There are many models of mechanical multimeters, and there are differences in functions between different models. When purchasing a multimeter, it is usually necessary to pay attention to the following aspects.
1. When used to repair weak electronic devices such as radio. Be sure to pay attention to the following three aspects when choosing a multimeter.
1) The sensitivity of the multimeter should not be lower than 20KΩ/V. Otherwise, when testing the DC voltage, the multimeter has too much influence on the circuit, and the test data is not accurate.
2) Shape selection
When you need need home repair, you should choose a multi-meter with a slightly smaller shape, such as the 50-type U201. If you do not need home repair, you can choose NMF47 or MF50 multimeter.
3) Frequency characteristic selection (commonly known as anti-peak):
The method is to use a DC voltage to balance the high-frequency circuit (such as the line output circuit voltage of the color TV) to see whether the nominal value is displayed. If yes, the frequency characteristic is high: if the indication value is high, the frequency characteristic is poor (not resistant to the peak value), This multimeter cannot be used for the detection of high frequency circuits (it is best not to choose this type).
3. Check the damping balance of the meter head.
Firstly, mechanical zeroing is performed, and the multimeter is swayed back and forth in the horizontal and vertical directions. The pointer should not have obvious swing: when the table is rotated horizontally and vertically, the deflection of the needle should not exceed one small square: when the needle are rotated 360", The pointer should always oscillate evenly around zero. If the above requirements are met, it means that the meter has reached the standard in terms of balance and damping.