Search for hidden wiring: how to find, types, devices, methods, detector, indicator, multimeter, metal detector, smartphone

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Anyone who has begun to redevelop housing will face a big problem associated with electrical wiring hidden under a layer of plaster. You can find hidden wiring with different tools. Sometimes completely unsuitable household appliances can help. Of course, many of them will show the location of the electrical wires inaccurately, but still this method is simple and does not require large expenses.

The content of the article:

  • Basic types of search
    • Using a hidden wiring detector
    • Search by radio
    • Hearing Aid Search
    • Using an indicator screwdriver
    • Using a multimeter
    • We use a metal detector
  • Non-standard verification methods
    • Compass
    • Smartphones

Basic types of search

Tools and devices with which you can search:

  • special tools: detectors and line detectors (cable testers);
  • multimeter;
  • radio;
  • hearing aid;
  • indicator screwdriver;
  • metal detector.
Search for hidden wiring

Using a hidden wiring detector

The principle of operation of the hidden wiring detector is based on the technology of searching for metals. The device works almost exactly the same as a metal detector.

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Electrical wires are metal conductors made of aluminum or copper. When an electric current passes through them, a magnetic field is formed around them. That is what the detector detects. It reads the field signal and transmits it to the display. And the more voltage in the wiring, the brighter the signal.

Varieties of this device:

  1. Those that detect wiring that is only energized.
  2. Detect wiring that is without voltage.
  3. Combined models.

In the devices of the last two groups, a magnetic field generator is installed. It creates the perturbation of the metal. Therefore, these models more accurately determine the location of wires and cables, hence their higher practicality and functionality.

There are a huge number of hidden wiring detectors on the market, which differ from each other in functionality. Some are easy to work with, others will first need to be sorted out by reading the instructions from the manufacturer, and then trying in practice.

In the instructions, you need to pay attention to the depth of the search. This indicator varies in the range of 50-100 mm. At the same time, some models can detect steel reinforcement, wood, plastic. Each material has its own function.

The work of the search detector is that this device is used to examine the wall, moving it along the location of the alleged hidden wiring. The maximum sound signal or indicator on the screen indicates the presence of wires.

Route finders differ from detectors in their more accurate search. This professional device consists of two blocks:

  1. Detector, aka receiver.
  2. A generator that emits a high frequency electromagnetic signal. Masters often call him a transmitter.

The receiver, as a separate element, works like a conventional hidden wire detector, capable of detecting live cables. By connecting a transmitter to it, a device with wide functionality is obtained. With it, you can detect a broken wire, for which it is valued. The detection depth is up to 2 m, which makes it possible to use the locator to search for wiring in an underground type laying.

Choosing one or another device, you need to learn how to use it correctly. To do this, it is recommended to try it on open wiring or pipes. This will help to understand - to what objects and how he reacts.

In the store, the device must be checked on open wires. For example, put the phone on charge and bring it to its wire. The detector or locator should respond differently depending on the search distance. You can strengthen testing if you close the wire from the phone with a plastic object or paper folded in several layers. Cardboard will work too.

The simplest hidden wiring detector is the Woodpecker E121 brand. Multifunctional device, light and compact. Tracks not only live wires, but also their breakage. It can also find a neutral or phase wire. This device belongs to the category of electrostatic devices.

There are electromagnetic models on the market that are more effective than electrostatic ones. They are also looking for hidden live wiring. In this case, the load should not be less than 1 kW. It can be an ordinary electric kettle.

Using a hidden wiring detector

How to choose

It all depends on what goals are set for the device. If you just need to find hidden wiring, then you should not buy expensive models. If, in addition to electrical wires and cables, you need to look for a metal frame or pipes, then it is better to purchase more sensitive devices.

The second selection criterion is the search depth. Many models can detect wiring at a depth of no more than 20 mm. In many buildings, the thickness of the plaster layer is 40 mm. That is, such devices will not help here.

The third criterion is signaling. It is usually sound and light. The best option is a device with a display that shows complete information.

Search by radio

This household appliance can show where the wires are located in the wall when tuned to a frequency of 100 kHz. In this case, the wiring must be energized. If the cable going to the outlet is checked, then the load must be connected to the latter - any household appliance, even a low-power one.

The radio receiver must be driven along the wall in the place of the alleged hidden wiring. Noise from the speaker, crackling and other signals that are atypical for work indicate that wires hidden in the thickness of the wall were found. And the louder the noise, the more accurate the place of laying. To enhance the search effect, it is recommended to wear headphones.

It is necessary to drive the radio receiver along the wall directly on the surface. The denser the better.

Hearing Aid Search

Some hearing aids have a feature called "telephone". Its mission is to enable hearing-impaired people to talk on the phone without sound interference.

The hearing aid perceives electromagnetic vibrations, on the basis of which all phones work.

To search for hidden wiring, you need to do everything in the same way as with the radio:

  • connect wiring to voltage;
  • move the device along the wall in search of hidden wires;
  • a crackle in the earpiece confirms the detection of the latter.

Using an indicator screwdriver

You can find hidden wiring in the wall with an indicator screwdriver, but not always. With its help, you can find the wires laid under the plaster, which are no deeper than 20 mm. This already creates search problems if the cable, for example, is laid in a concrete wall, additionally leveled with drywall or a thick layer of putty.

