Long distance intelligent metal detector

The present invention relates to metal detectors comprise a large distance intelligent smart AVR microcontroller determines and interactive system (1) or the like, the square wave generated by the microcontroller via the mode conversion frequency selective amplifier integrated circuit (5), (2) establishing a set of transmit coil electromagnetic field; receiver coil (3) acquisition signal receiving circuit (4), by a switched mode modulator circuit RMS integrated low-pass filter (6) organized into a controllable rms level, by IU converting circuit (7) to obtain a readily identifying a voltage signal; system (1) determines the voltage signal; and holding the reference level drift compensation integrated circuit (8) provided in IU comparison level converting circuit (7), and to compensate for signal drift; negative supply stable modular machine power pressure circuit (10) operating voltage. Metal detector according to the present invention is intelligent parameter adjustment, and improve the stability and anti-jamming metal detector; also low cost, simple circuit, the advantage of a large detection range.