What should be noted when using a digital multimeter
Digital multimeters are popular among radio enthusiasts due to their advantages such as accurate measurement, convenient value selection, and complete functions. The most common digital multimeter generally includes resistance measurement, on/off sound detection, and diode forward conduction voltage measurement. AC/DC voltage and current measurement, transistor amplification factor and performance measurement, etc. Some digital multimeters have added functions such as capacitance measurement, frequency measurement, temperature measurement, data memory, and voice counting, which bring great convenience to actual testing work. However, improper use of digital meters can easily cause damage to the components inside the meter and result in malfunctions during actual testing. Based on the actual situation that caused damage to the digital multimeter, I have summarized the precautions for using the digital multimeter for beginners to refer to, in order to prevent damage to the digital multimeter as much as possible.
In most cases, damage to a digital multimeter is caused by incorrect measurement gear. For example, when measuring AC mains power, the measurement gear is set to the resistance gear. In this case, once the probe contacts the mains 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
Some digital multimeters are damaged due to the measured voltage and current exceeding the range. For example, measuring mains power in the AC 20V range can easily cause damage to the AC amplification circuit of the digital multimeter, causing it 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 faults in the meter. When measuring current, if the actual current value exceeds the range, it generally only causes the fuse in the multimeter to blow 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 place the measurement gear at the maximum position, measure its value, and then shift gears to obtain a more accurate value. If the voltage value to be measured far exceeds the maximum range that a multimeter can measure, a high resistance measurement probe should be provided separately. Such as detecting the anode high voltage and focusing high voltage of black and white color televisions.
The upper range of the DC voltage of the multimeter is 1000V, so when measuring the DC voltage, the highest voltage value is below 1000V, and the multimeter is generally not damaged. If it exceeds 1000V, it is very likely to cause damage to the multimeter. However, the upper limit of measurable voltage for different digital multimeters may vary. If the measured voltage exceeds the range, resistance voltage reduction can be used for measurement. In addition, when measuring high DC voltage between 40O and 1000V, the probe must be in good contact with the measurement point without any shaking. Otherwise, in addition to causing damage to the multimeter and inaccurate measurement, it may also cause the multimeter to show no display in severe cases. When measuring resistance, it is important to be careful not to measure it with electricity.
