How do I connect the pins of my PCI 6221 to make a 4 wire resistance measurement?

[marc france]

Hello,

I would like to use my PCI 6221 card to make a  four wire resistance measure ( with labview 8.0 & XP ). I don't seem to be able to find any clear infomation on how to connect the pin's to the resistance I want to measure. Would anybody know how to do this with a PCI 6221 card?

The only thing I have found is this link but it's not detailed engouh : 

http://zone.ni.com/devzone/cda/tut/p/id/3610

By the way, does the PCI generate its own courrent for the measurment or does it just read it ( so the current needs to be generated externaly) ?  I hope I am clear enough   🙂

Thanks for your,

Regards,

Marc

[AnalogKid2DigitalMan]

The 6221 just generates and reads voltages- not currents.

You will have to make your own current source and sensing front end- not a trivial task. You have not supplied any specs- what range of resistances you need to measure, resolution, accuracy, throughput.

I would advise instead of trying to make a 4 wire ohms instrument that you purchase an off-the-shelf DMM with such capability and control it via GPIB or serial port.

NI does make a 6 1/2 digit DMM card that is PCI based and does 4 wire ohms measurement- search the porduct manuals on NI 4070.

Good Luck

[marc france]

Hi AnalogKid2DigitalMan,

Thanks for your answer. Actually, I was looking into what could the PCI 6221 card do because I haven't succeeded in making my HP 34401A run faster than 1 sample per 400 ms, which is too slow...I would need to take at least one 4 wire measurement every 100 ms. I have tried all of the 5 examples of the Labview library...

Regards,

Marc

[AnalogKid2DigitalMan]

Are you measuring the same component every 100msec or are you switching components in and out every 100msec?

[marc france]

I am measuring the same component : It's  the resistance of a surface of a thin layer that changes value according to a heater under it. It is heated for 14 ms every second and I would like the follow the value of the resistance every 100 ms as the surface cools down...to see the effect of the heater on the resistance value.

Regards,

Marc

[AnalogKid2DigitalMan]

What's the expected range of the resistance of the thin film?

[TCPlomp]

I think you have the wrong tools...
In this case I would go for a stabalized current source, and measure the voltage drop over the layer. Make sure you don't have any ground loops


Ton