How to measure the quality of a varistor?

Varistor is a strain sensitive element with high sensitivity, fast response time, and small size, widely used in fields such as electronics, communication, vehicles, diagnosis, and treatment. However, due to its unique working principle, varistors are easily affected by factors such as environment, temperature, and humidity, thereby affecting their performance and lifespan. Therefore, it is very important to measure the varistor correctly.

1、 Preparation before measuring varistors

Connect two electric pens (regardless of positive or negative) to both sides of the resistance to measure the actual resistance value. Select a range based on the nominal value of the measured resistance to improve detection accuracy. Due to the non-linear relationship of the ohmic block scale, the division of the intervals is relatively detailed. Therefore, the pointer indication value should fall into the middle position of the scale as much as possible, that is, the starting arc range of the full scale is 20% -80%, making the measurement more accurate. Depending on the level of resistance deviation. There is a permissible deviation of ± 5%, ± 10%, or ± 20% between the reading value and the nominal resistance value. If it does not match and exceeds the error range, it indicates a change in resistance.

2、 The quality of the measurement method varistor is mainly judged by measuring its resistance. There are generally the following measurement methods:

1. The maintenance resistor can be connected in series with a suitable voltage source to apply voltage to the varistor, measure the voltage value of the varistor, and see if it is within the nominal value. If so, it can be considered that the component is good. If there is a significant error from the nominal value, there is a problem with the varistor.

2. Use a multimeter to set the gear position to 10K and connect an electric pen to both sides of the resistor. The multimeter will display the resistance value of the varistor. Whether the varistor is damaged can be inferred from the displayed value. However, the multimeter detection is not accurate.

3. Another method is to use an instrument called a "varistor DC parameter meter" for testing, which is more accurate and specifically used for varistor testing.

3、 Measurement precautions

1. The measurement environment should be dry: Varistors are particularly sensitive to environmental humidity and should be measured in a dry environment to prevent water vapor from affecting the measurement results.

2. The measurement temperature should be stable: The resistance value of the varistor changes with temperature, and the temperature should be kept stable during measurement to prevent temperature from affecting the measurement results.

3. Low measurement current: Due to the small resistance of the varistor, a smaller current should be used during measurement to prevent the varistor from burning out due to excessive current.

4. High detection accuracy: The resistance value of the varistor is small, and a high-precision resistance meter or multimeter should be selected during measurement to prevent measurement errors.

5. Short measurement time: Due to the susceptibility of varistors to environmental factors, the measurement time should be as short as possible to prevent inaccurate measurement results.