Expected frequency stability of Siglent SDG2122X? - Page 1
Forum section: electronics / testgear

author: watchmaker
author_rank: Unknown
timestamp: April 17, 2025, 10:35:08 pm
content: Ok. Likely user error.I was trying to use the trigger on CH 2 to trigger a sweep at 10.7MHz (zero span) from the Siglent. Could not get a solid lock using normal trigger.The sweep was set to 10.7MHz with no span which was confirmed by start and stop freq.I then noticed the freq was actually varying by more than 50kHz.Went to no sweep and triggered off ch 1. Freq varies 10.658MHz to 10.723MHz.These details are from freq max and min in measurements.I would have thought that freq stability was a given on these units. BTW, it was warmed up for over two hours at this point.Is this to be expected or is this a warranty issue?THANKS!

author: Martin72
author_rank: Super Contributor
timestamp: April 17, 2025, 10:42:26 pm
content: Hi,Take a look at the datasheet from the gen...

author: bdunham7
author_rank: Super Contributor
timestamp: April 17, 2025, 10:43:46 pm
content: There's likely an error somewhere in your setup. The frequency accuracy and stability should be many orders of magnitude better than that--I'd expect errors to be single-digit Hz. I quickly turned mine on and checked, I'm seeing errors of 0-2Hz after 1 minute of on-time.You can look at the reference out on the back and see if that is stable. Got to UTILITY/SYSTEM/DEFAULT and set the unit back to its default startup settings in case something didn't get changed back after you were trying to do the sweeps.Quote from: watchmaker on April 17, 2025, 10:35:08 pmI actually don't completely understand that sentence. Could you expand on the specific details?

author: tautech
author_rank: Super Contributor
timestamp: April 17, 2025, 10:49:19 pm
content: First and foremost; firmware version in use.Zero Sweep of a 10.7MHz tone don't make sense.Are you wanting an amplitude sweep ?

author: watchmaker
author_rank: Unknown
timestamp: April 17, 2025, 11:27:49 pm
content: Bdunham7 and Tautech,I was following the instructions for getting a S curve on an AM/FM kit we are going to use for a STEM project. First, there are a lot of errors in the Elenco Kit which two of us overcame and successfully built two kits. But the manual is atrocious and I will create my own lab manual for the kids to follow. So who knows what their test setup instructions were intended to convey. ( I talked w/Elenco about this and they acknowledged that over the years junior employees were tasked to update the manual (cut and paste) but that I am apparently the first to go through it line by line). Lots of complaints about this kit, but when successful, it rivals my 1970 Panasonic RF 933.OK. Forget about the zero sweep at 10.7MHz; although yes, that IS what I was doing and using the trigger output so channel two could be used for the scope trigger. I had the trigger and signal on the scope together so I knew what I was doing with the trigger level.But forget about that. I then went to normal wave mode, single sine wave at 10.7MHz, disconnected the external trigger and just triggered off Ch 1 as normal.That is where I recorded the variation from 10.658MHz to 10.723MHz. I just connect the two instruments via coax and a 50 ohm terminator. See the print screen below. I didthis in a hurry and I hope that not bothering to trigger "normal" is not an issue. If so, I will redo it but the results are the same as when I did it correctly. (Look at max/min)Tautech, Firmware is.2.01.01.38R4; HW=06-02-00-46-00. Unit was purchased form Saelig less than 1 month ago.Also, I still have my 1062. I will set that up in the morning. Just thought of that. Oh, and the 1062 is what I used to align the kit originally.THANKS TO ALL OF YOU. I know it can frustrating dealing with idiots.

author: tautech
author_rank: Super Contributor
timestamp: April 17, 2025, 11:43:02 pm
content: Increase the DSO sensitivity and see if the frequency stats improve.You may have too little sensitivity for measurements to be stable.

author: watchmaker
author_rank: Unknown
timestamp: April 17, 2025, 11:50:17 pm
content: Will do in the AM; getting close to bedtime here. Will also compare with the other AWG.OH, and those tariffs hit these damned kits. 50% increase. Had to look hard to find 10 kits that were not tariffed. Amazon and Elenco literally did a price increase overnight on inventory that was already in country! Hold onto your wallets.

