Capacitive Sensor Interconnection Capacitance Cancellation
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Solution Overview
Problem
Capacitive sensors face errors due to interconnection capacitance changes caused by environmental conditions like temperature and humidity, which cannot be accurately measured without disconnecting and reconnecting the sensor, leading to inaccurate readings.
Innovation Solution
A method involving a compensating interconnection that calculates a weight coefficient to subtract the compensating interconnection capacitance from the total sensor capacitance, effectively canceling out changes in relative permittivity-induced errors, thereby improving the accuracy of sensor readings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If shielding arrangements are used to minimize interconnection capacitance, then interconnection capacitance is reduced, but device complexity and manufacturing difficulty increase due to multiple conductor and dielectric layers
Solution Approach 1:
The invention extracts and separates the interconnection capacitance measurement from the sensor measurement by introducing a dedicated compensating interconnection. This allows the interconnection capacitance to be measured independently through the second input of the interface circuitry, then subtracted from the total sensor capacitance measurement to obtain the true sensor capacitance value, eliminating the need for complex shielding structures
Solution Approach 2:
The compensating interconnection acts as an intermediary element that mimics the electrical characteristics of the sensor interconnection without being connected to the sensor. It provides a reference measurement of the interconnection capacitance under the same environmental conditions, which is then used to compensate the sensor measurement through mathematical subtraction in the interface circuitry
2Measurement precision
If the sensor is disconnected to measure interconnection capacitance separately, then measurement accuracy improves, but time loss and operational complexity increase
Solution Approach 1:
The compensating interconnection is pre-configured parallel to the sensor interconnection before any measurements are taken. This allows the system to continuously measure both the sensor capacitance and the interconnection capacitance simultaneously through different inputs of the interface circuitry, eliminating the need for disconnection and reconnection operations
Solution Approach 2:
The measurement system is segmented into two independent measurement paths: one path measures the total sensor capacitance (sensor + interconnection) through the first input, while the other path measures only the interconnection capacitance through the second input. This segmentation allows both measurements to occur simultaneously without interfering with each other or requiring sensor disconnection
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 allows for accurate compensation of interconnection capacitance errors, resulting in improved sensing accuracy that is independent of environmental changes in relative permittivity.
Implementation Method 1
an interconnection from a circuitry performing analysis of capacitance values provided by the sensor circuitry often introduces an additional parallel capacitance
Implementation Method 2
This interconnection capacitance may cause significant error in the detected capacitance value... a change of the relative permittivity is indicated by a change of the dielectric constant
Data Source
AI summary
The present invention relates to a method for cancelling effects of changes in interconnection capacitances on capacitive sensor readings, and an apparatus configure to perform such method. The sensor readings are provided by a capacitive sensor connected with an interface circuitry. The interface circuitry has at least two interconnections comprising a sensor interconnection and a compensating interconnection. The method comprises obtaining a total sensor capacitance value from the capacitive sensor, and obtaining a total compensating interconnection capacitance value from the compensating interconnection, calculating a compensated sensor capacitance value by reducing the obtained total compensating interconnection capacitance value multiplied with a weight coefficient from the obtained total sensor capacitance value and providing at an output of the interface circuitry an electrical signal corresponding to the compensated sensor capacitance value. The weight coefficient is independent of changes of relative permittivity in the immediate environment of the capacitive sensor and its interconnections.