Oscillation Sensor Calibration Using Frequency-Synced PWM
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Solution Overview
Problem
Existing 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 are difficult to filter, especially when the duty cycle affects the calibration of the sensor.
Innovation Solution
An oscillation sensor with a calibration unit that provides a modulated calibration control signal with a cycle frequency dependent on the oscillation frequency, reducing modulation effects by synchronizing the cycle frequency with the oscillation frequency to minimize harmonic interference and improve signal quality.
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 introduced that degrade the signal-to-noise ratio
Solution Approach 1:
The patent applies periodic action by using pulse width modulation to control the calibration element, where the duty cycle of the periodic control signal adjusts the effective resistance. This enables electronic calibration while the periodic nature of the control signal can be synchronized with the oscillation frequency to minimize harmonic interference.
Solution Approach 2:
The patent changes the parameter of the control signal from a fixed frequency to a variable frequency that adapts to the oscillation frequency. By adjusting the cycle frequency of the pulse width modulation signal to match or synchronize with the oscillation frequency, the system minimizes the introduction of low-frequency harmonics while maintaining electronic calibration capability.
2Device complexity
If the cycle frequency of the calibration control signal is fixed, then the control is simple, but modulation effects occur when the frequency does not match the oscillation frequency
Solution Approach 1:
The patent applies dynamics by making the cycle frequency of the calibration control signal variable rather than fixed. The control signal's frequency dynamically adapts to match the oscillation frequency, which eliminates modulation effects and improves signal quality while maintaining relatively simple control circuitry.
3Manufacturing precision
If laser calibration is used for the calibration element, then high precision calibration is achieved, but the cost is high and recalibration is not possible
Solution Approach 1:
The patent replaces the mechanical/optical calibration method (laser calibration) with an electronic control method using pulse width modulation. This substitution maintains calibration precision through electronic duty cycle control while enabling low-cost manufacturing and flexible recalibration capabilities.
Solution Approach 2:
The patent enables self-service calibration by allowing the system to perform its own calibration electronically through the pulse width modulated control signal. This eliminates the need for external laser calibration equipment and enables easy recalibration without additional manufacturing costs.
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 across a broad range of oscillation frequencies, allowing for better sensitivity and operating point adjustments while compensating for parasitic effects like temperature variations.
Implementation Method 1
the sensing coil produces an alternating magnetic field which is substantially affected by the presence of conductive objects
Implementation Method 2
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
Figure 1~2
Figure 3a~3b
Figure 4a~4b
AI summary
The invention relates to an oscillating sensor (2) for a measurement device (1) comprising: - an oscillator comprising: ∘ a resonance circuit (21) for providing an oscillation signal; ∘ a gain stage (22) configured to provide a feed-back to the resonance circuit to inject energy for excitation of the oscillator to maintain oscillation; ∘ at least one calibration element (224, 225; 226, 227) to adjust the open loop gain of the oscillator; - a calibration unit (24) to provide a modulated calibration control signal to selectively adjust an electrical measure of the at least one calibration element (224, 225; 226, 227) based on at least one predetermined duty cycle, wherein the calibration unit (24) is further configured to provide the modulated calibration control signal with at least one cycle frequency which depends on the oscillation frequency.