3-36 Basic DMM Operation Model 2701 User’s Manual
Thermistors
For thermistors, the temperature measurement range is -80°C to 150°C (0.01°C
resolution). Thermistor types that are supported include the 2.2kΩ, 5kΩ, and 10kΩ types.
The thermistor is a temperature sensitive resistor. Its resistance changes non-linearly with
changes in temperature. Most thermistors have a negative temperature coefficient. As
temperature increases, the resistance decreases. The Model 2701 measures the resistance
of the thermistor and calculates the temperature reading.
Of all the temperature transducers, the thermistor is the most sensitive. It can quickly
detect minute changes in temperature. It is a good choice when measuring very small
changes in temperature. The downside for this increased sensitivity is the loss of linearity.
Since they are especially non-linear at high temperatures, it is best to use them for
measurements below 100°C.
NOTE Curve fitting constants are used in the equation to calculate thermistor
temperature. The thermistor manufacturer’s specified curve fitting constants
may not be exactly the same as the ones used by the Model 2701.“Thermistor
equation,” page F-6, provides the equation and the constants used by the Model
2701. It also explains how to select a thermistor when the manufacturer’s
constants and the ones used by the Model 2701 do not match.
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