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What should the resistance of a thermistor be

What should the resistance of a thermistor be

This article explains how to test a thermistor to determine if it is OK.A thermistor is a resistor whose resistance varies with the temperature to which it is exposed.There are two main types of thermistors: negative temperature coefficient (NTC) and positive temperature coefficient (PTC) thermistors.

An NTC thermistor is a type of thermistor whose resistance value decreases with increasing temperature. Therefore, as the NTC thermistor heats up, its resistance value decreases accordingly.PTC thermistor is a thermistor whose resistance value increases with the temperature to which it is exposed. Therefore, when heat is applied to a PTC thermistor, its resistance value increases accordingly.


 
Since a thermistor is a device that changes its resistance as a function of applied heat, we can use this property to test them.

To test a thermistor, we only need an ohmmeter or a multimeter with an ohmmeter. We then use the ohmmeter to check the resistance after a few test steps to see if the thermistor behaves according to its characteristics. If it does, it is OK. If it does not, it is defective.

Equipment needed to test thermistors

Thermistor (must be tested)
Heater, dryer fan or other.


How to test an NTC thermistor
Again, an NTC thermistor is a thermistor whose resistance decreases as the temperature to which it is exposed increases.

We will test this function to see if it behaves as it should.

First, check the thermistor's nominal value before applying heat to it. For example, a thermistor can be 100Ω, 1KΩ, 10KΩ, 100KΩ, etc.

The resistance value of the thermistor should be very close to the nominal resistance value before heating it.

For example, if you are testing a 10KΩ thermistor, its resistance should be very close to 10KΩ before heating up. if you are in a relatively warm area, it might be about 9.3KΩ. if you are in a cooler area, it will be worth more.


 Testing the thermistor with a multimeter
This is the first preliminary test to see if the thermistor is OK. If it's close to your resistor, then it's OK so far. If it is too far away or strays too far from its rated value, the thermistor is defective and should be discarded.

Another test is to apply heat to the thermistor. This can be done with a heater, dryer fan or other type of heating device.

Testing thermistors with heat
When the body of a thermistor is heated, the value of its resistance should drop steadily within a few seconds of heating. If the NTC thermistor exhibits this behavior, then it is OK. If it does not, then it is defective and should be discarded.


Testing PTC thermistors
Testing a PTC thermistor is the same as testing an NTC thermistor.

First, test the thermistor without heat using an ohmmeter. With the PTC thermistor at room temperature or below, the thermistor should have a very low measured resistance.

The resistance value of the PTC thermistor should gradually and steadily increase within a few seconds after power-up.

If the resistance value increases steadily, the PTC thermistor is not defective. If it does not, it is defective and should be discarded.

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