The possible hidden cost of the DS1054Z bandwidth upgrade hack - Page 1
Forum section: electronics / testgear

author: Lightages
author_rank: Unknown
timestamp: December 22, 2014, 11:26:55 pm
content: Yes, you get a 100MHz scope when you do the upgrade, but the probes that are supplied are not up to the task. The RP2200 probes are rated for 150Mhz. When compared to the RP3300 probes that I received with my DS1052E there is a noticeable difference in shape of a 2MHz square wave. The RP3300 probes have a rated bandwidth of 300MHzSo when you buy the higher models instead of hacking you get better probes and if you want to take advantage of the extra bandwidth count on spending another $100 or more on probes to keep up with the upgrade. That is assuming that the DS1104Z comes with the RP3300 probes.Anyone with a DS1104Z or DS1074Z care to check their probe models and comment?

author: sync
author_rank: Frequent Contributor
timestamp: December 22, 2014, 11:53:11 pm
content: I got RP2200s with my DS1052E and DS1074Z. I don't think it's normal to get 300Mhz probes with a 50MHz scope.Edit: According to the datasheet the DS1104Z comes with RP2200 too.

author: SharpEars
author_rank: Unknown
timestamp: December 23, 2014, 01:38:22 am
content: Quote from: Lightages on December 22, 2014, 11:26:55 pmOK and for about $30 USD, eBay will solve that problem for you with a pair of Chinese made 10x probes of decent quality that can do 500 MHz.

author: Syntax_Error
author_rank: Regular Contributor
timestamp: December 23, 2014, 01:41:26 am
content: And you really only need one of those higher bandwidth probes, since the only way to get adequate sampling rate at higher speeds is to limit yourself to one channel. It's not a bug, it's a feature!

author: Solder_Junkie
author_rank: Frequent Contributor
timestamp: December 23, 2014, 09:09:24 am
content: My 1054Z looks to have a bandwidth close to 100 MHz without hacking. Checking with a terminated RF signal generator the waveform drops by 25% at 98 MHz, not quite 100 MHz, but darn good for the money.Given the reports of not being able to change the hacked scope's software model back to 1054, it might be worth leaving it alone until at least the warranty expires.

author: macboy
author_rank: Super Contributor
timestamp: December 23, 2014, 04:01:09 pm
content: Quote from: Solder_Junkie on December 23, 2014, 09:09:24 amThe hack doesn't add bandwidth to the analog section. I believe that it just increases the sampling frequency and gives extra (shorter) horizontal time bases. Limiting actual analog bandwidth by software would be quite a feat, requiring extra circuitry and cost; limiting the sample rate is a no-brainer.Bandwidth of a system is usually determined by the -3 dB point. So it is the point where the voltage response is down to 70.7% of nominal. By this definition, your scope probably has a bandwidth slightly more than 100 MHz.However, Oscilloscope bandwidth usually follows a Gaussian rolloff*, so the -3 dB point is not such a true indicator of bandwidth. The conventional way to define oscilloscope bandwidth is actually by the pulse response, specifically the rise time. We say that BW = 0.35/Tr. For example, with a 1.75 ns rise time, the calculated bandwidth is 200 MHz. To measure rise time, you need a flat-top pulse with a rise time significantly faster than the scope under test. So, for your ~100 MHz scope, you would want a 2 ns or faster pulse generator.* the reason for the Gaussian response is that it gives no overshoot or ringing to a step input. This means that the only aberration that the scope lends to a step input is the limited rise time; it specifically does not add any ringing or overshoot (ideally). So if you see ringing, it should not be due to the high frequency roll-off in the scope input. If the response was tuned to be a maximally flat passband (like a butterworth filter), the -3 dB point would be quite a bit higher, but you would have terrible ringing in the step input.

author: Howardlong
author_rank: Super Contributor
timestamp: December 23, 2014, 04:19:08 pm
content: Pretty sure it _does_ change the analogue front end. There are some op amps on the front end and the filters are adjusted by switching in and out a caps or two on each channel according to the model number. The MSO1074Z-S I am aware of had a 91MHz -3dB point measured with an HP 8656B RF signal generator and an inline 50 ohm termination at the scope prior to upgrade and 141MHz afterwards.As far as I am aware there is no change to the sampling rate.

author: macboy
author_rank: Super Contributor
timestamp: December 23, 2014, 04:33:24 pm
content: Quote from: Howardlong on December 23, 2014, 04:19:08 pmThen I stand corrected.

