How To Use a Circuit Tester

Electric tester picture

Afraid of electric shock? Electric shock is quite dangerous and life threatening. So stop guessing about the presence of electricity. Whether you want to check if there is electricity present in the plug or if your appliance’s surface has turned electric, a circuit tester sure will be useful.

A circuit tester is an electronic device used for a DIY testing of electric components. It detects if electricity is present in circuits by simply putting the probe on suspected areas. The tester’s light (sometimes a bulb and sometimes LED) lights up if the probes detect electricity. It is easy to use, affordable and can be bought at electrical shops almost everywhere.

Before knowing how to use a circuit tester, let me first explain the very basics of electronics. Electric power is determined by how much an electric current (i) is being pushed by a voltage (v). Power is equal to v times i.

In order to understand it well, let me use a waterfall as an example. The current is like the amount of water falling from the waterfall. The voltage can be compared to the height of the waterfall. Power is the impact of water from the falls to the rocks or river beneath the falls. As you can observe, the higher the waterfall is, the greater is the impact to the river. In the same manner, the more water is flowing from the falls, the greater too is the impact. Remember this idea well, as it will be very useful.

But if you go and buy yourself a circuit tester what will you do then? Don’t worry. Using a circuit tester is as easy as counting one through five. Ensure safety. You do not want to be electrified, do you? For safety follow these rules:

  1. Make sure there are no metals attached to your body like a wristwatch or jewelry.
  2. Make sure that you have no conductive connection to the earth or a ground. Simple static electricity in any circuitry will give you a shock if you are connected to the ground. Be sure that you are wearing your slippers or shoes, and that they are dry.
  3. In some cases you may need to wear insulated gloves and protective goggles. This is required if you are dealing with high-powered appliances and electrical sources. High electric current (measured in amperes (A)) can cause big sparks. Take note: the higher the voltage is the easier the spark can start.
  4. See to it that you bought the correct circuit tester. There are three kinds of circuit testers: AC circuit tester, DC circuit tester and combination AC/DC circuit tester. If you are using the combo make sure that the selector is set to the correct type of electricity to be tested. When dealing with electricity from your energy company, AC (alternating current – high voltage, low current) is the type of electricity being supplied. If you are testing a battery or battery-operated devices, the setting should be DC (direct current – low voltage, high current).
  5. Turn off the switch or circuit breaker of the outlet you want to test. If you are testing an appliance, unplug the appliance first. This part is not required when dealing with batteries.
  6. When testing an outlet, put the two metal ends of the test probe to the two slots of the wall socket. When testing a battery put the red probe or the probe with the (+) sign to the positive terminal of the battery and the black probe (the probe with (-) sign) to the negative terminal. If you are testing an appliance, put one probe to the body of the appliance and the other to the ground (any metal that is connected to the earth ground).
  7. For AC outlet: the test probe’s light should be off. If the light turned on even if the switch is off, this is a major problem and may cause horrible accidents or fire. Contact an electrician immediately. If there is no light, it is a good result. For batteries: Since there are no switches involved, the probe light should be lit. If not, the battery is discharged or dead. For appliances: If the probe light is lit even if the appliance is not plugged in, then there is static electricity that is connected to the body of the appliance. Bring the appliance to a service center. If there is no light on the probe then it is a good result.
  8. Turn on the switch or circuit breaker. For AC outlets: the probe light should be lit. If it is not lit, there is a faulty wiring on your electrical system. Call for an electrician to solve your problem. For appliances: plug in and turn on the appliance. Put one probe to the appliance’s body and the other to the ground again. There should be NO LIGHT. Otherwise, there is a wire inside the appliance that is poorly insulated and the appliance may cause electric shock to the user. Bring the appliance to an authorized service center.

The circuit tester is a very basic kind of electric tester. If you need a tester for multiple purposes, you may want to have an electric multi-tester or multi-meter instead. It has voltmeter, ammeter and ohmmeter integrated on one device. This meter is best suited for making electronics projects and testing of circuit boards or printed boards.


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