Measuring AC and DC with a Multimeter: Operating Instructions
① Digital Multimeter for AC Voltage Measurement: Connect the black test lead to the COM or ground jack (marked on the jack), and the red test lead to the AC jack (or the jack marked with V and a wavy line ~). Set the range selector to the 750 V range (some models have 1000 V) under the AC~ section for measuring 220 V mains power. Touch the two test leads to the two terminals of the power socket respectively, and the reading shown is the AC voltage value.
② Analog Multimeter for AC Voltage Measurement: Connect the black test lead to the negative or ground terminal and the red test lead to the positive terminal. Switch the range to AC~ 500 V. Perform measurement in the same way as with a digital multimeter. Read the pointer value against the maximum full-scale mark on the right side of the scale. For the 500 V range, use the scale row marked with a maximum value of 50 on the right. If the pointer points to 20, the measured voltage is 200 V.
③ Digital Multimeter for DC Voltage Measurement: The wiring is similar to AC measurement. The red lead is connected to the positive jack and touches the positive pole of the power source. Set the selector to the DC range (marked with V and a solid horizontal line). Select the range starting from the highest and reduce it step by step according to the measured object. For example, select the 2 V range when testing an AA battery. If the polarity is reversed, a minus sign "-" will appear before the reading.
④ Analog Multimeter for DC Voltage Measurement: The measuring operation is similar to that of a digital multimeter, and the reading method follows the AC voltage measurement described above. When the positive and negative poles of DC voltage are unknown, first treat it as AC for testing without recording the reading. Reverse the test leads and test again. Observe which measurement causes the pointer to deflect normally; this connection indicates the correct polarity. Then switch to a proper DC voltage range to take the final reading.
