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Rallez

Analog Discovery 2 - Calibration Data (C++)

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Hi Digilent

Im currently working on my finals in electronics development, including a hardware setup and a custom-made C++ application for my Analog Discovery 2. However it seems that the calibration data made with WaveForms does not apply to the hardware when using custom C++ applications. I've been looking through the manual and haven't encountered any examples of how it is done.

I hope you can help me

Kind regards

Rasmus Pforr-Weiss, Brüel & Kjær SV

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Hi @Rallez

The calibration are applied the same way when used from WaveForms or custom application.

Why do you think the calibration is not used? What problem do you see?

Edited by attila

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jpeyron
Thanks for your feedback, i appreciate you effort

Attila
I'm seeing a slight offsets on the osciloscope input (aprox 2,5mV) even tough the Discovery BNC board is set into AC. And since the calibration data seems to be saved on the computer being opened by Waveforms upon launching, i'm not quite sure the calibration loads with my C++ console application.

Kind Regards

Rasmus Pforr-Weiss, Brüel & Kjær SV

Edited by Rallez

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Hi @Rallez

The calibration is stored in the device in eeprom and handled by the dwf library. The WF application uses the same dwf functions as provided for custom applications.

For the same setup you should see similar offset value in the WF application too.

The reasons for errors/differences could be:
- offset settling: the scope offset has 10-100ms RC time.
- the AD scope inputs have two gains: 5/50V pk2pk, ~3/0.3mV resolution, the offset error could be higher with high range (FDwfAnalogInChannelRangeSet)
- noise in case using decimate sampling: the WF application by default uses average sampling (FDwfAnalogInChannelFilterSet), the average number depends on the sample rate/time base
- temperature drift: ~m/uV /10*C

The devices are calibrated in the factory at ~45*C device temperature for a certain precision. The users can recalibrate it with WF application, under Settings/Device Manager/ Calibrate.

 

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Hi Rallez,

I noticed a DC temperaturedrift of 40 mV over a timerange of 2 ours in my device, see here;

I don't know if you see this too and i don't think you can use my workaround but perhaps this knowledge gives a route to to solve your problem.

Have fun, Hans

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