Also, the entire surface of the wall can flicker. This sometimes happens for unknown reasons. For example, metal inclusions in concrete or other wall material. Even finishing can fonit: metallized wallpaper, ceramic tiles.

The quality of the search is affected by the sensitivity of the screwdriver. Some models will not respond to anything at all. Therefore, it is recommended to first test the indicator on the current wiring.

The process of searching for hidden wiring is carried out as follows:

  1. Use your fingers to pinch the tip (metal tip) of the screwdriver.
  2. The opposite indicator side must be attached to the wall and driven along the surface until the light, which is located in the transparent handle of the tool, lights up. This is the location of the live cable.

The method is inaccurate, but sometimes it helps if there are no other options.

Another thing is if you use contactless screwdrivers for searching, in the design of which there is a battery. It is she who creates electromagnetic waves acting on metal wiring. In the latter, an electromagnetic field is formed, which fixes the tool. Either the LED lights up or the display lights up. In both cases, an audible signal sounds.

The radius of action of the screwdriver is small. But with its help, you can find wires under plaster or under a not too thick layer of cement. The only negative is that the battery quickly weakens, so it has to be changed often.

Manufacturers today offer contactless electronic-type indicator screwdrivers. They find cables and wires hidden in the wall and energized from 12 to 250 volts. At the same time, the tool not only finds them, but also shows under what voltage they are currently working.

Using an indicator screwdriver

Using a multimeter

The multimeter itself will not detect hidden wiring. He needs an addition in the form of a VT field effect transistor. You can use one of two brands: KP103 or KP303. We need a field one, because it is controlled by an electromagnetic field. There are current controlled bipolar transistors. They will not help in finding hidden wiring.

Three wires stick out of the transistor, each of which has its own name: drain, source and gate. The multimeter must be connected with its two alligator contacts to the first two wires (drain and source), as shown in the photo below. They are located on the left, if you look at the transistor from above directly. It does not matter which crocodile to which wire will be connected. That is, polarity does not play a role here.

The third posting, also known as the shutter, remains free. For ease of use, you need to solder a short copper wire to it - within 5 cm. This is a kind of antenna that will capture the radiation of the electromagnetic field of hidden wiring.

On the multimeter you need to set the operating mode. This resistance is within 200 kOhm. Ready for operation, the device must be driven around the area where the electrical wiring should be laid. When the shutter enters the electromagnetic field, the multimeter will immediately respond, showing the maximum value set. The farther from the wiring, the less resistance on the screen.


You can use a field effect transistor without a multimeter. But it will require an ohmmeter that connects to the drain, and a power source, for example, a battery, that connects to the source. A speaker can be included in the circuit for an accurate search, notifying that hidden wiring has been found. Its connection is in series with the transistor.

To increase the search effect, you can change the circuit by inserting not one field-effect transistor into it, but three in series (grade C945). In this case, you can abandon the ohmmeter, leaving only the battery. For the circuit to work, you need to insert one current-limiting type resistor into it in parallel with the transistors. Its resistance is 1 kOhm.

The antenna connected to the gate should not be a straight wire, but twisted into a spiral. This increases the efficiency of capturing the electromagnetic field. If you connect an LED light bulb to the sources connected to each other, which is inserted into the resistor circuit, then the detection of hidden wiring can be seen by its glow. The closer to the source of the electromagnetic field, the brighter the light bulb glows.

When creating a circuit, there is no need to connect all the details to each other through a plateau. This is clearly seen in the photo below.


We use a metal detector

This device, like the search detector concealed wiring, the most accurate. It's all about how it works:

  1. In the design of the metal detector there is a coil that, under the influence of an electric current, generates or, in another way, generates electromagnetic waves. They directly act on the wiring hidden in the wall.
  2. Under their action, eddy currents appear in the wires.
  3. The latter generate electromagnetic waves, which are picked up by the metal detector.

There are models that can only find black metal. But even they detect hidden wiring, not to mention those devices that are designed to search for non-ferrous metals.

It must be taken into account that the accuracy of a modern metal detector depends on the power of the coil. Therefore, different models have different errors that do not exceed 5 cm.

With this device, wires can be found even if they are not energized. In fact, a metal detector is the same detector, only with an inductive action.

Non-standard verification methods

There is a lot of information in the public domain about how you can search for hidden wiring with improvised means that many people have at home. One of them is to use a regular compass.


The needle of a magnetic compass will deviate under the influence of an electromagnetic field. But a cable laid in a concrete wall and under tension cannot create a sufficient strength of this field. That is, its electromagnetic waves are not strong enough to change the position of the arrow.

The same goes for a magnet suspended on a thread. It will not sway when approaching hidden wires.


Another supposedly non-standard option. Use smartphones that have a special application downloaded. Plus - the phone must have a magnetic sensor. This option does not work even if the wiring is under load.

Still, you should not use household appliances to look for metal in the walls. It is better to buy a detector that has a low price. Simple models do not require special knowledge. In the instructions, everything is clearly spelled out how and which button to press so that the tool works correctly.

How to find hidden wiring in the wall using a smartphone: video.

If someone knows other ways to search for hidden wiring - share in the comments. Save the material in bookmarks so as not to lose effective search methods.

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