Common Misunderstandings in the Use of Digital Multimeters
Due to the advantages of accurate measurement, convenient value selection, and complete functions, digital multimeters are very popular among radio enthusiasts. The most common digital multimeters generally have resistance measurement, on-off sound detection, and diode forward voltage measurement. AC and DC voltage and current measurement, triode 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 the actual detection work. However, due to improper use of digital square meters, it is easy to cause damage to the components in the meter and cause malfunctions during actual testing. Based on the actual situation of damage to the digital multimeter, I have summarized the precautions for the use of the digital multimeter for reference by beginners, so as to prevent damage to the digital multimeter as much as possible.
Some digital multimeters are damaged because the measured voltage and current exceed the range. If the mains power is measured at the AC 20V gear, it is easy to cause damage to the AC amplifier circuit of the digital multimeter, and the multimeter loses the 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 the current, if the actual current value exceeds the range, generally only the fuse in the multimeter will be blown, 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, and then change gears to measure after measuring its value to obtain more accurate values. If the voltage value to be measured is far beyond the maximum range that the multimeter can measure, it should be equipped with a high-resistance measuring probe.
In most cases, the damage of the digital multimeter is caused by the wrong measurement position. For example, when measuring the AC mains, the measurement position is selected to be placed in the electric barrier. In this case, once the test pen touches the mains, it will instantly damage the internal components of the multimeter. damage. Therefore, before using the multimeter to measure, be sure to check whether the measurement gear is correct. After use, set the measurement option to AC 750V or DC 1000V, so that no matter what parameter is mismeasured in the next measurement, it will not cause damage to the digital multimeter.
The upper limit range of the DC voltage of the digital multimeter is 1000V, so when measuring the DC voltage, the maximum voltage value is below 1000V, and generally the multimeter will not be damaged. If it exceeds 1000V, it is very likely to cause damage to the multimeter. However, the upper limit of measurable voltage may be different for different DMMs. If the measured voltage exceeds the range, it can be measured by resistance drop method. In addition, when measuring the DC high voltage of 400 ~ 1000V, the test leads must be in good contact with the measuring place without any jitter, otherwise, in addition to possibly causing damage to the multimeter and making the measurement inaccurate, in serious cases, the multimeter can also be used without any vibration. show.
