MEMS Sensor Calibration via Electrostatic Stimulus
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Solution Overview
Problem
Conventional methods for calibrating and compensating MEMS sensors require expensive and time-consuming mechanical testing, which can be damaging and do not account for changes in sensor characteristics over time, necessitating multiple test stations and initial calibration values that become outdated.
Innovation Solution
A system and methodology for calibrating and compensating MEMS sensors using electrostatic stimuli, enabling concurrent calibration of multiple axes without physical mechanical stress, allowing for real-time or offline testing and recalibration without removing the sensors from their application.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If mechanical testing is used to calibrate MEMS sensors, then calibration data can be obtained, but the process becomes expensive, time-consuming, and potentially damaging to the system
Solution Approach 1:
The patent replaces mechanical testing with electrical testing by applying electrostatic forces to the proof masses through actuator electrodes. This substitution eliminates the need for physical mechanical test equipment, reducing both time and cost while avoiding potential damage to the sensor during calibration.
Solution Approach 2:
The patent creates an electrical model that replicates the mechanical stimulus-response relationship. By applying known electrostatic forces and measuring the resulting proof mass displacement through capacitance changes, the system generates calibration data without requiring actual mechanical stimuli, effectively copying the calibration process in the electrical domain.
2Measurement precision
If mechanical testing is used for calibration, then trim values can be determined, but numerous test stations must be designed and built for each application
Solution Approach 1:
The patent implements a universal electrical calibration method that can be applied to any MEMS sensor with electrostatic actuators through software control. The same calibration circuitry and methodology work across different sensor types and applications, eliminating the need to design and build separate mechanical test stations for each application.
Solution Approach 2:
By replacing mechanical test stations with an electrical calibration system controlled by a processor, the patent eliminates the need for complex physical test equipment. The calibration is performed through electrical signals and digital processing, significantly reducing device complexity.
3Measurement precision
If initial calibration is performed mechanically, then trim values are obtained, but the calibration becomes outdated over time as sensor characteristics change
Solution Approach 1:
The patent enables the MEMS sensor to perform its own calibration through electrical testing. The sensor can self-diagnose and self-calibrate by applying electrostatic forces to its proof masses and measuring the response, allowing for periodic recalibration throughout its operational life to maintain accuracy as characteristics change.
Solution Approach 2:
The patent transforms calibration from a static, one-time mechanical process to a dynamic, repeatable electrical process. The electrical calibration method can be performed multiple times throughout the sensor's lifetime, allowing the trim values to be updated as needed to maintain calibration accuracy despite changes in sensor characteristics over time.
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 reduces the cost and duration of calibration, enables efficient recalibration throughout the sensor's life, and allows for calibration without physical mechanical stimuli, ensuring accurate and adaptive sensor performance.
Implementation Method 1
A control circuit is electrically coupled to the MEMS sensor. When the switch system enables the test mode, the control circuit is configured to provide a first stimulus signal to the first movable element and a second stimulus signal to the second movable element
Implementation Method 2
A first sense contact is configured to provide a first output signal corresponding to physical displacement of the first movable element and a second sense contact is configured to provide a second output signal corresponding to the physical displacement of the second movable element
Data Source
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AI summary
A system includes a MEMS sensor having dual proof masses capable of moving independently from one another in response to forces imposed upon the proof masses. Each proof mass includes an independent set of sense contacts configured to provide output signals corresponding to the physical displacement of the corresponding sense mass. A switch system is in communication with the sense contacts. The switch system is configured to enable a sense mode and various test modes for the MEMS sensor. When the switch system enables a sense mode, output signals from the sense contacts can be combined to produce sense signals. When the switch system enables a test mode, the second contacts are electrically decoupled from one another to disassociate the output signals from one another. The independent sense contacts and switch system enable the concurrent compensation and calibration of the proof masses along two different sense axes.