Home generalPhase tester / voltage tester - mode of operation and instructions

Phase tester / voltage tester - mode of operation and instructions

  • How does the current flow in the house "> The single-pole voltage tester
    • application
  • Bipolar phase tester
  • Tools for electrical work
  • Tips for quick readers

The phase tester or voltage tester is a basic tool when it comes to the installation of wall switches, sockets and hanging lamps. There is a distinction between single-pole and two-pole voltage testers. Proper handling of a voltage tester protects against serious, possibly even fatal injuries. This guide will teach you what to look for when working with a phase tester or voltage tester.

Correct working with the voltage tester

When handling electric current, caution is the top priority. An electric shock with 240 V home current is rarely fatal in the rarest cases. In any case, it is very painful and can, for example, if you are on a ladder, lead to fatal falls. Of course, you can switch off the main fuse when working on the house electrics for safety's sake. However, there are practical reasons, for example, the difficulty of working in the dark. With the right tools and the knowledge to use them correctly, it is usually not necessary to kill the entire apartment.

Legal situation when working with household electricity

The commercial work on 230 V lines is reserved in Germany exclusively trained technical personnel. Purely by law, do-it-yourselfers, janitorial services or non-specialist craftsmen, eg painters and upholsterers, may not carry out any work on live cables in the house without suitable qualifications! If damage to health or building damage is caused when handling 230 Volt lines, this can also lead to difficulties in accident and household s insurance. The basic advice for all electrical work in the house is therefore: consulting a specialist guarantees a correct execution, excludes accidents and consequential damages and avoids legal consequences. Home-based electrical work therefore always happens at your own risk! All liability claims resulting from the following information and instructions are therefore excluded.

How does the electricity flow in the house ">

The electricity arrives from the substation via the free or ground line in the house. It is distributed via the main power and fuse box to the individual sampling points. These sampling points are the sockets or the leads for lamps and switches. They consist of three cables. A cable is the "hot" line, ie the line that carries the current. Usually it is marked with a blue, brown or red cable. The second line is earth or neutral. This is the return of the stream. It leads to the ground, from where the stream flows back into the power plant. The earth conductor is provided with black insulation as standard. The third cable is the protective conductor. It is yellow-white or yellow-green striped and is used to trigger the safety contact fuse in the event of a short circuit.

Switched off does not have to mean "off"

A light switch disconnects or closes the circuit, depending on how it is switched. However, a switched-off light does not mean that there is no current flowing through the wiring of the lamp. It does not matter to the circuit at which point it is interrupted. The normal state should be that a circuit at a switch is always interrupted at the phase, ie the live conductor. However, if closed due to lack of knowledge of the ground wire to the circuit breaker, but the switch still works properly. The light can also be switched on and off as normal with this circuit. If now a previously switched off ceiling lamp to be suspended, it is only a matter of time until the craftsman gets a proper electric shock. To prevent this, the voltage testers are used.

The single-pole voltage tester

To say it in advance: The single-pole voltage tester is no longer used by professional electricians as standard. It is really just a rudimentary tool that can help a home improvement with small works around the house installation. However, the single-pole voltage tester is no longer recommended.

The single-pole voltage tester looks like a small flat-head screwdriver. Striking are the following features:

  • Crystal clear handle
  • some models have a red end cap with metal contact
  • Isolated neck

Inside the crystal-clear handle, the test screwdriver has a glow lamp. This lights up when it is held against a live conductor. It is important to know that a test screwdriver is only approved for a certain voltage range. Common are areas of 6-24V and 100-240V. In order not to confuse them, the test screwdrivers for the automotive sector, ie for voltages of 6-24V are mostly yellow or green. In addition, they have usually grown an additional crocodile clip. They are very well suited for detecting creepage currents on the vehicle.

The test screwdrivers for higher voltages, however, are clearly white. A clear differentiator is not the color of the test screwdriver. Some manufacturers of automotive voltage testers make no visual difference to the voltage testers for home use.

The quality of voltage testers varies widely. Low-priced models are already available from 3.50 euros. High quality devices can cost up to 20 euros. The quality of the devices affects less the test function, but rather the isolation and the material quality in the screwdriver tip. This means that the tips of over-priced devices break off very easily when opening and closing luster terminals. Brand test screwdrivers, however, are already available from 4.50 euros onwards


The test screwdriver is used to identify a live cable. These can be found in a household in the form of connections to sockets or on bare wires on wall and ceiling, to which lamps are hung.

The test screwdriver is inserted one after the other into both openings of the sockets at a socket. When touching the metal contact on the back of the test screwdriver with your thumb, the built-in test lamp detects whether or not there is any voltage present. Also, the protective contact is checked, recognizable by the bare brass conductor, which is installed transversely to the axis of the openings for the plug in the socket. You can hold the voltage tester to the central screw, as it is connected to the protective contact.

NEVER work with two voltage detectors at the same time! If you insert two test screwdrivers into the socket at the same time, a short circuit is made and the body is passed through with the full 240 volts.

