Method for measuring a characteristic of a conductive target material using a proximity probe

• US 6,850,077 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 A.
• Assistant Examiner(s): KOBERT, RUSSELL MARC
• Application Number:
  US10/452,161
• Publication Number:
  US 20030206004A1
• Time in Patent Office: 613 Days
• Field of Search: 324/222, 324/691, 324/693, 324717-719, 324/158.1
• US Class Current: 324/693
• 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 characteristic of a conductive target material disposed adjacent a proximity probe, the steps including:

providing a length of cable having a first end and a second end;

determining a first impedance of the cable with the first end opened for defining a open impedance;

determining a second impedance of the cable with the first end shorted for defining a short impedance;

coupling the first end of the cable to a proximity probe and having the second end of the cable coupled to a digital eddy current proximity system;

measuring, at the second end of the cable, an impedance of the coupled cable and proximity probe;

calculating the proximity probe impedance as a function of the measured impedance, the open impedance, and the short impedance for compensating for cable length residuals;

correlating the proximity probe impedance with a characteristic of a conductive target material disposed adjacent the proximity probe.

2. The method of claim 1 further including the step of determining a third impedance of the cable with the first end coupled to a load having a known value for defining a load impedance.

3. The method of claim 2 wherein the step of calculating the proximity probe impedance as a function of the measured impedance, the open impedance, and the short impedance for compensating for cable length residuals includes calculating the proximity probe impedance as a function of the measured impedance, the open impedance, the short impedance, and the load impedance for compensating for cable length residuals.

4. The method of claim 3 wherein said means for correlating includes a step of normalizing the proximity probe impedance and comparing the normalized proximity probe impedence to a plurality of previously compiled representations of normalized impedance of different conductive target materials for identifying the conductive target material.

5. The method of claim 4 wherein comparing the normalized proximity probe impedance to the previously compiled representations includes comparing the normalized proximity probe impedance to the previously compiled representations comprised of a plurality of gap locus lines, each defining a single gap value for different conductive target materials such that a gap line is identified for use in correlating the normalized proximity probe impedance to a gap between the proximity probe and the conductive target material.