author: EvgenyG
author_rank: Regular Contributor
timestamp: April 18, 2025, 04:07:43 am
content: Can you compare software(bottom left) vs hardware(top right) readings?The hardware counter is usually more precise than the software measurements. From your picture, the frequency looks spot on 10.7Mhz.

author: 2N3055
author_rank: Super Contributor
timestamp: April 18, 2025, 06:33:30 am
content: Tautech and EvgenyG are both correct.Software measurements (ones in the table) are analysing analog sampled data.If vertically amplitude is not stretched to use most of the scale, it is hard for a scope to depict signal from noise.Also if time base is too slow you start loosing accuracy horizontally.Frequency counter on top of screen is actual counter and works better in this situation.If we go to 200mV/div or 100mV/div (if it will fit on screen vertically), and 1µs/div, how do measurements look then?Software measurements will never be accurate to ppm level. If you compare measurements of sine and squarewave you will find that software measurements will show less P-P variation for squarewave. Because of the steep edges, there is less jitter in measuring 2 threshold points for frequency measurement.Let's try with SDG6000X.For instance, If I measure squarewave (2ns edges) 10,7 MHz signal, hardware counter will show steady 10.70010.Software measurement will show 10.700010 MHz average. Variation is 4kHz P-P and 410Hz RMS. That is your measurement noise. Sounds a lot, but average is spot on, and if you look at period, it is merely a 30ps P-P and 3.583ps RMS. That is absolutely great result, for a scope software measurements. On histogram you can see it is single frequency with little noise.If I try same thing by using OCXO based SDG7000A:Hardware counter again will show steady 10.70010.Software measurement will show 10.700010 MHz average. Variation is 3kHz P-P and 379Hz RMS. That is your measurement noise. Sounds a lot, but average is spot on, and if you look at period, it is merely a 30ps P-P and 3.308ps RMS.So this very inexpensive scope can detect the difference between these two instruments...... That is amazing in it's own right. But wait. 7000A has faster edges. Let's switch to pulse and make edges same.If I make edges also 2ns, it is now also 4kHz P-P variation, and 3,54ps RMS...So this clearly shows jitter in deciding where thresholds are directly influences measurements.Not let's try sinewave.Now this is different. Slow edges around threshold points allow the noise processes to interfere much more.P-P is now 47kHz and RMS is 5,380 kHz. But histogram shows very nice normal distribution pointing to random noise being the cause of jittering. Since real random noise can be very nicely averaged out, average frequency is spot on 10.70010, same as hardware counter shows..

author: 2N3055
author_rank: Super Contributor
timestamp: April 18, 2025, 08:20:25 am
content: If we go step further..SDG6502X, 10.7MHz, 1VP-P, sine.Modulation FM, 1kHz sinewave, modulation depth is 141 kHz P-P (100kHz RMS).We now observe several things. Measured Stdev of frequency is 100,28kHz. Spot on. P-P is 288kHz (instead of 282kHz ideal) that is measurement noise I spoke about. But still very good result.Histogram of frequency shows "Batman horns". That is how proper distribution of sinewave used for modulation should look like. This shape shows modulation was sinewave.So with this scope I am able to measure some parameters of modulated signal, and numbers do make sense.What scope (any scope, unless they have some specialized measurement) is not a tool for super precise frequency measurements, modulation etc.Those are domain of specialized instruments if you need super precise. But you can surely check some stuff to level that is good enough for many uses.Conclusion?Always measure something and then remeasure using different parameters, equipment, methods...If results stubbornly repeat, chance is they are correct. But if your measurement is sensitive to changes, then you need to verify what is going on..I would guess your AWG is just fine.

