How to prevent the digital multimeter from breaking down
A digital multi-meter (DMM) is an electronic instrument to be used in electrical measurements. It can have many special functions, but the main function is to measure voltage, resistance and current. Digital Multimeter, as a modern multi-purpose electronic measuring instrument, is mainly used in the field of physical, electrical and electronic measurements.
Multimeter measurement of voltage, current and resistance function is achieved through the conversion circuit part, and the measurement of current and resistance are based on the measurement of voltage, that is to say, the digital multimeter is expanded on the basis of digital DC voltmeter. The converter changes the analogue voltage quantity which changes continuously with time into digital quantity, then the electronic counter counts the digital quantity to get the measurement result, and then the decoder display circuit displays the measurement result. Logic control circuit to control the coordinated work of the circuit, under the action of the clock in order to complete the entire measurement process.
1, 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, it will not cause damage to the digital multimeter.
2, 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. In the measurement of DC voltage, the measured voltage exceeds the measurement range, also easy to cause the table circuit failure.
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. Such as detecting the second anode high voltage and focusing high voltage of black and white colour TV.
3, most of the digital multimeter DC voltage upper range for 1000V, so when measuring DC voltage, the highest voltage value in 1000V below, generally will not damage the multimeter. If it exceeds 1000V, it is likely to cause damage to the multimeter. However, different digital multimeters may have different upper limits of measurable voltage. If the measured voltage is out of 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 to make inaccurate measurements, and in serious cases can make the multimeter without any display.
4,When measuring resistance, it should be noted that it must not be measured with electricity.
