Eddy Current Sensor Temperature Compensation via Oscillator Regression
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Solution Overview
Problem
Eddy current sensors face challenges in providing precise measurements due to temperature variations, as existing methods require additional sensors or circuits, increasing complexity and cost, especially when measuring distance or material characteristics like vibration or eccentricity in rotating shafts.
Innovation Solution
A method involving calibration of eddy current sensors by measuring frequency and voltage or current at multiple temperatures and distances, using regression equations to determine temperature, gain, and offset adjustments, allowing for compensation to a standard temperature without additional electronics, thereby correcting for temperature effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If additional temperature sensors or separate temperature-measuring circuits are used to compensate for temperature variations, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent combines the temperature measurement function with the existing eddy current sensor by using the oscillator's frequency and voltage/current measurements that are already taken for distance measurement. The same oscillator circuit serves dual purposes: measuring distance through eddy current effects and determining temperature through its frequency and electrical characteristics, eliminating the need for separate temperature sensing components.
Solution Approach 2:
The oscillator circuit in the eddy current sensor is made multi-functional by utilizing its frequency and voltage/current outputs for both distance measurement and temperature compensation. The system extracts temperature information from the oscillator's characteristics without requiring dedicated temperature sensing functionality, allowing one component to serve multiple measurement purposes.
2Measurement precision
If additional temperature sensors or separate temperature-measuring circuits are used to compensate for temperature variations, then measurement precision is improved, but cost increases
Solution Approach 1:
The patent combines the temperature measurement function with the existing eddy current sensor by using the oscillator's frequency and voltage/current measurements that are already taken for distance measurement. The same oscillator circuit serves dual purposes: measuring distance through eddy current effects and determining temperature through its frequency and electrical characteristics, eliminating the need for separate temperature sensing components.
Solution Approach 2:
The eddy current sensor system performs its own temperature measurement and compensation using its existing oscillator and measurement circuits. The sensor utilizes its own operational characteristics (frequency and voltage/current of the oscillator) to determine temperature, making the system self-sufficient for temperature compensation without requiring external temperature sensing components.
3Measurement precision
If temperature is held constant to ensure precise measurements, then measurement precision is improved, but adaptability to varying environmental conditions deteriorates
Solution Approach 1:
The patent implements a feedback mechanism where the oscillator's frequency and voltage/current measurements are continuously monitored to determine temperature, and this temperature information is then used to adjust and compensate the distance measurement. This closed-loop approach allows the system to automatically adapt to temperature variations while maintaining measurement precision, eliminating the need for constant temperature environments.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables precise temperature compensation within eddy current sensors, reducing the need for extra sensors and circuits, allowing for accurate distance measurements across varying temperatures without increasing complexity or cost.
Implementation Method 1
Eddy current sensors operate by applying an alternating current to a coil in the sensor to create a primary magnetic field. The primary magnetic field tends to induce small currents in the target surface, which are called eddy currents.
Implementation Method 2
The eddy currents themselves create eddy magnetic fields that affect the impedance of the coil to some degree.
Data Source
AI summary
A method for calibrating an eddy current sensor for temperature. Both frequency and one of voltage and current of an oscillator driving the eddy current sensor are measured at a plurality of temperatures and a plurality of target surface distances. Temperature equations are regressed to fit the measured frequency and one of the voltage and the current for each temperature, where the temperature equations have a common number of equivalent factors, and factor equations are regressed for each of the equivalent factors. A gain adjustment and an offset adjustment pair for each of the plurality of temperatures is determined for an oscillator associated with the eddy current sensor, that compensates an output of the eddy current sensor to a standard temperature. A gain equation is regressed to fit the determined gain adjustments, and an offset equation is regressed to fit the determined offset adjustments. The temperature equations, factor equations, gain equation, and offset equation are provided with the eddy current sensor.