What resistance should a thermistor be?

Before any heat is applied to the thermistor, its resistance value should be very closely near its rated resistance value. So, for example, if we are testing a 10KΩ thermistor, before we apply any heat, its resistance value should be very close to 10KΩ. If you’re in a relatively warm room, it may be about 9.3KΩ.

What is the resistance of NTC thermistor?

NTC thermistors are usually characterised by their base resistance at room temperature, that is 25oC, (77oF) as this provides a convenient reference point. So for example, 2k2Ω at 25oC, 10kΩ at 25oC or 47kΩ at 25oC, etc. Another important characteristic of a thermistor is its “B” value.

How do you know if a thermistor is bad?

The most common way to know if a thermistor is bad if it starts displaying inaccurate temperature readings. This can be caused by excessive heat, improper handling, a thermal mismatch, or a dip in resistance accuracy due to regular use and age. An open circuit can also lead to thermistor issues.

What should a thermistor read?

A thermistor does not actually “read” anything, instead the resistance of a thermistor changes with temperature. How much the resistance changes depends on the type of material used in the thermistor.

Should thermistor have continuity?

The thermistor that you are asking about is a negative temperature coefficient sensor. It should always measure continuity. The resistance of this sensor is used by the control board to determine temperature. At room temperature, the resistance of the thermistor is normally about 12K ohms (12,000 ohms).

How do you find the resistance of a thermistor?

The actual resistance values of a particular NTC thermistor are obtained by multiplying the ratio RT/R25 (tabulated value) by the resistance value at 25 °C (specified in the data sheets).

Can you bypass a thermistor?

Generally speaking, a thermister is a resistor that is sensitive to/affected by ambient heat. When the ambient heat changes, it’s value will change. You can bypass it with a regular resistor, but you have to know the value associated with the thermister.

How do you test a thermistor with a multimeter?

Connect the multimeter terminals to the thermistor leads. Polarity is not an issue here. Now heat the thermistor by moving your heated soldering iron tip to it. Now you can see the multimeter reading smoothly increases or decreases depending on whether the thermistor under test is PTC or NTC.

How do you test a 10k thermistor?

Heat the soldering iron. Heat the thermistor by moving your heated soldering iron tip to it. Note the multimeter reading as you are applying this heat. A properly functioning positive temperature coefficient thermistor will show a smooth and steady increase in the multimeter resistance reading.

Why do thermistors decrease resistance?

NTC thermistors, resistance decreases as temperature rises due to an increase in conduction electrons bumped up by thermal agitation from valency band.

What is the difference between NTC and PTC thermistors?

An NTC, or negative temperature coefficient, thermistor’s resistance value decreases as the temperature increases. A PTC, or positive temperature coefficient, thermistor’s resistance value will increase as the temperature rises. These are commonly used as inline resettable fuses.

What is the negative temperature coefficient of resistance thermistors?

Negative temperature coefficient of resistance thermistors, or NTC thermistors for short, reduce or decrease their resistive value as the operating temperature around them increases.

What is the thermistor tolerance and B constant?

This is the thermistor resistance at a special temperature determined by the designer. The tolerance presents how much the resistance can differ from the particular value. B constant is a value that provides the relationship between the thermistor resistance and temperature. Maximum and minimum temperature of the operating level.

What is a PTC thermistor?

A PTC thermistor is a thermally sensitive semiconductor resistor. Its resistance value rises sharply with increasing temperature after a defined temperature (reference temperature) has been exceeded. The very high positive temperature coefficient (PTC) of the resistance above the reference tem- perature has given the PTC thermistor its name.

What type of thermistor is used for temperature sensors?

Generally, NTC thermistors are the most commonly used type of temperature sensors as they can be used in virtually any type of equipment where temperature plays a role. NTC temperature thermistors have a negative electrical resistance versus temperature (R/T) relationship.