Deciding between 2000 and 3000 series

Which product is right for your exact requirements
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tstalcup
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Deciding between 2000 and 3000 series

Post by tstalcup » Wed Jan 23, 2019 4:06 pm

I'm looking to buy a unit from either the 2000 or the 3000 series and I want to verify that it will work for my application. I'm currently using a Rigol DS2072A, but I want a more compact, easily transportable solution for travel needs.

I'll attach screenshots of the current scope screens to show what I'm talking about below.

I have two signals plus a sync pulse to use as the trigger. The trigger frequency is 20-30 Hz. Channel 2 in the attached screenshots is the one of interest. In correct operation, it is a sinusoid with a somewhat variable amplitude. If my source is adjusted poorly, there will be discontinuities and other deviations from a continuous sinusoid.

Currently, with a timebase long enough to see the entire scan, it is possible to see these discontinuities as changes in the shading/intensity of the displayed signal as seen in the first screenshot. This is what I want - I just need to know there are irregularities in the sinusoid, not exactly what they are. I also want this with at least a 10 Hz update rate, and a 30 Hz update would be even better. I'm adjusting my source, and real time feedback is critical.

I don't this persistence mode is exactly right - I don't want to build up a display from many scans, I want to display a single dataset with shading.

I'm considering either the 2406B or 3203D. I'm assuming the increased streaming rate of the 3203D will help with this application, but if the 2406B will do the job the four channels would be nice.

Thanks for the help!
Attachments
rigol_annotated_1.png
Newfile18.png

Gerry
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Re: Deciding between 2000 and 3000 series

Post by Gerry » Thu Jan 24, 2019 6:17 pm

Hi tstalcup,

I have created a screenshot and data file to show you what was possible with my PicoScope setups in both the 32033D and 2406B PicoScope models. From your screenshots it appears that you have a 5ms Timebase with a 100MS/s sample rate for a 7M point capture, and what appears to be a waveform with an average frequency of something like 100kHz.

So, regarding the main requirements you mentioned:

For the ability to perform analysis of signal integrity, and see anomalies in the waveform with the parameters of the example that you posted, I didn't create irregular anomalies as the modulated waveform I used already had regular anomalies in the form of a pattern of dense and less dense data. You can clearly see this, if you look at the image below (as you mentioned, these are single datasets with shading, as opposed to persistence mode). Also, I changed the look of the display to a closer match with the Rigol.
PS3203D - 5ms Timebase.png
PS3203D.psdata
(2.13 MiB) Downloaded 40 times

For the update rate I set similar parameters on the PS3203D, and used a trigger set to go off at a rate of 10Hz (from a square waveform source). As you will be monitoring and making adjustments continuously, the trigger mode has to be 'Repeat' so that the data is being captured and then sent to the computer in a continuous cycle. Once the waveform buffer in the PicoScope is full, in 'Repeat' Trigger mode, the new data will start overwriting the old data, so the capture doesn't stop, providing a constantly updating display. So, to show that the captures are keeping up with the triggers (i.e. no triggers are being missed because the update rate is too slow), I limited the number of triggers to 10, which you can see from the Signal Generator window (cycles per trigger) and as you can see from the 'Waveform buffer Index', which shows the number of the last waveform captured (and is the window just to the left of the icon that looks like a compass) the number of waveforms captured was 10. 10Hz is the limit of how fast I could get the waveforms updated, using this continuous triggering mode, in the PicoScope 3203D (i.e. if the Trigger cycle rate is increased, the number of waveforms captured will reduce.)

I also performed the same test with the PicoScope 2406B and it too captured all of the waveforms that were triggered, which shows that it can also be run in repeat trigger mode with a trigger source that cycles at 10Hz, using your parameters, and keep up with it continuously, on my setup. The update rate for the PicoScope 2406B is 4/5 of the PicoScope 3203D, which is clearly fast enough.

However, as the data is being transferred in between each trigger, it is important to note that the update rate could be greater or less depending upon the capability of the resources in your computer, along with your USB port/bus, and their availability, and the update rate may also depend (to a lesser extent) on the size of your display, as only enough data is sent to fill it. When I attempted to use a faster trigger rate both scopes started to drop captures, so with my setup (which is just an average PC setup) I would need to look at using one of our faster scopes for updating continuously, in real-time at faster rates.

The faster transfer rate of the PicoScope 3203D due to USB 3.0 would benefit streaming, but this application is not streaming. However, as you are analyzing data in real-time with continuous updates, the faster transfer rates will be beneficial if you are zooming in and out while capturing, because these will be faster.

Last of all for completeness, note that continuous updating in Scope Mode should only really be used if the anomalies are too small to be seen in Persistence Mode, and the waveform itself is continually changing (as in your case). If you are looking for anomalies in a static waveform that are too small for Persistence Mode and that only occur rarely in a static waveform then you can use 'Repeat' trigger to observe the anomaly and then stop the capture, once you have seen it occur, to analyze the data. But you may have more success by using a trigger mode with much shorter gaps in between triggers such as 'Rapid' Trigger Mode (although it will only capture until the buffer is full), as you will be effectively casting a much finer net, occasionally (as opposed to a much coarser net continually), to catch your event. For instance, using the same parameters as the example in this post for a static waveform, I used the same data file above in 'Rapid' trigger mode, at 30Hz (or faster) to capture a limited number of waveforms on both scopes. Doing a comparison between the scopes, for a 5ms timebase and 5M point captures, and 2 channels of data, you get 13 waveforms in the PicoScope 2406B, and 52 waveforms in the 3203D. in this instance, the storage capability of the 3203D is 4x that of the 2406B because it has twice as much buffer memory, and it has an external trigger input (so you don't need to use an input channel for triggering) while, with no external trigger input, the 2406B uses 3 input channels (so the waveform buffer is shared among 4 channels).

Regards,

Gerry
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tstalcup
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Re: Deciding between 2000 and 3000 series

Post by tstalcup » Wed Jan 30, 2019 9:16 pm

Thanks for the very informative response. It sounds like either would probably work, but I've decided to go with the 3000 series - since I really only need two channels + trigger, for the same price I get the USB3 advantages.

Thanks!

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