( 1 ) The normal temperature coefficient thermistor ( PTC )https://www.allicdata.com is detected by the nominal value, and the measured resistance and nominal resistance are blocked by the multimeter RX1 at room temperature ( about 20C ) the difference is normal within 20 % of the value. When the measured resistance is greater than 502 or less than 8.2, it can be determined that its performance is poor or damaged. ( 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.