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A.5 Thermistor
A thermistor is a temperature sensitive resistor that can be
used in temperature measurement, control and
compensation circuitry. For most thermistors, the
resistance decreases as the temperature rises and the
relationship can be expressed as:
3
1/T = A + B lnR
+ C (lnR
)
T
T
where R
is the resistance in ohms at the temperature T in
T
Kelvins (K = °C + 273.15). This is called the Steinhart-
Hart equation.
Thermistors typically work over a relatively small
temperature range of -60°C to 300°C. They are less stable
than RTDs. However, they exhibit a large change in
resistance proportional to a small change in temperature
than RTDs and a much higher nominal resistance. They
are less sensitive to lead resistance noise effects and can
be transmitted over a large distance. No compensation for
ambient temperature is needed. They are one of the most
accurate types of temperature sensors.
tM-TH8 User Manual, Rev: A1.1 7MH-018-A11
139
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