Inductive Sensor Detector Circuit Reducing Power Consumption
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Solution Overview
Problem
Inductive displacement sensors consume excessive current due to continuous excitation with high-frequency alternating current, necessitating a detector circuit with lower energy consumption that can detect loss thresholds in the magnetic circuit or inductance variations efficiently.
Innovation Solution
A detector circuit using a string of charge pulses to excite the coil, with a first flip flop supplying a voltage pulse to charge the coil to a threshold current, and a second flip flop generating an output signal based on the duration of the charge pulse relative to a reference pulse, allowing for low energy consumption and efficient detection of inductance variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If high-frequency alternating current is used to excite the coil continuously, then the sensor can detect inductance variations, but the power consumption becomes excessive
Solution Approach 1:
The patent applies periodic action by using intermittent charge pulses instead of continuous high-frequency alternating current to excite the coil. The detector circuit generates periodic voltage pulses that charge the coil temporarily, allowing inductance measurement during these brief intervals. This periodic excitation maintains measurement capability while dramatically reducing average power consumption, as the coil is energized only when needed for measurement rather than continuously.
2Use of energy by moving object
If charge pulses are used instead of continuous AC, then power consumption is reduced, but measurement precision and response time may be affected
Solution Approach 1:
The patent implements feedback through a comparator that compares the actual voltage across the coil with a reference voltage. The output of the comparator feeds back to control the charging process, ensuring that the coil is charged to a precise threshold level. This feedback mechanism compensates for variations in coil inductance caused by changes in the magnetic circuit, maintaining measurement precision even with intermittent charge pulses. The system automatically adjusts the charging process to account for inductance variations, ensuring accurate detection.
3Measurement precision
If the charge pulse duration is increased to improve detection accuracy, then measurement precision improves, but the response time and power consumption increase
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the charge pulse duration based on the detected inductance value. The comparator monitors the voltage across the coil during charging and determines when a threshold is reached, automatically terminating the charge pulse at the appropriate moment. This adaptive approach allows the system to use longer pulses when higher precision is needed and shorter pulses when rapid response is prioritized, optimizing both measurement accuracy and response time by changing the temporal parameters of the excitation signal.
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 achieves a sensor with significantly reduced power consumption, less than 10 microwatts, and latency of less than 100 microseconds, enabling effective detection of inductance changes while maintaining stability against electrical noise and mechanical vibrations.
Implementation Method 1
an electric voltage is periodically applied by a first flip flop BD1 to the coil placed in the variable reluctance magnetic circuit. At the moment of application of this voltage to the coil the current in the coil begins to increase at a given rate of RU/N2, where R represents the reluctance of the magnetic circuit, U the applied voltage and N the number of turns of the coil.
Implementation Method 2
The reluctance R of the magnetic circuit is equal to the sum of the reluctances of the segments formed by the fixed (f), movable (m) parts and the air gap (e), i.e. Lf/μ0μfSf+Lm/μ0μmSm+Le/μ9Se, where L represents the length of the segment of magnetic circuit, μ its relative magnetic permeability, S its section
Data Source
AI summary
A detector circuit for detecting a variation in inductance of the magnetic circuit of an inductive displacement sensor, the detector circuit including: a first flip flop arranged to supply a first signal including a voltage pulse of necessary and sufficient duration to charge a coil to a threshold current, wherein the first signal is applied to a first terminal of the coil; a pulse generator configured to supply a reference signal comprising a reference pulse; a clock signal generator arranged to trigger the voltage pulse and the reference pulse periodically and simultaneously; and a second flip flop arranged to generate an output signal taking a status of the first signal on a trailing edge of the reference pulse.