Inductive Sensor LC Resonant Circuit Frequency Independence
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Solution Overview
Problem
Inductive sensors face limitations in measuring variables due to frequency dependencies and cross-sensitivities, particularly in resonant systems which require multiple oscillators and are not optimally designed for multiple frequencies, and lock-in amplifiers which require a constant stimulus frequency, limiting measurement accuracy and resolution.
Innovation Solution
A device with a measuring inductance coupled to a capacitance forming a parallel resonant circuit, driven by an electronic control unit using an excitation frequency derived from a clock, allowing self-oscillation and independent frequency selection, thus avoiding the limitations of resonant systems and enabling efficient measurement without external amplifiers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a resonant system is used for inductive sensing, then measurement is simplified through frequency measurement, but the system exhibits frequency dependencies and cross-sensitivities that distort measurement results
Solution Approach 1:
The patent segments the measurement function by separating the excitation function (electronic control unit generating square wave) from the sensing function (LC-resonant circuit). This allows the resonant circuit to operate independently at its natural frequency without being influenced by the excitation frequency, eliminating cross-sensitivities while maintaining measurement simplicity.
Solution Approach 2:
The patent introduces an intermediary LC-resonant circuit between the electronic control unit and the inductive sensor. This resonant circuit acts as a frequency-selective mediator that filters out frequency-dependent distortions and cross-sensitivities, allowing accurate measurement of the sensor's characteristic values at its natural resonance frequency.
2Adaptability or versatility
If multiple independent oscillators are used to acquire multiple signals, then ratiometric or differential measurement is enabled, but device complexity significantly increases
Solution Approach 1:
The patent makes the single LC-resonant circuit universal by enabling it to measure multiple characteristic values (inductance, capacitance, resistance, quality factor) of the inductive sensor through different evaluation methods. This single multi-functional resonant circuit replaces what would otherwise require multiple specialized oscillators, maintaining measurement versatility while reducing system complexity.
3Ease of operation
If lock-in amplifier is used with constant stimulus frequency, then measurement is performed at fixed frequency, but operation at resonance cannot be utilized and measurement accuracy is limited
Solution Approach 1:
The patent transitions from the static fixed-frequency operation of lock-in amplifiers to dynamic resonant operation. The LC-resonant circuit automatically operates at its natural resonance frequency, which is determined by the sensor's characteristic values. This dynamic adaptation to resonance enables higher measurement accuracy while maintaining operational simplicity through automatic frequency adjustment.
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 reduces energy consumption, simplifies the system, and provides a stronger signal with improved electromagnetic compatibility, allowing for precise measurement across a range of frequencies without the need for external amplifiers, enhancing measurement accuracy and resolution.
Implementation Method 1
a capacitor, which is connected to the first inductor to form a parallel resonant circuit
Implementation Method 2
Inductive sensors typically rely on a change in one or more parameters of a system of one or more inductive components due to a measured quantity
Data Source
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AI summary
The invention relates to a device for measuring a measurement variable, wherein a first inductance (LP, L1) is supplemented by a capacitance (CP) to form a parallel resonant circuit and is excited by a micro-controller (MK). A measurement inductance (LS1, LS2, LS3, L2) coupled to the first inductance (LP, L1) is measured by the micro-controller (MK). Therefore, a measured variable can be deduced and only very few components are required in addition to a micro-controller (MK) .