pmI did not watch that video to the end, sorry. The Fourier series for standard waveforms are well-known, so we need no educational video for that.Well, let’s start with the reference again. What does the 80 MHz square wave with 1 ns rise time look on a DSO that is actually fast enough to handle it?Ref-Spec_Square_1ns_80MHzOf course, it all starts with the fact that the square wave itself is far from textbook-perfect. The spectrum contains also even harmonics with a constant level of about -55 dBc, even though there shouldn’t be any at all. We can also see aberrations in the time domain, most obviously a little overshoot, hence we cannot expect a good conformity with the theoretical values.The Fourier series for a rectangular wave is like 2 * A / Pi * (h1 + h3 / 3 + h5 / 5 + h7 / 7 …);In the example above, the amplitude is 0.6 V, so the term in front of the parenthesis is 2 * 0.6 / Pi = 0.38197 Vp;We should now be able to calculate the individual harmonics:h1 = 0.38197 Vp = -11.37 dBV;h3 = 0.38197 Vp / 3 = 0.127 Vp = -20.91 dBV;h5 = 0.38197 Vp / 5 = 0.0764 Vp = -25.35 dBV;h7 = 0.38197 Vp / 7 = 0.0546 Vp = -28.27 dBV;h9 = 0.38197 Vp / 9 = 0.0424 Vp = -30.45 dBV;If we compare this to the Peak Table in the above screenshot, we get the following list:Freq. Calculated Measured Deviation   80 -11.37 -11.535 -0.165240 -20.91 -21.786 -0.876400 -25.35 -28.153 -2.803560 -28.27 -34.581 -6.311720 -30.45 -42.963 -12.513The fundamental at 80 MHz is pretty close to the theory, also the third harmonic at 240 MHz is not too far off. Yet all the higher harmonics are increasingly attenuated. Well, no wonder – the textbook calculates the Fourier coefficients for ideal square waves with zero rise time!What we want to do now, is not comparing a less than perfect square wave, captured with the SDS824X HD, to some textbook theory, but rather with the reference. The outcome is only all too predictable: at 80 MHz the measurement result will be similar, at 240 MHz almost 3 dB too low and drop off pretty quickly at even higher frequencies.SDS824X HD_Square_3.5ns_80MHzYes, the prediction comes true.Freq. Calculated Measured Deviation   80 -11.37 -11.827 -0.457240 -20.91 -24.514 -3.6400 -25.35 -40.954 -15.6Unexpectedly, the level for the even order harmonics is a little bit higher too, with -44 dBc for the 2nd harmonic.Verdict: this is a nominal 200 MHz instrument. The true 3 dB bandwidth is somewhere at 245 MHz, as long as we don’t activate more than two channels at the same time. The specified rise time is 1.8 ns, actually it is better than 1.5 ns. It has been shown that the SDS824X HD can handle pulses with 1 ns rise time, even though it cannot fully characterize them. The comparison of the Fourier series from the textbook with the real measurements was nothing more than a little fun, because in the real world a perfect square wave doesn’t exist.And the most important part: the frequency of a square wave is only important because it also dictates the maximum rise time of the signal. For instance, we cannot have a 200 MHz square wave with just 3.5 ns rise time. Other than that, especially for digital communications, we don’t need excessive bandwidth – just enough to capture the relevant part of the modulation spectrum, which has to be bandwidth limited at the transmitter side anyway. Sections “SPI Speed Test” and “The 200 Mbps SPI challenge” deal with fast digital signals, and as the title already reveals, it is possible to handle 200 Mbps communication with the SDS824X HD – just 245 MHz bandwidth are enough for that.

author: mawyatt
author_rank: Super Contributor
timestamp: March 13, 2024, 07:46:45 pm
content: Quote from: Performa01 on March 13, 2024, 06:30:14 pmNot sure about your results above??A unity +-1 volt square wave has 4/pi as the 1st component and each odd harmonic drops as 1/n.So if the squarewave is 0.3V peak (0.6VPP) then the 1st component h1 is 0.38197V (as stated) and 20Log(0.38197) is -8.359dBV, not -11.37dBV as stated??Edit:And,h3 should be -17.90dBVh5 should be -22.34dBVh7 should be -25.26dBvand so on.Also, think your "n" above should be pi.Am I missing something?Best,

author: gf
author_rank: Super Contributor
timestamp: March 13, 2024, 08:42:55 pm
content: Quote from: mawyatt on March 13, 2024, 07:46:45 pm4/pi is thepeakamplitude. FFT showsRMSamplitude, which is 2*sqrt(2)/pi. I.e. 3dB lower.

author: mawyatt
author_rank: Super Contributor
timestamp: March 13, 2024, 11:21:06 pm
content: Thanks gf, my badBest,

author: Performa01
author_rank: Super Contributor
timestamp: March 14, 2024, 06:36:37 am
content: Quote from: maxwell3e10 on March 12, 2024, 10:58:29 pmOther than the higher end devices (starting with SDS2000X HD), the SDS800X HD does not provide hardware-accelerated acquisition modes for ERES and Average. Math functions are processed way slower in software. The RAW acquisition rate is not affected by this though.Both ERES and Average preserve the sample rate. While not really surprising in case of Average, it means that ERES is implemented in a sliding, non-decimating form.The maximum number of 1024 Averages can be performed in 54 seconds, which is close to 19 averages per second.I don’t know for sure, but assume that it has to be finite time average, because it works with long records as well (I have tried 10 Mpts, where it slows down considerably) and the SDS800X HD doesn’t have 10 Gpts of memory.

author: gf
author_rank: Super Contributor
timestamp: March 14, 2024, 08:45:33 am
content: Quote from: Performa01 on March 14, 2024, 06:36:37 amI guess you rather meaninfinte? Like e.g. an exponential moving average?It is still unclear to me how it averages traces with different trigger point positions (i.e. at differentfractionalsample time)?Quantizing the trigger points to the nearest sample would introduce jitter in the amount of +-1/2 sample.And time shifting the samples of the traces to align them horizontally would imply the need for interpolation.[ If alargenumber of traces are averaged, then it may be an option to quantize, since statisitcally, the trigger point quantization + averaging effectively results in a convolution with the probability distribution of the fractional trigger positions, which is a lowpass filter. ]QuoteERES is just a lowpass filter then. If it happens to be simple boxcar averaging (i.e. sinc frequency response), then it is certainly not a proper anti-aliasing filter for decimation anyway. So it can even make sense to keep the sample rate and not decimate. Can you check the frequency response with ERES? Does it have typical sinc (or sincN) side lobes? Or is it a proprietary filter? If the latter, then ENBW would be interesting too to predict the expected noise reduction.

author: RoGeorge
author_rank: Super Contributor
timestamp: March 14, 2024, 09:43:07 am
content: Quote from: Muttley Snickers on March 11, 2024, 09:58:47 amThere is a plugin/extension for browsers (for Firefox-like browsers the addon is called 'SingleFile'https://addons.mozilla.org/en-US/firefox/addon/single-file/).'SingleFile' can save the entire webpage as a single html offline file, with pics, and it also retains the original links, to click later for the live content of the page. The saved filename can distinguish between forum pages, so it can save distinct pages (the "All" might be too much to continuously scroll, distinct pages are easier to navigate than jumping back and forth in a very long single scroll). Can make highlights or annotations on top of saved pages, cutouts, etc.

author: Performa01
author_rank: Super Contributor
timestamp: March 14, 2024, 11:18:34 am
content: Quote from: gf on March 14, 2024, 08:45:33 amNo, how should I? I’m following a simple logic here by asking myself: how can we compute a moving average if we don’t have a buffer big enough to store all the past records (plus the current one), which would have to be 1024 records in case of 1024x averaging, hence 10.24 Gpts = 20.48 GB of sample memory in case of 10 Mpts records?If on the other hand it is done piecewise, one block of 1024 records after the other, we just need a single counter and accumulators for each sample within a record – 22 bit would be sufficient for 1024x averages of 12 bit samples. Since math channels are limited to 10 Mpts, this requires the equivalent of 20 Mpts (=40 MB) memory, even if 32-bit accumulators are used. That’s just manageable. Consider all four math channels performing averaging at the same time – then 80 Mpts of the 100 Mpts total memory would already be used up.Quote from: gf on March 14, 2024, 08:45:33 amOf course the records have to be fine-adjusted to get their trigger points perfectly aligned. I think in current software generation the user setting of linear or sin(x)/x for the display rendering is used for trigger alignment as well (prior to that it has always been sin(x)/x).That happens all the time anyway, and any acquired record is processed that way, whether it is used to calculate an average or not.It’s also worth noticing that we cannot have a History when the Average acquisition mode is selected in one of the higher end DSOs that support this. The same restriction does not apply for ERES. Yes, of course, we can’t have the History as we know it, when we need almost all the memory for accumulators and counters…Quote from: gf on March 14, 2024, 08:45:33 amSorry, I’m not sure if I can follow you here – I’m neither a mathematician nor a DSP-expert.What do you want to quantize? And the probability distribution of the trigger position correction values can be seen whenever we use Dots display mode. I would expect the probability distribution to be just a straight horizontal line.Quote from: gf on March 14, 2024, 08:45:33 amOf course, ERES is (just?) a LP-Filter, no one has ever claimed otherwise. And yes, it might be just a boxcar filter, see screenshot below with ERES 2.0:SDS824X HD_FR_ERES2.0_2GSa

author: RoGeorge
author_rank: Super Contributor
timestamp: March 14, 2024, 01:33:13 pm
content: Quote from: Performa01 on March 14, 2024, 11:18:34 amMy conclusion (based on how Rigol DS1054Z was behaving, so don't know if this applies to Siglent, too) was that the moving average in Rigol was calculated by averaging the pixels of the screen only, not the raw data, so the buffer size was dictated by the number of pixels on the width of the display.

author: Performa01
author_rank: Super Contributor
timestamp: March 14, 2024, 02:11:20 pm
content: Quote from: RoGeorge on March 14, 2024, 01:33:13 pmWell, that's a whole different world. As alread stated in my previous post, math is limited to 10 Mpts per channel - that's about 10000 screen widths

author: 2N3055
author_rank: Super Contributor
timestamp: March 14, 2024, 03:00:39 pm
content: Quote from: RoGeorge on March 14, 2024, 01:33:13 pmDon't confuse how DS1000Z was doing things.Has nothing to do with that.This is about averaging of data as acquisition mode.It works on full buffer size, from repetitive triggers.If it says 10MPts, it is 10MPts.I presume it is something similar to Continuous averaging as defined by LeCroy..Continuous AveragingContinuous Averaging, the default setting, is the repeated addition, with unequal weight, of successivesource waveforms. It is particularly useful for reducing noise on signals that drift very slowly in time oramplitude. The most recently acquired waveform has more weight than all the previously acquired ones:the continuous average is dominated by the statistical fluctuations of the most recently acquiredwaveform. The weight of ‘old' waveforms in the continuous average tends to zero (following anexponential rule) at a rate that decreases as the weight increases.You determine the importance of new data vs. old data by assigning a weighting factor. The formula forcontinuous averaging is:new average = (new data + weight * old average)/(weight + 1)By setting a Sweeps value, you establish a fixed weight that is assigned to the old average once thenumber of sweeps is reached. For example, for a sweeps (weight) value of 4:Sweep no. ---- New Average1 (no old average yet) (new data +0 * old average)/(0 + 1) = new data only2 (new data + 1*old average)/(1 + 1) = 1/2 new data +1/2 old average3 (new data + 2 * old average)/(2 + 1) = 1/3 new data + 2/3 old average4 (new data + 3 * old average)/(3 + 1) = 1/4 new data + 3/4 old average5 (new data + 4 * old average)/(4 + 1) = 1/5 new data + 4/5 old average6 (new data + 4 * old average)/(4 + 1) = 1/5 new data + 4/5 old average7 (new data + 4 * old average)/(4 + 1) = 1/5 new data + 4/5 old averageetc...That way you only need one buffer for averages accumulation and you grab new capture, recalculate in place and move on to next trigger.

author: gf
author_rank: Super Contributor
timestamp: March 14, 2024, 03:52:37 pm
content: Quote from: 2N3055 on March 14, 2024, 03:00:39 pmWhat you describe is an exponential moving average (EMA), which is an IIR filter (i.e.infinte).Performa01's guess was that SDS800X averaging is stillfinite(FIR). But a true SMA is not possible w/o keeping the complete tail. All you can do with limited memory is to deliver a SMA at a (significantly) lower frame rate than the trigger rate, or to do some approximations which may again involve recursions that make them IIR at the end.

author: Performa01
author_rank: Super Contributor
timestamp: March 14, 2024, 04:06:33 pm
content: Quote from: 2N3055 on March 14, 2024, 03:00:39 pmThanks for pointing out LeCroy's method of processing a continuous Average.Siglent don't have a weighting factor but a "number of averages" instead. Of course, this could be used to derive the weighting factor for continuous averaging.The memory requirement is still high, it still means a maximum of 80 Mpts of memory for 4 channels, assuming that the current record has to be buffered somewhere, for the continuous calculation of the new average.Btw, LeCroy don't offer this as acquisition mode, it's always been a math function.Another pointer might be Siglent's reluctance to provide high numbers of Averages. We have to make do with 1024 (even though this really should be enough for all practical purposes, SDS6000 has 8k), whreas the competition offer up to 64k.

author: maxwell3e10
author_rank: Frequent Contributor
timestamp: March 14, 2024, 04:26:58 pm
content: Some scopes offer simple finite average where the trigger stops after required number of averages, this does not require storing all the data in memory. Other scopes offer history average, which would be equivalent to a simple moving average and limited by total memory. If there are no additional options and the update does not stop after reaching the number of averages, then it must be exponential moving average.The trigger rate must be reduced while it's doing the averaging (or any math operation) or it just skips frames to be included in the average.

author: gf
author_rank: Super Contributor
timestamp: March 14, 2024, 06:58:07 pm
content: Quote from: Performa01 on March 14, 2024, 11:18:34 amThanks for the screenshot.Yes, looks like a 16 tap boxcar filter. The spacing of the zeros is N*125 MHz, is it? (Hard to see exactly on the log scale.)The sidelobes decay too fast for a boxcar filter, but that's certainly caused by the frontend frequency response.So ERES 2.0 obviously means +2 ENOB, while the resolution enhancement is even +4 bits.[ Not exactly +2 ENOB, of course, since the noise floor is not white. ]

author: Performa01
author_rank: Super Contributor
timestamp: March 15, 2024, 08:01:52 am
content: Zoom ChallengeSome folks have the need for a high dynamic range, i.e. the ability to inspect small details in a signal. To accomplish this, they usually increase the vertical gain of the DSO and use the position control to center the region of interest on the screen. This way, even 8-bit oscilloscopes can display some detail – as long as the signal distortions, caused by overdriving the oscilloscope frontend, don’t affect the displayed portion of the signal too much. The distortions are especially bad with general purpose oscilloscopes, as they use the well-known split path input buffer with its problematic overload recovery behavior.Now let’s examine our options with the Siglent SDS800X HD.First, we could try to use the traditional technique in overloading the scope. Without too much thinking, we can just connect a strong signal and then “zoom in” by increasing the vertical gain of the oscilloscope.In the following example we have a 2 Mbps PRBS-signal with 3 V amplitude connected directly, hence a 1x probe factor applies.SDS824X HD_PRBS-4_A3V_V1V_P1Now we try to take a closer look at the pulse tops and increase the sensitivity. This works reasonably well down to 200 mV/div, but at 100 mV/div we hear a relay clicking and the signal gets distorted:SDS824X HD_PRBS-4_A3V_V100mV_P1With a distorted signal like this, it makes no sense to try to look at any details in the signal. So, this obviously is the wrong approach.For most applications, it is not the overload recovery of the semiconductor devices, like clamping diodes and transistors, which cause the problem. The overload recovery time of these devices is usually in the low (or even sub-) nanoseconds and is only really of concern in multi-GHz instruments.Our problem is the clamping in the split-path input buffer, which causes clean clipping in the LF-path, but a differentiation of the waveform in the HF-path. When the clipped LF-path is recombined again with the both offset- and phase-shifted HF-path, the result is heavily distorted and has little similarity with the original signal.Knowing all this, we are able to find a solution: just don’t drive the input buffer so hard that the clamps get activated. Keep the input signal well below 1 Vpp by using 100x probes if necessary. This also has the advantage of a much lower capacitive load at the probe tip and the low noise of the SDS824X HD makes the use of x100 probes unproblematic.The next screenshot demonstrates a 1 MHz square wave with 5V amplitude and a 10 mVpp 40 MHz sine riding on it, using a ten times probe.SDS824X HD_OVD_5V_10mV_P10Yes, the trace is noisy. It would be much better if we could use the 20 MHz bandwidth limiter – but unfortunately, this would also affect the 40 MHz signal we are interested in. Averaging would help a lot, but we want to be able to watch dynamic signals, hence it is not an option either.We can still see the 40 MHz sine clear enough to know it is there – and that for a signal amplitude ratio of 1:500! That’s what a low noise high resolution DSO can do for you…There might be situations, when we just cannot get that low – maybe because the signal levels are so high that the output of even x100 probes would still exceed ~500 mVpp. Then a combination of (moderately!) overdriving the scope and vertical zoom could be the best solution.Consider a 1 MHz Square wave with 5 V amplitude – maybe as output of a x100 probe, so the original signal would be 500V - unbelievable, isn’t it? It could be some 625 watt transmitter – but these wouldn’t output a square wave and hopefully there wouldn’t be any subtle signal details to observe, which would not be better analyzed by using the FFT, but I digress…Here is that familiar 40 MHz sine wave again, riding on the square wave:SDS824X HD_Ref_5V_10mVppFirst step is to increase the vertical gain, i.e. dial in lower numbers, just before the relay would click. We could use the fine adjust to get 102 mV/div (because this is the highest gain we can get without changing the attenuator setting), but this shouldn’t be necessary for now. So we finally end up with 200 mV/div:SDS824X HD_OVD_limit_5V_10mVppWe can already see the little wiggles on the top of the square, it is much smaller than the overshoot and ringing at the rising edge. Yet now we engage the Zoom mode to take a closer look:SDS824X HD_OVD_limit_5V_10mVpp_Z20mV_ERES2.0The above screenshot demonstrates two things: first is the ERES2.0 math trace in the main window, that lets us look at the 40 MHz sine at 10 mV/div. It is ugly, because ERES cannot get rid of the 1/f noise, so there’s no use displaying it in more detail in the zoom window. But secondly, we have the regular trace in the zoom window at 20 mV/div, which is at least as clear as the overdrive zoom before.One more time it should be remembered that we have a signal ratio of 500:1 here.

author: gf
author_rank: Super Contributor
timestamp: March 15, 2024, 03:03:13 pm
content: Quote from: Performa01 on March 15, 2024, 08:01:52 amIt looks like the ERES trace was displayed without persistance.Is that generally not supported for math traces? Or did you just turn it off?

author: Performa01
author_rank: Super Contributor
timestamp: March 15, 2024, 04:10:57 pm
content: Quote from: gf on March 15, 2024, 03:03:13 pmI never use persistence display mode (other than the inherent 1/framerate of the display), except when I explicitely mention it.What you probably see is the vast difference in waveform update rate; the signal traces are updated 6590 times per second in this very scenario, whereas the math trace is much slower, even though it looks fast on the screen. I cannot think of a method to measure the waveform update rate of a math trace - it's probably just a few dozen updates per second at best.I have re-created this test-scenario and enabled 5 seconds persistence this time:SDS824X HD_OVD_limit_5V_10mVpp_Z20mV_ERES2.0_Pers5

author: RAPo
author_rank: Super Contributor
timestamp: March 15, 2024, 05:04:19 pm
content: A bit off topic, but do you know the refresh rate in the x-y plot window (or even better a way to measure it on non-siglent oscilloscope)?Quote from: Performa01 on March 15, 2024, 04:10:57 pm

author: Performa01
author_rank: Super Contributor
timestamp: March 15, 2024, 08:56:13 pm
content: Quote from: RAPo on March 15, 2024, 05:04:19 pmAs you quoted me, I don't know a way to measure it if it is done in software. If it is integrated into the HW, like in the SDS800X HD, we can measure it just like the waveform update rates in regular y-t mode, see the result table in Reply #90 here:https://www.eevblog.com/forum/testgear/sds800x-hd-review-demonstration-thread/msg5360858/#msg5360858

author: maxwell3e10
author_rank: Frequent Contributor
timestamp: March 15, 2024, 09:13:40 pm
content: For measuring how fast the average is calculated one can use this method:https://www.eevblog.com/forum/testgear/scope-with-fast-waveform-averaging/msg4340002/#msg4340002For X-Y plot, I would use two sine waves with 90 degree phase shift at low frequency (say 1 Hz) and set the scope to a fast time scale (say 10 nsec/div). If the display is in dot mode, you would expect a series of dot blotches appearing around the circle. The number of blotches tells you the number of updates in 1 second. Depending on persistence, one could also set a finite number of triggers, so the blotches don't run around the circle and start to overlap.Edit: should still be visible in line mode if the number of blotches around the circle is small, so frequency of sine wave can be increased.

