Failure prevention measures for digital multimeters
A digital multimeter (DMM) is an electronic instrument used in electrical measurements. It can have many special functions, but its main function is to measure voltage, resistance and current. As a modern multi-purpose electronic measuring instrument, the digital multimeter is mainly used in physics, electrical, electronic and other measurement fields.
The function of measuring voltage, current and resistance of a multimeter is realized through the conversion circuit part, and the measurement of current and resistance is based on the measurement of voltage, which means that the digital multimeter is expanded on the basis of the digital DC voltmeter. The converter converts the analog voltage that changes continuously with time into a digital quantity, and then the electronic counter counts the digital quantity to obtain the measurement result, and then the decoding display circuit displays the measurement result. The logic control circuit controls the coordinated work of the circuit and completes the entire measurement process in sequence under the action of the clock.
1. In most cases, the damage of 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 block. In this case, once the test leads contact the mains power, the multimeter can be damaged instantly. Internal components are 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.
2. 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 to the highest 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 second anode high voltage and focusing high voltage of black and white color TV sets.
3. 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 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.
4. When measuring resistance, be careful not to measure while it is live.
