Probe compensation problem

[thoriam]

Hi I have a problem with probe calibration in analog discovery 2.

I have read

But the problem still exist.

When I turn trimmer on probe nothing change. I checked probe on another scope and it looks ok (when I trimm capacitor on probe, edge changes). Im using bnc adapter.
What I didn;t do is trimm capacitor on board (red one) because Im not prettu sure which one is which.

 

[attila]

Hi @thoriam

You probably have the AC/DC coupling jumpers on the BNC adapter board in AC position, set this to DC.

[thoriam]

I set it correctly on DC coupling so its not the issue

[JColvin]

Hi @thoriam,

Could you provide a picture of your physical setup so that we can help better determine what the problem might be?

Thanks,
JColvin

[thoriam]

@JColvin Setup is really basic. I connected probe from AWG1 to CH1with BNC adapter. When I trimm capacitor on probe (red circle), edges of square wave doesn't change at all. 0 Ohm on AWG, DC coupling on CH1. Probe is set to x10 (square wave looks like in y first post) but also x1 doesn't work (square wave looks ok but trimming change nothing)

[Bianca]

Hi @thoriam,

It seems, that you didn't connect the ground of the probes. You can't calibrate the probe without connecting the minus. Connect the Ground of the AWG to the ground of the Scope and try again. 

Regards,

Bianca

[thoriam]

@Bianca I assume that generator and scope has common ground so don't need to connect. Also try it and same problem

[Bianca]

@thoriam,

You are right, however, I encountered the same issues with your set-up and I was able to calibrate the probe as soon as I connected the ground. So you tried it with the GND connected  and it still doesn't work?

Thanks,

Bianca

[thoriam]

@Bianca Now i actually solve the problem beacause my probe was connected from generator to scope not from scope to generator. Actually maybe you have right about GND.

[attila]

Hi @thoriam

On the BNC adapter the Scope inputs are single ended. The negative inputs are connected to the same ground as the AWG GND/shield.
For high frequency or low amplitude signals it is recommended to connect the scope probe ground clip too.
When measuring other devices/circuits, with separate supply, the ground connection is mandatory.

The trimmer on this scope probe is on BNC side, in parallel.
When you have connected this side to the AWG it didn't count because of the low impedance of the AWG output.

Other probes which have the trimmer in series on the 9M, on the tip side, the direction is less essential but important

Picture source:
https://www.electronics-notes.com/articles/test-methods/oscilloscope/scope-probe-compensation.php