Digital Multimeter Failure Precautions
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 the fields of physics, electrical, electronics, and other measurement areas.
The function of measuring voltage, current, and resistance with a multimeter is achieved through the conversion circuit, while the measurement of current and resistance is based on voltage measurement. In other words, a digital multimeter is an extension of a digital DC voltmeter. The converter converts the continuously changing analog voltage into a digital value, which is then counted by an electronic counter to obtain the measurement result. The decoding display circuit then displays the measurement result. The logic control circuit coordinates the operation of the control circuit and completes the entire measurement process in sequence under the action of the clock.
1. In most cases, damage to a digital multimeter is caused by measurement gear errors. For example, when measuring AC power, if the measurement gear is set to the resistance gear, once the probe contacts the power, it can instantly cause damage to the internal components of the multimeter. Therefore, before using a multimeter for measurement, it is necessary to check whether the measurement gear is correct. After use, place the measurement selection at AC 750V or DC 1000V, so that no matter what parameter is mistakenly measured in the next measurement, it will not cause damage to the digital multimeter.
2. Some digital multimeters are damaged due to the measured voltage and current exceeding the range. For example, measuring the mains power in the AC 20V range can easily 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 can also easily cause circuit faults in the meter.
When measuring current, if the actual current value exceeds the range, it usually only causes the fuse in the multimeter to burn out and will not cause any other damage. So when measuring voltage parameters, if you don't know the approximate range of the measured voltage, you should first set the measurement gear to the highest gear, measure its value, and then shift gears to obtain more accurate values. If the voltage value to be measured far exceeds the maximum range that the multimeter can measure, a high resistance measuring probe should be provided separately. To detect the second anode high voltage and focusing high voltage of black and white color TVs.
3. The upper limit range of most digital multimeters for DC voltage is 1000V, so when measuring DC voltage, the highest voltage value is below 1000V, which generally does not damage the multimeter. If it exceeds 1000V, it is highly likely to cause damage to the multimeter. However, the upper limit of measurable voltage may vary among different digital multimeters. If the measured voltage exceeds the range, the method of resistance voltage reduction can be used for measurement. In addition, when measuring high DC voltages ranging from 40O to 1000V, the probe must be in good contact with the measuring point and there should be no shaking. Otherwise, in addition to causing damage to the multimeter and inaccurate measurements, in severe cases, the multimeter may also have no display.
4. When measuring resistance, be careful not to measure with electricity.
