DC is common in batteries and other low-voltage sources of power. AC is used in buildings, electronics, and anything else that requires multiple currents.
For example, if you have a 12V battery, test it using the 20V setting. Using any settings beyond that would lead to a less accurate result. Most modern multimeters are autorange, meaning they set the proper range once you begin the test. If you’re not sure what voltage setting to use, start at the highest one. Work your way back until you get an accurate result. The voltage readout will change to 1 if you go too far.
The mAVΩ port is meant for currents rated at 200 milliamps (mA). In most cases, you will end up using this port. Use the 10A port to test strong currents greater than 200 mA. If you don’t know the strength of the current you are testing, plug the red probe into the 10A port to avoid damaging the multimeter.
To get accustomed to using a multimeter, test it on a battery. Hold the black probe against the negative terminal and the red probe against the positive one. If you’re attempting to test live wires, find the screws pinning the wires in place. Touch the black probe to one screw and the red probe to another. Be careful to avoid touching active wires or metal parts, since it could lead to an electrical shock. Also, the multimeter could short-circuit if you bump the metal tips of the probes together.
The multimeter range has to be set to the correct maximum voltage for the circuit in order to get the most accurate result possible. If it is set too high, it will have a hard time detecting the voltage of a weaker current. If the multimeter displays a negative number, for example, the probes are most likely in the wrong place. Reverse them so that the electrical current flows properly between them. If you don’t see any readout, the circuit may not be receiving any electrical power at all. Test the multimeter on something active, such as a battery or outlet, to make sure it still works.
Use the AC setting to test wall outlets and most electronic devices. DC is for batteries and other low-voltage power sources.
For instance, most home outlets maintain a 120-volt current. Set the multimeter to 200v or the next closest setting above 120. Most multimeters have fuses that protect them from serious damage, although inexpensive ones sometimes don’t. Using the wrong setting could destroy the multimeter. If you’re unsure what setting to use, start at the highest one and move down until the multimeter reacts.
If you reverse the probes, you won’t get an accurate test result. If you notice the multimeter needle moving in the wrong direction, check the probes first.
You can test the multimeter using a battery first. The positive and negative terminals on the battery are labeled and easy to spot. Handle the probes one at a time to avoid touching the tips and short-circuiting the device.
If the needle doesn’t move much, turn the multimeter’s voltage setting down a little bit. It often doesn’t react when the voltage setting is too high. Also, make sure the testing device is active. If the needle moves all the way to the right, pull the probes out. Set the multimeter dial to a higher range, then perform the test again. Try to avoid having this happen, since it could damage the multimeter.