author: tautech
author_rank: Super Contributor
timestamp: March 15, 2024, 09:22:18 pm
content: Quote from: maxwell3e10 on March 15, 2024, 09:13:40 pmNot available in XY mode.

author: BRZ.tech
author_rank: Regular Contributor
timestamp: March 16, 2024, 12:35:08 am
content: Quote from: Performa01 on March 13, 2024, 06:30:14 pmThe frequency as well as pulse response of the SDS800X HD have been presented in some detail in the opening posting (sections “Bandwidth” and “Pulse Response”). Why do you think you need a special frequency response for square waves?...Dear @Performa01,1. You asked me, and you deserve an Answer:In message #175 I asked if you accept “beginners” asking you questions about “obvious things”.In your message #180 you replied: “don’t mind people asking questions here, even newbie questions 😉”On YouTube, on the R&S channel and on the Teledyne LeCroy channel, there are “theoretical videos” on the subject of “square wave excitation frequency response”, in a different way from your presentation. They just don't have the practical part. In summary, they state that the BW of the DSO must be greater than 5x the frequency of the fundamental wave signal.2. In my opinion as a “beginner”, for a non-SIGLENT user (not yet), the fact that it presents the “Bandwidth” of a sinusoidal signal, and “Pulse Response” does not allow us to conclude that the frequency is tolerable with deformations, for the square wave SDS800X, is f=80MHz (photo: SDS824X HD_Square_3.5ns_80MHz).Based on the “Bandwidth” of sine signal, and “Pulse Response”, how did you reach the conclusion of BW for square wave?3. As you demonstrated that for the SDS800X, BW = 245MHz for sinusoidal signal, I just divided it by 5, and asked you to start the test at f=50MHz, and increase the frequency, and you arrived at f=80MHz with a “square wave” (“photo: Ref-Spec_Square _1ns_80MHz”), which 80 x 3 = 240MHz…The SDS824X HD managed to faithfully display the “1 fundamental”, the “3 harmonic” and the “5 harmonic”.The richness and detail of your analysis is impressive... Maybe someday I will be able to repeat your essays, to learn many things. Unfortunately, not everything is as obvious to me, as it is to you and other colleagues working on the topic.4. As for the video by “Professor Michel van Biezen”, for experts, the issue comes down to just the photo at the beginning of the video… the equation and the Fourier Series Coefficients.In my “beginner” analysis, it doesn’t matter much if the theoretical equation doesn’t support a square wave signal of 1ns risetime…Note that the objective is didactic, and may contain an error, for example of 20%, in practical measurements in relation to theoretical calculations… In HAM, we are not so orthodox in relation to the perfection of comparing measurements…I think it's better to start with 20% error, and aim to reduce this number a lot. But I really appreciate your orthodoxy, and your method of analysis. Maybe someday I will be able to understand almost everything you taught, and teach some beginners in the HAM universe, and I will cite you as a source.5. As for the Fourier Series, you learned another formula that I had never seen. This Fourier Series formula has many ways to learn it.TKS.Having observed your comments, it is still not possible to understand whether the “Fourier Series Coefficients” should be placed in Vp, Vpp, Vrm, or something else.Request: Even if it contains errors greater than 20%, as there is no perfect square wave, if you can assemble and present an equation of the Fourier Series, with f=80MHz, of the square wave, I will be very grateful. As in the formula presented in the video by “Professor Michel van Biezen”.6. In the photo: “Ref-Spec_Square _1ns_80MHz”, in the “Peak Search Table”, in “Marker 6” it has f=880.00000MHz. I said here that it has “8 digits”, but you repeatedly state that the SDS800X has “7 digits” in the Counter. Do you count from “0 to 7”, or from “1 to 8”?7. After your “class”, I agree with you that the “Risetime” is the starting point for buying an AWG, and “the good one is the 1ns”, but it is the top of the line, and is far above of my hobby budget.TKS.73.

author: gf
author_rank: Super Contributor
timestamp: March 16, 2024, 09:42:35 am
content: Quote from: BRZ.tech on March 16, 2024, 12:35:08 amThe bandwidth, wich is just a single number, is indeed insufficient (unless you make some additional assumtions), but the impulse response defines a LTI system completely1). Particularly for a square wave signal, the impulse response (or the step response2)) gives you a good idea what defomations of the square wave edges you have to expect. The top and the bottom of a low-frequency square wave are flat anyway, so the key is the deformation of the edges. Only at high frequencies, the deformation of the rising and falling edges begin to overlap and add up. Then it is no longer so obvious what the exaxt shape will be. Still you can calculate it from the impulse response. The old question what bandwidth is enough for displaying a square wave cannot be answered in general. It is up to you what YOU consider "good enough" (or good enough for a particular use case). You just need to be aware that what you see is never the reality. This applies whenever you measure anything.EDIT:1)If you know the impulse response of a linear system, then you can calculate the response toanyinput signal.2)Note that the step response is just the integral of the impulse response, so each one can be derived from the other.QuoteIt is just a matter of scaling/normalization. You can re-write the Fourier series equation in terms of peak, peak-to-peak or RMS values for the coefficients.FFT on the scope is usually normalized to display RMS values, and it does not display positive and negative frequencies of the raw DFT spectrum separately, but displays only the combined power of positive and negative frequencies.Also note that FFT on the scope displays only the magnitude, but not the phase. However, the amplitude of the peaks in the displayed FFT outputis not sufficientto derive the sin() and cos() coefficients of the Fourier series for anarbitraryperiodic signal. In order to separate sin() and cos() coefficients for the same frequencyyou need phase informationas well.

author: gf
author_rank: Super Contributor
timestamp: March 16, 2024, 10:52:16 am
content: @Performa01, please let me ask two more questions regarding averaging:1) I wonder what happens if an averaged trace is displayed in dots mode? Are the averaged dots now evenly spaced with 1/sample_rate interval, or do they still retain fractional horizontal positions? [Particularly when a large number of traces are averaged.]2) I think to rememer that you (or was it somebody else?) did demonstrate in a different thread that FFT(average(Cx)) resulted in a higher FFT sample rate than the original sample rate of Cx, on either the SDS2000 or SDS6000 (don't remember which one). Obviously the signal was implicitly up-sampled/interpolated to a higher rate. I wonder if the same applies to the SDS800X?

author: Martin72
author_rank: Super Contributor
timestamp: March 16, 2024, 11:28:23 am
content: Hi,It was at the 2000xplus:https://www.eevblog.com/forum/testgear/math-problems-on-sds2k-(trying-to-display-bandwith)/msg4174879/#msg4174879

author: RAPo
author_rank: Super Contributor
timestamp: March 16, 2024, 02:19:56 pm
content: Thanks, that is a clever method (if and when there is a dot mode on the xy-plot window).Quote from: maxwell3e10 on March 15, 2024, 09:13:40 pm

author: rf-loop
author_rank: Super Contributor
timestamp: March 16, 2024, 03:20:27 pm
content: Quote from: gf on March 16, 2024, 10:52:16 amHere, Dots, Persistence and Average 256 so there can see that samples have been in all possible fractional positions (here sample interval 2ns)Ch3 and Ch4 on only for drop samplerate (traces out of screen)mathNote that math trace in wfm/s is slower than channel direct wfm/s

author: Martin72
author_rank: Super Contributor
timestamp: March 16, 2024, 04:56:41 pm
content: Quote from: gf on March 16, 2024, 10:52:16 amUnlike the SDS2000xplus (at that time, this may have been fixed), the 800X HD "sticks" to the entered interpolation coefficient, in this example 20 (40GSa/s).

author: gf
author_rank: Super Contributor
timestamp: March 16, 2024, 05:01:58 pm
content: Quote from: Martin72 on March 16, 2024, 04:56:41 pmThanks! Good that it honores the requested upsampling factorEDIT:But I wonder how it can do a 16k point FFT @40GSa/s if the captured record length is only 200 points? 20x interpolation gives only 4000 point, which is less than 16k.[ Theoreticaly it would be possible to window the 4000 points and then zero-pad to 16k before invoking the FFT. This would result in an interpolation in the frequency domain. But that's just speculation]But I actually meant FFT(Average(Cx)), without d/dx or explicit interpolate in the formula.IIRC, it did interpolate, too, although not explicitly asked to do it.

author: Performa01
author_rank: Super Contributor
timestamp: March 16, 2024, 09:40:01 pm
content: Quote from: BRZ.tech on March 16, 2024, 12:35:08 amYes, you are right. I might have just been a bit surprised. Since this is a “Review & Demonstration” thread for a specific digital oscilloscope, I expected a newbie-question in this context to be from someone unfamiliar with Siglent scopes – or even digital scopes in general, so I was prepared to deal with DSO specifics, but not with basics of signal theory and Fourier series for imaginary signals that can never exist in the real world.Quote from: BRZ.tech on March 16, 2024, 12:35:08 amWell, I don’t think much of such videos. Firstly, we need not tell serious users of an oscilloscope what bandwidth they require for displaying a square wave, and even more importantly, there’s no use in telling some street number like “5 times the square wave frequency”. Because it is simply not correct.Quote from: BRZ.tech on March 16, 2024, 12:35:08 amRise time is the key and I’ve demonstrated it. Here is how I would deal with it on a theoretical basis:We were talking about the SDS824X HD, an oscilloscope whose bandwidth has been measured to be about 245 MHz. There is the well-known formula to estimate rise time from bandwidth:tr = 0.35 / 245 MHz = 1.43 ns.The SDS824X HD is specified for 1.8 ns (which it probably has if more than two channels are active), yet with just a single channel, I had estimated its rise time from my measurements as ~1.5 ns and the formula tells us that it might actually be even a tad lower than that. For the ease of use and the sake of this exercise, let’s just continue working with the initial assumption of 1.5 ns.We can calculate the total rise time tr from the signal rise time trs and the scope frontend rise time trf:tr = √(trs² + trf²);The error would then be: err = (tr / trs - 1) * 100 [%];Rewriting this formula to get the permissible signal rise time for a given error margin leaves us with:trs = √(trf² / ((err / 100 + 1)² - 1));How big an error are we willing to accept?1%? Then the signal rise time should not be faster than 10.6 ns.2%? Then the signal rise time should not be faster than 7.5 ns.5%? Then the signal rise time should not be faster than 4.7 ns.10%? Then the signal rise time should not be faster than 3.3 ns.15%? Then the signal rise time should not be faster than 2.65 ns.20%? Then the signal rise time should not be faster than 2.26 ns.Or we don’t care? Then everything is fine, as long as at least the fundamental frequency does not exceed the bandwidth of the DSO.I’ve always used the spectrum of a signal to decide how much bandwidth is needed to get a faithful reproduction on the DSO, just as I’ve demonstrated it in my earlier post with the 3.5 ns rise time square wave. Once again, it’s up to the user to decide what level of harmonics needs to be within the acquisition bandwidth. And of course we cannot accurately determine the expected error from this, but with some imagination and experience, we can know what we really need, also depending on the task on hand.I have already pointed out that in digital communications we never had any bandwidth to waste, so all the digital modulations always really transported more or less distorted sine waves, which only get converted back into square waves within the receiver.Quote from: BRZ.tech on March 16, 2024, 12:35:08 amI’ve shown the two extremes. First, the benign and still fairly accurate 3.5 ns, where we can expect an error of max. 8.8%. Second, aggressive 1 ns rise time with up to 80% error. The actual errors were lower, partly because the rise time of the SDS824X HD is a little faster than the 1.5 ns that we’ve assumed here. Anyway, we could define a “square-wave-bandwidth” only if we have a clear error margin in mind. The 80 MHz square wave with 3.5 ns rise time was rendered perfectly okay by the SDS824X HD, even though it looked pretty much like a sine. Yes, there are irritations, because some folks probably expect to get a trapezoid waveform instead of a sine, and that is actually where the bandwidth limited square wave collides with our imagination. But how do you define aberrations in the expected shape of a signal edge? As a consequence, I would say the signal rise time is the more readily available and less complicated metric.Quote from: BRZ.tech on March 16, 2024, 12:35:08 amI have to admit that I have difficulties understanding what you actually want. In a previous post you wanted me to show how the Fourier coefficients of the DSO measurements match the theory shown in that video, now you claim that accuracy doesn’t matter for you.Quote from: BRZ.tech on March 16, 2024, 12:35:08 amWell, in practice me at least do not deal with instantaneous time-domain values like cos(ω * t), but with harmonic signal levels from the frequency domain.Quote from: BRZ.tech on March 16, 2024, 12:35:08 amIn my example it has quite obviously been a mixture of all. The formula, which originally includes 4 times the peak value (which is actually half the amplitude) as first term, has been simplified by me by using double the amplitude instead. It goes without saying that the amplitude of an ideal square wave is identical with its peak-to-peak value, hence Vpp. The Fourier coefficients are still related to half the signal amplitude; hence they are peak values, which I have clearly stated in my article (Vp). Finally, I have converted the peak values to dBVrms. Yes, I’ve just written dBV, because dBVrms happens to be the only dBV unit available in Siglent DSOs (and many others).Quote from: BRZ.tech on March 16, 2024, 12:35:08 amSorry, I honestly don’t know what you want. The equation for a Fourier series looks always the same, no matter if it is for 1 kHz or 80 MHz.Maybe someone else can chime in, because I personally am at my wit’s end. All I can do now is strongly recommend that you stop fixating on that video.Quote from: BRZ.tech on March 16, 2024, 12:35:08 amYes, the math might show more digits in order to provide more resolution for detailed analysis, but that is not necessarily accurate in absolute terms.What I am referring to is the always visible trigger frequency counter in the top right corner of the screen. This is the closest thing to a real frequency counter and it has class-leading 7-digits resolution, albeit only pretty average 25 ppm absolute accuracy.Quote from: BRZ.tech on March 16, 2024, 12:35:08 amOnce again, I’m not sure to understand you. While it is obvious that it’s quite nice to have a professional grade AWG that can deliver fast rise time signals, this is a completely different topic. I was always trying to get the message through, that a square wave should be primarily judged by its rise time and not frequency, even though – and this once again is something I’ve already stated – the two are somewhat related. A square wave at 240 MHz just cannot have a rise time significantly slower than 1 ns.The actual message is: on a SDS824X HD you can faithfully reproduce a 50 MHz square wave with 3.5 ns rise time, while you are not able to do the same with a 1 kHz square wave that has 1 ns rise time - even though the scope-bandwidth is 245000 times the square wave frequency!

author: ebastler
author_rank: Super Contributor
timestamp: March 16, 2024, 09:51:38 pm
content: Quote from: Performa01 on March 16, 2024, 09:40:01 pmI think I know where the misunderstanding lies. Let me try to paraphrase:Performa01's message is: When considering how well you canobservea given square wave, it's the risetime which counts, i.e. which is the critical parameter (and not so much the frequency). Whereas BRZ might have misunderstood it as: When considering how to bestgeneratea square wave, aim for the generator with the fastest risetime.The latter is a misinterpretation. In fact, I would say one should avoid faster-than-necessary risetimes in many cases, due to the problems in signal propagation and detection which the high-frequency components bring. (As discussed by Performa01 in the context of the challenges they bring when observing square waves on an oscilloscope.)

author: Performa01
author_rank: Super Contributor
timestamp: March 16, 2024, 10:03:09 pm
content: Quote from: gf on March 16, 2024, 10:52:16 amYes, they retain fractonal positions, as rf-loop has nicely demonstrated. Yet as we already know, Average as a math function is not so fast and we have to make do with about 19 averages per second, whereas the original signal trace is orders of magnitude faster.Quote from: gf on March 16, 2024, 10:52:16 amI personally have never used FFT(Average(Cx)), because it doesn't make sense to me. Tests have shown that it makes matters much worse in case of weak signals, because removing all the noise also prevents all the implicite or explicite resolution enhancement techniques from working. Not to mention the fact that we could only watch static signals with that anyway.I've just tried it now and quite unsurprisingly, it does not change any sample rate and I'm pretty sure it never did.Also Interpolate() always worked correctly. It was the Derivative() in conjunction with Interpolate(), which resulted in too high numbers as sample rate in the FFT - but that was only observed in the SDS2000X Plus, not in any other Sglent SDS model.

author: BRZ.tech
author_rank: Regular Contributor
timestamp: March 17, 2024, 01:07:20 am
content: Quote from: Performa01 on March 16, 2024, 09:40:01 pm

author: Bad_Driver
author_rank: Frequent Contributor
timestamp: March 17, 2024, 08:39:51 am
content: Dear Performer01thank you very much for the many very insightful explanations and tips on using the SDS800.I have to admit to my shame that I am also doing many things for the first time and understood that I have never found or used on my SDS2000X+, which has been on my desk for 4 years.

