Thermistor detection methods and key points1

Thermistor is a kind of sensitive element, also can be used as a circuit element to instrument circuit temperature compensation and thermocouple cold junction compensation. Thermistor is mainly used for electrical equipment overheating protection, gas analyzer, non-contact relay, etc.

detection, the multimeter ohm ( Depending on the nominal resistance to determine gear, is commonly R x 1 block) , the concrete can be divided into two step: first detected at room temperature ( Indoor temperature close to 25 ℃) With alligator clip instead of the pens and grip the PTC thermistor respectively two pins to measure its real value, and with the nominal value, the difference within the plus or minus 2 Ω is normal. If the actual value and the nominal resistance difference is too large, then its performance is bad or damaged. The second heating test, on the basis of the normal temperature test normal, can the second step tests - Heating detection, a heat source ( Such as soldering iron) Observation of the heating, close to the thermistor universal said, as at this time of readings and subject to change with the temperature rising, this shows that the resistance in the gradual change ( Negative temperature coefficient thermistor NTC resistance becomes smaller, the positive temperature coefficient thermistor PTC resistance get bigger) , when the resistance to change to a certain value display data will gradually stability, explain thermistor is normal, if there were no changes in resistance, its performance becomes bad, can't continue to use.

when testing should be paid attention to the following:

( 1) Rt is the manufacturer when the environment temperature is 25 ℃ is measured, so when using a multimeter to measure Rt, should also be carried out in ambient temperature of 25 ℃ near the end of the, to ensure the credibility of the test.

( 2) Measuring power shall not exceed the specified value, so as to avoid current measurement error due to thermal effect.

( 3) Pay attention to proper operation. Test, don't hold the thermistor body with the hand, in order to prevent the human body temperature influence on the test.

( 4) Be careful not to make too close or the heat source and the PTC thermistor depend on direct contact thermal resistance, to prevent to be burnt.

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key words: thermal resistance, thermocouple, thermal resistance, platinum resistance, PT100, PT1000, pressure sensor and digital temperature sensor