THORLABS CLD101 Series, Руководство по эксплуатации

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6 Appendix
81
Thermistor - Properties and Calculations
R(t) diagram of a TH10K thermistor
A thermistor is a resistor with a
negative temperature coefficient (as
for this, also known as NTC). It's
resistance decreases exponentially
with temperature. The significant
change
of resistance with
temperature predestines a NTC for
temperature
measurements. The
diagram to the left shows the typical
curve for a 10kΩ thermistor.
Usually, it's nominal resistance is
referenced to 25°C. The dependency
of resistance vs. temperature can be
described using several methods.
The most accurate method is the
Steinhart-Hart equation, a third-order approximation, it delivers an error less than 0.02°C over a
200°C range.
where
A
,
B
and
C
are the Steinhart-Hart coefficients, to be specified for each individual device.
A commonly used alternative to the Steinhart-Hart equation is the β equation (often called
exponential method ) which is derived from the Steinhart-Hart model:
where T
0
and R
0
are the reference values and β - the device-specific constant.