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1. (WO2001001065) METHOD FOR INDUCTIVE MEASUREMENT OF A DIMENSION OF AN OBJECT

Pub. No.:    WO/2001/001065    International Application No.:    PCT/SE2000/001328
Publication Date: Fri Jan 05 00:59:59 CET 2001 International Filing Date: Fri Jun 23 01:59:59 CEST 2000
IPC: G01B 7/00
G01B 7/02
G01B 7/12
G01D 5/20
G01N 27/72
Applicants: ABB AB
LINDER, Sten
Inventors: LINDER, Sten
Title: METHOD FOR INDUCTIVE MEASUREMENT OF A DIMENSION OF AN OBJECT
Abstract:
A method for non-contact measurement of dimensions such as thickness or diameter and electrical characteristics of an electrically conductive object (6) based on electromagnetic induction and a time-varying magnetic field. A substantially constant current is supplied to at least one transmitter coil (3) such that an electromagnetic field penetrates the object (6). Current to the transmitter coil (3) is cut off and a voltage induced in at least one receiving coil (8) by at least one decaying magnetic field. The voltage in receiving coil (8) is measured from a first time following decay of a magnetic field in the air (T3) until a time when the field has decayed to zero (T4, T5, T6) and the signal is integrated. A value for a physical dimension of the object (6) is calculated from this integral. The method is accurate, undisturbed by surface contamination or object movement, and applicable to different geometric forms including plate, bar or tube.