author: Performa01
author_rank: Super Contributor
timestamp: March 17, 2024, 10:58:06 am
content: FFT-SetupLike all Siglent DOSs, starting with the venerable SDS1202X-E, the SDS800X HD have a very useful FFT implementation. To get the most out of it, we should be able to set it up correctly.The FFT-length in the SDS800X HD can be up to 2 Mpts. This enables low resolution bandwidths and low noise, but it's still “only” a 12-bit DSO, hence results below -73 dBFS shouldn’t be trusted blindingly. In many cases, the usable dynamic range with decent accuracy can be up to 100 dB though.Some hints for proper setup of the FFT on Siglent DSOs in general and the SDS800X HD in particular:FFT-Bandwidth and RBWThis is quite different to a traditional SA (spectrum analyzer). There is no menu for the resolution bandwidth and also no direct setting for the FFT-bandwidth, even though we have a menu item for the horizontal display parameters, i.e. start/stop frequencies for wideband measurements and center frequency/span for narrowband applications. But this is just for zooming into a longer FFT result; for best speed and lowest RBW (resolution bandwidth) we need to make sure that no high zoom factor is required to get the desired display. The following rules apply:• The analysis bandwidth (FFT-BW) is always half the FFT sample rate (FFT-SR).• The frequency step Δf is the sample rate divided by the number of FFT points.• In the Acquire menu, a constant sample rate can be set in order to also limit the FFT-sample rate.• The resolution bandwidth (RBW) is the frequency step multiplied by a factor specific for the window function in use.The maximum number of FFT points can be up to 2 Mpts, but it also depends on the record length, which increases with slower time base settings, which in turn might be limited by the maximum memory as defined in the Acquire menu. Apart from that, the number of FFT points can be further limited by the corresponding setting in the FFT-Config menu.RBW = Δf * k, where k is the 3 dB bandwidth factor in bins, depending on the window function:k: Rectangle 0.99, Blackman 1.74, Hanning 1.62, Hamming 1.64, Flattop 3.73.Blackman and especially Flattop are the most universal and useful window functions in practice. You definitely should stick to these two as long as you cannot prove that some other window would actually work better in your specific application.Thus: Δf = RBW / 4 (rounded) in case of the flattop window or RBW / 2 for Blackman.To get the proper settings for any given FFT-BW and RBW pair, proceed as follows:Determine the FFT sample rate: SR = FFT-BW * 2 [Sa/s];Determine the number of FFT points: FFT-pts >= SR / Δf ;Determine the time base: TB >= FFT-pts / SR / 10 [s/div];As mentioned earlier, you can lower the FFT-sample rate by setting a constant acquisition sample rate; this can be useful when you want really low FFT-sample rates but do not want to use very slow time base settings, which would slow down the acquisition considerably.Setting up the FFTEven from the best FFT implementation, we can only expect good results as long as the scope has been set up properly for that specific task. How many so called “reviews” have we seen where FFT has been engaged and some scope settings randomly altered just to get a halfway plausible but actually not very meaningful FFT graph, which was then either praised or criticized?Of course we can get away with some quick & dirty setup if the requirements are low, but even then we should never ignore the most important parameters like FFT bandwidth, which should always cover the full signal spectrum, otherwise aliasing artefacts could easily spoil our measurement results.For optimal speed, frequency resolution and dynamic range, we need to put a little more effort into a proper setup, which has quite different requirements compared to the usual Y-t view (aka time domain). Below there is a complete checklist how to properly set up the DSO for analysis in the frequency domain (most of these topics should be obvious, but still listed for completeness):1. Set acquisition mode to normal. Use ERES only for a good reason and stay away from average. Avoid Peak Detect under all circumstances and without any exception!2. Use edge trigger in auto mode to make sure signal acquisition doesn’t stop even when the signal amplitude drops below the trigger sensitivity. FFT doesn’t require a stable trigger, so you can also use AC-line trigger for that.3. Determine the lower bandwidth limit for the FFT analysis. If it is >10 Hz, use AC-coupling for the input channel to ensure maximum dynamic range even with large DC offsets and/or high input sensitivities. If DC-coupling has to be used, use the vertical position control to compensate for any DC offset, so you can optimize sensitivity, hence get the highest dynamic range.4. Determine the upper bandwidth limit for the FFT analysis. In order to avoid aliasing artifacts, this should not only cover the desired analysis bandwidth, but include the highest expected input frequency. In general, it’s best to start with a higher upper bandwidth limit and reduce it only after it has been confirmed that there is no significant signal content above the desired final limit.5. Choose the frequency step size according to the explanations given earlier in this article, which would be about one quarter of the required resolution bandwidth when using the Flattop window.6. Find an appropriate set of horizontal time base setting and the number of FFT points; refer to the explanations given earlier in this article. You should watch the displayed FFT parameters while altering the time base and double check that they match your expectations. Be aware that the desired resolution bandwidth might not be achievable due to the limited choice of sample rates and FFT lengths and/or the maximum specified FFT length of 2 Mpts.7. Engage FFT mode, select the correct source channel and start with Split Screen mode.8. Set the vertical gain so that the peak amplitude of the input signal is between ±2 to ±4 divisions.9. Set the horizontal FFT display parameters according to the bandwidth you want to display and select linear/decade mode for the frequency axis. Decade is advantageous for wideband measurements, whereas linear is best for narrowband applications.10. Set the vertical FFT display parameters, i.e. the desired level units (dBV or dBm, forget volts!) and make sure the external load impedance matches reality whenever working with power levels, i.e. dBm. Set the reference level and vertical scale so that the FFT amplitude range of interest makes best use of the available screen space.11. Setup (at least) automatic peak-peak measurement for the input channel. During frequency domain analysis, especially in Exclusive mode, keep an eye on the Vpp measurement for the input channel to make sure no overload occurs.12. Make sure the desired window function is selected.Hint: stay in Split Screen mode until the amplitude setup is finished and the levels are reasonably stable, then switch to Exclusive mode. By keeping an eye on the peak-to-peak measurement of the input signal, you can still detect an overload condition instantly; the scope indicates that by displaying > instead of = in front of the measurement value.Example:Pk-Pk >851.875mVinstead ofPk-Pk 755.000mV.FFT Window FunctionsFor the ones who try to understand the consequences of certain settings in the FFT analysis – this is about the window functions.Why are there so many different windows (only few of them available on the SDS oscilloscope)? What is the best window to use?There have been times when processor systems haven’t been nearly as powerful as today. Non-RISC architectures with just 1 MHz clock frequency and less than 1 kB RAM were not uncommon during the seventies of last century. Instruments that could compute a FFT at all have been rather exotic, and FFT-lengths like 64 points were quite common. In the light of this, there is no wonder that less than ideal FFT-window functions optimized for certain tasks were popular.Sometimes there are descriptions about the benefits and drawbacks of the various window functions, yet most folks would rather not care and want a universal setting that works for them every time. Just like with a traditional SA (spectrum analyzer) with analog RBW (resolution bandwidth) filters in the final IF (intermediate frequency) path. And fortunately, there is one…There are several features of a window function, and two of them are amplitude accuracy and resolution bandwidth. If we look at just these two properties, then the rectangle window would have the narrowest resolution bandwidth but the worst amplitude error, whereas it’s just the opposite for the Flattop window.So, whenever we need the best frequency resolution, we just sacrifice a bit of accuracy and use the Rectangle window?It’s not that simple. An FFT divides the entire analysis bandwidth into frequency bins. If, for instance, we have an FFT-length of 32768 points, then we get 16384 such frequency bins and at an effective sample rate of 2 MSa/s, each of them will be 61.04 Hz wide. In this case, 61.04 Hz is the bin width and the bin spacing at the same time. The center of a bin will always be an integer multiple of the bin width.Now FFT-windows behave differently, depending on the offset of the input signal frequency from the bin center. I did a selectivity test for the various window functions available on an SDS800X HD and used the before mentioned parameters:FFT-sample rate = 2 MSa/sFFT-Length = 32768 ptsBin-width = 61.03515625… HzThe test will be for amplitude accuracy and the -20 dB, -40 dB and -60 dB selectivity. I define the latter at the frequency distance for a -20, -40 or -60 dBc signal to still produce a visible 3 dB peak in the spectrum (and not drowned out by the leakage of the neighboring o dBc reference signal).The -3 dB bandwidth might be most important for characterizing the passband of any two-port network, but for a filter, where the selectivity is the main concern, the bandwidth at a useful attenuation is even more important.The metric of a filter shape factor exists, which is usually defined as the ratio of the filter bandwidth at -60 dB and -6 dB. The shape-factor might even be the most important property of any RBW filter at all, because it ultimately defines selectivity. Consider what a proper BP (Band-Pass) filter, as it might be found in any traditional SA, looks like:Ref-BP_Cheby9_0.2dBThis is a 9th order Chebyshev BP filter with 0.2 dB passband ripple. It has a -3 dB bandwidth of about 10 kHz and less than 16 kHz bandwidth at -60 dBc. The 3/60 shape factor is thus ~1.57. The lower the shape factor, the higher the selectivity.What does it mean in practice? We can distinguish a strong signal at 0 dBc together with a weak signal at -60 dBc next to it, as long as the distance is at least ~13 KHz, i.e. 1.3 times the RBW. That is excellent and makes for a useful analysis in the frequency domain.An FFT is quite different to a classic continuously swept spectrum analyzer. If we feed a stable sine wave into a swept analyzer, we’ll get the frequency response plot of the RBW-filter.The FFT doesn’t plot a continuous filter response, but simply shows the outputs of the individual frequency bins, and ideally only the one bin covering the input frequency responds with the correct amplitude (and phase, but that’s not displayed). It is like a huge filter bank with a bunch (16384 in our next example) of filters, all working in parallel. What we see is different from the RBW-filter response; we rather see the “leakage”, i.e. signal outputs from neighboring “filters” (bins), sometimes even far away from the signal frequency - and there are amplitude errors for the main bin.A 0 dBm test signal of 499.99342 kHz has been used for the first test, which is equivalent to precisely 500 kHz if the time base of the SDS800X HD were accurate. this is precisely 8192 times the bin width, hence the exact center of a bin.What do we get?Window Ampl. Selectivity  -20 dB -40 dB -60 dBBlackman 0.0 236.58 236.58 236.58Flattop 0.0 366.58 416.58 416.58Hamming 0.0 168.58 168.58 168.58Hann 0.0 171.58 171.58 171.58Rectangle 0.0 98.58 98.58 98.58Look at the rectangle window, with two signals, the 0 dBm reference signal (carrier) and the 2nd signal at -40 dBc (with an enormous amplitude error of 2.8 dB), which creates just a 3 dB peak at a distance of 98.58 Hz, as an example:SDS824X HD_FFT_Rectangle_0.0_S40dB_500092HzWith a distance of just 1.615 bin widths, selectivity is quite good. Yet real-world signals will usually not be an exact integer multiple of the bin-width, so we need more tests.In any practical application where the FFT of a general-purpose oscilloscope is to be used, we cannot freely define the signal frequencies, hence they will be more or less off center. Even if we could select a frequency, most related signals like intermodulation (mixer) products and spurs can still have any frequency offset with regard to the bin spacing. Consequently, we need to take the worst case into consideration, that is a frequency offset of half the bin-width.A 0 dBm test signal of 500.02394 kHz has been used for the following test, this is precisely 8192,5 times the bin width, hence the exact bin-border for my individual sample of the SDS824X HD.Window Ampl. Selectivity  -20 dB -40 dB -60 dBBlackman -1.0 206.06 266.06 426.06Flattop 0.0 386.06 386.06 451.06Hamming -1.8 196.06 196.06 -Hann -1.3 203.06 326.06 586.06Rectangle -3.8 381.06 2780.06 -This looks very different, doesn’t it? All of a sudden, the rectangle window has 3.8 dB amplitude error and its selectivity isn’t all that good anymore. In fact it is unbelievable >45 bin-widths for the -40 dBc selectivity! By contrast, the Flattop window hasn’t changed at all: the amplitude error is effectively zero as it was before and also the selectivity has only marginally changed. That means more than -60 dBc attenuation at 300 Hz (less than 5 bins) distance from the center.Hamming does not have a 60 dB attenuation within a reasonable bandwidth – in fact it is so wide that I could not be bothered to measure it. The same applies to the Rectangle window, where the -40 dBc selectivity test didn’t reveal anything useful:SDS824X HD_FFT_Rectangle_0.5_S40dB_502800HzWhat do we want for a proper RBW filter for spectrum analysis, in order to get serious and accurate measurements?1. High dynamic range. We have no use for a RBW filter that has no proper stopband attenuation, hence picks up all the garbage from the neighborhood.2. Fast transitions into the stopband, which is equivalent to a low shape factor.3. A reasonably flat passband without massive amplitude errors, as soon as the signal frequency gets off center a bit.4. And most importantly, all these parameters shall be constant and independent of the exact input frequency.The only window that appears to be perfect in almost all regards is the Flattop window. It has a very high dynamic range, low shape factor, a totally flat passband, and even more important, its properties remain constant and do not depend on the signal frequency. Only downside: it has the widest bandwidth of all candidates. Yet in modern equipment, where at least 1 Mpts FFT have become standard, we need not desperately look for a windows function that sacrifices a lot of good properties just for a little narrower RBW.Blackman is the only alternative that I can recommend from the selection in the Siglent SDS800X HD. It has less than half the RBW of the Flattop window and the shape factor is still reasonable. It works down to -60 dBc even with the worst-case frequency offset of half a bin width, and the passband flatness, hence also the amplitude error, is not too high. This is generally true for all window functions of the Blackman-family, especially Blackman-Harris. Siglent only implements the original Blackman window though.You can take a look at all the remaining window functions in the attachment, albeit only for worst case frequency offset, indicated by “0.5” in the file name.

author: ebastler
author_rank: Super Contributor
timestamp: March 17, 2024, 11:28:30 am
content: Brilliant, thank you Performa01!You should really think about converting this material into a (PDF?) booklet -- an "Application Guide to Digital Oscilloscopes" or such. Maybe something Siglent could fund, and distribute as either a separate document or merge into the user manuals?As a short-term step, would it make sense to reorganize the "table of contents" in the initial post? It is currently organized chronologically. But since you have re-visited some topics over time, and the total amount of material is becoming too much to grasp even the whole TOC at a glance -- could the links to the individual posts be grouped into a few larger topic areas? I am not sure what that meta-structure would best look like. Maybe start with basic horizontal and vertical settings and performance, move on to measurements/cursors/math, then specific application areas?In any case -- thank you again for the huge effort you have and continue to put into this thread. I have not seen anything like it, anywhere and on any scope!

author: iMo
author_rank: Super Contributor
timestamp: March 17, 2024, 11:52:05 am
content: I wonder why that hints above cannot be somehow suggested to the user by the o'scope itself. It cannot be such a rocket science to implement those into the o'scope's system. Simply navigate the user with short messages with above hints when he/she messes up with the settings in a suboptimal or even wrong way..

author: Grandchuck
author_rank: Super Contributor
timestamp: March 17, 2024, 11:59:12 am
content: Many thanks to professor Performa01 for bringing us oscilloscope university.

author: gf
author_rank: Super Contributor
timestamp: March 17, 2024, 01:58:46 pm
content: Quote from: Performa01 on March 17, 2024, 10:58:06 amWell, the -3dB bandwidth of a rectangular window is always about 0.884*Δf, which is about 54 Hz for the given parameters.The root cause why youmeasurea horribly wrong value of 6.4 Hz is thelinear interpolationbetween adjacent frequency points, which is not appropriate here. With a proper sinc interpolation you would see the true shape of the window function's frequency response and measure the correct bandwidth. In the time domain, you would not sample a sine wave signal with (say) 2.3 points/period either, interpolate the samples linearly and expect that you can still recognize it as sine wave. But the same happens here in the frequency domain. The scope fools you by connecting the frequency points (which are correct) with straight lines. It is important to be aware and not to trust these straight lines blindly.

author: mawyatt
author_rank: Super Contributor
timestamp: March 17, 2024, 04:37:50 pm
content: Quote from: gf on March 17, 2024, 01:58:46 pmGood catch, it "looks" like 64Hz as we didn't spot the decimal point!!Linear interpolation of sparse data, one should expect errors, some cases significant with interpolated results. This was the limiting dynamic range in SPICE like Time Domain simulations even tho SPICE utilized quadradic interpolation, and why in 80s we developed a version that "forced" the simulation at exactly the proper times with a-priori knowledge of the expected post FFT implementation. Doing 2-Tone IMD of ultra-linear systems reveled the SPICE limitations, later Cadence picked up on this.However, this certainly doesn't take away from the superb efforts of Performa01 which really shows the incredible versatility of these Fine Instruments when in the hands of a MasterAnd we "discredit" these as just DSOsBest,

author: radiohomebrewer2000
author_rank: Contributor
timestamp: March 17, 2024, 04:56:15 pm
content: If someone comes up with a guide for the SDS800X HD scopes like the material that Performa1 has been provided with explanations on how to do them as well, I would buy this book. Seriously.I have looked at the documentation for the SDS800X HD series ahead before it is delivered so I can some idea of what to expect. But, the documentation is very terse. Maybe I am just used to the manuals (spoiled) for my commercial ham radios from companies like Kenwood, ICOM, Yaesu that provide very good manuals with their ham radios.Again, I am willing to buy a book for US$50 for more.

author: mawyatt
author_rank: Super Contributor
timestamp: March 17, 2024, 05:02:27 pm
content: Didn't you already "Buy the Book", and the SDS814 was just the "Special Promotion"That's how we "Explained" it to our "CFO/CEO"Best,

author: tszaboo
author_rank: Super Contributor
timestamp: March 17, 2024, 05:25:25 pm
content: OK, so I had a go at the Bode plot module. This is a SDS800HD together with a SDG1000X measuring a current transformer-opamp module called ZMCT103C. I was interested in it's transfer function (the current transformer is 1:1000 turns )The setup only requires a BNC-BNC cable and a BNC-Crocodile cable and a resistor, everything else comes with the instruments. CH2 on the AWG is set to tracking mode, no other settings are necessary on the AWG. The scope is connected to the AWG with a USB cable, it recognized it automatically, CH2 of the AWG is connected to the scope. Other than that, I just had to enter the frequency range, and the number of points, set up the channels.One thing I noticed that the Bode plot will measure 3 outputs if set up, that's a nice touch that doesn't really cost anything. It would be nice if the save button would work in the bode plot menu, but now it does nothing and the save location has to be entered manually. Overall I'm very satisfied with this setup, and the capabilities of both the scope and the AWG so far.

author: Performa01
author_rank: Super Contributor
timestamp: March 17, 2024, 05:57:09 pm
content: Quote from: gf on March 17, 2024, 01:58:46 pmThank you for pointing this out. Something isn’t quite correct and I will definitely look into this and try to come up with a test that documents the practical usefulness of the various window functions and also passes under the strict eyes of our Guru “gf” at the same time 😉

author: electronics hobbyist
author_rank: Regular Contributor
timestamp: March 19, 2024, 08:57:42 am
content: Thanks a million to professor Performa01.This review book is so great, so I translated it into Chinese and published it on Zhihu (similar to Quora), and I have only completed 20% so far.The main purpose is to learn for oneself, and it would be even better if other people could also learn about these oscilloscope knowledge.If you feel it's not suitable, I will hide it.Thank you again.The following English image is translated from Chinese to English through Google.

author: Performa01
author_rank: Super Contributor
timestamp: March 19, 2024, 11:52:24 am
content: I have revised the FFT-Window article, which should now convey my points without major inaccuracies.Quote from: ebastler on March 17, 2024, 11:28:30 amThank you very much! I have planned to make this available as a PDF document sooner or later. In fact, I’m already working on it and this will of course be better organized. Since I don’t want to create updates all the time, I’ll wait until I’ve got the feeling that I’ve reached a consistency point, the inspiration for new articles fades a little, and this thread has settled a bit.EDIT: forgot to answer the 2nd part of your suggestion:Regarding the reorganization of the current TOC, this makes not much sense, because I’ve initially reserved a number of posts where I cramped as much content as possible into every single posting, and these cannot be grouped in a different way anymore. The idea was to have all the information all in one place so that it can be found easily.When I ran out of reserved postings, I realized that it doesn’t matter much where the postings are within the thread, as long as we have an overview with that table of content in the OP.

author: gf
author_rank: Super Contributor
timestamp: March 19, 2024, 01:34:05 pm
content: Quote from: Performa01 on March 17, 2024, 10:58:06 amSorry if I disagree again, with this statement. There is not really a difference. Like the SA, the FFT also shows the filter resonse, centered at the frequency of the sine wave stimulus frequency. But the FFT does not plot the continuous filter resonse, but it samples the filter resonse at discrete frequency points (-N/2...N/2-1)/N*sample_rate. And the result of the FFT areonly the frequency domain samples. And that's where all the confusion comes from. Mentally we are not able to reconstruct the continuous filter response from the samples (although the reconstruction can be done mathematically), and connecting the samples with straight lines gives a wrong impression either.The blue curve in the attachments is the continuous frequency response of a rectangular window function. And the three plots also show the resulting samples, when the continuous curve is sampled at three different frequency offsets. Note that the samples look quite different, although the shape of the continuous curve is the same. As said, from each set of samples, the continuous (blue) curve can be reconstructed - but not "mentally"EDIT: The samples at the bottom of figure1.png are actually located at -Inf dB, since they hit the zeros of the frequency response. For clarity, I just wanted to keep them inside the plot. In practice they would be at the noise floor.

author: Performa01
author_rank: Super Contributor
timestamp: March 19, 2024, 03:11:44 pm
content: Quote from: gf on March 19, 2024, 01:34:05 pmThanks again for being alert – I’ve rephrased this paragraph one more time and now tried to describe the reality properly instead of just making a sloppy statement…

author: rf-loop
author_rank: Super Contributor
timestamp: March 20, 2024, 12:28:55 pm
content: Here measured Rectangular window -3dB BW.Based toKeysight, Uniform window -3dB width is 0.8844 x ΔfInput 125kHz (128xΔf), dBm (external 50 ohm). (f input matched with oscilloscope reference)Input freq rised up 0.8844 x Δf/2Result as expected -3dB drop. (lack of enough level measurement resolution)As can see oscilloscope FFT display also RBW. But what kind of "RBW" it is? Least it is not main lobe -3dB BW.(Mostly least I think RBW as normal spectrum analyzer RBW)There is Δf 976.56Hz and then RBW 966.80Hz. This looks like based to 0.99But perhaps 863.7 Hz is more right value for RBW(3dB)?Rectangular (aka Uniform, aka Boxcar) window is nice for noise measurements because its noise BW is just Δf.

author: Performa01
author_rank: Super Contributor
timestamp: March 31, 2024, 10:30:32 am
content: I have promised to provide a condensed PDF version of my Review & Demonstration articles, and today I present a revised document which also includes additional content and a complete list of bookmarks for easy navigation.Due to space restrictions for forum attachments, I had to split this into two parts. Here comes the first part, including the following main topics:Document HistoryIntroductionBasic InformationAcquisitionDisplayTriggerMeasureCursorsMathAnalysisProbes

author: Performa01
author_rank: Super Contributor
timestamp: March 31, 2024, 10:31:25 am
content: Here is the second part, including the following main topics:MSOHAM TestUser CommentsFiguresTables

author: eTobey
author_rank: Super Contributor
timestamp: April 04, 2024, 04:48:58 am
content: Quote from: Performa01 on March 31, 2024, 10:30:32 amOn page 23 you wrote: "At 5 μs/div, the SDS824X HD takes an average of 650 μs/frame and a maximum of <2 ms/frame." I dont get what these 650us/frame mean. I would think it would be a constant 50us as you can see on the screen?

author: 2N3055
author_rank: Super Contributor
timestamp: April 04, 2024, 05:48:48 am
content: Quote from: eTobey on April 04, 2024, 04:48:58 amAt 5µs/div 50µs is interval shown on the screen.To do that scope has to trigger, capture, process signal, display and all measurements, and reconfigure to get ready to get another trigger.That is called retrigger time.Retrigger time hence consist of time when actual capture is happening and so called "blind" time, while scope processes data and going back to Ready status.So that sentence means that that when scope is in 5µs/div retrigger time is 650µs/MAX 2msFull table of retrigger times(triggers/s) is on pg. 24.Make note that with same settings, in sequence mode retrigger time is 52us, meaning "blind time" is 2µs.That is why it is recommended to use sequence mode if you need to capture fast bursts of signal.

