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PicoScope 3224/Software changing values!!!

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PicoScope 3224/Software changing values!!!

Postby yallaen » Thu Oct 21, 2010 8:45 pm

We have found troubling incidents regarding PicoScope and the Picoscope software. Here is the setup on how we are using the hardware and software:

PicoScope v.6 loaded onto a Win 7 laptop. The PicoScope 3224 is being attached to various test leads on a prototype device. The data is captured at various points and compared between pre and post modifications. So, let's say we are attached to point A...we take a measurement pre-modification, then take a measurement post-modification, and we are comparing the results.

We usually run pre measurements first, from points A, B, C, and D, then run the post-measurements. This might be superfloeous information, but I want to ensure we have this correct.

So, when we are taking a data point, we capture the data by hitting "STOP". The data is recorded two ways.

1. The readings from the various channels are read outloud and recorded on a paper chart. The recording person reads that value back and is double-checked again by the person actually operating the pico scope.
2. The data is then logged into the "notes" section on the Picoscope software.

Once all the data is logged on the notes section, we then do a "save current waveform as", and save it with a filename that tells us what voltage, pre or post modification, and the date.

This is repeated for all test points both pre and post modification.

So, here lies the problem, which we have just discovered and are pretty upset about!! The PicoScope software is somehow CHANGING THE DATA!!!! How is this occurring? Why is this occurring?

So, for example...
I took a data sample at point "a", pre-modification. I clicked "stop" to freeze that particular waveform. I looked on the data chart below the waveform in the PicoScope software, and read the "average" number. That was logged by my partner on the paper sheet. Let's say it was 443.8mV. He then read that back to me, and I confirmed that it was the same, 443.8mV.

I then took that number, and put it into the "notes" section of this waveform. I then Save Current Waveform..and give it a specific filename.

About an hour later, we decided to compare some of the values. I pulled up the file name, and we started noticing...several of the data sets were DIFFERENT than we had JUST RECORDED!!!! The numbers logged on the paper chart, and on the "notes" section still matched, but the numbers in the actual data area were DIFFERENT! :evil: :x

This is causing great concern and we are losing trust in this product. Is it something the software is doing, and if so, why? Or is it operator error? To me, once we click on "STOP", all activity should cease, and that particular waveform set should be frozen. Once saved, there should be nothing to change those values..yet they are being changed!!

Please help!
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Joined: Thu Oct 21, 2010 8:21 pm

Re: PicoScope 3224/Software changing values!!!

Postby Timmy » Mon Oct 25, 2010 5:46 pm


The Average is the arithmetic mean of the measurements from the last n captures, where n is number of captures to average that is set in the General page of the Preferences menu.
When you save the current waveform the statistics are not saved with the file so when the file is reopened the average will be blank or read the same as the current value reading as it has nothing to average it with.

If you save all the files and reopen the record the average value will still not be correct, the software does not automatically calculate the average when the file is opened. To update the average you have to scroll through the waveform buffer and the average will update with each capture.

A workaround could be to save all waveforms and when you reopen the file cycle through each capture one by one, until the capture count (shown to the right of the average column) has reached its max (defined in preferences), then your numbers should match.

The risk is that the average is updated with every capture you go to in the waveform buffer so as you scroll through the waveforms the number will change every time – even if you have already viewed that particular waveform.

I am sending in a bug notification on this issue.

I hope this helps,

Timothy Snead
Crag Technologies
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Joined: Mon Oct 18, 2010 2:16 pm

Re: PicoScope 3224/Software changing values!!!

Postby ziko » Mon Nov 01, 2010 11:49 am

Hi , Timmy is correct what I will add is that you have to go through to start from capture 1 and then go each buffer. This is a bit of a nuisance I will admit, however we are aware of it and we will be fixing this section soon.

Kind regards

Technical Specialist
Zen Master
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