Metal detector

• US 7,791,337 B2
• Filed: 07/19/2007
• Issued: 09/07/2010
• Est. Priority Date: 07/19/2007
• Status: Active Grant

• Current Assignee: Carnes Company, Inc.
• Original Assignee: Carnes Company, Inc.
• Inventors: Simon, Joseph S.
• Primary Examiner(s): LeDynh; Bot L
• Application Number:
  US11/779,959
• Publication Number:
  US 20090021252A1
• Time in Patent Office: 1,146 Days
• Field of Search: 32420715-20719, 324/219, 324/225, 324/228, 324/234, 324/236, 324/239, 324256-259, 324326-327, 324/329
• US Class Current: 324/228
• CPC Class Codes: G01V 3/104 using several coupled or uncoupled coils G01V3/101 takes precedence

Abstract

A vibration canceling circuit for a metal detector. The metal detector includes a transmit coil, first and second receive coils, a differential circuit coupled to the first and second receive coils, a controller coupled to the differential circuit, and a vibration canceling circuit coupled to the controller. The controller uses a signal provided by the vibration canceling circuit to remove a vibration component from a metal detection signal.

Claims

1. A metal detector comprising:

a transmit coil;

first and second receive coils inductively coupled to the transmit coil;

a differential circuit coupled to the first and second receive coils;

a controller coupled to the differential circuit; and

a vibration canceling circuit coupled to the controller, the vibration canceling circuit including an accelerometer configured to generate a first signal indicative of movement along an axis, the vibration canceling circuit generating a second signal based on the first signal;

wherein the controller receives the second signal from the vibration canceling circuit and a third signal from the differential circuit, the controller using the second signal to modify the third signal and generate a metal detection signal, the metal detection signal having a component related to movement of the metal detector substantially removed.

2. The metal detector of claim 1, wherein the first and second receive coils are positioned substantially equidistantly on opposite sides of the transmit coil.

3. The metal detector of claim 1, wherein the vibration canceling circuit includes a vibration detection circuit which provides a plurality of first signals indicative motion on two or more axes, wherein each axis is orthogonal to the other axes.

4. The metal detector of claim 1, wherein the vibration canceling circuit includes a filter and an amplifier.

5. The metal detector of claim 1, wherein the vibration canceling circuit includes a vibration detection circuit providing a plurality of first signals, each first signal indicative of motion on an axis.

6. The metal detector of claim 5, wherein the plurality of first signals are filtered and combined, and the combined signal is amplified and provided to the controller.

7. The metal detector of claim 1, wherein the accelerometer is coupled to a passageway, the accelerometer detecting vibration of the passageway.

8. The metal detector of claim 1, wherein the second signal is converted to a digital value before being provided to the controller.