What is a positive temperature coefficient thermistor?

1.The parameters of the positive temperature coefficient thermistor.

The positive temperature coefficient thermistor is also called PTC, and its resistance increases with the increase of temperature. It can be applied to valley seed circuits.

The main parameters of the positive temperature coefficient thermistor ( PTC ) are :

( 1 ) nominal resistance Rt also known as zero power resistance value, that is, the resistance value on the device ambient temperature resistance below 25℃.

 ( 2 ) The resistance temperature system teaches at it that the relative change of the resistance value caused by the change of 1℃ in the zero power condition is % /℃.

 ( 3 ) The rated power thermistor is called rated power under the specified technical conditions, the allowable consumption power of long-term continuous load. The normal power rating given is the rated power at + 25℃.

( 4 ) The time constant refers to 63.2 % of the difference between the temperature of the resistor and the final temperature when the ambient temperature is mutated in the reactive power state the time required is also called thermal inertia.

( 5 ) Measurement of power. It refers to the power consumed when the resistance value changes less than 0.1 % caused by the heating of a measuring power supply at a specified ambient temperature. It is used for unified testing standard and basis for testing instruments. 

6 ) Dissipative coefficient It refers to the power dissipated by the thermistor at a temperature of 1℃. Resistors common resistance specifications ( room temperature ) are 122, 1502, 180, 220, 2702, 400 and so on. Different circuits, the choice of resistance is not the same.

2.Measurement of positive temperature coefficient thermistor

 ( 1 ) The normal temperature coefficient thermistor ( PTC ) resistance is detected by the nominal value, and the measured resistance and nominal resistance are blocked by the multimeter RX1 at room temperature ( about 20℃ ) the difference is normal within 20 % of the value.

( 2 ) Good or bad judgment. If the resistance of the positive temperature coefficient thermistor ( PTC ) resistance is normal at room temperature, the heating test should be carried out, the specific method is to use a heat source to heat the positive temperature coefficient thermistor, such as baking iron or placing it in water at different temperatures, because the water is convenient for temperature control and temperature measurement, the multimeter is used to observe whether the resistance value is increased with the increase of temperature. If so, it indicates that the positive temperature coefficient thermistor ( PTC ) resistance is normal, otherwise its performance has become worse and can not be used.

This article is from ALLICDATA ELECTRONICS LIMITED.