How Does A Non Contact Voltage Tester Work?

I worked hard when it comes to rewiring my house, and I have to say that one thing I find must-have is a non-contact voltage tester.

This device is really high, which I would definitely recommend for anyone, pros and amateurs alike.

But the question that may arise in your mind,

How does a non-contact voltage tester work?

Let’s take a look at the ways how a non-contact voltage tester works.

What is a non-contact voltage tester?

When working on a ruined asset or troubleshooting, voltage existence is essential. The most significant device you will need is a non-contact voltage tester.

This pocket-sized device is also known as a voltage detector that can immediately detect the voltage presence.

At the tip of this device, you will find a built-in sensor that can identify the voltage presence while touching a conductor.

You will use the ground source via capacitive coupling when it comes to holding the voltage tester. The voltage tester beeps while the tip glows red and shows you that the voltage is present.

How does a non-contact voltage tester work?

A non-contact voltage tester gives a safe and secure way of making sure that electrical supply cords do not have power without getting to touch them.

  • This device works by identifying the magnetic fields related to AC voltages. Usually, these fields arrived close to the live electrical supply cords. Therefore, there is no need for immediate contact with the conductors.

Note: Both the professional and regular users can use this tester around the house.

  • The tip of the device is plugged into the socket to check for live electrical supply cords.

Note: You should test all the cords (including the neutral), only if there is any faulty wiring. 

  • The magnetic or electrostatic fields make a current that flows via the tester, once you place the device close to the live cord. This allows the machine to detect the voltage presence by lighting up and creating a sound or both.

You will find this device active to test any live conductors, including those protected by insulation. Nevertheless, this device is useless when it comes to testing via a metal shielding.

Also Read: Best Ratcheting Wire Crimper in 2020 

The activities of a non-contact voltage tester:

Usually, you will find two types of sensors.

Magnetic induction testers:

The magnetically coupled tester comes with a sensor winding at the top. A voltage is initiated in the winding while this winding is positioned within the magnetic field. You will see the light or hear a sound via a circuit within the device.

Capacitive sensor element:

The voltage tester needs capacitor coupling to identify an electric field. Also, it is ideal for identifying live conductors if in a perfect circuit or not.

Why Do you need a non-contact ac voltage tester?

  • A non-contact ac voltage tester is a must-have tool to test any electrical work around the home
  • It does not need uncovered wires to detect voltage
  • It allows you to work without coming into touch with the voltage source.

Non-Contact Voltage Tester vs. Multimeter

Non-Contact Voltage Tester:

  • A voltage tester is designed to test for the voltage presence.
  • It can identify AC, DC, or RF voltage.
  • These testers are ideal for electrical engineering & household tools
  • They only detect the presence of a live conductor


  • A multimeter can measure different factors, including the current, resistance, and voltage to inductance, humidity, and frequency.
  • Multimeters can be used for multiple purposes.
  • They are ideal for power supplies, domestic wiring systems, motor controls, electrical equipment, laboratory testing, and industrial work.

Restriction on non-contact voltage testers:

  • The non-contact voltage tester is not ideal for DC voltages because the capacitors & transformers do not work with DC.
  • They do not measure the actual amount of voltage present.


There you have the answer how does a non-contact voltage tester work. This non-contact ensures you do not need to touch any wires when measuring the voltage presence. It is the safest way to measure the voltage indeed.

This is significant in making sure that power to the device is off before opening it for maintenance. Nevertheless, a non-contact voltage tester only measures the AC voltage.

Thanks for staying with us until the end of this article. Have you ever used a non-contact voltage tester? Do you have any questions about its functions and operations? If so, please share your thoughts and leave a comment below.

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