author: leppie
author_rank: Frequent Contributor
timestamp: December 23, 2014, 05:50:45 pm
content: The probes are quite shitty it seems.I tested a 125MHz crystal oscillator with a standard probe and a Texas 250MHz (both 10X).Code:Vpp:Std: 3.8VTexas: 6.0VEdit: Just recalled the Texas probe is not compensated. Will do that and see if there is a difference.Update: not sure why the difference in offset now (, bad averaging?):Code:Vpp (avg):Std: 1.86VTexas: 4.16V

author: Solder_Junkie
author_rank: Frequent Contributor
timestamp: December 23, 2014, 06:02:10 pm
content: From Dave's YouTube video of reverse engineering the 1054Z, if I recall it correctly, there is a switchable low pass filter in each input. These are normally used when you set the bandwidth limit to 20 MHz. There is additional switching that seems to be the means of limiting the bandwidth across the models in the range.Ignoring the keygen bandwidth hack, it looks possible to "dry joint" a transistor to open the bandwidth...The signal level on mine drops sharply above 98 MHz, although the waveform doesn't distort up to at least 150 MHz. Unfortunately I only have an RF signal generator and a very basic function generator, so can only measure bandwidth at the 3 dB point.I've just checked the 1000Z data sheet and the minimum sweep speed is 5 nS for all three models in the range. The only difference seems to be analogue bandwidth.

author: Lightages
author_rank: Unknown
timestamp: December 23, 2014, 09:21:32 pm
content: I wonder why they only put a 5ns sweep on this instead of 2ns.Just looking on ebay at random probes for sale, there are some Chinese ones that have a nice low price but who knows about the quality or performance?I really think that Rigol cut more corners than they should have for the DS1000Z series. Probes are an integral part of the performance and the RP2200 model I got definitely show a different waveform than the RP3300. I can't say anything about the absolute performance of the RP2200 and if they limit the bandwidth below 100MHz or if I am seeing stuff far above that.I did not know that there is no going back once the bandwidth is upgraded. I thought it was possible using some commands in console.

author: Retep
author_rank: Regular Contributor
timestamp: December 23, 2014, 09:49:12 pm
content: Quote from: Solder_Junkie on December 23, 2014, 09:09:24 amBandwidth of an oscilloscope is specified at the -3 dB point, i.e. the frequency at which the oscilloscope shows the amplitude of a sine wave 30% lower than it actually is. So if you see 25% drop at 98 MHz chances are that it does meet the 100 MHz bandwidth specification.QuoteAccording to the postings on this forum you can uninstall the hack via the network interface by sending :SYSTem:OPTion:UNINSTall to it. Of cause that onkly works if the scope is not totally dead.

author: orin
author_rank: Frequent Contributor
timestamp: December 23, 2014, 11:38:07 pm
content: Using the rise time test, my DS1054Z had a rise time of about 4.4 ns, giving a bandwidth of around 80 MHz. I used an ADCMP580 comparator to generate a pulse for the rise time test which has a rise time in the order of 50 ps. (An HP 54510A shows a rise time of less than 1ns for this pulse generator, so I'm confident I'm seeing the rise time of the scopes.)I have RF signal generators and I would not use them for this task. For example, the HP 8657A has absolute amplitude accuracy of +/- 1.5 dB 0.1 to 123.5 MHz and flatness of +/- 1 dB 0.1 to 990 Mhz. It is also difficult to accurately measure the amplitude of a signal generator output - the meters are cheap, but not the sensors - try pricing a working 8482A power sensor - probably $400.

author: Lightages
author_rank: Unknown
timestamp: December 23, 2014, 11:40:46 pm
content: orinWhat probes did you use for your test? RP2200?

author: orin
author_rank: Frequent Contributor
timestamp: December 24, 2014, 12:53:56 am
content: Quote from: Lightages on December 23, 2014, 11:40:46 pm50 ohm through terminator at the scope via about 2ft of RG188 coax. The ADCMP580 directly drives a 50 ohm load.I haven't even tried the probes that came with the scope yet.

author: sync
author_rank: Frequent Contributor
timestamp: December 24, 2014, 01:26:57 am
content: All six of my RP2200 overshoot. They are bad probes IMHO. I compared different probes. I used the sync out of my function gen as signal source with a 50 ohm coax and a feed through terminator at the end. The white reference line was the terminator directly connected to the scope. The probes were connected with a BNC to probe adapter to the terminator.1st: Rigol RP2200 150MHz2nd: cheap chinese P6100 100MHz3rd: Conrad C3000 150MHz (Testec LF-312)4th: Tek 6109 150MHz

author: tautech
author_rank: Super Contributor
timestamp: December 24, 2014, 01:44:21 am
content: Quote from: sync on December 24, 2014, 01:26:57 amWOW, that confirms the general belief the P6000 series probes are OK.Could you show both risetimes and maybe edit your post with added text or new images?

author: dmmartindale
author_rank: Contributor
timestamp: December 24, 2014, 03:30:08 am
content: This may be obvious, but you didn't mention it: Did you adjust the probe compensation of each of the probes you tested before measuring it?Any 10:1 probe I have ever used has a compensation adjustment, either in the probe handle or in the body of the connector where it plugs into the scope. This is used to set the attenuation of high-frequency components of the signal to be equal to the low-frequency attenuation, so the waveform is minimally distorted. (The low-frequency attenuation is set at 1/10 by the fixed 1 Mohm input resistance of the scope and a fixed 9 Mohm resistor in the probe. But scope input capacitance varies, and the probe capacitive divider must be adjusted to match the scope input every time you move a probe to a new scope. Brand new probes are likely not properly compensated either, even if they came with the scope.- DavePS: those 800x480 screen grabs look lovely compared to the tiny 320x234 images from my Instek GDS-1062A!

author: pickle9000
author_rank: Super Contributor
timestamp: December 24, 2014, 03:52:53 am
content: Quote from: tautech on December 24, 2014, 01:44:21 amYup, good enough for daily use and disposable because of the cost.

author: TMM
author_rank: Frequent Contributor
timestamp: December 24, 2014, 09:32:40 am
content: Quote from: Lightages on December 23, 2014, 09:21:32 pmHigher display resolution per division.

author: Lightages
author_rank: Unknown
timestamp: December 24, 2014, 10:00:35 am
content: That sounds like a reasonable answer.

author: rf-loop
author_rank: Super Contributor
timestamp: December 24, 2014, 11:16:36 am
content: Quote from: dmmartindale on December 24, 2014, 03:30:08 amIt can see very easy that these have been well compensated (least equal with each others). Also note that this usual "compensation" is for low frequency compensation (aka LF compensation). As you can see scope horizontal scale is 5ns/div. In images you can see overshoot around first <20ns of edge. With LF compensation you can not do anything for this. You can try - then you know. If take this situation just as in pictures, and turn compensation you can see only that pulse level change. In good professional passive high frequency probes there may be extra adjustments ( under cover) for high frequency compensation (aka HF compensation) and also for calibrate attenuation (DC adjust).HF compensation need good and medium fast edge pulse source, example <300ps risetime without bad overshoot and after edge, quite flat top. (useful tool also for adjust low or middle frequency BW oscilloscopes front end edge responses etc))Example with HP probes there is R1 and R2 for HF compensation.http://exodus.poly.edu/~kurt/manuals/manuals/HP%20Agilent/HP%2010400A%20Series%20Operating%20Note.pdf(starting page 14)

author: sync
author_rank: Frequent Contributor
timestamp: December 24, 2014, 03:19:11 pm
content: Quote from: dmmartindale on December 24, 2014, 03:30:08 amSorry that I don't wrote it. I adjusted each probe before measurement.

author: sync
author_rank: Frequent Contributor
timestamp: December 24, 2014, 03:37:53 pm
content: Quote from: tautech on December 24, 2014, 01:44:21 amWhich rise times should I measure? For the probe measurements they are in the screen shots (~3.1ns). With the direct connection it's ~3.9ns (more capacitive loading?).Regarding the P6000 probes. It looks like there are quality variations or they got worse over time.https://www.eevblog.com/forum/testgear/pos-ebay-%27scope-probes/msg406194/#msg406194

author: Unknown
author_rank: Unknown
timestamp: December 24, 2014, 04:14:06 pm
content: Quote from: Howardlong on December 23, 2014, 04:19:08 pmIn Dave's reverse engineering video he shows a pair of caps in parallel presumably used for BW limiting under control of the CPU. There appears to be a separate, single cap used for getting the 20MHz BW control too. But the pair of caps to limit the device model is the interesting part -- what could the four possibilities be?Both caps switched in = 50MHzLarger cap switched in = 70MHzSmaller cap switched in = 100MHzNo caps =Anyone tried running the scope with both caps removed?Jamieson

author: Lightages
author_rank: Unknown
timestamp: December 24, 2014, 06:19:49 pm
content: I have some generic P6300 robes on the way. We will see in a month when they arrive.