author: watchmaker
author_rank: Unknown
timestamp: April 18, 2025, 02:23:54 pm
content: First, thank you all. I have to re-read what you wrote, but here is what I found.First, the scope software is reporting 26-54 kHz variations with straight connections to AWG putting out a 10.7MHz sine wave,nomodulation.When I use my SDG1062 as a counter, the SDG2122x is dead on down to uHz. So what I am observing is NOT the generator.Below are pics of the Freq counter results and a print screens of the scope results with theunmodulated 10.7MHz sine wave. Please forget about the modulation. I am now down to more basic stuff.There are two screen prints. One at 3Vp-p and another at 1Vp-p. Notice the Freq spread. There seems to be a correlation between spread and amplitude.So it ain't the AWG. So it either is me (most likely suspect) or the scope. I also included a pic of the setup so you can see how I did the setup.I am now officially confused, befuddled and probably confounded. Thanks again to all.

author: tautech
author_rank: Super Contributor
timestamp: April 18, 2025, 03:00:39 pm
content: Press Sweep button to turn it to OFF.

author: bdunham7
author_rank: Super Contributor
timestamp: April 18, 2025, 03:03:10 pm
content: Quote from: watchmaker on April 18, 2025, 02:23:54 pmThat all looks completely normal. Your hardware frequency counter in the upper right corner is giving you a better answer. To understand this, add one more measurement--the period. Then ask yourself how much jitter--and thus variation in the period--it would take to account for the variations in measured frequency that you are seeing. A 10.7MHz signal has a 93.45ns period and your scope has how many samples per second? Also, the reason that amplitude matters is that noise is another component of jitter.Here's the same signal on my scope. You see the peak-to-peak period variation is 1.25ns, that's 1.3% of the 93.45 mean. The peak-to-peak variation of the frequency is 144kHz, that's 1.3% of the 10.7MHz mean. That's not a coincidence! And the HW frequency counter is spot on.I'd also note that unless there are a lot of coincidences, it appears that at these particular settings the scope can only measure the period with a resolution of 0.25ns.

author: watchmaker
author_rank: Unknown
timestamp: April 18, 2025, 11:17:07 pm
content: Quote from: tautech on April 18, 2025, 03:00:39 pmThank you Bdunham7; and all the others.You gave me what I needed (Tolerances of precision); but I can see I will have a hard time learning to use my tool without the benefit of formal education. Controls are one thing, interpretation is a whole nuther nut.This is similar to what I ran into with watchmaking. For 25 years I did pickup courses, reading, failing and learning, and a decent friend/teacher. But I always felt like the corner store owner who could do simple math but not read. I knew I was missing important concepts, but had no clue what they were. That is where the year in Switz (at the too late age of 55) really helped solidify my understandings.I have no idea where I would be without the backup from all you. I mean it sincerely.FWIW, I do study W2aew's, Dave's and the Siglent videos. But there are limits on how a self learner can put all that together. Matrix algebra is easier.Warmest,Dewey

author: tautech
author_rank: Super Contributor
timestamp: April 18, 2025, 11:26:19 pm
content: Quote from: watchmaker on April 18, 2025, 11:17:07 pmNot all controls/settings are as plainly visible to the user as an illuminated buttonbut in the Utility menu we have the choice to select Default to return the unit to the most basic settings.As you keep finding the modern instrument is capable of some quite advanced operation when most often we only need KISS capability.Knowing your instruments capabilities and knowing how to use them with skill are different things....Have fun and never stop learning/experimenting....someone can help when you get stuck.

author: bdunham7
author_rank: Super Contributor
timestamp: April 18, 2025, 11:50:05 pm
content: Quote from: watchmaker on April 18, 2025, 11:17:07 pmI don't think that's true and I'm not even sure where you'd go for a formal course in....scopeology? Tektronix and HP used to publish app notes, articles and even instructional videos (and they still do to an extent) that served as the education. What you asked is not necessarily a basic question and I had to set my scope up to do an experiment or two to verify that it was doing the frequency measurement by measuring the period of every cycle and then displaying the reciprocal. I also had to think a second to figure out what you were trying to do, which if I understand it is to measure the frequency deviation of an FM signal by looking at the peak deviation of the frequency measurement. This can be done in theory, but with your numbers (10.7MHz and 100kHz deviation) the errors drown out the signal.Here's a shot of a 10.7MHz signal with 1MHz FM deviation at 100Hz. You can see that this results in a reading of just over 2MHz pk-pk which is what you'd expect and although there is still significant error it doesn't completely overwhelm the result. The scopes frequency measurement could be made more useful IMO if they would measure the combined period of all the cycles on the screen and then divide by the number of cycles before calculating the reciprocal. IDK, perhaps this can be done somehow with gates, but I haven't explored that.

