analog discovery studio Analog Discovery Studio: Can't calibrate oscilloscope and waveform generator puts out unexpected voltages

[Kornelis]

Hi,

We purchased an analog discovery studio to evaluate for possible future student use for the college I work at a little while ago.  It had been sitting around for a bit and now I finally had a chance to play around with it.  Initially, the waveform generators seemed to function fine but my oscilloscope measurements seemed off.  (I was using generic probes first but now I think Im using the probes that came with it that dont have the 1X&10x switch commonly seen.) After some scoping around the manual, I found the calibration section.  Initially, the waveform generator calibrated as expected putting out close to the produced voltages as measured by my DMM.  However, when I tried calibrating the oscilloscope, the values were quite off. (see enclosed images) I did double check my probe connections and they were as per instructions (however, I did also connect the waveform N connector the same GND as the oscilloscope probes at some point even though the instructions only mention to connect the oscilloscope probes to GND. See image)  When I tried to recalibrate the waveform generator after that to make sure I hadn't missed anything or something had drifted, the voltages were completely off all the sudden. I measured about half the voltage I was expecting for all voltages (see images.) Do you have any suggestions on how to get the device properly calibrated or is something faulty perhaps?

Looking forward to hearing from you.

Kind regards,

 

 

Kornelis

[JColvin]

Hi @Kornelis,

My initial reaction was that the probes would be the source of error, but based on your description and setup I'm less inclined to think that this is the case.

BNC probes do tend to have some sort of circuitry in them (though I am uncertain if this is the case for probes that don't have a 1x/10x switch), so you could potentially get a better measurement by not using a BNC probe from the Wavegen and instead just connecting to the MTE pin, but this really shouldn't matter for DC signals.

Within the WaveForms Device Manager, there is the option to choose to load the factory calibration settings within the Reset dropdown (more details are within the section 4 of the WaveForms section of the Help tab). If resetting the factory calibration and individually measuring the wavegen output directly with the DMM after power cycling the device (no oscilloscope connected) does not result in close/reasonable voltage outputs that can't be corrected through the manual calibration process, then I would be inclined to think that ADS is potentially damaged in some way.

Let me know what you learn.

Thanks,
JColvin

[Kornelis]

Hi JColvin,

Thank you for your fast response. I found the culprit: the provided probes actually do have a x1/x10 switch.  I didn't notice it because to me they're not clearly visible on these probes. All switches need to be set to x1. When the switch is set to x10 during wave gen calibration you will read about .5xthe target voltage coming out of the wave generator on a DMM and measurements during oscilloscope calibration will be completely off.  :) Looking at the two images enclosed you can see that everything looks reasonable now.  One more question: both oscilloscope readings are the right voltage but slightly offset.  Can I only further improve this by moving the offset manually with tools the oscillator window or should I do another calibration session for better results?

Thank you again for your help.

 

Kornelis

 

[JColvin]

Hi @Kornelis,

After zooming in and verifying that the offset isn't a weird visual artifact on the Scope plot (and triple checking the ground connections), I would personally go for another round of calibration since that should calculate any needed offsets.

Let me know how it goes.

Thanks,
JColvin