Common Faults and Countermeasures of Digital Multimeter
The most common digital square meters generally have the functions of resistance measurement, on-off sound detection, diode forward voltage measurement, AC and DC voltage and current measurement, triode magnification and performance measurement. Some digital multimeters have added capacitance measurement, frequency The functions of measurement, temperature measurement, data memory and voice reporting bring great convenience to the actual detection work. The digital multimeter has the advantages of safe measurement, convenient value acquisition, and complete functions, so it is very popular among radio enthusiasts. . 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. The matters needing attention in the use of the digital multimeter are for beginners to use for reference, so as to prevent damage to the digital multimeter as much as possible. The analysis and countermeasures of common faults of digital multimeters are introduced in detail as follows:
Ø The damage of the digital multimeter is caused by the wrong measurement position in most cases. For example, when measuring the AC mains, the measurement position is selected to be placed in the electric block. Component damaged. 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.
Ø Some digital multimeters are damaged because the measured voltage and current exceed the range. For example, when measuring the mains 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 the voltage parameters, if you do not know the approximate range of the measured voltage, you should first set the measurement gear, and then change the gear measurement after measuring its value to obtain a safer value. If the voltage value to be measured is far beyond the maximum range that the multimeter can measure, a high-resistance measuring probe should be equipped. Such as detecting the anode high voltage and focusing high voltage of black and white color TV.
Ø The DC voltage upper limit range of most digital multimeters is 1000V, so when measuring 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.
Ø When measuring resistance, be careful not to measure with electricity.
