Capacitive Sensor Circuit Parasitic Capacitance Suppression
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Solution Overview
Problem
Capacitive sensors face accuracy reduction due to parasitic capacitances, which often require additional measurements, increasing power consumption and reducing processing speed.
Innovation Solution
The common electrode is driven to the same voltage as the sense electrode, suppressing parasitic capacitance influence by using a buffer element to maintain constant charge on the capacitive element during measurement, thereby reducing the impact of parasitic capacitances on signal reading.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If additional measurements are introduced to reduce parasitic capacitance influence, then measurement accuracy is improved, but processing speed is reduced and power consumption increases
Solution Approach 1:
The common electrode is driven to the same voltage as the sense electrode, creating an equipotential condition that eliminates potential differences across parasitic capacitances. This prevents charge redistribution on parasitic capacitances during measurement, thereby eliminating their influence on measurement accuracy without requiring additional measurements or slowing down processing.
Solution Approach 2:
The voltage of the common electrode is dynamically changed to match the sense electrode voltage during the measurement process. This parameter change ensures that parasitic capacitances remain charged but do not redistribute charge, allowing accurate measurement without additional processing steps.
2Measurement precision
If additional measurements are introduced to reduce parasitic capacitance influence, then measurement accuracy is improved, but power consumption increases
Solution Approach 1:
By maintaining the common electrode at the same voltage as the sense electrode, the patent eliminates the need for additional compensation measurements. This single-measurement approach reduces power consumption while maintaining high measurement accuracy.
Solution Approach 2:
The patent extracts and eliminates the harmful effect of parasitic capacitances by driving the common electrode to the sense electrode voltage, thereby removing the need for additional measurement cycles that would consume extra power.
3Measurement precision
If the common electrode is actually shorted to the sense electrode, then parasitic capacitance influence is reduced, but charge from the second parasitic capacitance transfers to the sense electrode causing measurement error
Solution Approach 1:
Instead of directly shorting the common electrode to the sense electrode, the patent uses a buffer element as an intermediary. The buffer element drives the common electrode to the same voltage as the sense electrode without creating a direct conductive path, thereby preventing charge transfer from the second parasitic capacitance while still eliminating the influence of parasitic capacitances on the measurement.
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 more accurate measurement of physical or chemical quantities by minimizing the influence of parasitic capacitances, enhancing processing speed and reducing power consumption.
Implementation Method 1
parasitic capacitances may affect or reduce an accuracy of the measurement
Implementation Method 2
the capacitive element having a capacity depending on the physical or chemical quantity to be measured
Data Source
AI summary
A sensor circuit for measuring a physical or chemical quantity comprises a capacitive sensor. A sense and a base electrode of the sensor form a capacitive element with a capacity depending on the quantity. A common electrode of the sensor forms a first and a second parasitic capacitance together with the sense and the base electrode, respectively. The sensor circuit is adapted to store a charge on the capacitive element and to read out the stored charge via the sense electrode. A buffer element is connected between the sense electrode and the common electrode and adapted to drive the common electrode at a voltage applied to the sense electrode.