Digital multimeters are very popular among radio enthusiasts because of their advantages such as accurate measurement, convenient value acquisition, and complete functions. The most common digital multimeter generally has resistance measurement, on-off sound detection, and diode forward voltage measurement. AC and DC voltage and current measurement, triode 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 bring great convenience to actual detection work. However, due to improper use of digital square meters, components within the meter may be damaged and malfunction may occur during actual testing. Based on the actual situations that cause damage to digital multimeters, I have summarized the precautions for using digital square meters for the reference of beginners, so as to prevent damage to digital multimeters as much as possible.
In most cases, the damage to the digital multimeter is caused by the wrong measurement gear. For example, when measuring AC mains power, the measurement gear is placed in the electrical barrier. In this case, once the test leads contact the mains power, the internal components of the multimeter can be damaged in an instant. damage. Therefore, before using a multimeter to measure, be sure to check whether the measurement gear is correct. After use, set the measurement selection to AC 750v or DC 1000v, so that no matter what parameters are mismeasured 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, if the mains power is measured at the AC 20V range, it is easy to cause damage to the AC amplifier circuit of the digital multimeter, causing the multimeter to lose its AC measurement function. When measuring DC voltage, if the measured voltage exceeds the measurement range, it is also easy to cause circuit failure in the meter. When measuring current, if the actual current value exceeds the range, it will generally only cause the fuse in the multimeter to blow out and will not cause other damage. Therefore, when measuring voltage parameters, if you do not know the approximate range of the measured voltage, you should first set the measurement range to the large range, measure the value and then change the measurement range to obtain a more accurate value. If the voltage value to be measured is far beyond the maximum range that the multimeter can measure, an additional high-resistance measuring pen should be used. Such as detecting the anode high voltage and focusing high voltage of black and white color TV sets.
The upper limit of the DC voltage range of most digital multimeters is 1000v. Therefore, when measuring DC voltage, the maximum voltage value is below 1000v, which generally does not damage the multimeter. If it exceeds 1000v, the multimeter is likely to be damaged. However, different digital multimeters may have different upper limits of measurable voltage. If the measured voltage exceeds the range, a resistance step-down method can be used to measure it. In addition, when measuring a DC high voltage of 40o ~ 1000v, the test leads must be in good contact with the measuring point without any jitter. Otherwise, in addition to causing damage to the multimeter and making the measurement inaccurate, in serious cases the multimeter may not have any show.
