Common faults and countermeasures of digital multimeters
The most common digital square meter generally has functions such as 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 add capacitance measurement, frequency Functions such as measurement, temperature measurement, data memory and voice reporting bring great convenience to actual detection work. Digital multimeters are very popular among radio enthusiasts because of their advantages such as accurate measurement, convenient value taking, and complete functions. . However, due to improper use of digital square meters, components within the meter may be damaged and malfunction may occur during actual testing. Precautions when using a digital multimeter are provided for reference by beginners to prevent damage to the digital multimeter as much as possible. The analysis and countermeasures of common fault causes of digital multimeters are introduced in detail as follows:
Ø 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, it will instantly cause internal damage to the multimeter. Component is damaged. 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.
Ø Some digital multimeters are damaged because the measured voltage and current exceed the range. For example, when measuring mains power 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 gear, measure the value and then change gears 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.
Ø The upper limit range of DC voltage 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 measurement 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.
Ø When measuring resistance, be careful not to measure while it is live.