With bare wires on ceiling lamps, it is different. As there is a need to climb a ladder to hang the ceiling light, special precautions are required.

Before you should inform yourself about the power cord colors. The appropriate contribution can be found here: power cable colors

First, the fuse for the room is turned off. It is ideal if an old lamp is still hanging on the ceiling. If not, a consumer connected in the room (eg radio or floor lamp) can serve as an indicator for the circuit. Simply switch off all fuses until the room is disconnected from the mains.

Now you climb onto the ladder and carefully check all the cables. To do this, the test screwdriver is held to the bare tips of the wires. If there is still power, the ceiling light is connected to another circuit. The fuses must be switched off until no current flow is indicated. If no power is displayed, the wires are bent so far that they can not touch each other. Then the fuses can be switched on again. Now the wall switch is checked. To do this, it is switched on and the lines that are bent far apart are checked with the current tester. The following five cases can now occur:

  • Unfortunately, the phase carries electricity
  • Only the neutral carries current
  • Only the protective conductor carries electricity
  • No conductor carries electricity
  • Several conductors carry electricity

If only the phase, recognizable by the blue, red or brown wire, carries current, then the light switch is switched off. Now if the phase is out of power, the switch is OK and the ceiling lead is wired correctly. Now the ceiling lamp can be safely mounted.

If only the neutral carries current, the switch is wired incorrectly. Here only helps to open the wall switch and to check the wiring. The same applies if the protective conductor is identified as a live cable.

If no conductor carries current both when connecting and disconnecting the wall switch, then there is a cable break. The cable should then be replaced as soon as possible so that no consequential damage can occur.

If the test lamp indicates voltage on several conductors, then there is a case of induction current. This is why test screwdrivers are very reluctant to be used by professional electricians: the informative value of the glow lamp is simply too weak. Here it must now be checked with a two-pole voltage tester, which of the lines is the current leading.

Bipolar phase tester

A two-pole phase tester is the much better tool than the test screwdriver for quickly identifying the live wire and for many other purposes. Priced, the Bipolar phase controllers are very affordable today. Useful devices for the DIY sector are already available from 15 Euro.

A two-pole phase tester consists of two very well insulated test probes connected by a cable. One of the probes is equipped with a scaling or display, with which numerous information can be retrieved.

The more you invest in a two-pole phase tester, the greater the range of functions that can be accessed with this device. The basic functions are:

  • phase testing
  • Checking the voltage level
  • Continuity test
  • DC / AC testing
  • polarity test

With higher quality and better equipped two-pole phase testers, numerous other functions, such as the RCCB tripping, can be added.

The work is much faster, safer and clearer with a two-pole phase tester. In contrast to the single-pole voltage tester, two cable ends or both openings of a socket can be checked simultaneously with the two-pole version. The two-pole phase tester not only indicates which is the current-carrying line. Also, the amount of voltage and the polarity are equal to indicated. However, it can not be screwed with a two-pole voltage tester. An appropriate tool set is therefore additionally necessary.

Tools for electrical work

The most important thing for tools that are to be used for electrical work is complete isolation. These tools are usually recognized by the red casing. Common tools for electrical work are:

  • Electric screwdriver
  • Electric Pliers set
  • Abisolierzange

Electric screwdrivers cost in usable quality in the set from about 25 euros. Electric pliers, so-called cable shears, are also recognizable as the screwdrivers on the thick insulation on the handles. If there is no insulation, the pliers can not be used for electrical work! A high-quality cable cutter costs from about 25 euros.
A very sensible investment is the wire stripper. This removes with a handle a well-defined amount of insulation from the tip of a cable. The laborious cutting with a carpet knife eliminates with these practical tools. A wire stripper costs from about 18 euros.

Know the limits

Although input is clearly pointed to the legal situation when working on sockets and ceiling lamps. However, it is not realistic that the reasonably savvy home improvement can be dissuaded from hanging a ceiling lamp. But even the most motivated DIY person should know his limits.

electric stove

To connect an electric stove is definitely a matter of a trained electrician. This service costs at most specialized companies with the appropriate qualifications a maximum of 100 euros. But the user has the certainty that the cooking experience is not clouded by burning electronics, live housing or ever-triggering fuses.

Heavy Duty Power Connectors

An electric shock with 220 volts is very unpleasant, in the rarest cases but immediately deadly. At 400 volts, however, it looks different: The likelihood of fatal cardiac arrest is absolutely given in power accidents in the 400 volt range. So if a high-voltage connection in the house is desired (for example, for welding equipment in the garage) their installation is reserved for specialist shops.

Tips for quick readers

  • Work on 230 Volt lines is legally reserved for specialized companies only
  • A single-pole current tester only gives inaccurate results
  • Never use two single-pole current detectors at the same time
  • Two-pole current testers are more informative
  • Electric cookers, air conditioners and power sockets should only be installed by qualified personnel
  • Pay attention to high-quality tools that are permissible for electrical work
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