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

• US 6,850,078 B2
• Filed: 05/30/2003
• Issued: 02/01/2005
• 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, Richard D.
• Primary Examiner(s): Zarneke, David
• Assistant Examiner(s): KOBERT, RUSSELL MARC
• Application Number:
  US10/452,712
• Publication Number:
  US 20030214283A1
• Time in Patent Office: 613 Days
• Field of Search: 324/603, 324/607, 324/662, 324/671, 324/691, 324/699, 324/713, 324/715, 324/716, 324/207.15, 324/207.16, 702/155, 702/158, 702/166
• US Class Current: 324/699
• 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, said method including the steps of:

digitally measuring an electrical impedance of a proximity probe located adjacent a conductive target material;

combining a predetermined digitized impedance with the digitally measured impedance of the proximity probe wherein the step of combining the predetermined digitized impedance with the measured impedance of the proximity probe includes combining an equivalent digitized impedance of an analog circuit with the digitally measured impedance of the proximity probe, and

correlating the combined impedance to a gap interposed between the proximity probe and the conductive target material being monitored.

2. The method of claim 1 wherein the step of correlating the combined impedance to the gap interposed between the proximity probe and the conductive target material being monitored includes the step of correlating both the combined impedance and a measured frequency of a signal driving the proximity probe to the gap interposed between the probe and the conductive target material being monitored.

3. The method of claim 2 further including the step of adjusting the frequency of the signal driving the proximity probe as a function of the combined impedance and the measured frequency for correcting any anomalous phase error and subsequently driving the proximity probe at the adjusted frequency.

4. The method of claim 1 further including the step of compensating the digitally measured impedance of the proximity probe by using compensation coefficients for eliminating probe cable effects included in the proximity probe.

5. The method of claim 4 wherein the step of compensating the digitally measured impedance of the proximity probe by using compensation coefficients includes the steps of performing an open, a short and a load measurement on the probe cable for determining the compensation coefficients.