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manymiles5

Analog Discovery 2 probe calibration issue

Question

I am a hobbyist, new to oscilloscopes.  I recently purchased the Analog Discovery 2, the BNC Adapter and the BNC Oscilloscope 1X/10X Probe pair.

I've read this post and this post, and followed this video on calibration, but, I'm not sure the AD2 and/or the probes are measuring properly or not.  I cannot get square off the signals.  The screenshots indicate the maximum I am able to deflect the signal when rotating the screw within the probes.  From my understanding, rotating the screws in the probes should make the signals become square.

Here's other information which may be indiscernible in the attachments, which may or may not be relevant (cuz I'm a noob).

  • Both probes have the 1X/10X switch set to 10X
  • The probes are both clipped to the W1 pin on the BNC Adapter board
  • Both probes have their ground clip connected to one (and the same) of the flywire ground pins
  • Both probes are set to DC Coupling on the adapter board
  • JP4 and JP5 on the adapter board are set to 50 Ohm, though I don't think that matters because I'm not actually using the Waveform connectors on the adapter board
  • In the screenshots, the channels are configured for "Attenuation: 1X" within the Waveforms software, but, a similar non-squareness occurs when set to "10 X"
  • I'm using Waveforms 3.12.2 64-bit Qt5.6.3 on Ubuntu 18.04.4
  • The AD2 is connected to a USB3 port, directly attached to the computer (no USB hub)

Any advice and/or guidance would be greatly appreciated, especially considering I may have missed something that would be obvious to an advanced user.

Screenshot from 2020-06-10 11-47-43.png

Screenshot from 2020-06-10 11-48-53.png

irl.jpg

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10 answers to this question

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Hi @manymiles5

The probes look to be faulty or at least not in the specs.
Please contact the support at digilentinc dot com specifying the Date of Purchase, Seller and Purchase Order/ Web order Number.

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Posted (edited)

Thanks for the speedy response.

I've rotated both trimmers through more than 360 degrees.  When I do that, the readings only get as high as 176 mV on Channel 1 and 141 mV on Channel 2 before they start to reduce again.  (I *think* they are supposed to get REALLY close to 200 mV, right?)  (Note that I've included those readings in the Y Cursors window)

 

Edited by manymiles5

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Hi @manymiles5

Did you get P6100 probes?
Your probes look a bit different than the ones I have.
It may be different brand or version, with different adjustment range...

image.png.e172d5f6f54cc21d871db8c70d019eb7.png

With these I can adjust the compensation with the following limits:

image.thumb.png.207cabeb8221971f37f01a33502fe80c.png

image.thumb.png.f304880743bf7b385389bf369cfefb1a.png

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And I am not able to obtain the readings you did by twisting the trimmer.  It never goes above 3.3V.

 

I've now tried it on two different computers (both using Ubuntu 18.04.4)

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