Oscillation Sensor Calibration with Variable-Frequency PWM
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Solution Overview
Problem
Oscillation sensors face challenges in calibration due to the introduction of low-frequency harmonics from pulse width modulation, which degrade the signal-to-noise ratio and make it difficult to eliminate these harmonics effectively.
Innovation Solution
The oscillation sensor employs a calibration unit that provides a modulated calibration control signal with an irregularly varying cycle frequency, reducing the modulation effect by ensuring no predominant frequency is introduced into the amplitude signal, thereby improving the signal-to-noise ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If pulse width modulation is used to control the calibration element, then electronic calibration is enabled, but low frequency harmonics are injected into the circuitry degrading the signal-to-noise ratio
Solution Approach 1:
The patent applies dynamics by making the PWM cycle frequency variable rather than fixed. The calibration unit varies the cycle frequency of the PWM signal dynamically, which prevents the injection of consistent low frequency harmonics at a single frequency, thereby improving the signal-to-noise ratio while maintaining electronic calibration capability
Solution Approach 2:
The patent changes the parameter of PWM cycle frequency from a fixed value to a variable parameter that can be adjusted by the calibration unit. By changing this parameter, the system maintains the benefits of PWM-based electronic calibration while avoiding the degradation of signal-to-noise ratio that occurs with fixed frequency PWM
2Stability of the object's composition
If a fixed duty cycle PWM signal is used for calibration, then the calibration point is stable, but specific frequency harmonics are consistently introduced that are difficult to filter
Solution Approach 1:
The system maintains calibration stability through controlled dynamics by varying the PWM cycle frequency in a controlled manner. The calibration unit adjusts the cycle frequency to different values at different times, which prevents consistent harmonic injection while still allowing the system to maintain stable calibration points through the varying frequency approach
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 significantly enhances the signal-to-noise ratio by randomizing the energy injection variation, preventing specific frequency overlays and reducing amplitude modulation, leading to improved sensor performance.
Implementation Method 1
an oscillator comprising a resonance circuit for providing an oscillation signal
Implementation Method 2
the sensing coil produces an alternating magnetic field
Implementation Method 3
a gain stage configured to feedback to the resonance circuit to inject energy for excitation of the resonance circuit to maintain oscillation
Implementation Method 4
the presence of an object in the sensing range leads to a decrease of a quality factor of the resonance circuit caused by an energy loss due to the production of eddy currents in the object
Data Source
AI summary
The present invention relates to an oscillating sensor for a measurement device comprising:an oscillator comprisinga resonance circuit for providing an oscillation signal;a gain stage configured to feedback to the resonance circuit to inject energy for excitation of the resonance circuit to maintain oscillation;at least one calibration element to adjust the open loop gain of the oscillator;a calibration unit to provide a modulated calibration control signal to selectively adjust an electrical measure of the at least one calibration element based on at least one predetermined duty cycle,wherein the modulated calibration control signal has an irregularly time-varying cycle frequency.