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What Is a Tester Screwdriver?

By Anna B. Smith
Updated: May 16, 2024

A tester screwdriver is a handheld tool that is used to determine whether electricity is flowing through circuitry. This type of tool may also be used to determine which wires in a system are hot, neutral, or grounded. The tip designed to detect electricity must be placed directly against exposed wire or metal to receive an accurate reading. It is shaped like a traditional flat head screwdriver so that it may also be used to adjust screws used in the repair process. It may be purchased through online ordering or from a local home improvement store.

This type of tool is long and cylindrical in shape, and tapers to a flat head. The handle is typically enclosed in plastic to protect the user from receiving an electrical shock while holding the tester screwdriver. The flat head is metal, and is the portion that should be placed against any electrical circuitry being examined. This type of head matches most screws frequently used to secure electric panels and face plates to hidden circuitry, and is convenient for general use during repair work.

The plastic handle of the tester screwdriver is often clear and contains a small, colored light inside. This light is illuminated when the screwdriver head is touched against a wire that is conducting electricity. The internal light source is frequently made from an LED bulb and may receive power from a small battery.

A tester screwdriver may also be used to check the polarity of electrical wiring. All electrical outlets using alternating current feature at least two prongs into which equipment may be plugged. One prong is connected to a hot wire, conducting the largest amount of electricity, and the other is connected to a neutral prong. Those which feature three prongs provide a third opening for grounding purposes. The screwdriver will light up when it is touched against the hot wire.

The metal head of the tester screwdriver should be placed directly against an exposed wire or bare metal during the examination process. If the head is touched to wire that is enclosed in a plastic sheath, it will automatically create a negative signal even though the wires may be conducting electricity. If exposed wires are in contact with bare metal, such as a screw that is holding several wires in place, then the head of the screwdriver may be placed against this metal, which will naturally conduct the current, to receive an accurate reading.

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Discussion Comments
By cardsfan27 — On Oct 15, 2011

I have been thinking about buying a tester screwdriver. I do a lot of home improvement work, and I am always worried about getting shocked. I always flip off the breaker for whatever I am working on, but sometimes it is nice to have that extra reassurance.

I have an electrical tester pen that someone bought for me, but I think it would be easier to just have the screwdriver that would be an all in one fix.

How much does a good tester screwdriver normally cost? The article talks about them having a flat head. Can you get ones with Philips heads? It would be even better if you could get ones with interchangeable heads, but I'm not sure if that would compromise the purpose of the tool.

By TreeMan — On Oct 14, 2011

@kentuckycat - It sounds like the tester screwdriver you had was meant for automotive uses. They look just like the ones for residential use, but they have the additional wire at the end. The purpoes of the wire with the clamp is so that you can connect it to a battery terminal and check for a charge.

The reason it didn't work was probably because it got fried using it on an electrical outlet. The ones for cars are usually just meant to be testing circuits in the 12 volt range. Indoor outlets are 120 volts or more.

Unfortunately, the screwdrivers never have any sort of labeling on them, so if you didn't know from the beginning that is was for cars, there wasn't really a lot you could do to save it.

By kentuckycat — On Oct 13, 2011

I used to have one of these laying around my house, but I don't think it really worked right.

At first I didn't even know what it was, but I finally looked it up online and found it. Even when I put it into a circuit that I knew had a charge, it didn't light up. I changed the battery and still didn't have success. I never did figure out why, but I finally just tossed it out.

The one I had also had a cord with a clip at the end of it, too. I'm not sure what you would have used that for unless you were checking to see if a strip of metal had a charge or something.

By JimmyT — On Oct 12, 2011

I got a tester screwdriver for my mom one year for her birthday.

For some reason, she has an irrational fear of unscrewing any screws that are attached to something that might be connected to electricity. Even the screws in light switch covers she thinks might be able to give her a shock. I got her the screwdriver, so now at least she can be sure there is no charge going through the screw before she puts the screwdriver on it.

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