Keithley 2701 Current Sensing

[usm1]

Hi All,

I am using a Keithley 2701 DAQ and a 7700 20 channel multiplex module. For my experiment, I need to sense small values of current (nanoAmps), so I can detect changes in that current. I'm using LabView and the provided Keithley drivers to read the two current sense channels on the multiplex module. The Keithley has a resolution of 6.5 digits. That's set by default actually. The range is set at AutoRange. I tried sensing the current; however, I had no luck. It seems that the Keithley machine was not able to resolve the nanoAmp signal it was being given. All I got was noise.

I've been assured by the Keithley engineers that the device has a resolution of down to 10nanoAmps; however, the resolution is already set at the highest value in LabView. Is there another feature I've been overlooking in the Keithley drivers?

[Dennis_Knutson]

I would recomend that you first try to measure the current manually and without going through the mux (ie using the instrument's front panel) . If you can measure the expected current, then try it through the mux. If that works, you can start to look to see how your program differs from the manual setup. If you can't measure the signal, you may actually have noise in your signal so you may want to use a scope to look at the input to the meter.