RESONANT CIRCUIT APPARATUS FOR DETECTING ELECTROMAGNETIC CONDUCTIVE BODIES

• US 3,719,882 A
• Filed: 11/12/1970
• Issued: 03/06/1973
• Est. Priority Date: 11/12/1970
• Status: Expired due to Term

• Current Assignee: Anthony Godfrey Pincus
• Original Assignee: Anthony Godfrey Pincus
• Inventors: Pincus, Anthony Godfrey
• Primary Examiner(s): Strecker, Gerard R.
• Application Number:
  US05/088,944
• Time in Patent Office: 845 Days
• Field of Search: 324/3-6,7,41
• US Class Current: 324/330
• CPC Class Codes: G01V 3/108 the emitter and the receiver coils or loops being uncoupled by positioning them perpendicularly to each other

Abstract

An apparatus for detecting the presence of electromagnetic conductive bodies comprises two coils which are coupled through a high gain, high impedance amplifier and tuning capacitor with the other end of each coil going to ground so as to form a tank circuit. The coils are mounted so as to be essentially de-coupled with their axes mutually perpendicular. One of the coils is self resonant with a natural resonant frequency in the audio range. The circuit is tuned to the natural resonant frequency by the tuning capacitor and inductive coupling between the coils improves when the circuit is near an electromagnetic conductive body. A capacitor circuit is employed to detect and measure shift in one or more of the tank circuit parameters including output signal level, frequency and phase.

Claims

1. Apparatus for detecting electromagnetic conductive bodies, including:

a. a tunable, resonant circuit comprising a first and a second coil, and amplifier means and tunable capacitor means connected in series between said coils;

said first coil being selfresonant with a resonant frequency in the audio range;

a first end of each of said first and second coils being electrically connected to each other through a ground for said tunable circuit so that each said first end of said coils is at ground potential with respect to said tunable circuit;

said first and second coils being rigidly, mechanically mounted with respect to each other so that their inductive axes are substantially mutually perpendicular and so that the inductive coupling between them is minimal; and

output means from said tunable circuit across said second coil and with respect to the ground potential of said tunable circuit;

b. a comparator circuit means having an input thereto from the output of said tunable circuit, including a ground for said comparator means electrically connected to said ground of said tunable circuit;

said comparator circuit means including means to indicate a shift of a signal parameter of the signal received at the input of said comparator, said shift of a signal parameter being in terms of the comparison of said signal parameter to the state of such signal parameter received from said tunable circuit when in its tuned, quiescent state;

c. said resonant circuit being operative at the resonant frequency of the self-resonant coil so that, in the presence of electromagnetic conductive bodies, said resonant circuit exhibits Q-multiplier effect substantially at the resonant frequency of said first coil.

2. The apparatus of claim 1 where said first coil and said tunable capacitor are each mechanically removable and replaceable in said tuned circuit.

3. The apparatus of claim 2 where said comparator means includes output indicator means to indicate the presence of a shift of a parameter of the input signal thereto with respect to the quiescent state of the signal parameter.

4. The apparatus of claim 2 including quantitative output means in said comparator means to give quantitative indications of the signal parameters of the input signal thereto.

5. The apparatus of claim 2 including means for mounting said tunable circuit remote from said comparator means, and electrical interconnection means there-between.