Professional electricians use a variety of testers to check a wide range of electrical functions in residential and commercial electrical wiring, and DIY homeowners will also find some of these tools useful. Learning to identify these testers, understanding their functions and learning how to use an electrical tester will greatly expand your expertise when it comes to working on electrical wiring.
What is an electrical tester?
A circuit tester, electrical tester or voltage tester is an instrument used to determine the presence of electricity in a piece of equipment. This tool is simpler and less costly than a measuring instrument such as a multimeter, and often suffices for checking for the presence of voltage on a conductor. Some testers are multifunction devices that can perform most, if not all, of the common electrical testing duties, while others are single-function devices that test for one attribute. Various electrical testers can be used to check voltage levels in both AC and DC circuits and to test for amperage, continuity, short circuits, open circuits, polarity and more.
How to use an electrical circuit tester
A circuit tester plugs into a wall outlet to test how it is wired. The main reason is to verify that the outlet is delivering AC power to any device plugged into it. If you plan to work on home wiring, the most important thing of all is knowing how to test for the presence of live voltage. That is why it is always better to have prior knowledge of how to use an electrical tester to check for anomalies within your electrical outlets.
Many homeowners are also able to verify the status of their electrical system with the aid of a tester. However, as important as it is in every household with electrical systems and appliances, only a few people know how to use an electrical tester the right way.
Basically, you would use one anytime you need to determine whether a household circuit is powered, live and hot. Common reasons would be:
- Testing a light switch.
- Identifying wires in a wall.
- Testing for grounding of wires.
- Testing an outlet.
Types of electrical testers and when to use them
Here’s a brief overview of the many types of electrical testers:
- A plug-in circuit analyzer — such as an electrical outlet tester, receptacle tester or socket tester — is a small device containing a 3-prong power plug and 3 indicator lights. It’s used for quickly detecting some types of incorrectly wired electrical wall outlets. The tester is easily carried in a pocket, can be used with little training and can easily identify some common wiring problems. If the outlet to be tested is an old 2-prong nongrounded one, you can use a 3-to-2-prong adapter, available at any hardware store. Some versions can also test the special features of a GFCI (ground fault circuit interrupter) outlet.
- A noncontact voltage tester (sometimes called a voltage sniffer) detects electricity in a wire or outlet just by getting near it. It is the size and shape of a fat Sharpie pen, and the detection occurs at the probe tip — which, in many cases, is designed to be pushed into an outlet. Because electrical shocks are unpleasant at best and extremely harmful at worst, this tool is useful for even the lightest electrical work, such as troubleshooting a thermostat or installing a dimmer switch.
- A continuity tester is a device that is powered by batteries and has a probe at one end and a cord with either an alligator clip or another probe at the other end. If you touch the two together, you complete a circuit and light is illuminated on the body of the tester, indicating a complete circuit. A common use is to determine whether a single-pole (standard) switch is working properly.
- A multimeter (or multitester) is a test tool used to measure two or more electrical values — principally voltage (volts), current (amps) and resistance (ohms), along with continuity. While they are highly accurate, multimeters are overkill for most home electrical use by do-it-yourselfers. Also, multimeters can be difficult and confusing to use and thus may lead to injury. However, for lower voltages and for determining what that voltage is, you will need a multimeter.
- A neon voltage/circuit tester is used to test whether a circuit is energized. It uses a small neon bulb plus a resistor inside it, which make it simple for you to check whether something in your wiring system is energized or not. You connect the red test lead to the “hot” side (small slot) or black wire in an outlet and the black lead to the “neutral” side (large slot) or white wire in an outlet. Holding the body of the tester in your hand, if the light comes on, you’ll know the receptacle is unsafe to work on.
The cost of most testers ranges from $30 to $100.
Safety warnings when using an electrical circuit tester
Safety precautions when using an electrical tester
Electrical appliances that are poorly maintained or otherwise malfunctioning may turn out to become a safety hazard in your home. As when embarking on any project that involves electricity, safety is of the utmost importance. Follow these steps to stay safe:
- Understand the quantity you want to measure and avoid putting the test lead into a wrong socket to avoid the risk of electric shock.
- Be mindful of the voltage you are measuring. When measuring AC voltage (common household voltage), for instance, do not allow the probe tips to touch one another when they are still connected to their respective point on the electrical circuit. This is to avoid shorting the circuit, which can create a spark or ball of flame that can harm you.
- Do not use your test leads if the protective insulation on the leads or probes is cracked or worn. Your fingers may touch the probe conductor, and this might result in a very bad shock.
- Make sure the live (or hot) wires don’t touch anything other than the tester.
- Never touch live wires or let them touch anything else. Always hold the insulated portion of a wire while testing or use alligator clips if available.
- The leads of the tester must contact the live terminals of the device being tested, so the device, such as an outlet or light switch, might need to be removed from the electrical box to prevent the accidental touching of grounded parts with lead-touching live parts.
- To maximize safety, be sure to turn off the circuit immediately after testing.
- Wear work gloves for additional safety.
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