Any Electronic component needs to be measured during or before use. Thermistors are no exception, but for such electronic components, how to measure them? Next, let’s introduce how to measure thermistor.

Any electronic component needs to be measured during or before use. Thermistors are no exception, but for such electronic components, how to measure them? Next, let’s introduce how to measure thermistor.

Thermistor is a type of sensitive element, which is divided into positive temperature coefficient thermistor and negative temperature coefficient thermistor according to different temperature coefficients. A typical characteristic of thermistors is that they are sensitive to temperature and exhibit different resistance values ​​at different temperatures. The positive temperature coefficient thermistor has a larger resistance value when the temperature is higher, and the negative temperature coefficient thermistor has a lower resistance value when the temperature is higher. They both belong to semiconductor devices.

The purpose of measuring the thermistor is to be able to measure its resistance and accuracy.

When testing, use the ohm gear of the multimeter, which can be divided into two steps: first, test at room temperature, use alligator clips instead of test pens to respectively clamp the two pins of the PTC thermistor to measure the actual resistance value and compare it with the nominal resistance value , the difference between the two is within ±2Ω is normal. If the actual resistance value is too different from the nominal resistance value, it means that its performance is poor or damaged.

Secondly, heating test, on the basis of normal temperature test, the second test can be carried out – heating test, heat a heat source close to the thermistor, and observe the multi-function indicator. When the resistance value changes to a certain value, the displayed data will gradually stabilize, indicating that the thermistor is normal. If the resistance value does not change, it indicates that its performance is deteriorating and cannot be continue to use.

Detection of Positive Temperature Coefficient Thermistor

As with most methods of measuring resistance with a multimeter, when using a pointer multimeter to detect the quality of the positive temperature coefficient thermistor, we need to adjust the multimeter to R×1 gear. The specific operation steps can be divided into two steps. When performing normal temperature detection, first measure the actual resistance value of the two test pens in contact with the two pins of the PTC thermistor, and compare it with the nominal resistance value. If the difference between the two is within ±2Ω, it is normal. If the actual resistance value is too different from the nominal resistance value, it means that its performance is poor or damaged.

The heating detection of the thermistor is carried out on the basis of the normal temperature test. When the multimeter is used to test the resistance of the thermistor and is normal, the second step of the test – heating detection can be carried out. , place a heat source close to the PTC thermistor to heat it, and use a multimeter to monitor whether its resistance value increases with the increase of temperature. If it is, it means that the thermistor is normal. If the resistance value does not change, it means that its performance is not good , can no longer be used. At this time, it is necessary to pay attention not to make the heat source and the PTC thermistor too close or directly contact the thermistor to prevent it from being scalded.

Detection of Negative Temperature Coefficient Thermistor

When using the multimeter resistance measuring technology to test the quality of the negative temperature coefficient thermistor, the method is the same as the method of measuring ordinary fixed resistance, that is, according to the nominal resistance value of the negative temperature coefficient thermistor, select the appropriate electrical barrier, The actual value of Rt can be directly measured. However, because NTC thermistors are very sensitive to temperature, special attention should be paid to several issues during testing. First of all, ARt is measured by the manufacturer when the ambient temperature is 25°C, so when measuring Rt with a multimeter, it should also be performed when the ambient temperature is close to 25°C to ensure the reliability of the test. Secondly, the measurement power should not exceed the specified value, so as to avoid measurement errors caused by the thermal effect of the current. Then, be careful not to pinch the thermistor body with your hands during the test to prevent the temperature of the human body from affecting the test.

When using the multimeter to measure the resistance technology to estimate the temperature coefficient αt of the negative temperature coefficient thermistor, first measure the resistance value Rt1 at room temperature t1, and then use an electric soldering iron as a heat source, close to the thermistor Rt, and measure the resistance value RT2, and at the same time use a thermometer to measure the average temperature t2 on the surface of the thermistor RT at this time and then calculate. This test results are the most accurate.

The precautions for detecting thermistors are as follows:

Rt is measured by the manufacturer when the ambient temperature is 25°C, so when measuring Rt with a multimeter, it should also be performed at an ambient temperature close to 25°C to ensure the reliability of the test.
The measurement power should not exceed the specified value to avoid measurement errors caused by the thermal effect of the current.
Pay attention to correct operation. When testing, do not pinch the thermistor body with your hands to prevent human body temperature from affecting the test.
Be careful not to place the heat source too close to the PTC thermistor or contact the thermistor to prevent it from being scalded.

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