author: hfleming
author_rank: Regular Contributor
timestamp: April 19, 2025, 12:07:57 am
content: Yep, can remember going to a lot of HP and Tektronix seminars when still working. Every time I learnt something new, no matter how deep you delved into documentation, or how extensively you used the instruments on the bench… you fall into the trap of viewing the instrument and its meausrements from your POV, sometimes you just need another person to show you another way… modern test equipment are complicated, and you need to understand their functions, but also their limitations. Therein lies the danger…. In the old days without on-screen digital displays, you just had to be able to read whatever you could see on the graticules of the oscilloscope, and make your own interpretations. Nowadays it is a lot simpler, but it can also lead you into going into rabbitholes looking for something that does not actually exist…

author: 2N3055
author_rank: Super Contributor
timestamp: April 19, 2025, 08:20:08 am
content: Quote from: bdunham7 on April 18, 2025, 11:50:05 pmWell, that would not work for modulated signals.The idea of deep inspection scopes is to look into many measurements in the same capture, and gaining large number of measurement from single capture for statistical treatment.If signal is single frequency, average over sufficient number of periods yields same result as hardware counter, to the last digit, you just need to let it run for a minute.Problem is that measuring frequency to the ppm level requires low picosecond level accuracies. Scope (especially literally cheapest one from the 12 bit family of this manufacturer) is not really meant to measure that.Actually fact that does this well is a small miracle. I demonstrated above that trigger jitter for this little scope is on the order of 3,3ps RMS when fed good quality clock signal. That is just outstanding.A practical advice: scope frequency measurements are more than enough to verify work of noncritical oscillators. For instance, a microcontroller has quartz crystal and you check if it oscillates and what frequency it is. These will be in 20-30ppm class anyways, if not worse. This is handy for situations like where 12 MHz quartz was installed instead of 10MHz in a device that was brought to me for troubleshooting, for instance. For best results use hardware counter on top of screen. That will bring you to ppm levels, limited by scope timebase accuracy.For measuring frequency more accurately, a frequency counter is needed, 10 digit or more or something similar. and something with good TCXO or OCXO, and adjusted accurately.On my Signal Hound BB60C i have a very accurate frequency difference mode, and frequency counter mode on DG8SAQ VNWA.GPSDO (for accurate reference) is very welcome addition too to keep your reference right long term.

author: Mahagam
author_rank: Regular Contributor
timestamp: April 19, 2025, 09:01:40 am
content: Use theForceFFTIt`s clearly seen that the frequency span for an non-modulated signal is negligible.

author: nctnico
author_rank: Super Contributor
timestamp: April 19, 2025, 09:48:36 am
content: Quote from: bdunham7 on April 18, 2025, 03:03:10 pmBingo. If I do the same measurement on my RTM3004, I get a stddev around 500Hz (compared to 16kHz your scope is showing) and much more accurate results. The frequency measurement accuracy depends on how the algorithm to make measurements on the waveform is implemented.

author: 2N3055
author_rank: Super Contributor
timestamp: April 19, 2025, 10:09:39 am
content: Quote from: nctnico on April 19, 2025, 09:48:36 amRTM3000 scope shows 500Hz Stdev?With sinewave?Because same SDS800xHD shows 380Hz stdev when fed with high quality squarewave. 3.3ps stdev, 30ps P-P. For a 200MHz scope that is excellent.Also, that is comparison of 20000€ scope with a 500€ scope...

author: nctnico
author_rank: Super Contributor
timestamp: April 19, 2025, 10:13:31 am
content: I used the internal generator (sine wave) which isn't great. But it just goes to show that how the oscilloscope does the measurement impacts the result.

author: 2N3055
author_rank: Super Contributor
timestamp: April 19, 2025, 10:18:35 am
content: Quote from: nctnico on April 19, 2025, 10:13:31 amYou should try measuring external source so your source and sampling is not synchronous....Also RTM3000 samples at 5 GS/s so 2.5x more timing resolution to begin with..Like I said a 20000 € scope compared to 500€ scope.