author: BRZ.tech
author_rank: Regular Contributor
timestamp: April 14, 2024, 06:00:08 pm
content: Hi,Dear @Performa01I return with the “Newbie” questions.I am studying how to measure the Slew Rate of an Operational Amplifier in a DSO/MSO.In this case, I thought this video from Texas Instruments was really good:https://www.ti.com/video/4078676441001#:~:text=Slew%20rate%20is%20defined%20as,of%20the%20output%20signal's%20amplitudeIn order not to waste time, TI defined what the Slew Rate is (time 0min:28sec), and that the “Unit” of measurement is (V/us), photo attached.TI presented the Slew Rate of different Operational Amplifiers (time 04min:05sec), photo attached.In the SDS800X HD datasheet, on page 16, in “Horizontal Paramenters” and “Miscellaneous Parameters”, it does not state that it automatically measures Slew Rate.But it states in “Miscellaneous Parameters” that it automatically measures Positive Slope and Negative Slope.In the SDS800X HD datasheet, on page 17, it states in “Power Analysis” (optional): “Measure”, which automatically measures the Slew Rate.In the SDS800X HD datasheet, on page 06, “Parameter Statistics Function”, photo attached, that shows the measurement of a Square Wave Signal of Amplitude = 5Vpp, and f = 10MHz.In the “PSlope(C1)” column, it presents the “average value”, with: (Mean = 1.0282K V/us), which is extremely fast for an Operational Amplifier, considering data from the best TI OA, according to the attached table.“Newbie” Questions:1. Carry out a test with the SDS800X HD, with Square Wave excitation, with Amplitude = 5Vpp and f = 10MHz, repeating the test of: “Parameter Statistics Function”.Perform the measurement in “Unit”: (V/us), “Slew Rate” and “Positive Slope”.If there are, explain what are the differences between the “Slew Rate” and “Positive Slope” measurements?2. Regarding the “Slew Rate” and “Positive Slope” measurements, the performance measurement of the Operational Amplifier, is or is not, the same thing as performing the “Power Analysis” (optional) of the SMPS, for the automatic measurement of Slew Rate?If they are different, I suggest SIGLENT add the Slew Rate measurement to the SDS800X HD menu, “Horizontal Parameters”.Anyone on the topic can comment on my questions.Translation with Google Translate.Grateful for the attention.

author: 2N3055
author_rank: Super Contributor
timestamp: April 14, 2024, 06:09:57 pm
content: Quote from: BRZ.tech on April 14, 2024, 06:00:08 pmShort answer, yes, [Positive slope] is slew rate measurement of positive going signal and [Negative slope] is respectively is slew rate measurement of negative going signal.

author: Performa01
author_rank: Super Contributor
timestamp: April 14, 2024, 06:55:47 pm
content: Slew Rate MeasurementQuote from: BRZ.tech on April 14, 2024, 06:00:08 pmI’ve had a look at Texas Instruments and have found no less than 57 operational amplifiers capable of a Slew Rate of 2 kV/µs or faster. There are still 13 OpAmps with a Slew Rate faster than 5 kV/µs, the fastest being the THS3491, which manages 8000 V/µs.In the light of this, 1000 V/µs would have required a fast hybrid amp in the Seventies of last century, but isn’t particularly fast for a monolithic integrated OpAmp today.Quote from: BRZ.tech on April 14, 2024, 06:00:08 pmIt needs not be complicated. Here’s a 10 ns wide pulse with 2 ns rise-time, which is at the edge of accurate measurements with an SDS824X HD:SDS824X HD_Slew_Pulse_W10ns_RT2nsAs can be seen, the rise-and fall-times are accurately measured as ~2 ns. The slew rate should be 80% * 5 V / 0.002 µs = 4 V / 0.002 µs = 2 kV/µs. The actual measurement is off by some 2.76% for the positive slope.It should be kept in mind that the universal definition of the thresholds to be at 10% and 90% might not be valid in every industry, hence these thresholds are user-definable – see the measurement config submenu displayed in the above screenshot.Quote from: BRZ.tech on April 14, 2024, 06:00:08 pmIt is all the same thing – Slew Rate is Slew Rate, universally defined in volts per second, no matter what package uses this measurement. Positive and negative slope measurements just measure the Slew Rate on positive and negative transitions.

author: pdenisowski
author_rank: Super Contributor
timestamp: April 14, 2024, 11:29:47 pm
content: Quote from: BRZ.tech on April 14, 2024, 06:00:08 pmI recently made a short (< 6 min) video on slew rate measurements using an oscilloscope (primarily in the context of switch mode power supplies). It's the same measurement (delta_V/t) regardless of whether you're measuring an op amp or SMPS, although the way you acquire the voltage waveform may be different depending on the application.Slew rate is often included in "power analysis" option packages, but in my experience, most people just measure it "by hand" and don't really require a special option to do it.

author: Vitold
author_rank: Newbie
timestamp: April 20, 2024, 05:04:16 pm
content: Sorry if this is the wrong place to post, but I have a question about SDS800X trigger terminologie.For dropout trigger type, trigger is configured with "State" for "Over Time Type" But menu says "Slope Rising | Falling" I think it should be "Time High" and "Time Low" when "Over Time Type" = "State" (and "Rising" or "Falling" when Over Time Time = "Edge") This is confusing for me.Do other users have the same idea?Trigger works perfectly, only configuration parameter name is confusing

author: Vitold
author_rank: Newbie
timestamp: April 20, 2024, 05:19:35 pm
content: Quote from: Performa01 on April 14, 2024, 06:55:47 pmI have a question about "slope" trigger on SDS800X. This is the same as "slew rate" trigger on other scopes, correct?When I try to configure a "Slope" trigger, GUI says "Trigger when edge crosses two thresholds is inside or outside a selected time range". I can configure time range, but where can I configure upper and lower voltage thresholds? Or is this not really a slew rate trigger (like on other scopes)?

author: Performa01
author_rank: Super Contributor
timestamp: April 20, 2024, 06:12:22 pm
content: Quote from: Vitold on April 20, 2024, 05:04:16 pmThe terminology is correct. The Dropout Trigger watches for a transition within the specified Dropout time period. A transition can either be rising or falling. The trigger fires whenever the specified transition does not occur within the Dropout period.Quote from: Vitold on April 20, 2024, 05:19:35 pmIt would be effectively the same as a slew rate trigger, but maybe specified differently.As always, the thresholds are set by the trigger knob. Since there are now two of them, you can push the trigger knob in order to toggle between the two thresholds.In the attached screenshot, I’ve used Slope Trigger to trigger on the end of the sweep of a 1 Vpp sine wave. Sweep time is 100 ms and frequency range is 100 kHz to 1 MHz. Trigger condition is for a positive signal slope (rising) of less than or equal to 132 ns between -200 mV and +200 mV thresholds. This way, only the 1 MHz sine has a fast enough edge to trigger.SDS824X HD_Trigger_Slope_1MHz

author: Vitold
author_rank: Newbie
timestamp: April 20, 2024, 06:29:37 pm
content: Quote from: Performa01 on April 20, 2024, 06:12:22 pmThat is the thing I was missing - thank you!

author: Vitold
author_rank: Newbie
timestamp: April 20, 2024, 07:13:10 pm
content: I am sorry for all the questions, but I have my new SDS800X and I am experimenting with it - fun!Why does it have "GPIB" in I/O Setting? I don't see a GPIB interface on the back of the scope.

author: Martin72
author_rank: Super Contributor
timestamp: April 20, 2024, 07:26:58 pm
content: This question is better placed in the general thread:https://www.eevblog.com/forum/testgear/siglent-sds800x-hd-12-bit-dsos-coming/

author: tautech
author_rank: Super Contributor
timestamp: April 20, 2024, 09:02:21 pm
content: Quote from: Vitold on April 20, 2024, 07:13:10 pmTo support Siglents USB to GPIB adapter:

author: pdenisowski
author_rank: Super Contributor
timestamp: April 22, 2024, 06:32:50 am
content: Quote from: Performa01 on April 20, 2024, 06:12:22 pmI wonder if some of the confusion might be from the word "dropout" - some vendors (including R&S and also Tek, I believe) have a "timeout" trigger that triggers when the waveform stays above or below a given level for X amount of time. There doesn't need to be a transition (i.e. a "slope") for the trigger to occur. For example, I might want the scope to trigger if a line stays low for more than N seconds.I presume the Siglent trigger works the same way (and the poster says it does work), just different terminology.Out of all the T&M instruments I work with, scopes seem to be the least consistent in terminology between vendors.

author: 2N3055
author_rank: Super Contributor
timestamp: April 22, 2024, 08:00:37 am
content: Quote from: pdenisowski on April 22, 2024, 06:32:50 amI agree about terminology not having industry wide consensus...And that can be confusing sometimes...As for word dropout it is a valid signal condition and used a lot. In communications, power electronics...

author: ebastler
author_rank: Super Contributor
timestamp: April 22, 2024, 08:15:44 am
content: Quote from: 2N3055 on April 22, 2024, 08:00:37 am"Dropout" is obviously a valid and established term. But it covers only part of the scenarios well where this trigger type might be used. E.g. when monitoring a communication protocol, one may be interested in situations where it takes one station a certain (longer than usual) time to respond. There is nothing missing in the signal, no "dropout" in this case.So I think "timeout" is the better designation here since it is more general.

author: Performa01
author_rank: Super Contributor
timestamp: April 22, 2024, 09:09:38 am
content: Quote from: pdenisowski on April 22, 2024, 06:32:50 amJust think of it: in order to leave the low state in your example, there has to be a transition, right? And if that transition does NOT occur within the specified amount of time, then the trigger will fire.However the Siglent dropout trigger has two modes of operation: State and Edge.Yes, in case of Edge the Slope switch (Rising/Falling) is not quite right and should change to State (High/Low). The difference is that with State we actually trigger if there is no transition at all within the specified timeout period, whereas with Edge there might be still one additional transition that is the opposite to the trigger condition and consequently the final signal state might be high or low, but the relevant part is that the specified state change or transition does not occur within time.EDIT: I've just requested an UI-change to get an adapted switch in State mode.

author: 2N3055
author_rank: Super Contributor
timestamp: April 22, 2024, 10:05:56 am
content: Quote from: ebastler on April 22, 2024, 08:15:44 amTimeout is "giving up on waiting for something we consider valid to come". It is maybe too general.Dropout mostly implies completely missing signal or signal that drops out below defined threshold...For your example, there is no signaling (voltage transitions) most of the time, unless a side transmits something. What is idle voltage doesn't matter, because we know what idle voltage is considered inactive. In that case you can use Edge, Pulse, Interval or Dropout trigger.....

author: eTobey
author_rank: Super Contributor
timestamp: April 22, 2024, 10:22:06 am
content: I found this interesting information:Quote from: Performa01 on January 23, 2024, 08:35:34 amCan someone please explain, why is there a discontinuity in the rate?

author: tautech
author_rank: Super Contributor
timestamp: April 22, 2024, 10:42:36 am
content: Quote from: 2N3055 on April 22, 2024, 10:05:56 amNo, this is defined as a Runt.

author: ebastler
author_rank: Super Contributor
timestamp: April 22, 2024, 10:43:28 am
content: Quote from: eTobey on April 22, 2024, 10:22:06 amCould you please be more specific? What do you find unexpected? At which timebase setting(s)?Edit: What I personally find unexpected is that the waveforms/s do not keep increasing monotonously as we go to faster time bases, i.e. reading the table bottom-to-top. I would expect them to do that, maybe saturating at some point, when the frame time becomes dominated by the post-processing and trigger re-arming time.Instead the waveform rates keep increasing as we go from slow time bases to 50 ns/div, then start to drop again. Not a "discontinuity", but a non-monotonous behavious which is not obvious.

author: gf
author_rank: Super Contributor
timestamp: April 22, 2024, 11:12:13 am
content: Quote from: ebastler on April 22, 2024, 10:43:28 amIsn't that the point where interpolation joins in in order to display the trace?

author: ebastler
author_rank: Super Contributor
timestamp: April 22, 2024, 11:17:53 am
content: Quote from: gf on April 22, 2024, 11:12:13 amBut the non-monotonous change applies in dot mode as well. Interpolation should not be relevant there? And for the digital triggering I assume interpolation is used at any time base?

author: eTobey
author_rank: Super Contributor
timestamp: April 22, 2024, 11:26:44 am
content: Quote from: ebastler on April 22, 2024, 10:43:28 amFigured it out memory limit is reached and as you described the "overhead".Yes, "discontiuity" was the wrong word.

author: 2N3055
author_rank: Super Contributor
timestamp: April 22, 2024, 11:30:52 am
content: Quote from: tautech on April 22, 2024, 10:42:36 amDifferent potato ..

author: 2N3055
author_rank: Super Contributor
timestamp: April 22, 2024, 11:34:02 am
content: Please suspend all talk about Wfm/s rates from that table based on early FW.It will need to be re-tested again...When currently tested FW is released...

author: 2N3055
author_rank: Super Contributor
timestamp: April 22, 2024, 12:19:36 pm
content: Quote from: eTobey on April 22, 2024, 11:50:41 amWhere did I said that.I said that discussing a speed of FW that had changes in meantime is waste of time.It is equally relevant like discussing how tall was I when I was 18 while buying a coat today.Irrelevant.It needs to remeasured and then yap away all you like...

author: 2N3055
author_rank: Super Contributor
timestamp: April 22, 2024, 12:43:29 pm
content: Quote from: eTobey on April 22, 2024, 12:37:27 pmYou are provocateur, deliberately making inflamed pompous discussions..... Clickbait type of conversation.I do not intent to participate.I have a bad news for you.In a short time there will be new FW.That you will have to test all over again. Every. Single. Detail.All of the stuff you did and said will mostly matter no more.Have fun.

author: pdenisowski
author_rank: Super Contributor
timestamp: April 22, 2024, 02:11:12 pm
content: Quote from: tautech on April 22, 2024, 10:42:36 amI've usually seen "runt" defined as a signal whose amplitude crosses a lower threshold twice in a row without crossing an upper threshold. That is, a runt trigger requires defining a lower and an upper threshold (and optionally some other things, depending on the scope).Again, maybe another terminology mismatch between manufacturersEdit: very sorry (@ebastler) if this is in the wrong thread - so many SDS800X threads. I promise to be better if it is

author: 2N3055
author_rank: Super Contributor
timestamp: April 22, 2024, 02:58:34 pm
content: Quote from: eTobey on April 22, 2024, 01:06:10 pmI'm not going to say "no" or "yes" just placate your ego's need to control my narative.Even less I'm going to lie. Never, ever, even suggest that. Ever again.I'm not going to lie even if I could materially gain from it.It is called principles.I answered "it doesn't matter, it is rendered irrelevant" because that is the answer.Since modern digital scopes are based on FPGA cores, the Field Programmable Gate Arrays, it is possible for manufacturers to literally changed how hardware works. Significantly and fundamentally even.To the point that it practically becomes a new revision of hardware, on logical level.And since there was work done on hold-off in trigger, there were changes done on the very triggering.Making previous measurement mere historic curiosity.Until triggering is remeasured it is Tabula rasa to us. Complete mystery.We.Simply.Don't.Know.It might be slower than it was for all I know. Or faster. Or same. Or any other combination in-between.If we knew exactly what was done, we could extrapolate educated guess.But we don't know any details. So we don't know.

author: Martin72
author_rank: Super Contributor
timestamp: April 22, 2024, 04:22:47 pm
content: Quote from: ebastler on April 22, 2024, 01:23:08 pm+1(Please)

author: Performa01
author_rank: Super Contributor
timestamp: April 22, 2024, 04:27:50 pm
content: Well, I don't want to unveil too many details about a still unreleased beta firmware, yet a decent hint shall be allowed...You might have noticed that according to my review, the waveform update rate doesn't quite reach 120 kWfm/s, even though it is specified that way in the datasheet. People knowing me would not be surprised that this fact was in Siglents bug base the very next day.This is just one of many bugs that have been addressed.

author: eTobey
author_rank: Super Contributor
timestamp: April 23, 2024, 07:11:52 am
content: I just had a occasion, where the measurement could not keep up with a trigger rate of less than 166 times per second. Of 10 possible measurements, only 3 were measured/counted.https://www.eevblog.com/forum/testgear/sds800x-hd-bug-reports-firmware/msg5463370/#msg5463370Is there any information about where the limit exactly lies?It would be an idea to add this to the table in future measurement tests.

author: eTobey
author_rank: Super Contributor
timestamp: April 23, 2024, 07:29:34 am
content: Quote from: Performa01 on January 23, 2024, 08:35:34 amWhat do the values in the third column mean? I just dont get it. Even after the next day. I only see a proportinal relation to the record length.I have deleted my off-topic posts in here, and i suggest others to do the same.

author: electronics hobbyist
author_rank: Regular Contributor
timestamp: April 23, 2024, 08:22:44 am
content: Quote from: eTobey on April 23, 2024, 07:29:34 amWhat I see is the theoretical total number of points, which is the second column multiplied by the fourth column.In fact, a frame of data is not just points on the screen, but also needs to search for trigger points, so the actual frame of data is more than the screen points.Quote

author: Performa01
author_rank: Super Contributor
timestamp: May 02, 2024, 06:05:56 am
content: Mask Test 2Here’s another use case for the Mask Test: Power Line Monitoring. What I show is just a simulation, assuming a x100 Probe connected to an European 230V / 50 Hz power line.In this case we need not draw the pass/fail-mask ourselves, but let it construct automatically from a reference waveform, i.e. a pure sine without distortions and interferences plus some tolerance.Of course, I’ve exaggerated in this example and used very tight tolerances – I guess we would get lots of mask violations in a real world power grid. But then again, this is just a demo and tolerances can be tailored to the actual conditions and requirements.We can configure the Mask Test in several ways; one of them would be to make a screenshot for every detected mask violation. We just need to plug in some USB-stick and configure the screenshot properly, e.g. PNG format into the SIGLENT folder on the flash drive.After setting up the Mask Test, we can have the monitoring running as long as we desire – until the USB flash drive is full. With ~36 kB memory requirement per screenshot (for PNG) we can get lots of mask violations though – that is more than 110k screenshots per Gigabyte.Here are a few example screenshots; the violations are marked in red:SDS824X_HD_PNG_118SDS824X_HD_PNG_119SDS824X_HD_PNG_120If we have set up date and time correctly, we can see the exact date/time of the occurrence in the bottom right corner in the screenshots.Of course, for power supply monitoring tasks, we should operate the scope from an UPS to survive a power outage, but even without that all previous mask violations are still safely stored on the USB stick.

author: markone
author_rank: Frequent Contributor
timestamp: May 04, 2024, 09:31:14 am
content: I was playing with SDS814X FFT math (Hanning window) comparing results with my SSA3021X (Gaussian filter), in attachment some screens of 50MHz 0dBm CW sine wave (from SDG2042X) with different SPAN / RBW.I would lik to know your opinion about SDS814x spectrum images @ 100Hz RBW, there is something wrong.Am I doing something wrong or am I pushing the measure system over some limit ?

author: markone
author_rank: Frequent Contributor
timestamp: May 04, 2024, 09:58:28 am
content: I forgot to mention : trace average engaged with both instruments.In attachment 2 additional spectrums of 50MHz carrier AM modulated with 1KHz sine wave, 100%.

author: markone
author_rank: Frequent Contributor
timestamp: May 04, 2024, 11:37:19 am
content: Same topic, comparison with DHO1000 that does not show unwanted spuries :

author: Martin72
author_rank: Super Contributor
timestamp: May 04, 2024, 05:06:22 pm
content: Hi,What is that source-signal in your last post?

author: markone
author_rank: Frequent Contributor
timestamp: May 04, 2024, 07:15:02 pm
content: Quote from: Martin72 on May 04, 2024, 05:06:22 pm0 dBm 1 MHz carrier, AM modulated with sine wave 10Khz / 100%, sourced by SDG2042x, where SDS814x shows 2 additional lateral peaks that, of course, do not actually exist.It's only one example among many others that I spotted today, as soon as you push down the RBW the spectrum becomes a spurious fest, not present in DHO1000 FFT / SSA3021x spectrum sweep.

author: Martin72
author_rank: Super Contributor
timestamp: May 04, 2024, 07:51:08 pm
content: QuoteIn addition, you have changed the window to "Blackman" and manually reduced the sample rate to 10MSa/s, to complete the settings...Then I get the same result.I don't know if these are the right settings.In any case, anything below -72dBm can be doubted as to whether it actually exists.Possibly these "artifacts" below this threshold are faded out in the DHO, unfortunately I don't have any more to investigate this.

