Conductance measurement using NI PXIe 4492

[mb1982]

Hello,

I am applying AC voltage using NI PXI 4462 card and measuring the voltage output from my device using NI PXIe 4492. I use Lockin program to measure the amplitude voltage of the signal acquired. I need to convert this output voltage/amplitude into conductance but don't know how.

Any assistance to solve this problem is appreciated.

Thanks,

Mangesh

[Jake_H]

Hello Mangesh,

Conductance measurements require an accurate, simultaneous reading of voltage and current. Ideally you could use a Source Measurement Unit such as the PXIe-4141 to measure the phase between voltage and current, then divide the amplitude of the voltage by the amplitute of the current to find your impedance. Electrical conductivity is 1/electrical resisitivity. To find the resistivity you'll need various parts such as cross sectional area, length, material properties, etc.  

[mb1982]

Hello Jake,

Thank you for the reply.

Is there a way to use my current PXIe 4492 card to measure conductance? Or purchasing other hardware is the only option?

Secondly, can I use PXIe 4141 for lockin application?

Thanks,
Mangesh

[Jake_H]

Hello Mangesh,

The 4496 is a 16 channel AI module and the 4462 is a 4 channel AI module, so you will need a module to source the signal. Where is the AC signal coming from? You could set one of the channels to measure current with a shunt resistor and another channel to measure voltage. If you have those two measurments synchronized, you can calculate conductivity from there (assuming the modules have enough accuracy for the application). The delta-sigma ADCs of the 4492 and 4462 may not be ideal for measuring conductance, but will work for the lock-in amplifier.

A DMM would be the best in terms of DC accuracy. If you're just looking for DC conductance, you would use a DMM to measure resistance and take the inverse for conductance.