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Small resistor variation (Read 1227 times)

TF_electronics

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Small resistor variation
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

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Ken Kundert Global Moderator Offline Posts: 2384 Silicon Valley	Re: Small resistor variation Reply #1 - 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
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HdrChopper

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Re: Small resistor variation
Reply #2 - Feb 28^th, 2008, 4:27pm

Ken Kundert wrote 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

Hi TF,

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

Tosei

Keep it simple

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TF_electronics New Member Offline Posts: 2	Re: Small resistor variation Reply #3 - 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
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