b
= Ln(Rt1/ Rt2) / (1/T1 – 1/T2)
where
Rt1 =
Resistance at temperature 1
Rt2 = Resistance at temperature 2
T1 = Temperature 1 in °K
T2 = Temperature 2 in °K
The Beta-value of a NTC-thermal resistor is calculated here with two temperature value only and
used only in a pre-described range. This is not the most accurate way to calculate R for the
temperature curve.
Another more accurate method is the Steinhart-Hart equation, in which three temperatures are used
in one given range. This method is also complicated to calculate. The NTC thermal resistor should
be measured at three different temperatures to calculate the necessary coefficients a, b, and c. The
reading-points of temperatures should have the same gap, at least 10°.
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