Five Questions About Multimeters Answered
1. How to judge (detect) the AC voltage range (ACV) of the multimeter is good?
Answer: Household detection sources include AC adapters, household sockets (two-phase 220V, it is best not to measure three-phase 380V, because this voltage is more dangerous, and it is harmful to the instrument (at least a multimeter above CAT III 600V) and Users have higher requirements), for the sake of safety, it is recommended to measure a relatively small voltage first, such as the AC adapter, and then measure the voltage of the household socket. For specific safe operation methods, please refer to the product manual.
2. How to judge whether the resistance file (OHM Ω) is good or bad?
Answer: Note, please do not use the resistance gear to measure the voltage. When measuring online, the equipment should be powered off, and the line with capacitors or batteries should be fully discharged before measurement. This is easier to detect, generally engaged in electronic maintenance, there are some resistance elements on hand, just measure the resistance value directly.
3. How to judge whether the DC current file (DCA) is good or not?
Answer: If there is a known current source, input it directly in the current range. If not, it doesn’t matter. Just input the voltage in the current range. value, please also note the following:
A. Please do not input too high voltage, so as not to damage the instrument due to too much current. Commonly used sources that can be input are ordinary batteries, such as No. 5 and No. 7;
B. When measuring the current of the input voltage, because the resistance (load) of the internal resistance of the instrument is very small, if the input is too long, the source will be damaged, so try not to exceed 5 seconds for a single input;
C. Each high and low range, and adjacent ranges, generally have a relationship of 10 times.
4. How to judge whether the capacitor file (CAP) is good or bad?
Answer: Generally, it is to find a capacitor with a known value and insert it directly for measurement. The displayed value of each range should be in a 10-fold ratio; it is best to use a good metal capacitor for detection, which has stable capacity and high precision. It is not recommended to use electrolytic capacitors for inspection, because the stability and accuracy of electrolytic capacitors are poor.
5. What is the basic working principle of a digital multimeter?
Answer: The basic circuit of a digital multimeter is a meter circuit. The basic function it completes is to quantify the input DC voltage (analog quantity) and output it; other functions generally require additional external circuits. PS: Now the chip of the multimeter is more and more integrated, and the peripheral circuit is less and less, which has advantages and disadvantages. Advantages: high integration, simple external circuit, and fewer quality failures caused by component quality problems; Disadvantages: once the chip is broken, the replacement cost is high and troublesome, and sometimes the money for replacing a chip can buy another instrument, so Generally, if it is broken, it has to be scrapped.