author: black6host
author_rank: Contributor
timestamp: April 19, 2025, 12:56:43 pm
content: Watchmaker: Is the Elenco kit you mention the 108CK model? If so would you be willing to share your fixes? I've got 3 of them in various stages of completion and I'd sure be interested. Thanks! And DM is fine in order to keep this thread on point.

author: bdunham7
author_rank: Super Contributor
timestamp: April 19, 2025, 02:33:15 pm
content: Quote from: 2N3055 on April 19, 2025, 10:09:39 amCould you elaborate on that? What exact signal--frequency and amplitude--are you using? I'm not seeing how the trigger could interpolate a fast edge to that precision with the available sample rate.I think this is a comparison of methods not of quality. IMO the question is how the OP's goals might be accomplished. He had an idea and then a plan, it wasn't a bad plan but it just didn't work out. Apparently it would work on some other scopes that use a different method.QuoteIDK why you say it wouldn't work on a modulated signal. Of course it depends on the modulation type and level, but if it were gated or controlled in a way that was somewhat flexible I think it would work just fine. There would still be limitations on accuracy but you could do much better than what it does currently. Measuring frequency doesn't require any specific trigger accuracy as you have to always consider the other factor--gate time. That's assuming you are using a simple gated counter. One fairly simple way to do this would be to simply add up the period of all the cycles on the screen and make the reciprocal one frequency measurement instead of n measurements as my scope does now. I was actually looking for an option to do this when discovered my firmware was borked (fixed now).

author: bdunham7
author_rank: Super Contributor
timestamp: April 19, 2025, 02:37:17 pm
content: Quote from: nctnico on April 19, 2025, 09:48:36 amDo you get varying results depending on how many cycles are shown on the screen? If you FM modulate a 10.7MHz signal with 100kHz deviation @ 100Hz, will you get a peak-to-peak statistic of 200kHz or so?

author: 2N3055
author_rank: Super Contributor
timestamp: April 19, 2025, 05:03:40 pm
content: Quote from: bdunham7 on April 19, 2025, 02:33:15 pmI posted images of 5 different measurements. All done with SDS800xHD, different AWG and signal. 10.7MHz as OP asked. All parameters are there.Excuse me for not retyping them down. One picture, thousand words ...Of course it can interpolate to faster timing resolution than samples. That is what interpolation is for.Are you confusing how frequency counter (the top of the screen) works with software measurements from waveform data?.Frequency counter (the top of the screen) is using signal coming from triggering engine to actually count in hardware. That is your basic gated counter.Software frequency measurements are performed on actual analog sampled data as a secondary operation. And R&S does it exactly the same as Keysight and Siglent and everybody else does. There is some kind of threshold detector that detects passing through zero, depicts what time is for one period and does 1/t.As for the other question I don't understand what are you saying. You said that measurements could be performed by measuring combined time of say 100 periods and than dividing by 100 to get better accuracy. Yes that works for stable signal, because you have one 3ps jitter on 100x longer useful data period, so you make errors smaller.But if there is variations inside that period (aka FM modulation for instance) you loose that data and gain only average frequency.Did I misunderstand what you meant? If I did please, kindly, explain again what you meant.

author: bdunham7
author_rank: Super Contributor
timestamp: April 19, 2025, 05:37:25 pm
content: Quote from: 2N3055 on April 19, 2025, 05:03:40 pmOK, I didn't see that post before. I understand interpolation, but it appears to me at first glance that the scope you are showing will interpolate with a resolution of 10ps while measuring period. Mine appears to be limited to 250ps resolution doing the same thing, although obviously it can and does interpolate much more closely in other uses. I'll assume that this is due to limited processing power or something. It just so happens that this is the difference between a manageable error and total uselessness for the OP's attempted measurement. Of course when you switch to a sine wave the noise part of the jitter raises the error back to the point of not being useful--although with a 10-cycle gate it would work fine.QuoteNo, I'm not confused about that. That appears to have a 100ms gate time which would be too slow for the OP's application even if you could do something with the data. But it is a nice feature, just irrelevant here.QuoteIDK exactly how everyone else does it, but yes a 1/t for every period is how Siglent is doing it. On and old analog-ish scope, if I use cursors and delayed sweep I can do a 1/t for an arbitrary number of cycles. Same for the Siglent actually, but obviously this doesn't give me the numerical readout. With a multi-cycle method if there are variationswithin the measurement periodthen yes, they'll be averaged out. But if the FM modulation is 100Mhz and 100 cycles is less than 10µs then that error will be much, much less than the 100x gain in precision from using more cycles.So either the improved method of multiple cycle counts or an improved interpolation on period measurements would be helpful in this case.

