Multimeter attachment - metal detector

To give ordinary Chinese multimeter new function, you need to assemble a simple attachment that will turn the measuring device into a metal detector. This is a very useful modification, with the help of which you can not only search for metals in the ground, but also determine the passage of, say, reinforcement in a wall - which is very necessary during repairs. The device also reacts to hidden wiring and, with proper searching, easily determines its presence in a particular place.

What will you need?

Copper enameled wire 0.3 mm.
Capacitor 20 pF.

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Making an attachment for a multimeter - metal detector

A roll of tape was used as the frame of the reel. We wind 30 turns of wire around it.

We remove the coil from the tape and fix the winding with electrical tape in several places.

Into the nests multimeter insert the plugs from the old probes.

It is necessary to drill holes in the circuit board for these terminals of the installed plugs.

We clean the coil contacts from varnish.

Solder the pins to the plugs on the board.

At the same time, we solder the capacitor.

The console is ready for use.Depending on the model of the device, set the operation switch to generator mode. In this mode, the device display will display reactance readings, and a test audio frequency will be sent to the coil.

If your multimeter does not have this mode, it doesn’t matter, set the switch to the inductance test position. The “mV” measurement mode is also suitable, but in this position the sensitivity will be minimal and the metal detector cannot detect non-ferrous metals.

Initially the readings will be zero or have a small value. But as soon as you hold a metal object over the coil, the values on the display will change several times.

This metal detector can only operate in pulse mode and for a high-quality search, the coil must constantly change its position relative to the search object. In other words, when searching, you should always move the coil.

The device reacts not only to ferrous, but also to non-ferrous metals.