Phase or Line or Electric Mains Tester – How it Works?

What is Phase or Mains Tester?

Phase, electric mains or line tester is a basic tool which is used to test and identify Phase / Live/ Hot or Positive (+) wire / conductor in electrical installation also known as voltage or current detector.

Phase or Line Tester is also called Neon Screw Driver or Test Pin.

Good to Know: Phase, Line, Hot, Live and Positive are the same terms used for single item.

Construction of Phase or Line Tester

Following are the main parts of a typical Phase or Line Tester.

1). Metallic Rod and Mouth

It is a cylindrical metal rod. The flat end (mouth) is used as a screw driver or touch electrical conductors/wires to find phase or live wires and the other end is connected to the resistance, neon bulb, element and metallic cap screw respectively. The flat end of cylindrical metal rod is also covered with transparent insulated plastic for insulation proposes except mouth.

2). Body and Insulation

All these components (Resistance, Neon bulb, Element or metallic spring, and Metallic Cap screw) are covered in a transparent insulated body which made of plastic. The flat end of cylindrical metal rod is also covered with transparent insulated plastic for insulation proposes except mouth.

3). Resistor

Resistor is an element which opposes the flow of current through it. In a phase or line tester, resistor is connected between cylindrical metal rod and Neon bulb to prevent high current and reduces it to a safe value to protect the neon bulb. Without a resistor, high current may damage the neon bulb. Moreover it  may be dangerous to use this tool without resistor.

4). Neon Bulb

Neon bulb is connected between resistance and element (metallic spring). It is used as phase indicator bulb. When a small current flows through it, the neon bulb starts to glow. Due to neon bulb, a phase or line tester is also called a Neon Screw driver.

5). Element (Metallic Spring)

Element (metallic spring) is used to make connection between neon bulb and metallic cap screw.

6). Metallic Cap Screw and Clip

Metallic cap screw is used for to tight all the components inside the phase tester slot. In addition, metallic cap screw is connected with spring (element) and spring (element) is connected with neon bulb then. Moreover clip is used for holding the phase tester in pocket.

Working of a Phase or Line Tester

When we touch mouth (flat end of the metallic rod) of phase or line tester with naked Live / hot wire whereas one of our finger touch the metallic cap screw or clip of Phase/Line Tester, then circuit is completed and current start to flow in metallic rod, Hence the neon bulb inside mains tester glows.

Metallic rod is connected to the resistor which reduces high current to a safe value. The reduced current passes through Neon bulb which is connected to (metallic spring). Metallic spring is connected with metallic cap screw which is in contact of our fingers. A very small current passes through our body to earth and complete the circuit. When circuit is completed, current starts to flow and the filament of neon bulb starts glowing. This indicates that the touched wire with Phase / Line Tester mouth is Phase / Line / Hot.

If we perform the same action as mentioned above, and Neon bulb does not glow, it means that is a Neutral (-) Wire/Conductor or there is no mains supply in the phase wire or phase wire is broken in the middle.

Safety Precautions

• Never try to work on electricity without proper guidance and care.

• Work on electricity only in presence of those persons who has good knowledge and practical work to deal with electricity.

• Don’t touches the open wire/Conductor even tester shows absence of phase or hot supply.

• Use Line Tester only with 100V-500V.

• Don’t use Phase or Line Tester with High voltages.

• Don’t hit on the handle of Line tester otherwise, Neon bulb or element may damage.

• Doing your own electrical work is dangerous as well as illegal in some areas.Contact the licensed electrician or the power supply company before practicing any change in electrical wiring connection.

• Electricity is our enemy, if you give it a chance to kill you, Remember, they will never miss it. Please read all caution and instruction while doing this tutorial in practical.

• The author will not be liable for any losses, injuries, or damages from the display or use of this information or if you try any circuit in wrong format. So please! Be careful because it’s all about electricity and electricity is too dangerous.

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Petro-tite Brochure en Espanol

Commonly Ordered Parts

More line testing parts…