Tempco, wire, etc....

[Tony Clark]

> My physics book states:
> 
> R=R naught [1 + A(T - T naught)]  where R naught is the initial resistance
> at T naught, and A is really alpha, a temperature coefficient of resistivity
> in 1/C degrees.  Alpha for copper is = 0.00393 and for Nichrome alloy
> is = 0.0004.    (Also, T-Tnaught can be thought of as delta T (I think))
> 
> Hope this helps...
> 
> DAF

   Right, just for information (which I just looked up) pure Nickel wire 
(which is used at my business) has a temp. coeff of 0.0064 which is means 
its more sensitive to temperature change than pure copper.
   Nickel also has a higher resistivity than copper.  This would be great 
in reducing the size of those massive tempco resistors I've seen.  Now I 
haven't done any shopping for tempco resistors yet because I'm seriously 
thinking about getting some thermistors and trying those instead.
   After reading Mr. Pease's column about thermistors and temperature 
compensating, I'm really thinking that this is a better way to go.  For 
starters, thermistors are cheaper, smaller in size, come in a variety of 
resistance values up to 50K or higher, as well as positive or negative 
coefficients.
   Has anyone used these?!

   Tony

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I can't drive (my Moog) 55!
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Tony Clark -- clark at andrews.edu 
http://www.andrews.edu/~clark
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