Electrical testers are used to check both AC and DC voltage, continuity, circuit problems, amperage, shorted and open circuit problems, and to make sure the voltages are correct at the electrical panel.
Electricians use these electrical testers every day to see if a circuit or device is energized. They are crucial safety tools that keep electricians out of harms way and tell them if there is trouble on a circuit or device.
There are several different types of testers on the market, some with specific purposes only and some with multiple testing features. Here are the top 6 electrical testers used by professional electricians.
A continuity tester is a device that is powered by batteries and has a probe at on end and a cord with either an alligator clip or another probe at the other end. Basically, if you touch the two together, you complete a circuit and a light lights or a sound, like a buzzing sound, goes off to indicate there is a complete circuit. These testers are great for checking to see if something like a single-pole switch is working properly.
Beware! be sure to turn the power off to the circuit or device that you'll be testing!
Continuity testers are also great for checking wire runs for a complete circuit.You may also find short circuits in wiring with this tester, say two wires have melted together inside the outer jacket of NM sheathed cable.
By touching one probe to the white and the other to the black wire, if the light lights and the buzz sounds, the wires are identified as shorted together. Once again, be sure the power is off before doing any testing.
One of the easiest ways to check for faulty devices and parts, is to use a multi-tester, sometimes called a multi-meter.
Testing continuity by using the ohm setting will tell you if the connection through the device is complete or if it has opened and is no longer usable. For instance, if you place one of the test leads on one side of a fuse and the other lead on the other side of the fuse, you should show a short circuit or 0 ohms. If your meter shows infinite resistance, the fuse is bad and should be replaced.
To test something, turn the dial of the tester to the ohm setting. This portion of the dial has markings like X1, X10, XK1, etc... This simply means that on the X1 setting, the value of ohms shown on the dial is taken times 1 and that is the amount of ohms. Let's say it shows 50 ohms. That means 50x1=50 ohms. With the dial set at X10, if the dial shows 50, 50x10=500 ohms. You can see the theory here. By adjusting the dial to another setting the multiples increase.
With the test leads apart and not touching, the meter needle should be all the way to the right, showing maximum ohms. On a digital meter, the screen will show infinite resistance.
By touching the two test leads together, either tester should show a 0 ohms reading. The digital will likely show a 0.00 reading. Sometimes meters have an audible continuity setting that looks like a diode.
With this setting, when the test leads are touched together, the meter will show the reading and an audible alarm will sound. My tester has a constant beep sound.