Inductive Proximity Switch Differential Oscillator Compensation
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Solution Overview
Problem
Existing inductive proximity switches face challenges in compensating for environmental parameters such as temperature changes with significant additional circuit outlay.
Innovation Solution
An inductive proximity switch utilizing a signal oscillating circuit and a reference oscillating circuit, where the signal circuit's oscillation parameter depends on target position and the reference circuit's parameter is independent of target position, with a multiplexer circuit alternating their activation to minimize interference, and a differential principle to compensate for environmental disturbances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If temperature compensation is implemented using additional temperature sensors and signal processing circuits, then temperature-induced variations of oscillator properties can be compensated, but the device complexity and circuit outlay increase
Solution Approach 1:
A reference oscillating circuit is created as a copy of the signal oscillating circuit, but without the detection coil. This reference circuit experiences the same temperature drift and environmental influences, allowing its oscillation frequency to serve as a reference for compensating temperature effects on the signal circuit.
Solution Approach 2:
The reference oscillating circuit acts as an intermediary that indirectly measures temperature drift. Instead of directly measuring temperature with sensors, the system uses the reference circuit's frequency response to temperature changes to compensate the signal circuit's frequency.
2Measurement precision
If a reference oscillating circuit is introduced for differential measurement, then environmental parameter compensation is achieved, but the device complexity increases due to additional circuits
Solution Approach 1:
The reference oscillating circuit and signal oscillating circuit are merged into a single integrated circuit board, sharing common components such as the microcontroller, power supply, and evaluation electronics. This reduces overall device complexity while maintaining the differential measurement capability.
Solution Approach 2:
The multiplexer circuit provides multi-functionality by selectively connecting either the reference oscillating circuit or the signal oscillating circuit to the common evaluation electronics. This allows a single set of evaluation components to serve both circuits, reducing redundancy.
3Productivity
If both signal oscillating circuit and reference oscillating circuit are activated simultaneously, then measurements can be taken in parallel, but electromagnetic interference between the circuits increases
Solution Approach 1:
Instead of simultaneous activation, the system uses periodic alternation where the multiplexer switches between connecting the reference oscillating circuit and the signal oscillating circuit to the evaluation electronics. This time-division approach eliminates electromagnetic interference while maintaining measurement capability.
Solution Approach 2:
The system performs preliminary measurements by first activating the reference oscillating circuit to establish a baseline frequency, then switching to the signal oscillating circuit for target detection. This sequential approach allows comparison while avoiding interference.
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 design allows for simple and robust compensation of environmental influences, reducing hardware requirements and manufacturing costs while maintaining accurate target detection and distance measurement.
Implementation Method 1
In order to detect the intrusion of a target into a detection zone, a high-frequency electromagnetic field is generated and the influence of the target on this field is determined.
Implementation Method 2
The multiplexer circuit is set up to activate the signal oscillating circuit or the reference oscillating circuit alternately, in order to minimize interference between the two oscillating circuits.
Data Source
AI summary
An inductive proximity switch comprising signal oscillating circuit and a reference oscillating circuit; multiplexer circuit designed to alternately activate the signal oscillating circuit and the reference oscillating circuit; driver circuit having an oscillator designed to operate the activated signal oscillating circuit and the activated reference oscillating circuit with an oscillator frequency, respectively; detection module designed to determine a number of oscillations of the activated signal oscillating circuit measured within a predetermined gate time and a number of oscillations of the activated reference oscillating circuit measured within the predetermined gate time; and an evaluation module designed to determine a difference signal on basis of the determined number of oscillations of the activated signal oscillating circuit measured within the predetermined gate time and the determined number of oscillations of the activated reference oscillating circuit measured within the predetermined gate time, and to generate a control signal depending on the difference signal.