What is an electrical line or phase tester and how does it work? What are the parts of an electrical line tester?

A line tester is electrical equipment that can be used to detect the presence of electricity. A phase line tester can be considered a protective device that can protect our body from accidental shocks. The electrical line tester would only work if we touch its metallic part while checking the live wire or in a socket. So in order to do an electrical process, there should be a complete electrical path and that’s why we should touch the metallic part of the line tester so that we can complete the circuit. So our body is another part of this testing so we would act as earth. So there would be a return electrical path because of the person who is using this equipment.

What are the functions of an electrical line tester?

  • This device can be used to detect the live wires in the domestic circuitry
  • It can also be used to loosen or tighten small screws
  • We can also check the phase in a socket

What are the major components of an electrical line tester?

  • Resistor
  • Neon bulb
  • Metallic spring
  • Metallic cap screw and clip
  • Body and insulation

How does an electrical line tester work and is there any chance to get an electrical shock while using this device?

If we open an electric line tester we can see its major parts like a metallic cap, spring, neon lamp, resistor, and insulator body part. The neon lamp will have a connection to the spring. So when we connect the electric line tester in a socket to detect the presence of electric power, the supply will flow to the resistor after that it will reach the neon lamp and spring then it would reach the metallic cap after that the electric power would travel through our body to reach earth.

The major question that would arise is that why are we not getting shocked while we are using an earth line tester. So while connecting the line tester to a live wire and this could be 240Volt, the resistor that is used in this device is almost 1 mega-ohm. So when the electric power reaches the resistor the current will be reduced.

1 mega-ohms = 1000000

I = V÷R = 240 ÷ 1000000 = 0.00024 A

0.00024 × 1000 = 0.24ma

So this much of current will be there after it flows through the resistor, then there is a neon lamp, spring and metallic cap and all of them have resistance too and after that, the power would reach to our body. So the current that we would receive will be very low, in order to get shocked minimum 10 ma current is needed so that’s why we are not getting shocked. Because of using the high resistance, the voltage is decreased too.

What are the disadvantages of an electrical line tester?

  • It can only measure voltages between 100V and 300V
  • It needs a humid free environment
  • Its surrounding light must be, low
  • The damaged bulb or resistor can give false output and this could cause lethal shocks


post-graduate in Electronics & communication.

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