Induced signals between channels

[edmiles55]

I am trying to measure voltage and small currents. The current input, NRSE is directly connected to a function generator with a typical output <5V and <100Hz. The current is measured across a 15M resistor, differential input and at the moment is isolated from the voltage signal. In the future the voltage signal will drive a circuit and a load current will be measured. Even though the current measurement is isolated the channel can still detect the voltageinput to the SCB-68 break out box. I need to be able to detect the current independently of the voltage. Any suggestions would be helpful. The DAQ for this is a PCI-6052E. Thanks for the help.

[Henrik_Volkers]

Welcome to the world of small signals 😉

Most people will claim 15Meg as an isolator. My suggestion would be to do external signal conditioning and buffering close to the signal source (and active shielding).

Have a look at the bias currents !

Do you need that 15Meg for other reasons than current to voltage transformation? I would look for an active current to voltage amplifier with OPs. Search the application notes from linear, AD, NS  ( my personal sequence).