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What Type of Voltage Does a Multimeter Read?

A multimeter is an electronic testing device with a range of uses. Analog multimeters display readings on a variable scale by means of a swinging needle. Digital multimeters present readings on a screen as whole or decimal numbers. Most multimeters are capable of running many kinds of tests including continuity, resistance, capacitance and two kinds of voltage.

DC Voltage
- An analog multimeter displays results on a dial.
  
  DC means direct current. Direct current voltage is the type of power that is supplied by simple or complex storage batteries. Simple multimeters are capable of measuring DC voltages from 10 volts to 1,000 volts. To test DC voltages with a multimeter, the positive test probe is placed on the positive terminal of a direct current power source. The negative test probe is placed on the negative terminal. The voltage is displayed on a variable scale or a digital screen.
Testing DC Voltage
- A modern car battery operates with a direct current.
  
  Automobiles use the DC power of a battery to turn the starter, which cranks the engine until it fires. Set the multimeter to read above 12 volts. A fully charged automotive battery should test at 12.4 to 12.7 volts. Multimeters can measure the voltages of batteries that power flashlights, laptop computers, radios, portable CD players and many cordless power tools.
AC Voltage
- AC means alternating current. Alternating current is the type of electric power that is delivered to homes, businesses and factories by a system of power lines called the power grid. Alternating current is measured with multimeters having a range of voltages. Meters for hobbyists and home mechanics usually limit AC voltage testing to a range of 10 volts to 1,000 volts. Public utilities and power grid service personnel may use meters with much higher AC voltage ranges. Alternating current, unlike direct current, is a great deal more dangerous to test. AC voltages at 750 volts and higher are considered extremely dangerous but many individuals have suffered fatal shocks from 120-volt household AC current.
Testing AC voltage.
- Multimeters can test outlet voltage.
  
  A multimeter can be used to test the voltage output of a residential wall plug. Set the meter range switch to 250 volts AC. Because alternating current has no polarity, you may place either test probe in the outlet holes. If there is current at the outlet the meter will read 110 to 120 volts on the AC scale. If the outlet has a circular ground opening you can test to that point as well. With the positive probe in the bigger of the plug slots and the negative probe in the circular hole the meter should read 110 volts to 120 volts. A test from the small slot to the circular hole should read zero volts.

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