Precautions for using a multimeter

Digital multimeters are popular among radio enthusiasts because of their advantages of 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 magnification and performance measurement, etc. Some digital multimeters have added functions such as capacitance measurement, frequency measurement, temperature measurement, data memory, and voice reporting, which bring great convenience to actual detection work. However, due to improper use of digital multimeters, it is easy to cause damage to the components inside the meter and cause malfunctions during actual detection.

In most cases, the damage of digital multimeters is caused by the wrong measurement gear. For example, when measuring AC mains power, the measurement gear is set to the electric block. In this case, once the test pen touches the mains power, the internal components of the multimeter will be damaged instantly. Therefore, before using the multimeter for measurement, be sure to check whether the measurement gear is correct. After use, set the measurement selection to AC 750V or DC 1000V. In this way, no matter what parameters are measured incorrectly during the next measurement, the digital multimeter will not be damaged.

Some digital multimeters are damaged because the measured voltage and current exceed the range. For example, measuring the AC power at the AC 20V position can easily damage the AC amplifier circuit of the digital multimeter and make the multimeter lose its AC measurement function. When measuring DC voltage, the measured voltage exceeds the measurement range, which is also likely 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 you do not know the approximate range of the measured voltage, you should first set the measurement gear to the highest gear, measure its value, and then change the gear to measure, so as to obtain a more accurate value. If the voltage value to be measured is far beyond the maximum range that the multimeter can measure, you should equip it with a high-resistance measuring pen. For example, to detect the second anode high voltage and focus high voltage of black and white color TVs.

The upper limit of DC voltage range 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 cause damage to 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. When measuring resistance, you should be careful not to measure with power on.