Metal detector 6

Published:2011/7/29 2:47:00 Author:Ecco | Keyword: Metal detector | From:SeekIC

The metal detector circuitis composed of thedection oscillator, reference oscillator, the oscillation signal processor, mixing amplifier and ammeter PA and other components, it is shownas Figure 8-72. The working principle.Detection oscillator is composed of the oscillating tube Vl, exploring coil Ll, Cl-C4 capacitors and resistors Rl-R3 and so on. Reference oscillator is composed of the oscillating tube V2, inductor L2, capacitor C6-C9 and resistors R2-R4 and so on. Oscillation signal processor consists of six non-door (Dl-D6) integrated circuit IC and the external RC components. Hybrid amplifier is composed of a diode VD, resistors Rl2, R13, capacitor C13 and field-effect transistors VF. Turning on the power switch S, both the detection oscillator and reference oscillator start oscillation, the collector of Vl and V2 outputs two same frequency sine wave oscillation signals, they are amplified and transform processed by the oscillation signal processor to become two square wave signals with same frequency and amplitude and opposite phase, then mixed by RlO, RlI and VDl and sent to the the gate of VF. Before Ll detecting metal objects, the two square wave signals are with the same frequency, phase reverse, VF's gate voltage drops below 2.5 V, VF does not work, PA ammeter indicates 0 (ammeter pointer refers to the scale plate in the middle.)



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