r we able to male precise 1ohm resistance

If you can't write a sensible question, I guess the same applies for more things :-(

-- Uwe Bonnes snipped-for-privacy@elektron.ikp.physik.tu-darmstadt.de

Institut fuer Kernphysik Schlossgartenstrasse 9 64289 Darmstadt

--------- Tel. 06151 162516 -------- Fax. 06151 164321 ----------

--
Try posting to sci.electronics.dumfux or get 1" of wire that's rated
at 12 ohms per foot.

On Wed, 18 Apr 2007 07:01:22 -0500, John Fields Gave us:

He must be all doped up. Still, he seems smarter than some of the fare that has passed through the group in the last month.

Mr. Cool Groper

Learn to type real words, get a real news reader, post to a basic group if you have a basic question, learn how Usenet works and follow the conventions.

DITCH GOOGLE Google is not your friend; or ours.

Sorry That's probably way over your head. Try this:

Lern t ype wrds get a nwsrdr post t a basik grp w/ basik ques lern usenet don use ggle

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I hate to admit it, but John Fields is right, as far as he goes.

If you want a precise and stable 1.00 ohm reistance, it helps to use manganin or constantan wire. Both alloys have a very low temperature coefficient of resistance at room temperature

For low resistance resistors, it is a good idea to use the wire to make a Kelvin four-terminal resistor - the current through the resistor flows through two of the leads, and you measure the voltage drop across the 1.00 ohm length of wire through two other leads. See page 5 of the appication note below

-- Bill Sloman, Nijmegen

That depends on what you have to start with. Can you accurately measure voltage and current? Do you have an accurately-known resistance of some other value already? Do you have a way to control the temperature of the resistor after you make it, so that thermal drifts and thermal emfs won't destroy its accuracy? What materials do you have to make it from? Just how accurate do you want it?

The people who DO know how to make very stable, accurate resistors understand not only the theory but the art: they understand how to process the materials so that, for example, stresses don't destroy the accuracy.

Do a Google search for things like "history of resistance standards" and you'll find some info on it. The paper at

about resistance standards is pretty interesting; the NBS (now NIST) resistance standard from about 1931 up until 1990 was a set of 1-ohm resistors that are still in use today as transfer standards.

Cheers, Tom

read this

martin