How to Measure Alternating Current and Direct Current Using a Multimeter
Measuring AC Voltage with a Digital Multimeter
Connect the black test lead to the negative or ground terminal (marked on the jack), and the red test lead to the AC jack (or the jack marked with V plus a tilde symbol ~). Set the range to 750 V (some models have 1000 V) under the AC~ selection for measuring 220 V mains power. Touch the two test leads to the two holes of the power socket respectively, and the reading shown is the AC voltage value.
Measuring AC Voltage with an Analog Multimeter
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, then take the measurement in the same way as with a digital multimeter. Read the pointer against the maximum full-scale range on the right side of the dial: if the 500 V range is selected, read 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.
Measuring DC Voltage with a Digital Multimeter
The operation is similar to AC voltage measurement, except that the red lead connects to the positive jack and touches the positive pole of the power source. Switch to the DC range (marked with V and a short horizontal line). Select the range from high to low according to the actual condition. For example, select the 2 V range to test an AA battery. If the polarity is reversed, a minus sign will appear before the reading.
Measuring DC Voltage with an Analog Multimeter
The measuring procedure is similar to that of a digital multimeter, and the reading method is the same as for AC voltage measurement described above. When the positive and negative poles of DC voltage are unknown, you may first treat it as AC for measurement (ignoring the reading). Reverse the test leads and measure again. Observe which measurement causes the pointer to deflect normally; the lead polarity for that measurement is correct. Then switch to a suitable DC voltage range to take the formal reading.
