Read Voltage and Resistance Concurrently

[dimoreira]

Hi,

I would like to read both voltage and resistance across two electrodes either
concurrently or alternating using a Keithley 2700.

I currently have the leads connected to the front panel and am able to measure either
resistance or voltage accurately (I think). However, during the experiment I have both
the voltage and the resistance changing as a function of time and would like to record
both signals, but I only have the one pair of electrodes.

Is there a way to instruct the Keithley to take alternating voltage and resistance
measurements?

It's a low voltage application (millivolts), so I didn't want to split the leads into
two channels (Keithley also equipped with a 7700 card)...

Thanks ,

David

[Andrea C]

David,

What else can you tell us about your device?

If you use the 2700 to measure resistance, it will do this by applying some current, measuring the voltage and then computing and reporting the resistance. You can know how much current was used based upon which measure range is used (100 ohm range uses 1mA). So for your desire to know the voltage, you can compute it if you know the current and the resistance.

Will this suffice? Or do you need the open circuit voltage (with zero current flowing)?

Andrea

[dimoreira]

Hi Andrea,

Thanks for your prompt response.

The device is a charged fluid channel where I am trying to measure the streaming potential
(related to the flow of ions in the channel). In this case, the voltage would be the
open circuit voltage (with no external current flow).

The resistance is about 8 kohms. If to measure resistance the keithley applies a small
current, seems like one measurement would get in the way of the other?

D