Causes of digital multimeter failure and preventive measures

Digital multimeters are popular among radio enthusiasts because of their advantages such as accurate measurement, convenient value acquisition, and complete functions. The most common digital multimeters generally have resistance measurement, on-off sound detection, diode forward voltage measurement, AC and DC voltage and current measurement, transistor amplification and performance measurement, etc.

Some digital multimeters have added functions such as capacitance measurement, frequency measurement, temperature measurement, data memory and voice reporting, which greatly facilitates the actual detection work. However, due to improper use, digital multimeters are prone to damage to components in the meter and cause malfunctions during actual detection. The precautions for using digital multimeters are provided for reference by beginners to prevent damage to digital multimeters as much as possible. 

Digital multimeter failure causes and preventive measures: 

   1. In most cases, the damage of digital multimeter is caused by the wrong measuring gear. For example, when measuring AC mains, the measuring gear is set to the resistance block. In this case, once the test pen touches the mains, the internal components of the multimeter will be damaged instantly. Therefore, before using the multimeter to measure, you must first check whether the measuring gear is correct. After use, set the measurement to AC 750V or DC 1000V. In this way, no matter what parameter is measured incorrectly during the next measurement, the digital multimeter will not be damaged. 

   2. Some digital multimeters are damaged because the measured voltage and current exceed the range. For example, if the AC 20V gear is used to measure the mains power, it is easy to damage the AC amplifier circuit of the digital multimeter, causing the multimeter to lose its AC measurement function. When measuring DC voltage, the measured voltage exceeds the measurement range, which is also easy to cause circuit failure in the meter. When measuring current, if the actual current value exceeds the range, it generally only causes the fuse in the multimeter to burn out, and no other damage will be caused. Therefore, when measuring voltage parameters, if the approximate range of the measured voltage is unknown, the measurement gear should be set to the highest gear first, and then the gear should be changed to measure after measuring its value to obtain a more accurate value. If the voltage value to be measured is far beyond the maximum range that the multimeter can measure, a high-resistance measuring pen should be equipped. For example, to detect the second anode high voltage and focus high voltage of black and white color TVs. 

   3. The upper limit of DC voltage of most digital multimeters is 1000V. Therefore, when measuring DC voltage, the maximum voltage value is below 1000V, which generally will not damage the multimeter. If it exceeds 1000V, it is very likely to damage the multimeter. However, the upper limit of measurable voltage of different digital multimeters may be different. If the measured voltage exceeds the range, the method of resistance voltage reduction can be used to measure it. In addition, when measuring DC high voltage of 400~1000V, the test pen must be in good contact with the measuring point, and there must be no jitter. Otherwise, in addition to the possibility of damaging the multimeter and making the measurement inaccurate, in serious cases, the multimeter may not display anything.    4. When measuring resistance, be careful not to measure with power on.