Non-contact voltage testers - contactless, fast and safe testing

If faults occur in electrical devices or systems, a non-contact voltage tester does not usually have to wait long to be used. It reliably and quickly indicates sources of faults such as

• Is there a cable break?
• Has a fuse blown?
• Is my electrical device defective?

It also provides an initial, quick indication of whether voltage is present at all. The compact and mobile tools fit in any pocket and are therefore quickly to hand. As the name suggests, the non-contact voltage tester works without contact. At a short distance from the test object, the devices check whether an electric field strength is present. If the test produces a positive result, voltage is present. This is always indicated visually and sometimes also acoustically.

For simple home use, voltage testers that measure up to 230 V AC are sufficient. If you occasionally have to deal with devices that are connected to high voltage current, you will need a device that can measure up to 400 V AC. Professionals generally use voltage testers with a measuring range of up to 1000 volts AC.

Below we provide answers to the most frequently asked questions that arise in connection with non-contact voltage testers:

• How do phase testers and two-pole voltage testers differ from non-contact voltage testers?
• For which type of measurement and for which measuring range is a non-contact voltage tester suitable?
• What do the measurement categories mean?
• How reliable is a non-contact voltage tester?
• What else should you look out for when buying a non-contact voltage tester?
• Comparison of non-contact voltage testers from Wiha

How do phase testers and two-pole voltage testers differ from non-contact voltage testers?

Non-contact voltage testers differ from many other devices that are commonly referred to as voltage testers, volt detectors or voltage testers. A brief categorisation is therefore useful at this point:

Phase tester

This screwdriver-style tool can be found in pretty much every tool cupboard. A glow lamp is usually built into the transparent housing of the phase tester. This lights up as soon as the device is inserted into the live phase of a socket and the current can flow. The current can flow because the user's body is used as a conductor. For this to work, the user must touch the phase tester at the end of the housing. This allows a very small and therefore harmless current to flow. However, numerous factors and application errors can occur during this process that distort the result:

• In bright surroundings, the glow of the glow lamp may be so weak that you do not notice it.
• User errors, such as using the phase tester with gloves, in rubber boots or standing on a wooden ladder, result in an existing voltage not being recognised because the user's body is not sufficiently conductive in these cases to allow the lamp to glow.
• The phase tester only indicates a voltage if it is applied via the phase. The phase tester does not light up on the neutral conductor and earth, even if voltage is present.

An incorrect result can have dangerous consequences such as an electric shock. Because incorrect results are often obtained when using a phase tester, it is also known as a "lying pen". Its technology is outdated and the phase tester cannot fulfil modern standards in terms of high reliability and safety.

Two-pole voltage tester

This tester is the only device authorised by the VDE for the all-pole determination of the absence of voltage. They are subject to DIN EN 61243-3 VDE 0682-401 and therefore fulfil the highest regulations for working on live parts. Two-pole voltage testers measure the voltage between two poles. They are therefore integrated into the circuit. Whenever work is carried out in open circuits, this device must be used to determine the absence of voltage in advance in accordance with the applicable standards. You cannot do without this tester, especially in the commercial sector. 

All information about the two-pole voltage tester can be found in the shop.

To the  two-pole voltage testers

What type of measurement and what measuring range is a non-contact voltage tester suitable for?

The contactless voltage tester detects the alternating electric field. It is therefore suitable for displaying an alternating voltage! If you want to use your voltage tester for a wide range of applications, you should make sure that the measuring range is as high as possible.

• Low voltage range between 12 and 90 volts AC, e.g. for fairy lights with transformer
• 230 V AC for alternating voltage in the home. Sockets, lamps and household appliances that are not connected to high voltage current
• 400 V AC in the heavy current range e.g. electric kitchen cooker
• Up to 690 V AC in automotive electrics (eMobility)
• 690 - 1000 V AC in the operating electrics

What do the measurement categories mean?

As a test device, the non-contact voltage tester must be assigned a measurement category. The measurement category indicates the area of application in the low-voltage network for which the electrical measuring device is suitable. In this context, it is also referred to as a safety level because it is primarily intended to protect the user. There are four categories: CAT I to CAT IV, each of which is associated with a specific voltage range.

If you want to use your contactless voltage tester for a wide range of applications in the low-voltage network, make sure that the measuring category is as high as possible in addition to the wide measuring range. For home use, you are already very well equipped with devices from CAT 4 to 600V. Professional electricians like to use the highest CAT IV.

You can find more information about the measurement category here:

To the measurement categories

How reliable are non-contact voltage testers?

Non-contact voltage testers should only be used for quick and simple test procedures. Whenever work on open electrical systems is required, these devices are not suitable for determining the absence of voltage. You must then use a two-pole voltage tester.

Examples of quick and easy test procedures are

• If you are looking for initial clues as to why your electrical appliance is not working. Is the cause a fault on the cable or is the electrical appliance itself defective? Check the power source, usually your socket, with your non-contact voltage tester to find out whether it is live at all.
• Your fairy lights no longer light up. Is one of the bulbs defective or is the entire light chain defective? Use your voltage tester to check whether the cable is generally not live or whether the flow of voltage is interrupted at a certain point
• The non-contact voltage tester easily recognises defective fuses.

What else should you look out for when buying a non-contact voltage testers?

In addition to the measuring range and the measuring category, you should pay attention to these additional functions:

• EX protection to ATEX standard: For voltage testers used in potentially explosive atmospheres (industrial areas).
• Torch function: This is helpful if you often work in poor lighting conditions. For example, in cellars.
• Acoustic signal: It is convenient if the optical LED signal is supported acoustically. This allows you to concentrate fully on the object being measured. Poor lighting conditions are also less disruptive.
• Signal for estimating the voltage level: A phase tester is primarily used to locate sources of error. It is not intended to determine an exact voltage level. Nevertheless, it can be useful if the device provides an approximate representation of the voltage level. For example, using LEDs in different colours for low, high and very high voltage.
• Test probes: Make sure you use internationally adapted measuring probes if the device is to be used on different sockets worldwide.
• Automatic switch-off function: To save the batteries, it makes sense for the tester to switch off automatically when not in use. However, this function should only be activated after a few minutes. Otherwise, the device will switch off even after short interruptions.

Comparison of non-contact voltage testers from Wiha

Wiha offers three different non-contact voltage testers. All have the highest measurement category and a very wide voltage measurement range. All three devices are therefore very versatile. The range also includes a tester that is ATEX-protected and therefore also approved for use in potentially explosive atmospheres (measurement category II). The following table clearly summarises all the features: