# Measuring resistance between 0.9-5 OHM

Z

#### ZIV

Hello,
I have to measure a resistane of a wire, the resistence is between 0.9-5 OHM. the accuracy is x.xxx three digits aftee the point. help me please.

thanks.
ziv.

J

#### Johan Bengtsson

Is it a one time (or a small number of times) measurement or something you want to do a lot of times in full production or something you want to do continously on the same wire for a long time?

Well, anyway I assume you know how to get the resistance (U/I) so the accuracy is what really is the concern here.

First of all, you need to put a current thru the wire, and you want to make sure your current isn't too high to heat the wire up since that would change the resistance.

Second, you want to measure the wire alone, not connectors and feeding wires, this is most easy done by using a 4-wire measurement.
You use one pair of wires at each end like this:

A B
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---->|<----
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---->|<----
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C D

There are special connectors you can use for this if you want a "snap on" solution. The important point is that each of the four connections should be directly to the unknown wire and only connected to the other at the same end THRU the wire. The idea is to put the current tru for example A-C and measure the voltage drop between B and D, in that way you don't measure the voltage drop in the feeding cables and in the connection points.

Third, you do of course need to have a high enough accuracy of your current and voltage readings....

/Johan Bengtsson

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