Different analog measurement results between AD2 and ADP3450

[lyms]

Hello,

I am trying to measure a signal whose voltage fluctuates from 2V to 4V with a period of 10ms.
The measurement by the Analog Discovery 2 measured sinusoidal voltage fluctuations, consistent with standard oscilloscope results.

However, when the measurement device was switched to Analog Discovery Pro (ADP3450) and the same measurement was performed, a jump in signal voltage was observed.

Analog Discovery 2

Analog Discovery Pro (ADP3450)

Could you tell me the solution to the voltage jumps that are occurring in the ADP3450?

Thanks,

AD2.dwf3scopeacq ADP3450.dwf3scopeacq

[attila]

Hi @lyms

Could it be some grounding problem ?
Do you have ground connection between the device and tested circuit ?

Have you used the same connection method with the two devices?
The ADP3X50 bnc inputs are single ended. The shield is device ground.
The AD2 inputs are differential but not floating. For single ended operation the negative input should be connected to the gnd.

[lyms]

Hi @attila,

> Do you have ground connection between the device and tested circuit ?
> Have you used the same connection method with the two devices?

Yes. The connection method is the same.
In both cases of AD2 and ADP, Analog Discovery Ch1 and DUT are connected with BNC cables.

I have tried another oscilloscope and have not measured any ADP-like signal jumps.

I don't know why this occurs only with ADP3450.

Thank you.

[attila]

Hi @lyms

If it's not a grounding issue, I'd would suspect emi, but the scope inputs on ADP3X50 are shielded...
May I ask what signal source are you testing ? could it radiate ?
Have you tried a different position ? more distance and/or orientation between devices

[lyms]

Hi @attila,

The problem has been solved.
I asked the manufacturer of the DUT for impedance specs, and they answered that the impedance of the DUT is 50 ohms.
So, I added a terminator to the input port and suppressed the signal jumps.

Thank you!

ADP3450_50ohm.dwf3scopeacq