author: Martin72
author_rank: Super Contributor
timestamp: May 04, 2024, 08:31:15 pm
content: This is also nothing specific to the sds800.I know we've had this topic before.If I find it again, we should continue there.

author: markone
author_rank: Frequent Contributor
timestamp: May 04, 2024, 09:24:37 pm
content: Quote from: Martin72 on May 04, 2024, 07:51:08 pmThat's not the case, DHO noise floor is well below, simply they (spurious) are not there with the Rigol in this case as well as many others signal / settings combinations.I played a lot (read some hours) with both DSOs and what you mention normally happens quite beyond the rule 12 x 6 = 72dB dynamic range, in my humble opinion this is a fixable bug in FFT math.I was exploring the possibility to make use of SDS814x in place of SSA at least in some user cases, where for instance it is much faster, but considering what I've seen I can't trust it (and this is a pity).

author: 2N3055
author_rank: Super Contributor
timestamp: May 04, 2024, 09:55:56 pm
content: Quote from: markone on May 04, 2024, 09:24:37 pmFact that those are 72dB below carrier means they are beyond ADC dynamic range. At 200 mV/div scope full scale is cca 8 dBm. So those spurs are -80dB below full scale.Let's reverse the picture: if you create dual tone, let say 1MHz 0dBm combined with 1,1 MHz -80 dBm and feed that to Rigol what you will see?Will you see -80dBm peak?Following your logic, from your FFT plots this -80dBm should stick out nicely from noise floor.

author: Performa01
author_rank: Super Contributor
timestamp: May 05, 2024, 07:31:43 am
content: Quote from: markone on May 04, 2024, 09:31:14 amThe first thing I noted was the seemingly random usage of window functions. Hanning and Gaussian are not comparable and for a meaningful test we should stick with the Flattop window on both instruments.Then I wonder how the signal can actually be 50 MHz / 0 dBm. If so, then the SSA shows a level error of -0.91 dB, which might be attributed to the Gaussian window. But even the rather unsuitable (for spectrum analysis) Hanning window cannot explain a +0.97 dB amplitude error on the SDS800X HD.Let’s compare the first test with 30 kHz RBW now:SDS824X HD_FFT_50MHz_0dBm_RBW28kHzNow compare this with the SSA screenshot. The SDS level measurement isn’t too far off at -0.288 dBm, the filter shape factor is as expected for a spectrum analysis and the noise floor is <-90 dBm. At 51 MHz that is some 20 dB better than the SSA – and the difference would be even greater if we measure closer to the carrier.Next is 1 kHz RBW:SDS824X HD_FFT_50MHz_0dBm_RBW900HzYes, we see some modulation sidebands below -72 dBm now, and again we cannot decide if they would be visible on the SSA as well, as the noise floor there completely masks everything that low. By contrast, the SDS800X HD shows a noise floor of -100 dBm.But we can try the same scenario with a higher class DSO, like the SDS2000X HD:SDS2504X HD_FFT_50MHz_0dBm_RBW700HzThis proves that the signal source is clean and the spurious modulation happens within the SDS800X HD somehow.Finally 100 Hz RBW. This just isn’t possible at 50 MHz – the SDS800X HD is a DSO, hence a baseband instrument and not a spectrum analyzer. The FFT would need to compute at least 4 Mpts to handle this.Yet we can try to come as close as possible: using the full 2 Mpts at 250 MSa/s we can get about 440 Hz RBW with the Flattop window. In a pinch we could use the Blackman window, which has still acceptable amplitude accuracy and a great side-lobe suppression. This way we can get ~200 Hz RBW:SDS824X HD_FFT_50MHz_0dBm_RBW200HzYes, there are those spurious modulation sideband signals again, and these are not visible on an e.g. SDS2504X HD:SDS2504X HD_FFT_50MHz_0dBm_RBW165HzSo yes, the SDS800X HD has a problem there. Since the FFT should be the same across the platform, this is more likely to be a hardware issue.Quote from: markone on May 04, 2024, 09:58:28 amOnce again, 1 kHz is a tough request. It is just about manageable:SDS824X HD_FFT_50MHz_0dBm_RBW200Hz_Mod1kHzYet a closer look reveals a 10 kHz modulation frequency for the provided examples anyway, so here we go:SDS824X HD_FFT_50MHz_0dBm_RBW200Hz_Mod10kHzYes, there are various spurious signals again. On the SDS2504X HD we get the third order intermodulation products only:SDS2504X HD_FFT_50MHz_0dBm_RBW165Hz_Mod10kHzThese are not unexpected though. A wideband amplifier can only have so much linearity, and I’ve covered this topic in more detail here in this thread (reply #6, section “Distortion Measurements”):https://www.eevblog.com/forum/testgear/sds800x-hd-review-demonstration-thread/msg5293759/#msg5293759The main source of distortion in a modern DSO frontend would be the PGA, where third order intermodulation distortion is specified as -65 dBc (typically) at 250 MHz. Harmonic distortion is even worse at -50 dBc (typical) at 100 MHz. Both SDS meet the expectations at ~-67 dBc.https://www.ti.com/product/LMH6518BTW, in the SDS800X HD datasheet, the spurious-free dynamic range SFDR is specified as only ≥35 dBc.Quote from: markone on May 04, 2024, 11:37:19 amYes, that’s quite amazing. As stated above, such distortion figures cannot be expected with industry standard parts like the LMH6518.

author: markone
author_rank: Frequent Contributor
timestamp: May 05, 2024, 10:30:01 am
content: Quote from: 2N3055 on May 04, 2024, 09:55:56 pmI agree with your math, 200mV/div corresponds to about 8.06dBm, so those 2 dreaded peaks are about 80dB below that, but in most cases dither effect of the noise brings to higher dynamic ranges so i'm quite sure that if I put in place the test that you are suggesting the Rigol will "stick out" an injected frequency component @ -80dBm and even below, same should be valid for SDS814x.Even my 8 bits Picoscope 3203D is making a better work with AM modulated carrier in respect to its vertical resolution :Here lateral spurious are about 69dB below the carrier and79dB below the full scalethat is 10dBm (+/- 1V).I would dare to say that SDS814x, spurious wise, can (shall) do better in this regard thankfully to its 12bits ADC, as is doing the DHO1000) that as we all already know has quite poor math capabilities than SDS800x.Right now I do not have a 50 ohm RF splitter to proceed with this check, the internal SDG2042x wave combiner does not have such dinamyc range, but being quite curious about this matter I just put in the Amazon basket a cheap RF resistive divider.Instaed I'm able to feed a single signal below the theoretical "resolution" of the DSO, I will try later and I will post results.Anyway, your point does not explain i.e. this other case, clean 50MHz CW carrier, no modulation :here spurious are well above the dinamyc range limits, so there is for sure something that lurks in the shadows ...DHO1074, same signal :What the hell is going on ?

author: gf
author_rank: Super Contributor
timestamp: May 05, 2024, 11:22:19 am
content: Why do you use a lower signal level with the DHO1074?

author: newbrain
author_rank: Super Contributor
timestamp: May 05, 2024, 11:45:40 am
content: Quote from: gf on May 05, 2024, 11:22:19 amIt looks the same to me:0 dBm ~= -13.5 dBV (for a 50Z0}

author: gf
author_rank: Super Contributor
timestamp: May 05, 2024, 11:51:23 am
content: Quote from: newbrain on May 05, 2024, 11:45:40 amSorry, I missed dBm vs. dBV scale.

author: markone
author_rank: Frequent Contributor
timestamp: May 05, 2024, 12:05:29 pm
content: Quote from: newbrain on May 05, 2024, 11:45:40 amThat's correct, dear friend

author: markone
author_rank: Frequent Contributor
timestamp: May 05, 2024, 12:25:07 pm
content: Quote from: 2N3055 on May 04, 2024, 09:55:56 pmHere we go with test signal below the theoretical resolution limit 12x6 = 72 dB, I adjusted the vertical scale to fullfill the ADC range with 0dBm signal with 81mV/div :Then I applied a 40dB attenuator at the SDG2042x output :and I started to step down the signal level obtaining the following result :as expected the DSO is going well below the theoretical limit of 72dB and I would say that I like what I see ;-)For some reason @ -56dBm (-96dBm after attenuator) the peak is there with correct level but it does not appear in peak list, my guess is that the Peack list function is not working on the averaged signal but instead on the "clear" trace, I would call it a bug.Of course I expect that with a 2 components combined signal we will get some spurious here and there, but of course this will NOT cancel signal below 72dB full scale.HDO's measure coming.

author: markone
author_rank: Frequent Contributor
timestamp: May 05, 2024, 01:53:35 pm
content: Here below DHO measures, same signal approach with DSO input set at 81mV, first spectrum image with 0dBm signal, then the addition of 40dB attenuator and subsequent signal level stepping down.Being the DHO math system an utter shit compared to the SDS800x, we here are missing the average function on FFT (AFAIK), dBm scaling, so I stopped at -50dBm (last image, -90dBm at DSO input), where the signal peak is still clearly visible at 90dB under the full scale theoretical level, so the famous -80dB FS signal "stick out" with some margin (last but one image) :Anyway, shame on Rigol for the missing FFT average feature, this would change a lot the whole experience.

author: 2N3055
author_rank: Super Contributor
timestamp: May 05, 2024, 03:23:03 pm
content: Quote from: markone on May 05, 2024, 12:25:07 pmFor peak to be detected, both detection level and excursion needs to be set.

author: joeqsmith
author_rank: Super Contributor
timestamp: May 05, 2024, 03:41:48 pm
content: Vintage 8-bit DSO input -110dBm 1MHz applied.

author: mawyatt
author_rank: Super Contributor
timestamp: May 05, 2024, 04:04:46 pm
content: Interesting we see some signal "artifacts" on the Rigol #0 but not on the Siglent #52. Signal is from AWG (SDG2042X) at 2mvpp @ 50 ohms (-50dBm). Both have Flattop Windows, Signal has 4 average (not available on Rigol). BTW these artifacts originate within the Rigol and not from the AWG.Used a cheap 50 ohm termination and connected to both DSOs, and no the artifact is not from the Siglent contaminating the Rigol or vice versa as both were also checked by themselves!!Both read the correct level, altho the Rigol is in dBV as it has no dBm reference ability and both produce a nice FFT however we prefer the Siglent display and FFT setup.Edit: Added another plot with Rigol at a lower sample rate #1, and with Blackman Window #2 and Siglent with Blackman Window #53.As always YMMV.Best,

author: joeqsmith
author_rank: Super Contributor
timestamp: May 05, 2024, 04:05:42 pm
content: -120dBm 1MHz applied. Wrong tool for the job but gives some comparison of vintage tech.***Should add that the display update rate, with the scope set to maximize computations is about 7 seconds! It's too bad that used CPU upgrade did not work out as I am sure it would help in this case.

author: 2N3055
author_rank: Super Contributor
timestamp: May 05, 2024, 04:56:06 pm
content: SDS2000xHD 1MHz -125dBm applied.

author: 2N3055
author_rank: Super Contributor
timestamp: May 05, 2024, 05:17:41 pm
content: SDS3104xHD 1MHz -125dBm 1kHz 100% AM modulation applied.

author: mawyatt
author_rank: Super Contributor
timestamp: May 05, 2024, 06:04:42 pm
content: Impressive results from the LeCroy and Siglent@ 2N3055 the two sidebands are down 6dB as they should beBest,

author: joeqsmith
author_rank: Super Contributor
timestamp: May 05, 2024, 06:06:29 pm
content: Very impressive to see that AM modulation. How long does it take to display?

author: 2N3055
author_rank: Super Contributor
timestamp: May 05, 2024, 06:19:21 pm
content: Quote from: joeqsmith on May 05, 2024, 06:06:29 pmLong.Each acquisition run is 1 sec (100ms/div) , some time for FFT and then 16x averages. Didn't actually measure time. Maybe later.

author: 2N3055
author_rank: Super Contributor
timestamp: May 05, 2024, 06:21:18 pm
content: Quote from: mawyatt on May 05, 2024, 06:04:42 pmMike,that is what I wanted to show.Best,Siniša

author: Electro Fan
author_rank: Super Contributor
timestamp: May 05, 2024, 06:58:40 pm
content: Quote from: 2N3055 on May 05, 2024, 04:56:06 pm2N3055, thanks for doing and posting the measurements. A couple questions and maybe a request, please, thanks.1. Why is the amplitude measurement different with the 2kHD vs 3kHD?2. What happens when you run the modulation test on the 2k? Similar results but just takes longer to complete?

author: Performa01
author_rank: Super Contributor
timestamp: May 05, 2024, 07:05:04 pm
content: Since this thread is about the SDS800X HD, you shall not get the impression that it cannot do something similar. It can do it, despite its FFT producing spurious responses at lower RBW (error report has already been filed) – it is just a little less accurate and I had to look for a sweet spot in the spectrum where there were no spurious signals getting into the way…SDS824X HD_FFT_1.77MHz_-125dBm_AM100_10kHzThe signal was -125 dBm at 1.77 MHz, 100% amplitude modulated with 10 kHz.The level measurement is 1.175 dB high, and the sidebands are -5.668 and -5.276 dBc.Well, there should be a little gap between a low end SDS800 and the 2000/3000 series.Regarding the speed, it takes about 1.28 seconds to produce a single 2 Mpts FFT result (including acquisition). Even tough I’ve used 64x averaging in this example, usable (but less nice looking) results can be expected with just 4 averages already.

author: joeqsmith
author_rank: Super Contributor
timestamp: May 05, 2024, 07:08:40 pm
content: 1MHz -125dBm 1kHz 99.9% AM modulation applied.You can see the center spur and side lobes but they are lower than the scope's internal noise. Scope also will not readout this low. Turning off the 3D view does speed up the display but still a few seconds. Guessing most modern scopes would blow the doors off it.My SA can easily measure down this low. Note the -135dBm peak readout. I normally keep a 10dB attenuator attached. Using the right tool for the job can improve the measurements.

author: joeqsmith
author_rank: Super Contributor
timestamp: May 05, 2024, 07:11:54 pm
content: Quote from: 2N3055 on May 05, 2024, 06:19:21 pmI assume it uses a round robin buffer and once loaded up, you're about a second update. Much faster than mine.

author: markone
author_rank: Frequent Contributor
timestamp: May 05, 2024, 07:57:35 pm
content: Quote from: 2N3055 on May 05, 2024, 03:23:03 pmOf course this was the First thing that I checked, settings are ok but peak is not detected.

author: markone
author_rank: Frequent Contributor
timestamp: May 05, 2024, 08:14:47 pm
content: Quote from: Performa01 on May 05, 2024, 07:31:43 amI was aware about that but the focus was on spurious so I spent very little time on that so I chose the window type on the base of the peak shape well knowing to be in "uncal" condition, but to be honest ... i do not know how to select flattop on SA ... you sure it's possible with my model ? (SSA3021X)The good news is that higher HD models behave in a much better way and the problem is (sadly for me) related to the SDS800x product line, but considering the price, I agree this is fair.

author: 2N3055
author_rank: Super Contributor
timestamp: May 05, 2024, 08:41:15 pm
content: Quote from: joeqsmith on May 05, 2024, 07:08:40 pmI agree this kind of work is absolutely job for the SA. But like you, I was curious where the limits are.That is the first think you should know about your instruments, what theycan'tdo...

author: markone
author_rank: Frequent Contributor
timestamp: May 05, 2024, 08:52:55 pm
content: Quote from: mawyatt on May 05, 2024, 04:04:46 pmFor what is worth, my DHO1000, same signal :Here below what my SSA read :

author: 2N3055
author_rank: Super Contributor
timestamp: May 05, 2024, 09:19:06 pm
content: Quote from: Electro Fan on May 05, 2024, 06:58:40 pmOne is without and other one with modulation. Difference is about 1,5dB. I'm guessing it's the AWG when modulation got on.. I didn't care because what was important was accurate 6db relation.On 2k looks pretty much the same and pretty much lasts the same, because at this settings most of the time is acquisitions and averaging not FFT processing time.

author: mawyatt
author_rank: Super Contributor
timestamp: May 06, 2024, 01:02:51 am
content: Quote from: 2N3055 on May 05, 2024, 09:19:06 pmThe sideband power in each is 1/6 the total (-7.78dB), which leaves the carrier at 2/3 total (-1.76dB), so would expect it to be -6.02dB down from carrier as you've shown.Your impressive results at this power level with the SDS2000X HD and 3000X HD and followed up by Performa01 with the SDS800X HDBest,

author: joeqsmith
author_rank: Super Contributor
timestamp: May 06, 2024, 01:09:35 am
content: Channel 1 & 2 fed with a 1MHz 0dBm sinewave. Math used to add both channels. FFT then ran on the math channel. This is about the limit of the old LeCroy. It can display the separate peaks but the readouts will only display a single peak. Again, wrong tool for the job but I am curious how well your scopes can resolve two peaks like this. Feel free to use an external combiner rather than the math.

author: joeqsmith
author_rank: Super Contributor
timestamp: May 06, 2024, 01:14:16 am
content: Showing the two peaks closes enough that the readouts will no longer resolve it.

author: joeqsmith
author_rank: Super Contributor
timestamp: May 06, 2024, 01:36:59 am
content: Watched Dave's recent Rigol DHO800 review, the connector SNAFU and the oops retraction. Part of this video he is comparing with a low end Siglent off and on. Puts it in a bad light but I assume that was because he was beating the price drum.

author: mawyatt
author_rank: Super Contributor
timestamp: May 06, 2024, 02:44:31 am
content: Quote from: joeqsmith on May 06, 2024, 01:09:35 amFor the classic Two Tone IMD test you want to exercise the channel under test with the full 2 tone signals combined which implies summing the 2 tone before sampling the summation, then following with an FFT.Would expect a better result summing the 2 tones digitally after digitization with the math function from 2 separate digitized channels, than combining the 2 tones, then digitizing the combination followed by an FFT.Should be a simple test to perform, altho we haven't done the 2 channel version.Best,

author: tautech
author_rank: Super Contributor
timestamp: May 06, 2024, 04:26:43 am
content: Quote from: joeqsmith on May 06, 2024, 01:36:59 amAt that time Joe, Dave had zero idea of what was around the corner and coming from Siglent, zip, nada, zero.Therefore he could only compare it with existing Siglent models at a similar price point and probably had the 4ch X-E in his mind as a comparison.

author: 2N3055
author_rank: Super Contributor
timestamp: May 06, 2024, 09:03:57 am
content: Quote from: joeqsmith on May 06, 2024, 01:14:16 amSD6052X - Digital combiner, cca 1MHz combined with 1MHz+11,9Hz difference, -125dBm level.I'm not really sure that some 0.5dB difference is not coming from a foot long attenuator stack...4M FFT on scope. Von Hann WindowFull disclosure: first and second tone frequency and distance were fine tuned to land in the middle of frequency bin..So this is as ideal as it can get.

author: gf
author_rank: Super Contributor
timestamp: May 06, 2024, 11:16:03 am
content: Quote from: joeqsmith on May 06, 2024, 01:09:35 amIf both are 1MHz, why do you get two peaks? Is that due to inter-instrument error between two separate signal generators?[With a 2-channel AWG, I would expect the signals to be phase-locked if the frequency is the same.]Quote from: mawyatt on May 06, 2024, 02:44:31 amDigital summation with a math function does, of course, not introduce any IMD between the two signals. You just get the sum of the two (complex) spectra, since FFT(x+y) = FFT(x) + FFT(y).

