Method for measuring a gap between a proximity probe and a conductive target material

• US 6,842,020 B2
• Filed: 05/30/2003
• Issued: 01/11/2005
• Est. Priority Date: 10/22/1999
• Status: Expired due to Fees

• Current Assignee: Bently Nevada Incorporated (General Electric Company)
• Original Assignee: Bently Nevada Incorporated (General Electric Company)
• Inventors: Slates, Rich
• Primary Examiner(s): Tokar, Michael
• Assistant Examiner(s): KOBERT, RUSSELL MARC
• Application Number:
  US10/452,476
• Publication Number:
  US 20030214282A1
• Time in Patent Office: 592 Days
• Field of Search: 324/207.12, 324/207.26, 324/225, 324/720, 324/207.16, 702/67, 702/107, 702/91
• US Class Current: 324/720
• CPC Class Codes: G01B 7/003 for measuring position, not involving coordinate determination coordinate measuring G01B7/004
• CPC Class Codes: G01B 7/023 for measuring distance between sensor and object G01B7/082 and G01B7/102 take precedence
• CPC Class Codes: G01D 18/00 Testing or calibrating apparatus or arrangements provided for in groups G01D1/00 - G01D15/00
• CPC Class Codes: G01D 5/202 by movable a non-ferromagnetic conductive element G01D5/2033 takes precedence
• CPC Class Codes: G01N 27/9046 by analysing electrical signals

Abstract

A digital eddy current proximity system including a digital impedance measuring device for digitally measuring the proximity probes impedance correlative to displacement motion and position of a metallic target object being monitored. The system further including a cable-length calibration method, an automatic material identification and calibration method, a material insensitive method, an inductive ratio method and advanced sensing characteristics.

Claims

1. A method for measuring a gap between a proximity probe and a conductive target material, the steps including:

providing a proximity probe having a first end located adjacent a conductive target material and having a second end coupled to a first end of an extension cable;

measuring an impedance at a second end of the extension cable;

compensating the measured impedance by mathematically eliminating extension cable residuals from the measured impedance for defining a proximity probe impedance of the proximity probe wherein the step of compensating the measured impedance includes the steps of determining a first impedance of the extension cable with the first end opened for defining an open impedance and determining a second impedance of the extension cable with the first end shorted for defining a short impedance;

determining the proximity probe impedance as a function of the measured impedance, the open impedance, and the short impedance for defining the proximity probe impedance of the proximity probe, and

correlating the proximity probe impedance with a value representative of a gap between the proximity probe and the conductive target material.

2. A method for measuring a gap between a proximity probe and a conductive target material, the steps including:

providing a proximity probe having a first end located adjacent a conductive target material and having a second end coupled to a first end of an extension cable;

measuring an impedance at a second end of the extension cable;

compensating the measured impedance by mathematically eliminating extension cable residuals from the measured impedance for defining a proximity probe impedance of the proximity probe wherein the step of compensating the measured impedance by mathematically eliminating the extension cable residuals includes the steps of determining a first impedance of the extension cable with the first end opened for defining an open impedance, determining a second impedance of the extension cable with the first end shorted for defining a short impedance, and determining a third impedance of the extension cable with the first end coupled to a load having a known value for defining a load impedance, and

correlating the proximity probe impedance with a value representative of a gap between the proximity probe and the conductive target material.

3. The method of claim 2 wherein the step of compensating the measured impedance by mathematically eliminating the extension cable residuals from the measured impedance further includes the step of determining the proximity probe impedance as a function of the measured impedance, the open impedance, the short impedance and the load impedance for defining the proximity probe impedance of the proximity probe.

4. The method of claim 2 wherein the step of compensating the measured impedance by mathematically eliminating the extension cable residuals includes the step of using compensation coefficients stored in a memory means for defining the proximity probe impedance as a function of the compensation coefficients.

5. The method of claim 4 wherein the step of using compensation coefficients stored in a memory means includes the steps of determining a first impedance of the extension cable with the first end opened for defining an open impedance coefficient, determining a second impedance of the extension cable with the first end shorted for defining a short impedance coefficient, and determining a third impedance of the extension cable with the first end coupled to a load having a known value for defining a load impedance coefficient wherein the opened impedance coefficient, the short impedance coefficient and the load impedance coefficient are included in the compensation coefficients stored in the memory means for defining the proximity probe impedance.