Electronic anatomical probe

Abstract

A wire sensing coil is sealed in the tip of an elongate, rigid, plastic probe, and is connected by a coaxial cable releasably to a housing containing a fixed frequency, crystal-controlled oscillator, the output of which is applied through a high impedance resistor and the cable to the coil. The number of turns in the coil and the cable length are carefully selected so that the coil remains tuned to the frequency of the oscillator, except when the tip of the probe approaches a metal object, at which time the voltage drop across the coil decreases. The housing also contains an audible alarm, and a sensing circuit which detects the voltage drop across the coil, and which energizes the alarm when the voltage across the coil drops below a preset or predetermined level. The housing also contains a rechargable battery for supplying power to the oscillator and alarm circuits, and a recharging circuit for recharging the battery. A manually operable switch on the housing connects the battery to the oscillator when the switch is in its ON position, and connects the recharging circuit to the battery when in its OFF position.