Eddy Current Sensor Temperature Compensation via LC Resonance
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Solution Overview
Problem
Conventional turbocharger speed sensors face accuracy issues due to temperature changes, affecting both pressure sensors and eddy current type sensors, leading to decreased performance in high-temperature environments.
Innovation Solution
An eddy current type sensor incorporating a LC circuit with a detection coil and capacitor, where the oscillator supplies an alternating current at a specific frequency to minimize voltage difference changes with temperature, ensuring accurate conductor detection regardless of temperature fluctuations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a pressure sensor is used to detect rotational speed, then the sensor can operate at relatively low temperatures, but accuracy decreases when temperature exceeds maximum operating temperature
Solution Approach 1:
The patent replaces the pressure sensor (semiconductor device) with an eddy current type sensor that uses electromagnetic induction. The detection coil generates alternating magnetic field to induce eddy current in the conductor, and the rotational speed is detected based on impedance changes of the coil, eliminating temperature-related accuracy issues of semiconductor pressure sensors
Solution Approach 2:
The patent changes the detection principle from pressure-based (Pascal's law) to electromagnetic-based (eddy current and impedance). By using alternating current frequency and impedance magnitude/phase as detection parameters instead of pressure, the system achieves high-temperature operation with maintained accuracy
2Temperature
If an eddy current type sensor is used, then the sensor can operate at high temperatures, but accuracy decreases due to coil impedance changing with temperature
Solution Approach 1:
The patent introduces a feedback mechanism where the detected impedance changes (including temperature-induced changes) are fed back to the control unit. The control unit processes these signals to distinguish between temperature-related impedance changes and conductor-position-related impedance changes, compensating for temperature effects and maintaining accuracy
Solution Approach 2:
The patent uses multiple parameters (impedance magnitude, impedance phase, alternating current frequency) for detection instead of relying on a single parameter. By analyzing changes in multiple parameters simultaneously, the system can differentiate between temperature effects and conductor position effects, maintaining measurement accuracy at high temperatures
3Measurement precision
If the oscillation frequency is increased to improve detection sensitivity, then the voltage difference changes more with temperature, but detection precision improves
Solution Approach 1:
The patent optimizes the oscillation frequency parameter to achieve a balance between detection sensitivity and temperature stability. By selecting an appropriate frequency range and using multiple parameters (magnitude, phase, frequency) for detection, the system achieves both high sensitivity and temperature compensation capability
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
The solution effectively reduces the impact of temperature changes on sensor accuracy, allowing for precise detection of conductors across varying temperatures, thereby enhancing the reliability of turbocharger speed sensors.
Implementation Method 1
an alternating current is supplied to a coil so that the coil generates alternating magnetic field
Implementation Method 2
When the blade of the compressor passes through the magnetic field, the eddy current is induced in the blade
Implementation Method 3
The oscillator supplies an alternating current of a predetermined oscillation frequency to the LC circuit
Data Source
AI summary
An eddy current type sensor for detecting a conductor includes a LC circuit and an oscillator. The LC circuit has a coil and a capacitor connected in parallel with the coil. The oscillator supplies an alternating current of a predetermined oscillation frequency to the LC circuit. A signal voltage outputted from the LC circuit has a first voltage when the distance between the coil and the conductor is minimum and a second voltage when the distance between the coil and the conductor is maximum. A voltage difference between the first and second voltages has a first difference at a first temperature and has a second difference at a second temperature. The first and second differences become equal to each other at a first frequency and a second frequency. The oscillation frequency is set close to the first frequency or the second frequency.