Common misconceptions about the use of multimeters
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 resistance measurement, pass sound detection, diode forward voltage measurement. AC and DC voltage and current measurement, transistor 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. I cause damage to the digital multimeter according to the actual situation, summed up the digital multimeter in the use of the precautions for beginners to learn the first use of reference, in order to try to prevent the damage of the digital multimeter.
Some digital multimeter damage is due to the measurement of voltage and current over the range caused by 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 to lose 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 in the highest grade, 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.
The digital multimeter is damaged in most cases due to 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 use, put the measurement selection at AC 750V or DC 1000V, so that no matter what parameters are measured by mistake in the next measurement, it will not cause damage to the digital multimeter.
The upper DC voltage range of the digital multimeter is 1000V, so the multimeter will not be damaged if the maximum voltage value is below 1000V when measuring DC voltage. 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, 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, but also serious cases can make the multimeter without any display.
