Mismatch between raw data and PicoScope6 displayed data

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mldion1
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Joined: Mon Sep 24, 2018 7:13 pm

Mismatch between raw data and PicoScope6 displayed data

Post by mldion1 » Mon Sep 24, 2018 7:29 pm

Hello,

I am trying to write a short program in C++ to automate some testing I have to do using the PicoScope 5442A. I am using the sine wave generator and two channels in 15-bit mode. I use the Picoscope API to generate and acquire data in block mode. To double check if I am using the API correctly, I have been comparing the data I get from the PicoScope6 software with the raw data I get from the "ps5000aSetDataBuffer()" and "ps5000aGetValues()" functions. However, they don't seem to match up, and it's puzzling.

For example, let's say I apply a 1V 1MHz sine wave to my DUT at point A, and measure output signals B and C to compare the relative amplitude and phase. If I investigate using the PicoScope6 software, I get a relative amplitude of B compared to C of 0.42 and a phase offset of 93º. However, if I use the raw data from my custom program running the PicoScope API, I get a relative amplitude of 0.78 and a phase offset of 79º.

Qualitatively, the system behaves similarly in both cases, and plotting the raw scope data the system-specific waveform distortion I am expecting appears in both sets of data. It just seems like there's some scaling and time-offset issues perhaps...?

Matt

Martyn
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Re: Mismatch between raw data and PicoScope6 displayed data

Post by Martyn » Fri Sep 28, 2018 10:40 am

We will need to see your code, so if you could send it to support@picotech.com we can take a look in detail. If you also include the psdata file from PicoScope we can see the expected values and setup of the scope.
Martyn
Technical Support Manager

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