Understanding Principle of Metal Detector Circuit

If you’ve just received a new metal detector, you’re probably wondering what’s the principle of metal detector circuits.
A metal detector circuit is an electronic circuit that detects the presence of metal nearby, so today we’re going to show you how to understand it.

A metal detector circuit works by identifying metals and changes the output signal accordingly.
The principle is based on the fact that metals have magnetic properties.

Metal Detector Circuit:

The circuit basically uses two coils, one at 90 degrees to the antenna coil, and the other in series.
The antenna coil broadcasts an electromagnetic field, and the ferrous metal objects obstruct the field, causing a change in the electromagnetic field which acts on the secondary coil.
The secondary coil produces an output, which is proportionate to the object’s mass.

Disconnect the Battery

If the battery is connected to the circuit, disconnect it.
Remove All Components
Remove every component from the circuit.
Check for Continuity
Check continuity between each wire and positive and negative terminals.
Connect the Battery to the Circuit
Reconnect the battery to the circuit and check for any improvements.

Change Mode

You need to make sure that the mode you’re using in the metal detector circuit is the one you want.
When you set the mode to All Metal, it’s possible that small metal objects like coins and small change pieces will be detected.
So, try setting the mode to Iron only.

Change Tone

This looks for a change in impedance.
Change in Current
This uses current to indicate whether a metal object is present.
Change in Voltage
This uses voltages proportional to the amount of metal object present.