US Patent 7816920 Metal detector

An exemplary metal detector includes a detecting circuit, a SCM, a converting circuit, and a cymometer. The SCM cooperates with the detecting circuit to generate a current signal with a specific frequency, the converting circuit transforms the current signal received from the SCM to a voltage signal, and the cymometer displays a value of a frequency of the current signal according to the voltage signal. When the detecting circuit detects a metal nearby, the value of the frequency of the current signal displayed on the cymometer changes.