Strain Gauge Sensor Accelerometer Leverage Design
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Solution Overview
Problem
Existing MEMS and NEMS accelerometers face challenges in achieving a high resonant frequency and sensitivity while maintaining a minimal size and cost, often requiring compromises that lead to increased mass and moment of inertia, which affects measurement accuracy and stability.
Innovation Solution
The design incorporates a single lever arm with a central point connection to the mass, allowing for improved force amplification and reduced moment of inertia, along with closely positioned strain gauges for differential measurements, which enhances sensitivity and resonant frequency without increasing the overall size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the mass and moment of inertia of the accelerometer are increased to improve sensitivity, then the sensitivity to acceleration is improved, but the resonant frequency decreases and the size increases
Solution Approach 1:
The device is segmented into distinct functional components: a seismic mass for sensing acceleration, a lever arm for mechanical amplification, and strain gauges for signal detection. This segmentation allows optimization of each component independently - the mass can be kept small while the lever arm provides the necessary amplification gain, thus maintaining high resonant frequency while achieving sufficient sensitivity.
Solution Approach 2:
The lever arm acts as an intermediary mechanical element between the seismic mass and the strain gauges. It provides mechanical amplification by transforming the small displacement of the mass into a larger displacement at the gauge location, enabling high sensitivity without increasing the mass or moment of inertia of the seismic element.
2Quantity of substance
If the mass is reduced to minimize size and cost, then the fabrication cost and size are reduced, but the sensitivity and measurement accuracy deteriorate
Solution Approach 1:
The system uses dynamic mechanical amplification through the lever arm mechanism. The lever arm rotates about a pivot connection, creating a mechanical advantage that amplifies the force from the small seismic mass. This dynamic amplification allows the use of a minimal mass while maintaining measurement accuracy, as the amplification factor can be adjusted by the lever arm geometry.
Solution Approach 2:
The invention changes the physical parameters of the system by introducing a lever arm with specific length ratios. The amplification factor is determined by the ratio of the lever arm length to the distance from the pivot to the mass center of gravity. By adjusting this geometric parameter, the system achieves high sensitivity with minimal mass.
3Adaptability or versatility
If strain gauges are positioned far apart to improve differential measurement, then the measurement range is improved, but the technological variations between gauges increase and accuracy decreases
Solution Approach 1:
The invention merges the functions of differential measurement into a compact configuration by positioning both strain gauges on the same lever arm near the pivot connection. This merging of gauge positions minimizes the distance between them, reducing technological variations and fabrication tolerances effects, while still enabling differential measurement through their opposite orientations on the lever arm.
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 configuration enables a better compromise between mass, sensitivity, and resonant frequency, reducing measurement errors and temperature drift, while maintaining a compact size and low cost, and improving the accuracy of differential measurements.
Implementation Method 1
at least one piezoresistive gauge, said gauge or gauges has/have a smaller thickness than the seismic mass
Implementation Method 2
The lever arm enables transmission of force from the mass to the gauge whilst, in order to increase sensitivity, adding a gain between the force harvested by the mass and the force applied to the gauge
Implementation Method 3
The accelerometer includes a seismic mass adapted to move along the acceleration axis. It is suspended by at least one beam. The beam forms a pivot connection, the pivot axis being orthogonal to the plane of the device
Data Source
AI summary
An MEMS or NEMS accelerometer adapted to measure an acceleration along a sensing axis includes a substrate featuring a plane; a mass having a central zone and suspended relative to the substrate; a single lever arm comprising: a first end connected to the substrate by means of a first connection adapted to allow rotation of the lever arm about a rotation axis perpendicular to the sensing axis, and a second end connected to the mass by means of a second connection adapted to transmit movement in translation of the mass to the lever arm whilst allowing rotation of the lever arm about the rotation axis; the second end of the lever arm being disposed at the level of the central zone of the mass; at least one strain gauge comprising: a first end connected to the substrate, and a second end connected to the lever arm.