How to make a metal detector from a regular multimeter

Electronics / Useful and interesting 18 323 0

In essence, the principle of operation of a classic metal detector is simple: it consists of tracking changes in the search coil. You can also use regular Chinese for these purposes. multimeter.

This homemade metal detector is capable of detecting medium and large ferrous metal objects at a short distance.

Will need

PVC pipe 0.5 inches in diameter.
45 degree connector.
Wire 0.3 - 0.7 mm.
A piece of plywood.

Multimeters on AliExpress at a discount - http://alii.pub/62t1zq

Making a simple metal detector based on a multimeter

It is necessary to glue a search rod from a PVC pipe. Approximately 70 cm large elbow and 20 cm small, connected by a connector.

To make a coil, you need to drive 2 nails into the plywood at a distance of 20-30 cm.

We wrap 150 turns of wire around these nails.

Remove the winding and form a ring. We fix the coil with a piece of the same wire. We expose the wires for connection.

We connect it to a multimeter set to measure low resistance “200 Ohms”.

Let's check the work. Take any metal object and pass it near the coil.

The readings change, and therefore the metal detector works.

At the end of the forestay we will make a cut.

Secure the coil with tape. Secure the tester probes with an elastic band.

Closer to the beginning we will make a hole in the rod. Let's cut out a stand from plywood multimeter.

Install the stand into the hole. Apply hot glue and glue multimeter.

The metal detector is ready for use.

Operating principle and test in action

Ferrous metal, in any case, has a slight magnetization and has an insignificant magnetic field. If you place a coil next to it, an EMF appears in it, which in turn is reflected in the readings.

We search by moving the coil continuously. As soon as the readings begin to change, it will therefore find a metal object.

To “see” the result, you need to constantly move the coil. As soon as you stop moving, the readings stop changing.

Tip: if you have a more functional model multimeter, and it has an inductance measurement function, then switch the tester to it. As a result, the sensitivity of the device will increase and, in addition to ferrous metals, it will be possible to search for non-ferrous metals. Since the tester will monitor the inductance of the coil, and not its resistance.