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At 15:34 1/2/00 -0500, John D wrote:
... If you take ordinary Allen-Bradley carbon resistors and cool them
down, the resistance depends on temperature. This makes them useful as
secondary thermometers in the range of roughly 77 Kelvin to maybe 10
milliKelvin. There is a large range where the resistance is
exponential in the square root of temperature to remarkably high
precision. ...
John's description possibly suggests the equation
Resistance = exp(k*sqrt(temperature))
Allen Bradley carbon composition resistors decrease in resistance with
temperature. So the scaling constant k is evidently negative.
Taking a sample A-B 0.27ohm resistor:
Temp (K) Res (ohms)
0.3 10^6
1 10^2
3 3
10 1
30 0.7
100 0.3 (from a graph of Rose-Innes's)
I don't have a curve fitting package here. Can someone else
fit this?