(1) Before testing, first place the multimeter in a horizontal state and check if its needle is at zero (referring to the zero point of the current and voltage scales). If it is not, adjust the "mechanical zero adjustment" below the meter head to make the pointer point to zero.

(2) Select the correct measurement items and range switches on the multimeter based on the measured items. If the order of magnitude being measured is known, then select the corresponding range of magnitude. If the order of magnitude of the measured value is unknown, the measurement should start from selecting the maximum range. When the pointer deviation angle is too small to accurately read, the range should be reduced again. The reasonable range is generally based on a pointer deflection angle not less than 30 percent of the maximum scale.

② When the pointer deflection angle is greater than or equal to 30 percent of the maximum scale, try to choose a large number of range gears. Because the larger the range, the smaller the shunt resistance, and the smaller the equivalent internal resistance of the ammeter, the smaller the error introduced by the measured circuit.

③ When measuring a large current (such as 500mA), do not move the range selection switch during the measurement process to avoid arcing and burning the contacts of the transfer switch.

② Like the ammeter mentioned above, in order to reduce the error caused by the internal resistance of the voltmeter, when the pointer deviation angle is greater than or equal to 30 percent of the maximum scale, a large number of range ranges should be selected for measurement as much as possible. Because the larger the range, the greater the voltage divider resistance, and the greater the equivalent internal resistance of the voltmeter, the smaller the error introduced by the measured circuit. If the internal resistance of the circuit being tested is large, a higher internal resistance of the voltmeter is required to achieve high measurement accuracy. At this point, it is necessary to use a multimeter with higher voltage sensitivity (greater internal resistance) for measurement.

④ Do not move the range selection switch when measuring a higher voltage (such as 220V) to avoid generating an arc and burning the contact of the transfer switch.

⑤ When measuring high voltages greater than or equal to 100V, it is necessary to pay attention to safety. It is best to first fix one probe in the common of the circuit being tested and then use another probe to touch the other end of the test pilot.

⑥ In circuit systems, the level is commonly used to represent the effective value of the voltage at that point. Therefore, the multimeter has a level scale on the AC voltage range, and zero level refers to the power generated at a 600 ohm impedance of 1mW, which corresponds to a voltage effective value of 0.75V. If the impedance of the broken circuit is not equal to 600 ohms, the calculation should be carried out according to the following formula: actual electronic value=multimeter dB reading plus 101g (600/z). In the formula, z is the resistance value of the tested circuit. It is worth noting that the measurement should be placed on the 10V level, because the level scale of the multimeter is designed and calculated on that level. If the range is not enough, it needs to be changed to another level for measurement. The multimeter is only suitable for measuring volume and frequency levels, such as DC voltage on the circuit, It is also necessary to connect a 0.1uF/450V capacitor in series to isolate the DC before measuring it