Multi-coil proximity probe system: apparatus and method

• US 20030062891A1
• Filed: 10/02/2001
• Published: 04/03/2003
• Est. Priority Date: 10/02/2001
• Status: Active Grant

• Current Assignee: BN Corporation LLC
• Original Assignee: BN Corporation LLC
• Inventors: Slates, Richard Dale
• Granted Patent: US 6,803,757 B2
• Time in Patent Office: Days
• US Class Current: 324/207.26
• CPC Class Codes: G01B 7/001 Constructional details of gauge heads G01B7/012 takes precedence
• CPC Class Codes: G01B 7/14 for measuring distance or clearance between spaced objects or spaced apertures G01B7/30 takes precedence
• CPC Class Codes: G01D 5/2053 by a movable non-ferromagnetic conductive element

Abstract

A proximity probe system comprising a multi-coil proximity probe including a drive coil, a sense coil and a reference coil. The system includes a signal generator driving the drive coil with an alternating current for creating a magnetic field that induces eddy currents in a proximate conductive object resulting in an eddy current induced magnetic field emanating therefrom. The sense coil is interposed between the object and the drive coil for outputting an object induced alternating current that is detected by the system and correlated to a position of the object relative to the probe. The reference coil is positioned to be inductively coupled to the drive coil for carrying a drive coil induced alternating current that is detected, conditioned and feedback to the signal generator for controlling the magnetic field radiating from the drive coil while sensing the the object induced alternating current in the sense coil.

Claims

1. - A multi-coil eddy current proximity probe system, comprising in combination:

a drive coil located proximate a conductive target object and radiating a first magnetic field by carrying an alternating current for inducing eddy current within said conductive target object and causing a second magnetic field to be radiated from said conductive target object;

a control means operatively coupled to said drive coil for controlling said alternating current carried by said drive coil as a function of its own radiated said first magnetic field;

a sense coil interposed between said drive coil and said conductive target object for sensing, during the control of said first magnetic field radiating from said drive coil, said second magnetic field radiating from said conductive target object such that an alternating current correlative to a position between said sense coil and said conductive target object is induced within said sense coil, and

a processor operatively coupled to said sense coil for processing said induced alternating current in said sense coil and transforming said induced alternating current into output signals correlative to said position between said sense coil and said conductive target object.

2. - The multi-coil eddy current proximity probe system of claim 1 wherein said control means includes a closed feedback loop means for sensing said first magnetic field and for driving said drive coil as a function of said sensed first magnetic field such that said alternating current carried by said drive coil is controlled in response to its own radiated said first magnetic field.

3. - The multi-coil eddy current proximity probe system of claim 2 wherein said closed feedback loop means includes a reference coil located within said first magnetic field for sensing said first magnetic field by having an alternating reference current induced in said reference coil by said first magnetic field.

4. - The multi-coil eddy current proximity probe system of claim 3 wherein said closed feedback loop means further includes means for processing said induced alternating reference current and means for outputting a control signal correlative to said processed induced alternating reference current for controlling said alternating current carried by said drive coil and said first magnetic field radiated by said drive coil.

5. - The multi-coil eddy current proximity probe system of claim 4 wherein said closed feedback loop means further includes a controllable signal generator operatively coupled between said processing means and said drive coil for receiving said control signal and outputting said alternating current carried by said drive coil for controlling said first magnetic field radiated by said drive coil.

6. - A multi-coil eddy current proximity probe system, comprising in combination:

three concentrically disposed coils including a sense coil, a drive coil and a reference coil;

said drive coil interposed between said sense coil and said reference coil and operatively coupled to and coacting with a controllable current source for carrying a controlled alternating current delivered from said controllable current source and for radiating a first magnetic field from said drive coil to an adjacent conductive target object for generating eddy currents within said conductive target object resulting in a second magnetic field radiating from said adjacent conductive target object;

said reference coil inductively coupled to said drive coil by said first magnetic field such that a first current indicative of said first magnetic field is induced within said reference coil;

control means including a feedback loop means comprised of said reference coil and said controllable current source for processing said induced first current indicative of said first magnetic field and controlling said controllable current source as a function of said induced first current indicative of said first magnetic field for delivering said controlled alternating current to said drive coil such that said controlled alternating current delivered to said drive coil controls said first magnetic field radiated from said drive coil;

said sense coil inductively coupled to said target object for sensing said second magnetic field radiating from said conductive target object such that a second current correlative to a position between said sense coil and said conductive target object is induced within said sense coil during said control by said control means of said first magnetic field radiating from said drive coil, and

a processor operatively coupled to said sense coil for processing said induced second current in said sense coil and transforming said induced second current into output signals correlative to said position between said sense coil and said conductive target object.

7. - The multi-coil eddy current proximity probe system of claim 6 wherein said processor processes said induced second current in said sense coil as a function of an attenuation factor determined from said induced first current within said reference coil for transforming said induced second current into output signals correlative to said position between said sense coil and said conductive target object.

8. - The multi-coil eddy current proximity probe system of claim 7 wherein said processor divides a predetermined signal by said induced first current within said reference coil to determine said attenuation factor and divides said induced second current in said sense coil by said attenuation factor for transforming said induced second current into output signals correlative to said position between said sense coil and said conductive target object.

9. - A multi-coil eddy current proximity probe system, comprising in combination:

a first coil;

a signal generator operatively coupled to said first coil;

said first coil emanating a first magnetic filed by carrying a first alternating current delivered from said signal generator to said first coil,

said first magnetic field inducing eddy currents within an adjacent conductive target object causing a second magnetic field to emanate back toward said first coil;

a second coil inductively coupled to the adjacent conductive target object and interposed between said first coil and the adjacent conductive target object;

said second coil carrying a second alternating current induced by said second magnetic field and correlative to a position of the adjacent conductive target object;

a third coil located adjacent said first coil and carrying a third alternating current induced by said first magnetic field emanating from said first coil;

means for controlling said first alternating current carried in said first coil as a function of the said third alternating current induced by said first magnetic field radiating from said first coil for substantially holding said first alternating current carried in said first coil substantially constant, and

means for receiving said second alternating current and transforming said received second alternating current into output signals correlative to the position of the adjacent conductive target object while holding said first alternating current carried in said first coil substantially constant for monitoring the position of the conductive target object.

10. - A method for determining a position of a conductive target object of a machine for monitoring the machine for indications of incipient problems, the steps including:

locating a drive coil proximate the conductive target object;

interposing a sensing coil between the drive coil and the conductive target object;

driving the drive coil with an alternating signal for generating eddy currents in the conductive target object;

detecting a signal in the sensing coil induced by a magnetic field radiating from the conductive target object produced from the eddy currents in the target object, and

transforming said signal into a output signal correlative to the position of the conductive target object, and

determining if said output signal is an indication of an incipient machine problem.