author: watchmaker
author_rank: Unknown
timestamp: April 19, 2025, 06:07:17 pm
content: I just created a thread in Beginners about matching equipment to equipment, user expectations and the expected accomplishments for the next 5 years.Your responses got me thinking and I thought other non pros may (should?) find the topic relevant.https://www.eevblog.com/forum/beginners/matching-your-equipment-and-setting-up-for-your-expected-goals/Regards,Dewey

author: bdunham7
author_rank: Super Contributor
timestamp: April 19, 2025, 06:58:01 pm
content: Quote from: watchmaker on April 19, 2025, 06:07:17 pmI would be cautious about thinking that you somehow have the wrong instrument just because it couldn't do that measurement in the way you expected. I also would question the idea that an analog scope can do this any better, especially one that lacks cursors. Remember, the DSO is at it's core anoscilloscope, a device that draws pictures to represent your signal. Analysis and measurements are addtional features and have to be used judiciously. It is easy to think that all of those measurements will be of great precision because in fact some of them are. But sometimes they aren't and that's an issue for all sorts of measurements.So how would you do this on an analog scope? What results could you expect and could you do it just as well on your DSO?Here's one way of displaying FM modulation that works on either type. This is 10.7MHz w/ 75kHz deviation @100Hz. The settings are visible but ask if you don't see exactly what is going on. Notice that the measurements displayed are not helpful.But if you have a late model Siglent DSO the way to do what you are trying to do is this:

author: 2N3055
author_rank: Super Contributor
timestamp: April 19, 2025, 08:25:12 pm
content: Quote from: bdunham7 on April 19, 2025, 05:37:25 pmThank you for clarification. I know you understand interpolation just refering to it.Other scopes (like Keysight for instance, and R&S does the same AFAIK) only measure first sampled period in sample buffer and ignore rest 10000.They accumulate statistics over repetitive trigger. You must be careful what Nico says, because it was him not explaining anything of how it was measured. Note that I am not implying he is misrepresenting something. But as I have shown, changing parameters makes orders of magnitude change in error.Simply we need to compare at least with similar settings.Because of the way Keysight measures, it will favour shortest possible timebase that will fit one full period on screen. That will ensure maximum horizontal resolution.But this not primarily timing problem. It is vertical noise and vertical (voltage) discriminator threshold interaction.Still using SDS800xHD.Setup 10.7MHz signal, sinewave.1,4VP-P amplitudeScope 200mV/divCreate math channel F1. Use Averaging as function, 128x.Set measurements of frequency and period to measure from F1.What do we see?We have same result as with using very fast clean squarewave clock. 3-4ps RMS jitter and 30ps P-P. 400Hz RMS noise in 10.7 MHz measurement.When we filtered out amplitude noise from measurement chain by averaging, we get same result as with fast edge clock.And we can conclude that 3-4ps RMS jitter and 30ps P-P is limit of measurement with this device.And a result for a many people's favourite MSOX3104T.When measuring sine, it is achieving 20kHz RMS and 167.2ps RMSBut if we put it in 128x averaging acquisition mode, it gets better. 1,1488kHz RMS and 10 ps RMS.If we go to more averages, 256x produces even better results 860Hz and 7,5ps RMS. No image for that but you get the jist.Of course, when averaging (or using HIRES or ERES) we might be also averaging real signal changes...As for your note about modulation, you are absolutely correct. If modulating frequency is low enough, carrier frequency high enough and depth of modulation low, we could find a time base where it would be just fine. If we have the other extreme, not so much though.Nice discussion.Best,

author: bdunham7
author_rank: Super Contributor
timestamp: April 19, 2025, 08:36:07 pm
content: Quote from: 2N3055 on April 18, 2025, 08:20:25 amOther than the modulation, what is different about this capture that allows it to avoid the 47kHz error or noise that was evident in the earlier screenshot (your 3rd of 4)?QuoteAveraging doesn't work for modulated signals because even if you use a lower number of averages, say 5 cycles on screen and 32 or 64 count averaging, the acquisitions that are averaged are not sequential and thus are spread out over too long of a period.

