Notes on the use of digital multimeter and the advantages and causes of damage
Digital multimeter due to accurate measurement, easy to take values, full-featured and other advantages, so by the radio enthusiasts welcome, the most common digital multimeter generally has a resistance measurement, sound detection, diode forward conduction voltage measurement. AC DC voltage and current measurement, triode amplification and performance measurement. Some digital multimeter is increased capacitance measurement, frequency measurement, temperature measurement, data memory and voice reporting and other functions, to bring great convenience to the actual test work. However, the digital multimeter due to improper use, in the actual detection is easy to cause damage to the table components, resulting in failure.
Digital multimeter damage in most cases is caused by the measurement of the wrong gear, such as in the measurement of AC utility, the measurement of the gear selection is placed in the resistance block, in this case, once the pen contact with the utility, instantly can cause damage to the internal components of the multimeter. Therefore, before using the multimeter to measure, you must check whether the measuring position is correct. At the end of the use, the measurement selection will be placed in the AC 750V or DC 1000V, so that in the next measurement, no matter what parameters are measured by mistake, will not cause damage to the digital multimeter.
Some digital multimeters are damaged because the measured voltage and current exceed the range. Such as in the AC 20V gear measurement of utility power, it is easy to cause damage to the digital multimeter AC amplifier circuit, so that the multimeter lost the AC measurement function. When measuring DC voltage, the measured voltage exceeds the measuring range, which is also easy to cause the failure of the internal circuit of the meter. When measuring current, if the actual current value exceeds the range, it will only cause the fuse in the multimeter to blow, and will not cause other damages. Therefore, when measuring voltage parameters, if you don't know the approximate range of the measured voltage, you should first put the measurement gear at the maximum, and then change the gear after measuring its value to get a more accurate value. If the voltage value to be measured is far beyond the maximum range that the multimeter can measure, it should be equipped with another high resistance measuring pen. Such as detecting the anode high voltage and focus high voltage of black and white colour TV.
The upper range of DC voltage of most digital multimeters is 1000V, so when measuring DC voltage, the maximum voltage value is below 1000V, which generally will not damage the multimeter. If it exceeds 1000V, it is likely to cause damage to the multimeter. However, the upper limit of measurable voltage may vary from one digital multimeter to another. If the measured voltage exceeds the range, it can be measured by resistor step-down method. In addition, in the measurement of 40O ~ 1000V DC high voltage, the pen and the measurement must be in good contact, there can not be any jitter, otherwise, in addition to possible damage to the multimeter and make the measurement inaccurate, serious cases can also make the multimeter without any display.
When measuring resistance, care should be taken to be sure not to measure with electricity.