author: mawyatt
author_rank: Super Contributor
timestamp: May 06, 2024, 11:42:56 am
content: Quote from: gf on May 06, 2024, 11:16:03 amExactly!! The separate channel digitized signals can't "see" each other, thus no IMD should be present and why we mentioned such.Best,

author: pdenisowski
author_rank: Super Contributor
timestamp: May 06, 2024, 12:35:47 pm
content: Regarding the IMD tests: I'm not sure I completely understand what is being measured / quantified about the scope here.In my experience (and certainly in the case of spectrum analyzers and VNAs), IMD is most often measured by providing the DUT with an input signal that consists of two tones at different frequencies (F1 and F2) and then measuring the amplitudes of the close-in 3rd order products (2F1-F2 and 2F2-F1) at the DUT output relative to the amplitude of the fundamentals. This is the used to compute the theoretical intercept of the slope of the fundamental and 3rd order products and yields the third order intercept point (IP3 or TOI). A higher IP3 is generally desirable because it indicates greater linearity of the DUT, i.e. less IMD created by the DUT.If I wanted to quantify the IP3 of a scope's front end, I would simply generate two tones (ideally using completely separate sources and circulators) with slightly (~1 MHz or so) different frequencies, combine them externally, and then feed that combined input signal into a single scope channel. Then I would perform an FFT of the signal and measure the difference in amplitude between the fundamentals and above-mentioned 3rd order products and do the math (IP3 = Ptone + deltaP/2).I can understand why we might want to quantify the linearity of a scope's front end (vertical amplifier, etc.) but I don't think I understand the methodologies / results I'm seeing here. Sorry if I'm being dense

author: egonotto
author_rank: Super Contributor
timestamp: May 06, 2024, 12:36:10 pm
content: Quote from: mawyatt on May 06, 2024, 11:42:56 amHello,If I understand correctly, the combined signal is fed into C1 and the FFT would already show the interference of the input circuit and the ADC.Best regardsegonotto

author: mawyatt
author_rank: Super Contributor
timestamp: May 06, 2024, 12:46:05 pm
content: Quote from: egonotto on May 06, 2024, 12:36:10 pmYesHowever one must be careful when combining the signals to not introduce IMD due to interaction between the two signal sources before they enter the DUT, usually at smaller levels and with sufficient source isolation (>6dB) this isn't an issue.Best,

author: Performa01
author_rank: Super Contributor
timestamp: May 06, 2024, 12:50:17 pm
content: Quote from: markone on May 05, 2024, 08:14:47 pmI understand. Flattop is the default window on every general purpose SA, because amplitude accuracy and dynamic range (side lobe suppression) are the most important criteria. Most have some additional window (Gaussian, Nutall) and a few have even more to choose from. But for continuous signal analysis, where we can acquire plenty of data, the Flattop window is the obvious choice.Quote from: joeqsmith on May 06, 2024, 01:36:59 amYeah, some time ago I’ve analysed the FFT part and thoroughly disproved any unwarranted claims about the inferiority of the old little Siglent (reply #200):https://www.eevblog.com/forum/testgear/siglent-sds1104x-e-in-depth-review/200/Quote from: joeqsmith on May 06, 2024, 01:09:35 amI assume you meant two sine waves with close to 1 MHz frequency. Using the math channel for adding the two signals is a great way to simplify the cabling and avoid the 6 dB insertion loss.The SDS9824X HD does a reasonable job; its Marker Table doesn’t have the necessary frequency resolution and accuracy is generally poor because of the cheap 25 ppm quartz timebase (and it shows), but here you go:SDS824X HD_FFT_1MHz_Span500Hz_d5HzIn the above screenshot, a 999995 Hz sine was combined with a 1 MHz sine, hence the difference between the two signals is 5 Hz. The two signals are just distinguishable on the screen, and peaks search had to be configured for 12 dB excursion (instead of the 20 dB default) in order to find the two separate peaks. As mentioned before, Frequency resolution is insufficient, but at least the level accuracy is nothing to complain about.An SA would be better suited for such extreme use cases, but if it has to be a DSO, then why do I even try to compete with an upper midrange instrument from LeCroy by using a low-end entry-level device like the SDS800X HD? (Answer: because this is a thread about the SDS800X HD)The vintage of a LeCroy isn’t really important in this context. The extreme applications demonstrated here certainly exceed the capabilities of many other expensive scopes – but not for a midrange LeCroy, no matter how old it is.With all that said, I pull out a worthy contender for a change:SDS7404A H12_FFT_1MHz_Span100Hz_d0.5HzIn the above screenshot, a 999999.5 Hz sine was combined with a 1.0000000 MHz sine, hence the difference between the two signals is 0.5 Hz or 0.5 ppm. The two peaks are just distinguishable on the screen, and excursion for peaks search could be more than 50 dB. Displayed frequency resolution is sufficient here, but the actual resolution is not, as the 0.5 Hz is displayed as 0.79 Hz. Frequency accuracy is in the realm of 1 ppm and amplitude accuracy better than 0.15 dB in this scenario.

author: joeqsmith
author_rank: Super Contributor
timestamp: May 06, 2024, 12:50:35 pm
content: Quote from: 2N3055 on May 06, 2024, 09:03:57 amThanks for checking. Very nice. Here using an external combiner. The LeCroy has trouble resolving the two peaks once you get below 10Hz separation.As a side note, I recently installed the latest firmware available. While running this test, the scope threw some internal software error and had to restart. I've owned this scope for several years and have never had the firmware crash. Not impressed.

author: mawyatt
author_rank: Super Contributor
timestamp: May 06, 2024, 01:00:20 pm
content: Quote from: pdenisowski on May 06, 2024, 12:35:47 pmProbably a little guilty here as we "thought" the two tones were for evaluating the DSOs linearity as withchassisclassic IMD test. Rereading the post that started this discussion, now not sure that was the intent as it could be the separation of the 2 tones in the FFT display and how well the DSO could resolve such.Your description of the 2 Tone IMD test is spot on and much easier to implement than sweeping the input signal level and plotting the 3rd harmonic wrt fundamental to find the TOI, altho we've done both!!We've found that scope linearity is often overlooked by folks, as they seem more intrigued with number of bits, BW and noise levels rather than linearity.Best,

author: pdenisowski
author_rank: Super Contributor
timestamp: May 06, 2024, 01:03:29 pm
content: Quote from: Performa01 on May 06, 2024, 12:50:17 pmAt least on R&S spectrum analyzers, flattop is not necessarily the default window, depending on measurement mode.Also, I would expect any spectrum analyzer or oscilloscope FFT implementation to have a certain minimum set of user-selectable windows: rectangular ("no window"), flattop, Blackman(-Harris), and Gaussian. Hann, Hamming, Exponential, and Kaiser are also not uncommon.

author: 2N3055
author_rank: Super Contributor
timestamp: May 06, 2024, 01:07:10 pm
content: Quote from: pdenisowski on May 06, 2024, 01:03:29 pmRectangular ("no window"), flattop, Blackman, Von Hann and Hamming are on all Siglent scopes.

author: pdenisowski
author_rank: Super Contributor
timestamp: May 06, 2024, 01:09:44 pm
content: Quote from: mawyatt on May 06, 2024, 01:00:20 pmThanks - sometimes the hardest part of T&M is people using different methodologies / terminologies to describe the same thingI would assume the separating (or "resolving") two adjacent tones in spectrum is simply a function of the FFT resolution bandwidth.Quote from: mawyatt on May 06, 2024, 01:00:20 pmOuchThe sweeping methodology sounds painful.Quote from: mawyatt on May 06, 2024, 01:00:20 pmIndeed it is. The other thing that I think often gets overlooked is spurious emissions (spurs) generated within the instrument itself.

author: mawyatt
author_rank: Super Contributor
timestamp: May 06, 2024, 01:25:32 pm
content: Quote from: mawyatt on May 06, 2024, 12:46:05 pmMaybe of interest is some AWGs have the ability to "combine" the 2 channels internally, this could be done in "Digital Domain" before the DACs and channel amps/attenuators, or after the DACs in the "Analog Domain".Each would have advantages/disadvantages but both techniques could introduce IMD! Even in the "Digital Domain" combining since the combined digital summed signal then undergoes Digital to Analog conversion and subsequent amplification/attenuation before reaching the AWG output.Best,

author: 2N3055
author_rank: Super Contributor
timestamp: May 06, 2024, 01:34:30 pm
content: Quote from: mawyatt on May 06, 2024, 01:25:32 pmAnd what I have shown was exactly that: digital Channel Combine in SDG6000X.It is not as good as it would be with good resistive combiner, but plenty good enough for many uses.All you need to know and be aware of is what are the limits...

author: mawyatt
author_rank: Super Contributor
timestamp: May 06, 2024, 01:37:47 pm
content: Quote from: pdenisowski on May 06, 2024, 01:09:44 pmNot so bad if you have Grad Students do all the work"Indeed it is. The other thing that I think often gets overlooked is spurious emissions (spurs) generated within the instrument itself."Agree, spurs are bad in any instrument, especially SA, however since these DSO are being utilized as a low frequency SA they are particularly bad here as with SA.The absolute levels being shown and discussed are remarkable for any DSO much less at this price point, and this low level begins to reveal all that's underneath the Time Domain noise floor that's generally not viewable with typical scope usage!!Best,

author: joeqsmith
author_rank: Super Contributor
timestamp: May 06, 2024, 02:08:22 pm
content: Quote from: mawyatt on May 06, 2024, 01:00:20 pmSorry it wasn't clear but I was only curious about the scopes ability to resolve the two peaks.Quote from: mawyatt on May 06, 2024, 01:00:20 pmI had attempted to use my scope to measure AC line power by oversampling and decimation. In this case I drove the channels with a precision DAC and ran a least squares. Used the error to create a model for each channel. Again, not the best tool for the job but may provide some idea how the measurement could possibly be improved. First 7 minutes covered the setup.Guessing the new scopes would do a much better job of making these measurements.

author: joeqsmith
author_rank: Super Contributor
timestamp: May 06, 2024, 03:55:17 pm
content: Quote from: Performa01 on May 06, 2024, 12:50:17 pmI show the LeCroy to better explain what I am asking to see. Some of these low cost scopes are very impressive.Quote from: Performa01 on May 06, 2024, 12:50:17 pmThe 7404 is very tempting except it's not good enough to replace my old WaveMaster and it's way overkill for what I am looking for. After looking at what they offer, I am starting to lean toward the SDS2354X HD (?). It appears to offer some improvements, but I also give up in other areas. I would like to see where someone had ran this thing using the Ethernet interface. I've not found anyone showing any custom applications for it. Have you written custom software to interface with any of your Siglent products? If so, I would be interested in hearing how it went.

author: Martin72
author_rank: Super Contributor
timestamp: May 06, 2024, 05:24:54 pm
content: Today, at work...Lecroy Waverunner 9054(8bit), HDO6034A(12bit).FFT with 100khz span, source Siglent SDG1062X, 50Mhz, 0dBm, 50Ohm.Maybe we should have the last pages separated and moved to a new thread, title suggestion "FFT comparison and settings".

author: joeqsmith
author_rank: Super Contributor
timestamp: May 06, 2024, 07:25:12 pm
content: Quote from: Martin72 on May 06, 2024, 05:24:54 pmThat's fine. Personally I was really just asking how the low cost Siglent dealt with these cases I have brought up.

author: Martin72
author_rank: Super Contributor
timestamp: May 06, 2024, 08:11:02 pm
content: This is also a very exciting topic that "deserves" its own thread.Let's see if a moderator reacts, then he can also take this post with him.Again 50Mhz 0dBm, Siglent 824X HD, 50Ohm termination.Span 10khz, so far so clear.I have combined 2 tracks, the current one is at a vertical setting of 110mV/div (C1), the REF B track(purple) is at 100mV/div.(C1)

author: 2N3055
author_rank: Super Contributor
timestamp: May 06, 2024, 08:24:13 pm
content: Quote from: Martin72 on May 06, 2024, 05:24:54 pmSorry Martin,just a last one.Similar to LeCroys: 50 MHz, 0dBm,20dB/div, 100kHz span, 83Hz RBW , FlatTop W.200MHz BW limit on (HDO6034 is not 1GHz)I think it looks very good. Noise floor is good 10 dB better.

author: Martin72
author_rank: Super Contributor
timestamp: May 06, 2024, 08:43:41 pm
content: Nice."Fun" fact:The different modes (Average, Max Hold) are not available with the "normal" FFT from Lecroy.You have to buy them with the "Spectrum Analyzer" option....

author: EEVblog
author_rank: Unknown
timestamp: May 06, 2024, 11:54:49 pm
content: Quote from: Martin72 on May 06, 2024, 05:24:54 pmSplit from which post exactly?

author: Martin72
author_rank: Super Contributor
timestamp: May 07, 2024, 05:21:17 am
content: Hi Dave,Start with this please:https://www.eevblog.com/forum/testgear/sds800x-hd-review-demonstration-thread/msg5483791/#msg5483791

author: electronics hobbyist
author_rank: Regular Contributor
timestamp: May 08, 2024, 03:33:25 am
content: Quote from: Martin72 on May 04, 2024, 07:51:08 pmThe comparison chart of this keysight shows that the SDG output has these frequencies.

author: Performa01
author_rank: Super Contributor
timestamp: May 08, 2024, 05:58:39 pm
content: 50 Ω Termination and probingI sometimes see discussions about 50 Ω termination at the scope inputs. Some seem to believe that scopes with switchable 50 Ω inputs are just a luxury, that can easily be replaced by an external through-terminator or a BNC-T with end terminator.Even though I’ve often commented on this very topic already, I want to repeat it here with especially the SDS800X HD in mind.The commonly agreed industry standard for the maximum acceptable input VSWR is 1.5:1, which is equivalent to 14 dB return loss. This tolerates 4 % power reflection with its associated amplitude errors. It goes without saying that oscilloscopes with properly designed switchable 50 Ω inputs, like the SDS2000X series and anything above from Siglent, provide a VSWR ≤1.5:1 up to and beyond their full bandwidth.Now let’s have a look at all these emergency solutions, like external through-terminators and BNC-T with end termination, which all have a perfect VSWR of 1:1 up to 250 MHz when not connected to anything.First let’s connect the ancient hp10100C through-terminator to a real scope input, like the 1 MΩ // 17 pF in case of the SDS824X HD:hp10100C_SDS824X HD_VSWR_73MThe VSWR reaches 1.5:1 at 73 MHz. Beyond that, we’ll have to face substantial linear distortion.Here’s another test with the through-terminator RS-456-150-50Ω, which is the Tyco part B35 X13 • 999 X99, connected to the SDS824X HD:RS-456-150-50Ω_SDS824X HD_VSWR_78MThe VSWR reaches 1.5:1 at 78 MHz, hence is a tad better than the venerable hp10100C.Finally, the BNC-T with 50 Ω end terminator connected to the SDS824X HD:BNC-T50_SDS824X HD_VSWR_78MThe VSWR reaches 1.5:1 at 78 MHz, hence its effect is the same as the RS-456-150-50Ω.Just for orientation, here’s the VSWR-plot up to 3 GHz for the hp10100C not connected to anything:hp10100C_VSWR_1157MThe VSWR reaches 1.5:1 at 1157 MHz, hence would be useless for higher bandwidth oscilloscopes. By contrast, here’s the VSWR-plot up to 1.2 GHz for the SDS2504X HD and its 50 Ω input path:SDS2504X HD_V200mV_VSWR_1130MHere the VSWR reaches 1.5:1 at 1130 MHz, which is very similar to the hp through-terminator alone. Now, at the latest, it should become clear that 50 Ω input mode is more than just a resistor switched across the input connector. I do not have any SDS1000X HD here, but would not be surprised if its VSWR was similar to the SDS2000X HD.An oscilloscope without 50 Ω inputs is fine as long as you stick to the supplied probes, but circuit loading might become a problem at relatively low frequencies like 20 MHz already. Passive x10 “high impedance” probes with e.g. 10 pF tip capacitance represent a 200 Ω load impedance at 80 MHz after all. On the other hand, it can only perform up to some 80 MHz without noticeable linear distortion when using direct coax connection.Conclusion:Whenever you plan to do serious work at higher frequencies, then you should consider an oscilloscope with proper 50 Ω inputs. In order to avoid expensive active probes, you should better design appropriate 50 Ω test points into your prototype circuit.

author: Martin72
author_rank: Super Contributor
timestamp: May 10, 2024, 08:37:02 pm
content: Quote from: Martin72 on May 07, 2024, 05:21:17 amDave?

author: markone
author_rank: Frequent Contributor
timestamp: May 11, 2024, 01:13:38 am
content: Quote from: Martin72 on May 06, 2024, 08:11:02 pmHi Martin,could you try again with also 50KHz and 1MHz SPAN ?Here below my results, very same settings :10KHz SPAN :50KHz SPAN :1MHz SPAN :I would say unusable, in order to eliminate false spurious at this center frequency you have to raise RBW to a much higher value (222Hz ---> 3.56KHz) :and the whole picture is much less interesting.Useless to say, sourced signal is clean with SSA :where are missing also the small spurious present in 10KHz SPAN spectrum images (your and mine).I would say that SDS800x FFT is not usable at low RBW (in relation to the central frequency), if you guys can say with certainty that there are no bugs in the FW FFT implementation my interest in this functionality, apart from a few cases at quite low frequencies, ends here.

author: KungFuJosh
author_rank: Super Contributor
timestamp: May 11, 2024, 04:20:00 am
content: Quote from: electronics hobbyist on May 11, 2024, 01:30:39 amOpen the images in a new window or tab

author: electronics hobbyist
author_rank: Regular Contributor
timestamp: May 11, 2024, 05:45:48 am
content: Quote from: KungFuJosh on May 11, 2024, 04:20:00 amThank you, I have deleted the previous post. From these pictures, it appears that this phenomenon occurs when the number of points is >= 10M.

author: ebastler
author_rank: Super Contributor
timestamp: May 11, 2024, 06:27:20 am
content: Quote from: electronics hobbyist on May 11, 2024, 05:45:48 amSo, potentially an error in the down-sampling to the FFT's 2 MPt maximum?

author: gf
author_rank: Super Contributor
timestamp: May 11, 2024, 08:47:21 am
content: Quote from: markone on May 11, 2024, 01:13:38 am* Could you capture 100M samples of this signal at full 2GSa/s sample rate and post the .bin file?My feeling is that what you see in the FFT graph is already contained in the samples. I tend not to blame the FFT for that.* On a larger 0...1GHz span, how do the levels of the harmonics compare between FFT and SA?* Does a larger V/div (200mV/, 500mV/,...) reduce the amplitude of the close-in spurs (and harmonics)?Quote from: ebastler on May 11, 2024, 06:27:20 amNot necessarily an error. If there exist harmonics beyond 75 MHz then it is expected that they will fold into the first Nyquist zone, and if the carrier deviates only slightly from 50 MHz, the folded harmonics can indeed form a comb in the neighborhood the fundamental frequency.

author: ebastler
author_rank: Super Contributor
timestamp: May 11, 2024, 09:39:29 am
content: Quote from: gf on May 11, 2024, 08:47:21 amGood point. I just tried to reproduce the effect, and indeed it disappears when the incoming signal's frequency is adjusted such that the SDS800X HD sees it as exactly 50 MHz. The scope's time base clock is off by approx. 1..10 ppm -- well within spec of course.So do the other instruments, which markone and others compared with, have a better clock accuracy (either due to tighter specs or luck), and hence did not see the folded-back harmonics? And/or do they see less harmonics due to better linearity of the input stage?(Edit: Changed the stated time base tolerance -- it seems that I got lucky initially, with a 1 ppm deviation shortly after powering up the signal generator and scope. The deviation settled at about 10 ppm after a while, still well within the +- 25 ppm spec.)

author: gf
author_rank: Super Contributor
timestamp: May 11, 2024, 10:35:27 am
content: Quote from: ebastler on May 11, 2024, 09:39:29 amShould be easy to verify this on the other scope models, by adjusting the frequency.Could you also do a FFT with 0...1GHz span at 2GSa/s, in order to see the levels of the first 19 harmonics (w/o folding)?And if you have a SA, then for comparison the same also on the SA.The -30dB reading at marker 5 in markone's screenshot is quite a lot. What max. spur level do you see?

author: ebastler
author_rank: Super Contributor
timestamp: May 11, 2024, 11:09:22 am
content: Screenshots of the full 1 GHz spectrum and of my recreation of markone's settings are attached. The input signal was nominal 50 MHz from an (upgraded) SDG2042X.The highest spurious peak in the "folded back" setting is -30 dBm as well, as in markone's measurement. But in the full 1 GHz spectrum, all harmonics are below -50 dBm. What's happening there?

author: Martin72
author_rank: Super Contributor
timestamp: May 11, 2024, 01:01:43 pm
content: Quote from: markoneSame results, but won´t post it until the "new" thread exist..

author: markone
author_rank: Frequent Contributor
timestamp: May 11, 2024, 01:13:47 pm
content: Quote from: gf on May 11, 2024, 08:47:21 am100MSa are available @ 2GSa/s | 5ms/div, with this setting FFT works up to 25MHz, 50MHz CF is possible up to 2GSa/s | 2ms/div that corresponds to 40MSa, not relevant to you request but it's important to know.My feeling is that here we have a "beat" phenomenon between ADC sample frequency and input signal frequency, not an expert in FFT math but I guess there are techniques to mitigate it.Anyway, do you have an application able to dump the whole acquisition buffer ?Quote from: gf on May 11, 2024, 08:47:21 amIt's all up to RBW setting related to CF, any SPAN/CF combination has a RBW thereshold under which the spurious fest start, anyway the SSA provides this spectrum image :Quote from: gf on May 11, 2024, 08:47:21 amTried infinite settings, this is definitely not the case.Quote from: ebastler on May 11, 2024, 06:27:20 amThose spurious, that of course do not actually exist, appear with many FFT point size settings , as already mentioned to boredom it's all up to RBW setting toward CF value.