author: 2N3055
author_rank: Super Contributor
timestamp: April 19, 2025, 09:00:19 pm
content: Quote from: bdunham7 on April 19, 2025, 08:36:07 pmOk. Now I understand. Original question was not about modulation, but about suspicion of OP that his AWG when set to stable frequency was not stable enough.All my measurements, apart from one with modulation are single stable frequency measurements.Difference in last measurement is visible from last post and image.I used averaging math channel and then measured that, first two measurements on the left. I also kept measurements of original CH1 as two last measurements on the right.

author: Grandchuck
author_rank: Super Contributor
timestamp: April 19, 2025, 09:11:35 pm
content: Here is a SDG2122X set to 10.7 MHz, sine, 4Vpp.Scope isSDS2204X

author: bdunham7
author_rank: Super Contributor
timestamp: April 19, 2025, 09:27:52 pm
content: Quote from: 2N3055 on April 19, 2025, 09:00:19 pmI don't mean the one with averaging, I'm comparing your 3rd image in your first set of 4 with the one with the "batman horns", both with histograms. The first has deviations of 47kHz and 410ps, which would be in the same ballpark as what I see on mine. Then in the "batman horns" (those were ears, b/t/w) screenshot we see apparently accurate representations of the actual FM deviation and those errors don't appear whereas they do appear on mine and add signficantly to the total measured frequency and period deviations. If there's a visible difference in relevant settings I'm not seeing it.

author: nctnico
author_rank: Super Contributor
timestamp: April 19, 2025, 11:02:16 pm
content: Quote from: bdunham7 on April 19, 2025, 02:37:17 pmYes. And I re-tested with an external generator but the same results (forcing the scope to 2.5Gs/s to make a reasonable comparison with the image you posted). Appearantly the RTM3004 uses all visible cycles to calculate an average and base the measurement results on that. Maybe your Siglent uses a single cycle and it could even be configurable whether to use a single cycle for a measurement or multiple ones. There are pros and cons to each approach.

author: 2N3055
author_rank: Super Contributor
timestamp: April 19, 2025, 11:51:29 pm
content: Quote from: nctnico on April 19, 2025, 11:02:16 pmSiglent measures every period on screen. And calculates mean and that one is accurate to last digit.

author: bdunham7
author_rank: Super Contributor
timestamp: April 20, 2025, 12:02:19 am
content: Quote from: nctnico on April 19, 2025, 11:02:16 pmYes, although the need for that level of control would not have been apparent to me until this discussion arose since as2N3055points out, it displays the mean and that is pretty accurate pretty quickly, only bested by the hardware counter. I confirmed this for myself by doing some single-shot captures. Here's one with at 1µs/div which means 107 cycles (106 complete ones) on the screen. As you'd expect, the statistics counter shows 106 events. Interestingly, if you press the SINGLE button again the counter does not reset and you then have 212 displayed as the number of counts.

author: 2N3055
author_rank: Super Contributor
timestamp: April 20, 2025, 08:15:42 am
content: Quote from: bdunham7 on April 19, 2025, 09:27:52 pmOh I get it now what are you asking. Sorry for the confusion.I don't think I did anything special from what is visible on the screen.But you made me go and try again.Since we said errors are caused by noise, I tried again first with single stable frequency 10,7 MHz. SDG6502XThis time I kept Average math and all the measurements AND enabled 20MHz BW limit on CH1.You let it run for half a minute and reset stats (not Clear Sweeps, but a touchscreen round reset button in measurements). This is to make sure we are calculating stats for averaged data (128x averages take time to settle).That alone yielded RMS results without averaging that are almost as good as MSOX3104T with 128X averaging and full BW.Averaged waveform value (on the left) dropped to 1.25 ps and 124.7 Hz.Now I enable modulation on AWG. Averaged waveform makes no sense anymore so we disable F1 math channel. Look at measurements on the right.RMS frequency variation is 99,91 kHz (0,09% error).Settings are on the screen. Apart from what is on the screen, only thing to point out is to let it run a minute. Stats are over 25000 measurements.There is one thing to note: Since it is noise related, make sure that you stretch signal vertically to 90% or something like that. Use fine vertical control to do it if needed.

