Streaming from two 4824As simultaneously

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DanielBorg
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Joined: Sun Feb 11, 2024 10:26 am

Streaming from two 4824As simultaneously

Post by DanielBorg »

Hi!
I would like two use two 4824A to simultaneously acquire 16 channels.
The trace length would be about 50-100 µs and will be acquired as fast as possible.
At 80MS/S each trace should be 4000-8000 samples.

The signal to acquire is repetitive with 8 Hz so I would like to acquire about 64 waveforms to average.
Since the 4824 itself cannot perform on-board averageing, I will need to stream the data to LabView and do the averaging when acquisition is finished. With 8 Hz repetitive rate I need to transfer 64k samples from each oscilloscope every 125 ms.

Would two 4824As be a good solution to do this?

Best regards
Gerry
PICO STAFF
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Posts: 1173
Joined: Mon Aug 11, 2014 11:14 am

Re: Streaming from two 4824As simultaneously

Post by Gerry »

Hi Daniel,

I'm not sure if you are still looking for an answer to this, but if you are, then here it is.

To do what you are suggesting we need to (1) verify the method that you are using to capture all of the waveform data, and (2) verify the capability of the PicoScope 4824A to perform accurately enough, at the rate that you want it to, acquiring all of the data that you need.

1/ Your suggested method may be overlooking one important point, which is, "How are you going to synchronize the start of the captures between the 2 PicoScopes?". If all of your 16 waveforms are different then, to synchronize the capture start between the Scopes, you would need to split the capture of one waveform, across one Input Channel on both PicoScopes, in order to have the triggers firing at the same time (i.e. to within the synchronization accuracy that you need) for both Scopes.
However, if at least 2 of the waveforms that you are capturing will always have features (e.g. a rising edge) that occur simultaneously, then you can capture one of each on a channel of each PicoScope, and setup both Scope triggers the same for those Channels, to give you a synchronized start. If you don't have a synchronous feature between 2 waveforms then you will need to just work with 15 at a time (if you absolutely must have all 16 then you'll need to consider adding a PicoScope 4224A, and synchronising that as well, i.e. setting one of the Channels up with the synchronizing waveform and the other with the 16th waveform).

2/ For the sample rate, the maximum rate for 8 Channels captured simultaneously is actually 40MS/s (as you are using more than 4 Channels, see here: https://www.picotech.com/oscilloscope/4 ... ifications). So, you would need to relax your sample rate requirement to 40MS/s or, if you absolutely must have a rate of 80MS/s, then you would need to consider using using 6 PicoScopes with 4 Input Channels (for up to 18 Channels that can be synchronized, at 80MS/s) or 5 of them (for up to 15 synchronized channels at 80MS/s).

Everything else would be OK for the method and 4000 series PicoScopes.
In terms of synchronizing accurately enough, the Timebase Accuracy of the Scope (ignoring the Timebase drift) is ±20 ppm. So this means that, the worst case difference in timing between any two PS4424A's would be ([20+20]/1M) * 8k = 0.32 of a sample interval, after capturing only 8k samples. So, for such a short capture time, the complete data set, synchronized at the capture start for all PicoScopes, would remain synchronized, to the highest possible accuracy.
In terms of the transfer method to the computer, you would need to use Block Mode to achieve the previously discussed sample rates (as shown in the Specifications link I gave you) which means that you would need enough storage in the PicoScopes to capture the 64k samples from all Channels (while the size of the Sample buffer is 256M samples).

Regards,

Gerry
Gerry
Technical Specialist
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