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Measurements >> Other Measurements >> Small resistor variation
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Message started by TF_electronics on Feb 17^th, 2008, 5:08am

Title: Small resistor variation
Post by TF_electronics on Feb 17^th, 2008, 5:08am

Hey all,

I want to measure small resistor variations (0,1 up to 3 ohm).
I started testing with a constant current source of +/-1A (i used a LM117), the results are do-able but have to be better.
To measure i use a national instruments PXI 6040E - DAQ card.

As you know the (test)wires do allso have an resistor value

Maybee one of you hase the answer. ::)

Thanks

Title: Re: Small resistor variation
Post by Ken Kundert on Feb 17^th, 2008, 2:00pm

You need to use a 4 wire measurement. Two wires apply the test current. And two wires are used to measure the voltage. The latter two wires need to connect directly to the terminals of the resistor. In this way, the resistance of the wires has no effect on the measurement.

-Ken

Title: Re: Small resistor variation
Post by thechopper on Feb 28^th, 2008, 4:27pm

Ken Kundert wrote on Feb 17^th, 2008, 2:00pm:

Hi TF,

What Ken proposed is the way to go. Just for you to know this method is called "Kelvin".

Tosei

Title: Re: Small resistor variation
Post by TF_electronics on Mar 9^th, 2008, 4:31am

The results are excellent !

Thanks for the tip ;)

link that i used:

http://www.allaboutcircuits.com/vol_1/chpt_8/9.html