author: watchmaker
author_rank: Unknown
timestamp: April 20, 2025, 02:40:29 pm
content: 2N3055 and Tautech,When I was first learning how to use my Nikon digital, NikonUSA created a revenue stream by initiating in person seminars in several key cities. They were very helpful because we could try things in the class and have someone right there when we got lost.Given that Siglent is going for a wider market than professionals, and what others have posted above about the value to professionals of vendor seminars, can it be suggested that Siglent (NA, at least) consider this?It would ultimately reduce the number of chat requests from those like me learning how to do basic tasks.Just a thought.

author: tautech
author_rank: Super Contributor
timestamp: April 20, 2025, 10:17:15 pm
content: Quote from: watchmaker on April 20, 2025, 02:40:29 pmNormally we would trust the scope to show us what the AWG output is until we are confident with our settings....a bit like taking a picture to see the results of our settings.We should also consider our questions and resultant replies from those that know their instruments well as generic advice for those learning too......at one time we were all newbies to scope and arb use.Everyone learns different too and doing is learning to the point you grow to the next level of learning and personal advancement.Formulating any DSO/AWG fully comprehensive instructional guide is an almost impossible task as never can all usage scenarios be properly covered.However there is some guidance on Siglent websites in the the form of model product resources (App Notes, Videos and Operating Tips) although little as yet for SDS800X HD....this is where I would point you to another DSO with the same UI that's been around for a few years now, SDS2000X Plus.https://siglentna.com/digital-oscilloscopes/sds2000xp/#resourceshttps://siglentna.com/waveform-generators/sdg2000x-series-functionarbitrary-waveform-generators/#resourcesSDS800X HD capabilities are also fully explored in this wonderful thread:https://www.eevblog.com/forum/testgear/sds800x-hd-review-demonstration-thread/Have fun and never be shy about asking questions....everyone learns, even those trying to replicate you settings and posting to help.

author: Martin72
author_rank: Super Contributor
timestamp: April 20, 2025, 11:00:15 pm
content: Quote from: watchmaker on April 20, 2025, 02:40:29 pmGenerally an appealing idea; here are a few thoughts of my own.First of all, as you correctly pointed out, these are basic principles, so in my opinion it doesn't matter where these principles come from.In other words, you can refer to resources from other manufacturers who have been working on this longer than Siglent.These include the white paper archives from Tektronix, Keysight, Le Croy, and R&S.Siglent also has a corresponding “archive,” but naturally it is not yet as comprehensive.There are also regular webinars that are offered via email if you have registered with the manufacturers mentioned above.Siglent does not offer anything like this, but this is not a flaw considering their time on the market as serious professional competition.Then, services such as seminars/webinars/database setup and maintenance require human resources.Nothing is more expensive than personnel costs in a production line, which means that in order to offer such services free of charge to existing and potential customers, these costs must be passed on, and this is usually done through the products that are sold.In case anyone has ever wondered why Siglent and Co. can be cheaper than the “old hands” on the market despite their ever-improving products.If this is to remain the case, users will have to do without the corresponding services.Ultimately, there is a wealth of specialist knowledge available here that is essentially free of charge, thanks to the presence of users and their posts.I have learned an incredible amount during my almost seven years of membership here, and it never stops...The only dramatic thing about this is that this knowledge is scattered and randomly distributed across thousands of threads.Bundling it together in one section would be a gold mine for everyone.

author: tautech
author_rank: Super Contributor
timestamp: April 21, 2025, 08:48:21 am
content: Dewey, this video should help you: