Solutions for measuring large resistances (buffering the analog oscope)

[Dillon Rubi]

Hello,

We are trying to use a voltage divider to measure the drop across some custom strain gauges we are creating. The resistances of both are on the scale of 1 Mohm. The issue is that using the oscope on the discovery leads to inaccurate measurements because some current flows into the input of the analog discovery. 

Any suggestions on how to solve this problem?

 

Thanks.

[attila]

Hi @Dillon Rubi

The AD2 scope input impedance is 1.04M Ohms.
You can use this as reference to measure your resistor:
VCC -> resistor -> Scope 1+ ( internal 1.04M -> GND)
 

[Dillon Rubi]

Okay so basically use the internal impedance as the second resistor?

[attila]

Yes