Capacitance Motion Sensor Charge Pulse Control
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Solution Overview
Problem
Differential capacitance motion sensors face challenges in achieving linear output signals due to nonlinear electrostatic forcing functions, which require complex techniques and components like sample and hold circuits and comparator error amplifiers, leading to wear and tear over time.
Innovation Solution
A system and method utilizing control voltage and charging sequences with opposite polarity pulses applied during the same charge cycle time period to generate error signals directly, eliminating the need for sample and hold circuits and reducing charge leakage errors, thereby mitigating nonlinearities and parametric errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional electrostatic forcing with sample and hold circuits is used, then the sensor can measure charge on electrode structures, but the sensor experiences wear and tear over time due to prolonged charge application
Solution Approach 1:
The patent applies periodic charge pulses to the electrode structures instead of continuous charging. The switching circuit alternates between connecting the first electrode structure and the second electrode structure to charge sources during different time intervals within a charge cycle, enabling measurement without prolonged charge application that causes wear.
Solution Approach 2:
The patent applies charge pulses to the electrode structures before measurement occurs. By pre-charging the capacitive structures with controlled pulses and then quickly switching to measurement mode, the system obtains accurate charge measurements without requiring the structures to remain charged for extended periods, thereby reducing wear.
2Measurement precision
If opposite polarity charge pulses are applied during the same charge cycle, then charge leakage errors are reduced and error signals can be measured directly, but the switching circuit complexity increases
Solution Approach 1:
The patent divides the charge cycle into distinct time intervals where different electrode structures are charged with opposite polarity pulses. The switching circuit segments the charging process by selectively connecting either the first or second electrode structure to appropriate charge sources during specific time intervals, enabling direct error signal measurement while managing complexity through temporal segmentation.
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 enables precise detection of motion signals with reduced sensitivity to charge leakage, allowing for direct measurement of error signals and maintaining the sensor's moving element at a null position, thus improving the sensor's operational stability and accuracy over time.
Implementation Method 1
A capacitance sensor having an inertial proof mass disposed between a first electrode structure and a second electrode structure. A switching system is switchable between providing one of a positive charge pulse and a negative charge pulse to one of the first electrode structure and the second electrode structure.
Implementation Method 2
A capacitance sensor having an inertial proof mass disposed between a first electrode structure and a second electrode structure
Data Source
AI summary
A system includes a capacitance sensor having an inertial proof mass disposed between a first electrode structure and a second electrode structure. A switching system is switchable between providing one of a positive charge pulse and a negative charge pulse to one of the first electrode structure and the second electrode structure. A controller controls the switching of the switching circuit to provide one of the positive charge pulse or the negative charge pulse to the first electrode structure during a first portion of a charge cycle time period and to provide an opposite polarity charge pulse from that provided to the first electrode structure to the second electrode structure during a second portion of the charge cycle time period to generate an error signal with respect to the inertial proof mass of the capacitance sensor.