Oscillating Sensor Gain Control for Fast Recovery and Stability
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Solution Overview
Problem
Inductive sensors face challenges in maintaining high sensitivity and stability due to flat open loop gain characteristics, leading to prolonged recovery times and unstable operating points, especially during start-up or when objects with high attenuation leave the sensing range, and existing non-linear semiconductor-based solutions are temperature-dependent and lack reproducibility.
Innovation Solution
An oscillating sensor device with a resonance circuit and an amplifier featuring non-linear gain characteristics, controlled by a unit that adjusts the open loop gain to maintain a preset oscillation amplitude, using a control unit with feedback mechanisms and adjustable gain stages to compensate for energy losses and environmental variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the open loop gain characteristics of the oscillator is made flat (constant amplification) to ensure high sensitivity for dynamic attenuation, then the sensitivity for detecting objects entering the sensing range is improved, but the recovery time to bring the oscillation back to the operating point after substantial attenuation becomes too long
Solution Approach 1:
The patent applies dynamics by making the open loop gain adjustable rather than fixed. The control unit dynamically adapts the open loop gain of the amplifier based on detected oscillation amplitude deviations. When the oscillation amplitude deviates from the preset value (indicating substantial attenuation), the control unit increases the open loop gain to accelerate recovery. When the oscillation is stable, the open loop gain is reduced to optimize sensitivity for detecting objects entering the sensing range. This dynamic adaptation resolves the contradiction between high sensitivity and fast recovery time.
2Measurement precision
If the open loop gain characteristics is made flat (constant amplification) to ensure high sensitivity, then the sensitivity for dynamic attenuation is improved, but there might be no fixed operating point for unattenuated condition so that in steady state operation no stable operating point is reached
Solution Approach 1:
The patent employs feedback mechanisms where the control unit continuously monitors the oscillation amplitude and adjusts the open loop gain accordingly. The feedback loop ensures that when the oscillation amplitude deviates from the preset value, the control unit modifies the gain to restore the operating point. This feedback control stabilizes the operating point while still allowing the system to achieve high sensitivity when needed, resolving the contradiction between sensitivity and operating point stability.
3Adaptability or versatility
If non-linear semiconductor effects are used to form gain characteristics to adapt gain characteristics of amplifiers, then the gain characteristics can be adjusted based on preferred operating point, but the solution introduces high temperature dependency and suffers from low reproducibility
Solution Approach 1:
The patent substitutes semiconductor-based non-linear gain characteristics with a control electronics approach. Instead of relying on temperature-sensitive semiconductor effects to provide non-linear gain, the system uses a control unit that digitally or electronically adjusts the open loop gain of the amplifier based on detected oscillation amplitude. This substitution eliminates the temperature dependency and reproducibility issues inherent in semiconductor non-linear effects while maintaining the ability to adapt gain characteristics to different operating conditions.
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 provides high sensitivity and adaptability to environmental changes, ensuring stable operation and quick recovery from attenuation, with automatic adjustment of the operating point, reducing the need for further calibration and maintaining high signal-to-noise ratios.
Implementation Method 1
the resonance circuit has a resonance frequency which is determined by the inductance of the sensing coil and by the capacitance of the capacitor. By means of a feedback amplification, the resonance circuit is excited so that the oscillation is maintained
Implementation Method 2
the sensing coil produces an alternating magnetic field which is substantially affected by the presence of conductive objects. conductive objects which enter or leave a sensing range of the sensing coil or move in or out of the sensing range produce a change of the effective impedance of the sensing coil
Implementation Method 3
the presence of an object in the sensing range leads to a decrease of a quality factor of the sensing coil caused by an energy loss due to the production of eddy currents in the object
Data Source
AI summary
An oscillating sensor device, particularly for a proximity sensor, for sensing a dynamic change of attenuation caused by a measurable physical effect includes an oscillator including a resonance circuit and an amplifier fed back to the resonance circuit and configured to maintain oscillation of the oscillator, and a control unit configured to control the open loop gain of the oscillator. The amplifier comprises a non-linear gain characteristics defining an operating point at a preset amplitude of oscillation. The control unit is configured to control the open loop gain of the oscillator so that the operating point is set to a preset amplitude of the oscillation.