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Thermistor isa

Hi there just want know if u connect a thermistor to a digital multimeter does it also need to be connected to a different ac or dc power source.

Thanks

Reply 1

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Reply 2

Spandy

Depends on the resistances, not so sure about AC, but for DC, the answer is no

Reply 3

uberteknik

Original post by Hecate99

Hi there just want know if u connect a thermistor to a digital multimeter does it also need to be connected to a different ac or dc power source.

Thanks

A thermistor is in essence a slice of semiconductor material sandwiched between two conductors.

The voltmeter measures the potential difference across the semiconductor when a current flows through it and that pd is also proportional to the temperature of the semiconductor.

A voltage source is therefore needed together with a current limiter in the form of a series resistor so that the power source does not contribute significantly to heating the device. The negative resistance temperature-coefficient (of most common thermistors) may also cause thermal runaway which eventually destroys the device.

It is possible to use a thermistor with certain types of multimeter used on their own when set to measure current (the multimeter provides it's own test voltage).

I do not recommended this at all though, since you must first make sure the multimeter is the correct type AND the whole set-up must be thermally calibrated for that one multimeter alone. The experiment may not be accurately repeatable with any other multimeter and there will also be temperature limits over which the multimeter will be able to give an accurate reading.

Far, far easier to use a series resistor and external dc power source.