Precautions when using the multimeter:
(1) In the process of using the multimeter, do not touch the metal part of the test pen with your hands, so on the one hand, it can ensure the accuracy of the measurement, and on the other hand, it can also ensure personal safety.
(2) When the multimeter is in use, it must be placed horizontally to avoid errors. At the same time, pay attention to avoid the influence of external magnetic field on the multimeter.
(3) When measuring a certain amount of electricity, it is not possible to change gears while measuring, especially when measuring high voltage or large current, more attention should be paid. Otherwise, the multimeter will be destroyed. If you need to change gears, you should disconnect the test leads first, and then go to measure after changing gears.
(4) After the multimeter is used, the transfer switch should be placed in the maximum block of AC voltage. If it is not used for a long time, the battery inside the multimeter should also be taken out to prevent the battery from corroding other devices in the meter.
It is best to have one pointer and one digital. Amateur electronic production has an analog MF30 multimeter, which is a classic model. There are also veteran-level MF500 multimeters, and cheap MF50 multimeters, which are generally available in telecommunications stores.
Today's multimeters have added many new functions, especially digital multimeters, such as measuring capacitance value, triode magnification, diode voltage drop, etc. There is also a talking digital multimeter that can broadcast the measurement results in language. There are also many classic models of digital multimeters, such as DT830C, DT890D, etc. The suffix at the back indicates the difference in function. Among them, DT830C has been bought for more than 30 yuan, which is cheap enough.
Basically, A- is used to represent the DC current measurement, and the milliampere and ampere files are generally divided into several files. V- means to measure DC voltage, the multimeter of the advanced point has millivolt gear, and the voltage gear is also divided into several gears. V~ is used to measure AC voltage. A~ measure the alternating current. The resistance is measured in the Ω ohm range. For an analog multimeter, a zero adjustment is required every time the resistance range is changed. Zero adjustment is to put the red test lead and black test lead of the multimeter together, and then turn the zero adjustment button to make the pointer point to the zero position. hFE is to measure the current amplification factor of the triode. As long as the three pins of the triode are inserted into the corresponding holes on the universal panel, the hFE value can be measured. Note that PNP and NPN are different.
The following takes the MF30 multimeter as an example to illustrate the reading of the multimeter. The first scale line is the resistance value indication, the left end is infinity, the right end is zero, and the scale is uneven in the middle. There are R×1, R×10, R×100, R×1K, R×10K resistance gears, which respectively indicate the multiples of the scale indication and then multiply to get the actual resistance value (unit is ohm).
The biggest feature of the multimeter is that it has a range switch, and each function is switched by this switch. At present, there are two types of multimeters on the market: pointer type and digital type, and they each have their own advantages.
The above mainly introduces the use of the multimeter, that is, how to use the multimeter to measure AC and DC voltage, resistance, and DC current, the preparations that need to be done before using the multimeter and the precautions for its use.
