A multimeter is very useful in measuring and testing DC voltage. The multimeter can be a standard multimeter, a digital multimeter (DMM), or a auto-ranging digital multimeter. The source of the DC voltage can be from batteries, circuits, transformers, or any other electronic device that operates on DC voltage. Troubleshooting of DC electronics is made easier by using a digital multimeter to test in-circuit DC voltage and compare the results to an electrical schematic. Faulty components can be identified within the circuit in order to make repairs. This article makes working on DC electronics or batteries simple by describing how to test DC voltage using a multimeter.
Things You Will Need
Multimeter with probes
Start by setting up the multimeter to test DC voltage. Insert the + red probe into the red voltage test (V) port and the - black probe into the COM port. Make sure both probes are firmly pushed into the ports so their is no chance of damaging the multimeter.
Set the multimeter test dial to the DC voltage setting. The correct setting is shown in the photo. The setting is typically a V with a straight line over the V. Once the multimeter dial is set the meter will be on.
Step 3Determine what DC voltage will be tested. The multimeter can test a battery voltage, circuit voltage, a AC to DC transformer output, or any other DC voltage. The back of most multimeters show the limits for DC current (amps). Make sure the the maximum current will not be exceeded for the voltage that will be tested.
Turn on the power to the circuit or plug in the AC-DC transformer. To test voltage a supply of voltage must be present. Measure an in-circuit DC voltage by holding the red probe on the positive side of the circuit and holding the black probe to the negative side. To determine the charge to know where to place the probes refer to the circuit diagram or look for +/- labeling.
For a battery test touch the red probe lead to the + terminal of the battery while you touch the black probe lead to the - terminal of the battery.
Read the DC voltage amount on the screen of the multimeter. If no voltage is registering check to make sure the power is being applied to the circuit. If the voltage is a small amount and the multimeter is not auto-ranging, turn the dial of the multimeter to a lower DC voltage setting such as mV. Try to test the circuit again using the multimeter.
If the test is for common household batteries, the results should indicate 1.5 Volts for AAA, AA, C, or D batteries if they are good. The multimeter should read 9 volts for a 9 volt battery to be considered acceptable.
Use the steps above to make measurements of any DC power source or DC voltage in a circuit. There are so many uses for this type of test. Multimeters have made working with DC voltage manageable.