Circuit for compensation for time variation of temperature in an inductive sensor

Abstract

A sensing device includes a circuit that compensates for time and spatial changes in temperature. The circuit includes elements to correct for variation in permeability of a highly permeable core of a differential variable reluctance transducer as temperature changes. The circuit also provides correction for temperature gradients across coils of the transducer.

Description

RELATED APPLICATION[0001]This application is a continuation-in-part of Provisional U.S. Patent Application 60 / 220,364, filed Jul. 24, 2000.FIELD OF THE INVENTION[0002]This invention generally relates to sensors. More particularly, it relates to variable reluctance transducers. Even more particularly, it relates to an improved system for greater accuracy in determining position or displacement in view of changes in temperature.BACKGROUND OF THE INVENTION[0003]Sensors are being developed for use in roads, bridges, dams, buildings, towers, and vehicles that may provide many information, including displacement, strain, speed, acceleration, temperature, pressure, and force.[0004]Temperature changes can effect components within a sensor, and one challenge has been that sensor output has varied with temperature of sensor components. The effect of temperature on inductive transducers limits their overall absolute accuracy. To reduce the temperature effect, inductive transducers, such as a d...

AI Technical Summary

Benefits of technology

This solution provides highly accurate displacement sensing independent of temperature changes, reducing errors and improving the accuracy of both single and dual coil transducers, with the ability to maintain precision across a wide temperature range.

Problems solved by technology

Temperature changes can effect components within a sensor, and one challenge has been that sensor output has varied with temperature of sensor components.

The effect of temperature on inductive transducers limits their overall absolute accuracy.

However, if one coil experiences a different temperature environment than the other coil, a signal proportional to the temperature gradient between the two coils will appear at the circuit output, significantly reducing absolute accuracy.

The '593 patent recognizes that a temperature gradient across the coils can provide a change in the resistance of the wire forming one of the coils more than it changes the resistance in the other coil, and this difference in resistance can change the differential impedance of the coils, essentially mimicking a change in position, resulting in an error in measured displacement.

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