Patent ID: 6139181
Filing Date: 2000-10-31
Classification: G05D

Abstract:
A method of determining temperature of at least one inductively heated element, comprising the steps of:(a) heating said element by passing an electric current through a primary winding inductively coupled to a secondary winding having at least part of said element formed as a load of said secondary winding;(b) in a calibration stage applying a predetermined constant primary voltage (U.sub.0) across said primary winding and(b.sub.1) measuring a first pair of values (I.sub.1) and (T.sub.1) of a current through the primary winding and a temperature induced thereby in said element and measuring at least one further pair of values (I.sub.2) and (T.sub.2) of the current through the primary winding and the temperature induced thereby in said element, and(b.sub.2) from at least two of the pairs of values measured in step (b.sub.1) calculating a calibration curve T=F.sub.0 .noteq.(U.sub.x /I.sub.x) for said predetermined constant primary voltage (U.sub.0) where U.sub.x and I.sub.x are measured values of voltage and current; and(c) in an operating phase of said element, determining an actual value of said temperature of said element by measuring an actual primary voltage (U.sub.x) applied across said primary winding and determining the corresponding actual temperature (T) by the relationshipT=F.sub.0 (U.sub.x /I.sub.x)+.DELTA.T(U.sub.x -U.sub.0)where .DELTA.T(U.sub.x -U.sub.0) is a purely voltage-dependent correction factor.