Capacitive Proximity Sensing Circuit With Compensation Feedback
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Solution Overview
Problem
Existing methods for detecting the approach of an object to an electrode device are sensitive to interfering influences, limiting sensor sensitivity and controllability.
Innovation Solution
A circuit comprising a send electrode, a generator for alternating voltage, a receive electrode, an output circuit, and a compensation circuit that adds a compensation current to the signal current from the receive electrode, allowing for high sensor sensitivity while preventing signal override, achieved by generating an alternating electric field and using a microcontroller for amplitude and phase compensation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the generator voltage is set as high as possible to achieve high sensor sensitivity, then the signal alteration increases, but the amplifier becomes uncontrollable and the circuit is overridden
Solution Approach 1:
The patent introduces a compensation electrode as an intermediary element that generates a compensating signal to counterbalance the harmful effects of high generator voltages. This mediator allows the main measurement electrode to operate at high sensitivity while the compensation electrode actively cancels out signal overload, enabling the amplifier to remain controllable even with high sensor sensitivity settings.
Solution Approach 2:
The patent implements a feedback mechanism where the compensation electrode continuously monitors the electric field conditions and adjusts its compensating signal accordingly. This feedback loop ensures that the amplifier receives a balanced signal within its controllable range while maintaining high sensor sensitivity, preventing circuit override through real-time signal regulation.
2Measurement precision
If the signal alteration is increased to improve detection capability, then sensor sensitivity improves, but environmental interference and harmful influences increase
Solution Approach 1:
The patent converts the harmful environmental interference into a beneficial measurement signal. By using a compensation electrode that detects the same environmental influences affecting the main electrode, the system transforms these harmful factors into compensating data that can be subtracted from the main signal, thereby improving detection capability while eliminating interference.
Solution Approach 2:
The compensation electrode serves as an intermediary that specifically targets and neutralizes environmental interference. It measures the harmful influences separately and generates a compensating signal that cancels these effects from the main measurement, allowing high detection capability without suffering from environmental interference.
3Measurement precision
If the amplifier gain is increased to detect small signals, then measurement precision improves, but the circuit becomes more susceptible to overriding and harmful influences
Solution Approach 1:
The compensation electrode acts as an intermediary that pre-processes the signal by canceling harmful components before they reach the amplifier. This allows the amplifier to operate at high gain for detecting small signals without being overwhelmed by interference, maintaining circuit stability while improving signal detection threshold.
Solution Approach 2:
The patent performs preliminary signal conditioning through the compensation electrode before the signal enters the amplifier. By pre-canceling harmful influences and preparing a balanced signal, the system enables high amplifier gain operation without susceptibility to overriding, as the damaging components have already been removed in advance.
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 enhances sensor sensitivity by maintaining signal alteration in the linear range, enabling longer sensor electrodes and simplifying production, with increased detection capabilities and reduced environmental interference.
Implementation Method 1
an alternating electric field in the frequency range of preferably 80 to 150 kHz is generated between a send electrode Tx and a receive electrode Rx
Implementation Method 2
there is a partial absorption of this field through the body which leads to a weakening of the receive signal fed to an amplifier connected to the receive electrode Rx
Data Source
AI summary
A circuit for generating an indicative signal regarding the approach of an object to an observation area has a send electrode device, a generator circuit for supplying alternating voltage to the send electrode device, a receive electrode device which extends in or along the observation area, and an output circuit for generating an output signal correlating with the field at the receive electrode device. A compensation circuit is provided to add a compensation current i2 to a signal current i1 flowing from the receive electrode device.