author: markone
author_rank: Frequent Contributor
timestamp: May 11, 2024, 01:14:51 pm
content: Quote from: Martin72 on May 11, 2024, 01:01:43 pmare you sure that it will never exist ... ?

author: Martin72
author_rank: Super Contributor
timestamp: May 11, 2024, 01:23:41 pm
content: I have now pressed the "Moderator Button" again, we are already way over here, but the topic itself is highly interesting, which is why I am in favor of it being outsourced.It's also not just the SDS800X HD, other scopes have the same behavior, so it's time it got its own thread.

author: markone
author_rank: Frequent Contributor
timestamp: May 11, 2024, 01:27:34 pm
content: Quote from: ebastler on May 11, 2024, 11:09:22 amLet's put it simple : the selected RBW values are not working correctly, it's useless to make comparison between utterly wrong spectrum images, if you want to get something similar to reality @ 50MHz CF / 1MHz SPAN, set RBW minimum at 3.36KHz (as I did in the "clean" spectrum that I posted).

author: markone
author_rank: Frequent Contributor
timestamp: May 11, 2024, 01:28:25 pm
content: Quote from: Martin72 on May 11, 2024, 01:23:41 pmDo you know a "fast" way to dump the complete sampling buffer ?

author: ebastler
author_rank: Super Contributor
timestamp: May 11, 2024, 01:51:27 pm
content: Quote from: markone on May 11, 2024, 01:27:34 pmI think the discussion has already moved beyond your "selected RBW values not working" and "utterly wrong" statements. gf's observation that the lowered sampling rates which are associated with your long captures (125 MSa/s only in your most recent screenshot!) will result in folded-back harmonics makes good sense to me.The presence of harmonics can be confirmed with a high-bandwidth FFT, and the foldback effect can be confirmed by carefully tuning the input signal to an exact 50 MHz (as perceived by the scope). Please take a step back and re-read the recent posts.

author: 2N3055
author_rank: Super Contributor
timestamp: May 11, 2024, 02:13:36 pm
content: Here is my scope.same settings, I even tuned the AWG for scope to show 50.00067 MHz so we can see if there are some specific beat frequencies..

author: markone
author_rank: Frequent Contributor
timestamp: May 11, 2024, 02:14:04 pm
content: Quote from: ebastler on May 11, 2024, 01:51:27 pmYou can move beyond what you want, but the sad truth is still "selected RBW values not working" and "utterly wrong"Quote from: ebastler on May 11, 2024, 01:51:27 pmNo need to re-read considerations based on false spectrum readings, because also your "high-bandwidth FFT" is fullfilled with non-existent spurious, if you want to look at the "truth" please make use of a real SSA as I'm doing.

author: markone
author_rank: Frequent Contributor
timestamp: May 11, 2024, 02:14:53 pm
content: Quote from: 2N3055 on May 11, 2024, 02:13:36 pmModel of your scope ?EDIT : please try to set the SPAM to 1MHz just to align settings.

author: 2N3055
author_rank: Super Contributor
timestamp: May 11, 2024, 02:16:10 pm
content: Quote from: markone on May 11, 2024, 02:14:53 pmWhat do you mean? SDS824xHD of course. That is one we are discussing here...

author: markone
author_rank: Frequent Contributor
timestamp: May 11, 2024, 02:18:15 pm
content: Quote from: 2N3055 on May 11, 2024, 02:16:10 pmGood, I know you have also something better ... anyway please align settings with ours, I mean :

author: 2N3055
author_rank: Super Contributor
timestamp: May 11, 2024, 02:27:46 pm
content: Quote from: markone on May 11, 2024, 02:18:15 pmFFT parameters are same:Sa=125MSa/sCurr=2MPtsdelta f=59.60HzRBW=222.33HzAverages are 16 but makes no difference.Is there anything else specific?

author: markone
author_rank: Frequent Contributor
timestamp: May 11, 2024, 02:30:41 pm
content: Quote from: 2N3055 on May 11, 2024, 02:27:46 pmSet SPAN to 1MHz, your spectrum image looks like SPAN = 500KHz.

author: 2N3055
author_rank: Super Contributor
timestamp: May 11, 2024, 02:36:12 pm
content: If you insist..It makes no difference. I set it to 500KHz to better see details..Attached 1, 2 and 10 MHZ span....

author: markone
author_rank: Frequent Contributor
timestamp: May 11, 2024, 02:39:39 pm
content: Quote from: 2N3055 on May 11, 2024, 02:36:12 pmTwo quick questions :1) Signal generator ?2) Last but not the least ... FW version IS ... ?EDIT :I would guess higher than mine :

author: 2N3055
author_rank: Super Contributor
timestamp: May 11, 2024, 02:51:57 pm
content: Quote from: markone on May 11, 2024, 02:39:39 pmAWG is SDG6052X.FW version is latest one without public number.

author: markone
author_rank: Frequent Contributor
timestamp: May 11, 2024, 02:57:49 pm
content: Quote from: 2N3055 on May 11, 2024, 02:51:57 pmOk, so for sure you signal is cleaner, do you know second and third hamonics level ?Do you maybe have an SDG2000X ?Quote from: 2N3055 on May 11, 2024, 02:51:57 pmIf the problem is not strictly harmonics related it could be that FW guys did some work on FFT math ... I want IT !

author: gf
author_rank: Super Contributor
timestamp: May 11, 2024, 03:00:33 pm
content: Quote from: 2N3055 on May 11, 2024, 02:36:12 pmOne difference I still see is 100mV/div versus 200mV/div.

author: Martin72
author_rank: Super Contributor
timestamp: May 11, 2024, 03:00:53 pm
content: The RBW can only be achieved by manually setting the sample rate in the menu.If you leave the settings on Auto, you get a different value - which RBW is the "right" one for a 50Mhz signal and 1Mhz span (50k, 10k)?For example, if I leave the SDS3034X HD as it is, I have approx. 700Hz RBW, but also no "problems" with the signal display.

author: ebastler
author_rank: Super Contributor
timestamp: May 11, 2024, 03:01:35 pm
content: Quote from: markone on May 11, 2024, 02:14:04 pmIs this one acceptable? SDS814X HD, upgraded to 824.

author: markone
author_rank: Frequent Contributor
timestamp: May 11, 2024, 03:07:23 pm
content: Quote from: ebastler on May 11, 2024, 03:01:35 pmWhat have you changed from your previous spectrum image ?

author: 2N3055
author_rank: Super Contributor
timestamp: May 11, 2024, 03:08:36 pm
content: Quote from: gf on May 11, 2024, 03:00:33 pmThat is not problem. I use 200mV/div, because IMD for close in peaks is few dB better that way.Even with SA you don't use full scale for distortion measurements.With 100mv/div, slightly more distortion, nothing else.

author: markone
author_rank: Frequent Contributor
timestamp: May 11, 2024, 03:11:00 pm
content: Quote from: gf on May 11, 2024, 03:00:33 pmI noted too, but in my case @ 200mV/div the spurious level up.

author: markone
author_rank: Frequent Contributor
timestamp: May 11, 2024, 03:12:27 pm
content: Quote from: 2N3055 on May 11, 2024, 03:08:36 pmI can confirm.

author: ebastler
author_rank: Super Contributor
timestamp: May 11, 2024, 03:13:03 pm
content: Quote from: markone on May 11, 2024, 03:07:23 pmAdjusted the signal generator frequency such that the scope "sees" an exact 50 MHz. I wanted to get the point across that we are seeing harmonics beyond the Nyquist limit, folded back in the spectral range, if the input frequency is slightly off. Doesn't look like a bug to me.My guess would be that 2N3055 sees less of them since he is using a better signal generator.

author: gf
author_rank: Super Contributor
timestamp: May 11, 2024, 03:25:00 pm
content: Quote from: markone on May 11, 2024, 02:57:49 pmThat's why I'd like to look at the raw samples, and why I asked for a .bin file with 100M points. And yes, I ask for 2 GSa/s first because I want to preserve as much information as possible from the original signal. I can downsample myself.

author: markone
author_rank: Frequent Contributor
timestamp: May 11, 2024, 03:26:22 pm
content: Quote from: ebastler on May 11, 2024, 03:13:03 pmJust replicated on my DSO, I had to shift down the generator frequency to 49.999350MHz to obtain a perfect 50MHz reading, normally I get 50.000650.Quote from: ebastler on May 11, 2024, 03:13:03 pmMy guess too, reason why I asked him levels of 2nd and 3rd harmonics, anyway I would be glad to try the new incoming FWIn this case the folded back harmonic/s would Zero beat with central carrier producing a clean near spectrum image.

author: markone
author_rank: Frequent Contributor
timestamp: May 11, 2024, 03:28:00 pm
content: Quote from: gf on May 11, 2024, 03:25:00 pmI would be glad to provide it but I have no time now to write an application program, do you guys know if exist something usable for the purpose ?EDIT : foldback should be feasable with decimated vector that supplies FFT Math, not with original data sampled @ 2GSa/s, right ?

author: gf
author_rank: Super Contributor
timestamp: May 11, 2024, 03:40:32 pm
content: Quote from: markone on May 11, 2024, 03:28:00 pmUser manual:QuoteSave the trace as Binary Data (.bin file).QuoteAlreadysamplingthe analog signal folds the spectrum.And down-sampling folds it again to an even smaller frequency range.Folding back is not possible in general, since the folding is a N:1 mapping in the frequency domain.

author: markone
author_rank: Frequent Contributor
timestamp: May 11, 2024, 04:03:55 pm
content: Quote from: gf on May 11, 2024, 03:40:32 pmI mean in respect to "real" sampleable harmonics that should be 2nd, 3rd and 4th, all below Nyquest @ 2GSa/s.Anyway :1) link to compressed bin file 100MSa @ 2GSa/s (size is about 95MB) :https://file.io/su83ZcbhPr4d2) link to compressed bin file 40MSa @ 2GSa/s (size is about 40MB) :https://file.io/hxDe9PqKBLGY

author: Performa01
author_rank: Super Contributor
timestamp: May 11, 2024, 05:04:19 pm
content: I don't expect the original sample data to reveal the true cause, which is already registered in Siglents internal bug list.In short: a problem can arise whenever the FFT sample rate is not equal to the acquisition sample rate. There seems to be an exception for the 1:2 ratio.In this particular test case, you can try using constant sample rate of 250 MSa/s and then, with 5 Mpts record length, the FFT will use 125 MSa/s, resulting in the smallest possible RBW at 50 MHz, without excessive spurious signals:SDS824X HD_FFT_C50M_S1M_Sa250_125

author: gf
author_rank: Super Contributor
timestamp: May 11, 2024, 05:08:04 pm
content: Quote from: Performa01 on May 11, 2024, 05:04:19 pmIf it is already a well-know and accepted bug, then there is not need to investigate further.

author: markone
author_rank: Frequent Contributor
timestamp: May 11, 2024, 05:43:46 pm
content: Quote from: Performa01 on May 11, 2024, 05:04:19 pmGood to know, this is exactly what I was hoping to with my lame post activitySo now we canofficiallysay that there is some margin of improvement in FFT performance, could you "disclose" if we will see something in regard with the incoming FW release?

author: Martin72
author_rank: Super Contributor
timestamp: May 11, 2024, 05:50:53 pm
content: Quote from: Martin72 on May 11, 2024, 03:00:53 pmWas this question too stupid ?Edit:Pics(1M,50k,10K)..

author: joeqsmith
author_rank: Super Contributor
timestamp: May 11, 2024, 06:23:49 pm
content: Quote from: Performa01 on May 08, 2024, 05:58:39 pmI've never heard of such a standard. Could you provide a reference? If you are making measurements, 1.5 seems really high.Looking at the manual for my LeCroy 7200, they spec the VSWR at 1.2, BW is 4GHz with a 125pSec transition for 50mV and up. Isolation is 60dB min at 1GHz.I recently looked at SJL's sampling scope and verified the port match.Quote from: SJL-Instruments on January 13, 2024, 03:00:49 amOnce you get up to 5GHz, the return loss is around -7 and you really need to add an attenuator to improve it.

author: markone
author_rank: Frequent Contributor
timestamp: May 11, 2024, 07:13:17 pm
content: Quote from: Martin72 on May 11, 2024, 05:50:53 pmNot stupid at all, some automation in FFT settings would be more than welcome, direct RBW setting would be first in the list as well as a "blocking" mechanism for impossible parameters combination, simply to mimic a true SSA, putting the timebase setting as a "slave" parameter.For instance, I hate a lot that when i loose the CF setting increasing the Timebase, as a consequence of this you have to re-set the CF manually, that is a huge PITA.

author: gf
author_rank: Super Contributor
timestamp: May 11, 2024, 09:06:58 pm
content: Quote from: markone on May 11, 2024, 04:03:55 pmThank you!I removed my previous post where I messed up the vertical scalingI've also received a .bin file from Martin72, so I decided to plot them side by side with yours.Attached are the corrected/updated plots.The similarity is amazing, although it is not the same instrument.For figure4, I did downsample with anti-aliasing filering (which the scope does not do).Compared to figure3, some of the spurs disappear (those that fold down from 62.5...1000 Mhz to 0...62.5 Mhz in figure3).

author: KungFuJosh
author_rank: Super Contributor
timestamp: May 11, 2024, 10:22:20 pm
content: They both have SDG2000X AWGs as the source? That is crazy similar for the signals.

author: Martin72
author_rank: Super Contributor
timestamp: May 11, 2024, 10:38:00 pm
content: Yepp,We have the same generator:https://www.eevblog.com/forum/testgear/sds800x-hd-review-demonstration-thread/msg5483791/#msg5483791

author: KungFuJosh
author_rank: Super Contributor
timestamp: May 11, 2024, 11:34:10 pm
content: Quote from: Martin72 on May 11, 2024, 10:38:00 pmI guess we all do lol.Did you use the 3kXHD or the 800 for your results?

author: Martin72
author_rank: Super Contributor
timestamp: May 11, 2024, 11:43:41 pm
content: Mostly the 800, except this one:https://www.eevblog.com/forum/testgear/sds800x-hd-review-demonstration-thread/msg5494624/#msg5494624

author: eTobey
author_rank: Super Contributor
timestamp: May 12, 2024, 05:29:05 am
content: Is there a way, to create a math formula, so one could easily see, what the duty cycle (yellow) roughly is?

author: ebastler
author_rank: Super Contributor
timestamp: May 12, 2024, 06:02:13 am
content: Quote from: eTobey on May 12, 2024, 05:29:05 amA "Measurement Track" (section 18.5 of the manual) should do what you want: Calculates time-dependent measurements within one capture and plots them like a trace.

author: Performa01
author_rank: Super Contributor
timestamp: May 12, 2024, 06:45:31 am
content: Quote from: joeqsmith on May 11, 2024, 06:23:49 pmI have no reference to such a standard – my statement is based solely on the impression left by various RF literature, experience and common sense. Sorry if it has been misleading.At least one example, showing that I’m not the only one who thinks 1.5:1 is the limit of acceptable (some might call it ideal) VSWR, can be found here:https://www.ahsystems.com/notes/VSWR-return-loss-sheet.phpQuoteVery few oscilloscopes have the input return loss / VSWR specified; one of the few exceptions was the now discontinued 2 GHz R&S RTE. From the data sheet Version 16.01:QuoteI take from this, that a company, that is renowned to be an RF-specialist since 1933, has no problems specifying a VSWR of 1.4:1 for frequencies >500 MHz on an instrument that isn’t exactly a cheap low-end product. There exists no VSWR-specification for its successor, the MXO5, anymore…Finally, the common-sense part: A VSWR of 1.5:1 means 4 % reflected power, i.e. 4 % power loss at the receiver end (scope input). That’s 0.17 dB = ~2% voltage error. It is less than the DC-accuracy specification of most oscilloscopes.As can be seen from my measurements, the 500 (actually 570) MHz SDS2000X HD provides a VSWR of <1.25:1 up to ~750 MHz. That should be in line with your expectations based on the LeCroy 7200.

author: joeqsmith
author_rank: Super Contributor
timestamp: May 12, 2024, 05:01:39 pm
content: Thanks for the response. It could very well be my lack of any common sense and experience causing my confusion.If I were considering the acceptable VSWR of my antenna system, I could see some general guidelines. If I were trying to measure the output power of my amplifier, I would have a different criteria for the load match of my power meter (mine is 1.05 for example). There is a reason you will find many application notes about using precision attenuators to improve port matching when making measurements. Consider some parts may have a very good isolation between their input and output and the measurement uncertainty would be much less.My vintage LeCroy 8500A specs 50+/-2%. 20log10(50*0.02/50*2.02) = 40dB return loss, but that's at DC. An 8-bit system like this is going to mask a lot of the errors which may be why manufactures didn't provide the details.I imagine as manufactures improve their products and users find more applications for them, spec's like return loss will become more important.Quote from: Performa01 on May 12, 2024, 06:45:31 am

author: Performa01
author_rank: Super Contributor
timestamp: May 12, 2024, 06:29:24 pm
content: Quote from: markone on May 11, 2024, 05:43:46 pmSorry, but even when it might appear that way, that issue isn't simply a programming error. Repair of the FFT would be relatively easy, but could affect other math and measurement functions in a negative way - and the perfect solution might take a lot of additional resources. So the viable solutions are still discussed internally and I cannot even know how much effort the final (safe) solution will be.

author: eTobey
author_rank: Super Contributor
timestamp: May 12, 2024, 06:33:13 pm
content: Quote from: ebastler on May 12, 2024, 06:02:13 amThanks.Thats kinda nice, but why didnt they include this in the math? Alignment is everything with a scope.2 Sentences in the manual, but 6 settings / buttons in the scope.

author: Performa01
author_rank: Super Contributor
timestamp: May 12, 2024, 06:48:24 pm
content: Quote from: joeqsmith on May 12, 2024, 05:01:39 pmNo need to be sarcastic.I thought it was clear that I was talking about oscilloscopes and not power meters, which commonly have an order of magnitude better accuracy. Consequently, I would also prefer a VSWR of 1.05 for the power meter.I thought it was clear that I was talking about oscilloscopes and not complete measurement setups. Nowhere did I state that a better VSWR could not be beneficial at times, and that it could not be achieved by adding an inline attenuator – even though in practice I’ve more often wanted to improve the output impedance match of a generator than the input match of an oscilloscope – but that’s just me.

author: joeqsmith
author_rank: Super Contributor
timestamp: May 12, 2024, 07:30:32 pm
content: There is no reason an oscilloscope could not measure power. In this thread we are seeing a lot more applications and I don't see this curbing anytime soon. I'm not suggesting an oscilloscope is a replacement for a power meter, network analyzer, spectrum analyzer.... Rather, modern scopes are slowly smearing the lines. As their performance improves and the features they support grow, I suspect such details will become more important. While a VSWR of 1.5 may be a good guideline when talking about antennas, it's not something I have ever considered when making a measurement in the lab. Certainly not a standard. Rather, I treat each measurement as a unique problem.Oh well, sounds like I have my answer and not trying to upset you. Thanks for the input.Quote from: Performa01 on May 12, 2024, 06:48:24 pm

author: RoGeorge
author_rank: Super Contributor
timestamp: June 19, 2024, 06:15:19 pm
content: Quote from: Performa01 on January 23, 2024, 08:33:24 amOutstanding demos and pdf documentation, thank you.You may want to add in the opening post a link to the second pdf, too (https://www.eevblog.com/forum/testgear/sds800x-hd-review-demonstration-thread/msg5422826/#msg5422826). The second pdf has only half the number of downloads than the first, would be a pity for the second part to remain lost somewhere inside the thread.

author: pdenisowski
author_rank: Super Contributor
timestamp: June 19, 2024, 09:27:45 pm
content: Quote from: joeqsmith on May 12, 2024, 07:30:32 pmThis is very true: what constitutes "acceptable" VSWR for an application is all over the place: in some applications, for example for amplifier inputs, a very low VSWR (< 1.x) is more or less expected. In some other applications, such as in EMC radiated immunity testing, seeing a VSWR of < 6 at the amplifier output for some portion of a frequency sweep might still considered okay - even when Tx power is in the range of 100s of watts (!!!)With regards to antennas, the "bandwidth" of an antenna is often defined as the frequency range over which VSWR < 2.0 (or sometimes even < 3.0). I actually was writing about this today as part of a presentation / video I'm about to release on antenna testing

author: MildInductor
author_rank: Regular Contributor
timestamp: September 26, 2024, 07:46:32 am
content: Is the SDS800X able to provide 5V at 2A out of the USB ports? I can’t see any specifications regarding this. I would like to use a little travel router with the oscilloscope.Perhaps someone feels like putting a 2.5ohm resistor into the USB along with a current meter

author: tautech
author_rank: Super Contributor
timestamp: September 26, 2024, 07:54:49 am
content: Quote from: MildInductor on September 26, 2024, 07:46:32 amUSB outlet is OL protected and if it trips rebooting the scope will restore it.

