How to Use a Pointer Multimeter for AC and DC Voltage Measurement

(1) Before testing, first place the multimeter in a horizontal position and check whether the pointer is at zero (the zero point of the current and voltage scales). If not, adjust the “mechanical zero adjustment” below the meter head to make the pointer point to zero.

(2) According to the measured item, correctly select the measurement project and range switch on the multimeter.

If the magnitude of the measured quantity is known, select the corresponding range. If the magnitude is unknown, start measuring from the maximum range. When the pointer’s deflection angle is too small to read accurately, reduce the range. Generally, a deflection angle of at least 30% of the maximum scale is considered a reasonable range.

(1) Connect the multimeter in parallel to the circuit being measured. When measuring DC voltage, pay attention to the polarity of the measurement point, connecting the red probe to the higher voltage side and the black probe to the lower voltage side. If the polarity is unknown, use a trial method; if the pointer deflects to the right, measurement can proceed; if it deflects to the left, switch the positions of the red and black probes before measuring.

(2) To minimize errors introduced by the internal resistance of the voltmeter, choose a large range when the pointer deflection angle is greater than or equal to 30% of the maximum scale. The larger the range, the larger the voltage divider resistance, and the smaller the equivalent internal resistance of the voltmeter, which reduces errors introduced to the measured circuit. If the internal resistance of the measured circuit is very large, the internal resistance of the voltmeter must be even larger to maintain measurement accuracy. At this time, use a multimeter with higher voltage sensitivity (greater internal resistance) for measurement.

(3) When measuring AC voltage, there is no need to consider the polarity issue; just connect the multimeter in parallel across the two points being measured. Additionally, it is generally unnecessary to select a large range or a multimeter with high voltage sensitivity, as the internal resistance of AC power sources is usually small. Note that the measured AC voltage must be a sine wave, with a frequency less than or equal to the allowable working frequency of the multimeter; otherwise, significant errors may occur.

(4) Do not switch the range selector while measuring high voltages (e.g., 220V) to avoid arcing, which could damage the contacts of the selector switch.

(5) When measuring high voltages greater than or equal to 100V, safety must be prioritized. It is best to first fix one probe to the common ground of the circuit being measured and then use the other probe to touch the other test point.

(6) When measuring voltage in circuits with inductive reactance, disconnect the multimeter before turning off the power. Otherwise, when the power is cut off, the self-induction phenomenon of inductive components in the circuit may generate high voltage, potentially damaging the multimeter.

(1) Do not mistakenly switch the range when measuring current and voltage. If you mistakenly use the resistance or current range to measure voltage, it can easily damage the multimeter. When not in use, it is best to set the range to the highest AC voltage to avoid damage from improper use.

(2) When measuring DC voltage and current, pay attention to the “+” and “-” polarities to avoid incorrect connections. If the pointer reverses, immediately switch the probes to avoid damaging the pointer and the meter head.

(3) If you do not know the magnitude of the voltage or current being measured, start with the highest range and then select an appropriate range for testing to avoid excessive pointer deflection that could damage the meter head. The closer the selected range is to the measured value, the more accurate the measurement will be.

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