author: MildInductor
author_rank: Regular Contributor
timestamp: September 26, 2024, 08:01:06 am
content: Good to hear. It would be great to get some indication if 2A (or maybe even 3A but I think that is pushing it) is possible to draw. Perhaps someone has tried before?

author: tautech
author_rank: Super Contributor
timestamp: September 26, 2024, 08:22:00 am
content: Quote from: MildInductor on September 26, 2024, 07:46:32 amI use this AP set to Bridge mode all the time:https://www.tp-link.com/us/home-networking/wifi-router/tl-wr802n/#specifications5V 1ALook up the power requirement spec for yours.

author: 2N3055
author_rank: Super Contributor
timestamp: September 26, 2024, 08:31:58 am
content: Quote from: MildInductor on September 26, 2024, 08:01:06 amI highly doubt there is 2A available on those ports. Or at least I wouldn't try, protection or not.Those ports are meant for USB Sticks and HID devices. An USB disk too. 500mA, maybe 1A.Even SAG1021 (USB AWG device) draws miniscule current, output being limited to max 30mA.But as 10-15W power port ? Why risk a 600 € device to save using 10€ charger?

author: MildInductor
author_rank: Regular Contributor
timestamp: September 26, 2024, 11:39:34 pm
content: Quote from: tautech on September 26, 2024, 08:22:00 amThat’s useful to know because the router I am looking at using is very similar, so I am pretty sure it will work. Thanks tautech.I don’t want to use a wall adapter because this is meant to be a portable setup.

author: Goody
author_rank: Newbie
timestamp: November 11, 2024, 12:09:37 am
content: As an old geezer trying to make the transition from analog to digital scopes, (and struggling). Is there a way to display the volts per division permanently on the screen of my 802X?

author: KungFuJosh
author_rank: Super Contributor
timestamp: November 11, 2024, 01:08:45 am
content: Quote from: Goody on November 11, 2024, 12:09:37 amThat's usually shown for each channel. Look in the bottom left corner of the screen, and each channel should show what V/div is set for it in the small info box (note that it shows V/ not V/div: 1V/ or 100mV/, etc.).ETA: the axis on the screen will reflect whatever channel you selected last.

author: Goody
author_rank: Newbie
timestamp: November 11, 2024, 03:36:28 am
content: Thank You. I kept seeing it flash for a second in the middle of the screen near the bottom whenever you change the vertical knob. Operator error, no shortage of those.

author: 2N3055
author_rank: Super Contributor
timestamp: November 11, 2024, 06:34:11 am
content: Quote from: Goody on November 11, 2024, 12:09:37 amIn "Display" menu, slide the right menu up, and you will find there a "Axis labels settings".Click on that and switch axis labels On, set them to Moving, and select left right or middle for vertical labels.This will show calculated scales on graticules for currently selected channel.

author: hp lee
author_rank: Newbie
timestamp: November 13, 2024, 10:43:39 am
content: Quote from: MildInductor on September 26, 2024, 11:39:34 pmhttps://www.eevblog.com/forum/testgear/siglent-sds800x-hd-12-bit-dsos-coming/msg5697471/#msg5697471I recommend this. power consumption <1W. IMO ideal for portable setup.

author: Goody
author_rank: Newbie
timestamp: November 14, 2024, 10:22:58 pm
content: Thank You very much. It feels more familiar.

author: Bill3745
author_rank: Contributor
timestamp: December 07, 2024, 06:57:18 pm
content: Apologies if this is an obvious question that was addressed elsewhere, but what setup did you use for the bandwidth measurements? The closest I can do to approximate the FFT displays you presented was to feed a broadband noise signal into the scope and then run an FFT with averaging. I'm not questioning the bandwidth figures (I pretty much had similar results), but am stymied on how you produced them.

author: 2N3055
author_rank: Super Contributor
timestamp: December 07, 2024, 07:58:11 pm
content: Quote from: Bill3745 on December 07, 2024, 06:57:18 pmMost of the settings are visible in images posted.Use peak hold mode for FFT and sweep frequency by signal generator.

author: Bill3745
author_rank: Contributor
timestamp: December 07, 2024, 08:11:17 pm
content: Quote from: 2N3055 on December 07, 2024, 07:58:11 pmThanks, peak hold on the FFT answers my question as to how the graph was so smooth without averaging. However, how do you synchronize the generator frequency sweep with the FFT sweep? To me that implies something like a tracking generator on a SA, but not sure how you would duplicate on the SDS800X without some additional equipment.

author: Bill3745
author_rank: Contributor
timestamp: December 07, 2024, 08:24:54 pm
content: Quote from: Bill3745 on December 07, 2024, 08:11:17 pmScratch that. I'm guessing (can't test it right now) that the answer lies in the peak hold... Thanks.

author: gf
author_rank: Super Contributor
timestamp: December 07, 2024, 08:52:21 pm
content: Quote from: Bill3745 on December 07, 2024, 08:11:17 pmYou don't synchronise. You let the generator sweepvery slowlyso that the scope captures a large number of records during the sweep and combines them with peak hold. Don't use a too long record length (and number of FFT points) for this use case.

author: Martin72
author_rank: Super Contributor
timestamp: December 07, 2024, 09:01:06 pm
content: I use these settings when I want to determine the bandwidth using sweep and fft peakhold:https://www.eevblog.com/forum/testgear/bandwidth-limit-on-siglent-sds2000x-plus-oscilloscope/msg5208711/#msg5208711

author: Bill3745
author_rank: Contributor
timestamp: December 07, 2024, 09:15:17 pm
content: Quote from: Martin72 on December 07, 2024, 09:01:06 pmThanks, Martin (& gf). I ended up with the same setup after thinking a bit more about how max-hold operates

author: vsilves
author_rank: Regular Contributor
timestamp: February 22, 2025, 02:23:16 am
content: I just did a test. Used LBE-1420 GPSDO locked clock source as a makeshift signal generator. I think it has more constant Vpp than other sig-gens I have in that range. Coax terminated with 50Ω thru connector. Manually wrote down the average Vpp at some increasing frequencies for both converted (200 MHz bandwidth) SDS804XHD and converted (200 MHz bandwidth) SHS800X.The picture below shows the data, along with interpolated curves, and the -3 dB point for both. One of the traces had a glitch when I had to change the vertical resolution, but the results is not affected I think.

author: graybeard
author_rank: Frequent Contributor
timestamp: February 22, 2025, 09:10:51 pm
content: So far I have been very happy with my SDS824X HD Oscilloscope. I especially like the advanced statistics with the histogram. However I find the the Pk-Pk value is waste of valuable screen space since if offers no unique information. Pk-Pk is just the difference of the Max and Min values.Pk-Pk = Max - MinI hope Siglent eliminates the Pk-PK value or allows it to be disabled in a future firmware update.

author: 2N3055
author_rank: Super Contributor
timestamp: February 22, 2025, 10:02:33 pm
content: Quote from: graybeard on February 22, 2025, 09:10:51 pmIt does offer unique information. I performs Pk-Pk = Max - Min for you automatically, in real time.I strongly disagree. I simply hate when manufacturers don't calculate P-P. So I don't have to do that metal math all the time.I hope they don't get rid of P-P. Fact that you don't need or want it doesn't mean other people fell the same...It is very useful that you can directly compare P-P and Stdev so you can easily estimate crest factor for instance....We cannot simply say that whole planet does not need something because we don't.

author: graybeard
author_rank: Frequent Contributor
timestamp: February 23, 2025, 12:40:29 am
content: Quote from: 2N3055 on February 22, 2025, 10:02:33 pmWe cannot simply say that whole planet needs something because we do. Having the option to tun Pk-Pk off or on would be good.The most useful feature of the new statistics is the histogram of measurement values. You can see from the histograms of the example I uploaded that none of the measurements have a "normal distribution." That distribution, and it's limits, the high & low (Max & Min) values are typically all I want.

author: tautech
author_rank: Super Contributor
timestamp: February 23, 2025, 12:50:46 am
content: Quote from: graybeard on February 23, 2025, 12:40:29 amChris, does Measurements > Simple better suit your needs ?

author: graybeard
author_rank: Frequent Contributor
timestamp: February 23, 2025, 01:48:10 am
content: Quote from: tautech on February 23, 2025, 12:50:46 amThe Pk-PK in the advanced statistics is the the difference between the largest (Max) and smallest (Min) value for a given measurement. It has nothing to do with the Pk-Pk value of the waveform. Perhaps a better name for it would be measurement range.Consider the histogram measurement of the square wave duty cycle shown below.The Max value is 50.018%. That is the right most bin in the histogram with data.The min value is 49.923%. That is the left most bin in the histogram with data.The Pk-Pk value is range from the Min bin to the Max bin (Max-Min). It is 0.09492%. It has nothing to do with the Pk-Pk value of the waveform. Instead of Pk-Pk it might be better called span, since it is the range of bins in the histogram with data.To me I want to know where the edges of the histogram are, and then the shape of the histogram.

author: tautech
author_rank: Super Contributor
timestamp: February 23, 2025, 02:30:50 am
content: And Std Dev don't give you the info you want ?Have you tried a Math on Math ?Do you still have any contact with Siglent Chris now that Steve has retired ?

author: graybeard
author_rank: Frequent Contributor
timestamp: February 23, 2025, 04:54:09 am
content: Quote from: tautech on February 23, 2025, 02:30:50 amStd Dev (standard deviation) is an especially good number if the the distribution is normal (Gaussian). The best way to tell is to look at the histogram.Here is an example of pseudo random noise from anSDG112Xwith the output set to a Stdev of 200mV and a Mean of 0V. The output is set to 50Ohms and there is a 50 Ohm feed thru termination on the input to theSDS824X HD. This noise should be Gaussian.sIdeally one would look at the distribution of the instantaneous output voltage to see if it is normal, but that is beyond the capability of theSDS824X HD. However we can look at the mean and median values of the noise and would expect these to be normal as well. That is what is shown below.You can see that the histograms of the noise waveform mean, median, and standard deviation both appear normal, as does the histogram of the standard deviation.The measurment capability with the histograms is more powerful than any other oscilloscope I have used (a very small subset of what exists). This capability in a $700 scope (I bought from the year end sale) is great!

author: tautech
author_rank: Super Contributor
timestamp: February 23, 2025, 05:44:13 am
content: Quote from: graybeard on February 23, 2025, 04:54:09 amLooking forward to another one of your vids exploring its advanced features in detail.

author: 2N3055
author_rank: Super Contributor
timestamp: February 23, 2025, 09:32:07 am
content: Quote from: graybeard on February 23, 2025, 12:40:29 amChris,It is not the same. It is already there. So no work is needed. You are literally asking for someone to invest work to remove something that is already there. That has been used by people on dozen of model types for years before even you tried if of the first time. Invest work to make it less good. I gave you anecdotal evidence that between you and me, we already have 50:50 spread. So, respectfully, your opinion is now known and I respect that you have your thought process the way it is. Others have their own little idiosyncrasies and little mental helpers when doing things.And it is not the same. If calculation is there, that works for both. I use it, you are free to ignore it. If it is removed, then it is lost for everybody.Making it configurable would need redoing whole stats presentation code. If that ever happens i would venture it would be available on higher end models, not on the least expensive one. Also make note this is shared platform, and your "uses screen" comment is not really a thing on larger screens. I guess on 7" screen everything looks cramped...Instead of using valuable time on this, I would rather they spend time on adding new types of measurements that could be useful, or enhancing triggering or something else.Of course this is my opinion comment on your opinion. I don't think you are wrong that you claim you don't need something. What you need or don't is your prerogative.As for histicons and histograms, right there at your fingertip, I have been promoting this as best feature for years now. This is something I use all the time, and it IS the best way to understand statistical data.EDIT: Thinking about it, I would not mind if what is now called "P-P" in stats to be renamed to somethin like "span" or "spread". I agree with that. It might be less confusing to people so they do not confuse it for P-P value of the measurement itself.

author: mikes
author_rank: Regular Contributor
timestamp: February 23, 2025, 04:49:05 pm
content: Quote from: graybeard on February 22, 2025, 09:10:51 pmHow so? In your pictures, it's not obstructing anything useful, let alone "valuable." And it's not forcing some other measurement off the screen. What would this "valuable screen space" contain if it weren't there?

author: eTobey
author_rank: Super Contributor
timestamp: February 25, 2025, 08:19:37 am
content: Quote from: graybeard on February 22, 2025, 09:10:51 pmThere are more severe issues, and nobody really cares. Not even Siglent. So dont waste your time.

author: 2N3055
author_rank: Super Contributor
timestamp: February 25, 2025, 08:41:33 am
content: Quote from: eTobey on February 25, 2025, 08:19:37 am

author: Kleinstein
author_rank: Super Contributor
timestamp: February 25, 2025, 09:08:24 am
content: The peak to peak value makes sense in this context: it gives the scale for the histogram. With reading near zero one can calculate from the min and max, but it gets less convenient with values away from zero. In many cases one could as well skip the min and max values - but it depends on the use. Adding another option to customize adds complexity to the UI. So no easy solution that fits all.The measured curve and the calculated numbers compete for screen space - finding a good balance is tricky as it depends on the use case which part is more relevant to the user. Keeping screen clutter small is a valid target.

author: 2N3055
author_rank: Super Contributor
timestamp: February 25, 2025, 09:31:56 am
content: Quote from: Kleinstein on February 25, 2025, 09:08:24 amThank you for very nice summary. You said it better than I could.

author: awakephd
author_rank: Regular Contributor
timestamp: February 26, 2025, 12:18:46 am
content: Quote from: eTobey on February 25, 2025, 08:19:37 amInteresting. My own experience suggests that, if truly no one cares about something that I find very problematic, it generally means that I am the only one who has the problem. Of course, YMMV.

author: eTobey
author_rank: Super Contributor
timestamp: February 26, 2025, 08:02:03 am
content: Quote from: awakephd on February 26, 2025, 12:18:46 amIndeed, i am a poor guy, that could only afford a Siglent SDS800X HD. But at the same time, i am in a fortunate position, that i can turn ofa bunchof problems, with a simple button press.Just yesterday, i used my DSO quad, to decode USART, and to view more than 64 bytes at once. I simply did not "turn on" those "problems" (the Siglent).(The Siglent only shows like 7 bytes, and scrolling is a pain in the A. - The mouse scrollwheel has no function, and moving the scrollbar does not move the list at the same time.) BTW: those bytes on the DSO Quad are shown in ASCII and Hex at thesame time.

author: crysti
author_rank: Regular Contributor
timestamp: April 11, 2025, 05:25:31 am
content: Is there any chance of frequency calibration? My Siglent SDS814X HD shows 10.00014 MHz GPSDO reference frequency of 10MHz, that is 14ppm. I know it is within specifications, but I would like more accuracy.Another issue might be the input capacitance. I have measurement bridges with a precision of up to 0.001 pF, and I measured 19 pF on each input, with the Rigol DHO804 competitor, I measured 15pF. Impedance for 200MHz 15 pF > 53.05Ω 19pF > 42.58Ω.I would like to know what input capacitance others have observed.

author: EvgenyG
author_rank: Regular Contributor
timestamp: April 11, 2025, 08:08:48 am
content: Quote from: crysti on April 11, 2025, 05:25:31 amUnless there is updated information, the answer is no it is not adjustable. I'd love to do the same.

author: nanopico
author_rank: Contributor
timestamp: April 17, 2025, 12:50:59 pm
content: Quote from: crysti on April 11, 2025, 05:25:31 amEven if you could somehow do this calibration, which is only possible by changing the oscillator, the internal reference is not very accurate,aging processes will lead to frequency changes.The best method is to lock the oscilloscope to an external reference, a GPSDO for example.Most equipment can use an external 10 MHz reference (seems to be standard these days), so it is a good idea to invest in something like that (e.g. Leo Bodnar GPSDO).

author: crysti
author_rank: Regular Contributor
timestamp: April 17, 2025, 09:13:56 pm
content: Quote from: EvgenyG on April 11, 2025, 08:08:48 amI’ve now discovered why they’re all at + a few ppm: over time, the frequency decreases toward the nominal value due to aging. In the first few years the drift is larger; thereafter the rate of change slows down (logarithmic trend).

author: Martin72
author_rank: Super Contributor
timestamp: April 17, 2025, 09:27:08 pm
content: Hi,QuoteThe question that arises for me is, what for?All channels of the scope are “connected” to the same time base, so you will not initially experience any benefit from higher accuracy when displaying the respective signals.I would rather perform frequency measurements/adjustments using a measuring device designed for this purpose (frequency counter).Ultimately, it should not be forgotten that although this is a very capable scope, it is still limited in terms of price.

author: crysti
author_rank: Regular Contributor
timestamp: April 21, 2025, 05:46:53 am
content: I’ve created a small Excel tool to help you calculate the actual frequency, provided you are able to measure the real frequency deviation. I reduced the read frequency by -2 ppm by coating the oscillators on the motherboard with DUE-CI V-66 Isolating Lacquer Spray.Siglent only allows adjustment of the internal timebase offset on its top-end models (e.g., the 6000 or 8000 HD series), a feature that is very simply implemented via the PLL. In any case, the cost savings on the SDS800X are not significant, since the simple oscillator used costs €1, whereas a 0.3 ppm VCTCXO costs €8.Likewise, on the lower-end models they have removed the physical fan-speed control, even though it remains available in the service menu.

author: 2N3055
author_rank: Super Contributor
timestamp: June 14, 2025, 11:27:25 am
content: Quote from: crysti on April 21, 2025, 05:46:53 amSo what is your point?You would like also that 800xHD would cost 55 € and have OCXO, and active probe interface?And also have 10" screen and also.... Yeah that would be great but not realistic.There is a different made topic specifically about people expressing what they think might have been done differently. Your comments belong there, and it would be nice if you could move them there.This is a topic to demonstrate use and what scope can and cannot do, not about how you think you would be more happy with a scope that was made differently.At this moment there is no 8000 model in Siglent offering. There is 800xHD, 1000xHD, 3000xHD, 5000X, 6000A and 7000A.

author: pezcat19
author_rank: Contributor
timestamp: June 15, 2025, 11:52:18 am
content: Quote from: EvgenyG on April 11, 2025, 08:08:48 amMe too! Without a 10MHz input on these scopes, a user adjustable reference calibration (or frequency display offset) would be great. Mine sits around the same 10.00014 and appears surprisingly stable. It just needs a tweak.

author: crysti
author_rank: Regular Contributor
timestamp: August 04, 2025, 10:34:34 am
content: Has anyone else experienced acquisition memory limitations on the SDS824X HD with firmware version 1.1.6.5? When set to 10kpts, it drops to 5kpts at 5us/div, and the 100Mpts memory depth is only available for acquisition times of 5, 10, and 20ms/div. For other timebases, the available acquisition memory decreases. Is this an intentional limitation or a firmware bug? Thanks for any feedback!

author: 2N3055
author_rank: Super Contributor
timestamp: August 04, 2025, 11:16:53 am
content: Quote from: crysti on August 04, 2025, 10:34:34 amYour scope is sampling at 100Mpt/s?It is simple math.If you are sampling at 100e6 point per second, how many points you get in 50µs (50e-6) worth of time?

author: crysti
author_rank: Regular Contributor
timestamp: August 04, 2025, 11:29:30 am
content: Quote from: 2N3055 on August 04, 2025, 11:16:53 am5,000 points are obtained in 50μs at a rate of 100MSa/sBut the oscilloscope I know only has 1200 points per refresh

author: 2N3055
author_rank: Super Contributor
timestamp: August 04, 2025, 01:14:05 pm
content: Quote from: crysti on August 04, 2025, 11:29:30 amI don't understand, sorry.

author: rf-loop
author_rank: Super Contributor
timestamp: August 04, 2025, 02:19:24 pm
content: Quote from: crysti on August 04, 2025, 10:34:34 amWith memory management auto and one channel on, here can see how it use memory and use samplerate depending whatmaximummemory user have selected and what time base (t/div) is in use.It works just as it is designed.Yes there is some kind of exception if look this table. When step t/div down and samplerate drop after 500MSa/s it do not drop to 200MSa/s but it drop to 100MSa/s and because this, also memory need then reduce half for this step. Next step down in t/div speed do not drop samplerate, it stay 100MSa/s but it increase memory back to max selected.Naturally when two or three and four channels are in use then many of these numbers are different. This table is just only for what ever one channel is in use alone.

author: crysti
author_rank: Regular Contributor
timestamp: August 04, 2025, 04:00:52 pm
content: Quote from: rf-loop on August 04, 2025, 02:19:24 pmThank you!The attached Excel calculation is correct or not?