Piezoelectric Shear Sensor Discharge Guard for Noise Reduction
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Solution Overview
Problem
Shear mode accelerometer devices experience significant spontaneous discharge noise due to pyroelectric charge build-up on lateral edges of piezoelectric sensor elements during temperature changes, particularly in high-temperature applications, which is not effectively addressed by existing technologies.
Innovation Solution
A piezoelectric shear mode sensor element with a discharge guard made of an electrically conductive material is introduced, which alters and rearranges pyroelectric displacement charges on lateral side faces to counteract the pyroelectric effect, reducing noise from random discharge processes and leak currents. The discharge guard is designed to operate independently of sensor electrodes and can be connected to a charge reservoir or common ground.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If shear mode configuration is used to avoid pyroelectric artefact signals, then measurement precision is improved, but spontaneous discharge noise occurs due to charge build-up on lateral edges
Solution Approach 1:
A discharge guard electrode is introduced as an intermediary element between the pyroelectric charge build-up on lateral edges and the sensor electrodes. This guard electrode collects and redistributes the pyroelectric charges, preventing spontaneous discharge and the associated noise while maintaining the shear mode measurement capability
Solution Approach 2:
The harmful pyroelectric charge build-up on lateral edges is extracted and isolated from the main sensor signal path by providing a dedicated discharge guard electrode. This separates the harmful charge accumulation from the measurement function, allowing the sensor to maintain precision without noise
2Measurement precision
If sensor electrodes are arranged perpendicular to polarization axis for shear mode measurement, then pyroelectric artefact is eliminated, but charge build-up on lateral faces causes discharge noise
Solution Approach 1:
The discharge guard electrode acts as a mediator that handles the pyroelectric charge separation on lateral faces, preventing these charges from causing discharge noise while allowing the main sensor electrodes to accurately measure the piezoelectric response
Solution Approach 2:
The electrode system is segmented into separate functional components: sensor electrodes for measurement and discharge guard electrodes for charge management. This segmentation allows independent optimization of measurement precision and signal stability
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
The implementation of the discharge guard significantly reduces spontaneous discharge noise and improves the noise characteristics of shear mode sensor devices, achieving a substantial decrease in discharge pulses and leak currents, even under rapid temperature changes, thereby enhancing the accuracy of measurements in high-temperature environments.
Implementation Method 1
A displacement of the seismic mass with respect to the base results in a deformation of the piezoelectric material, which will generate a piezoelectric response
Implementation Method 2
Many of the piezoelectric materials of commercial interest for accelerometer applications also exhibit pyroelectric properties, where charges build up due to a charge separation in the material when subjected to temperature changes
Data Source
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AI summary
A piezoelectric shear mode sensor element comprises a sensor block made of a piezoelectric material having an intrinsic polarization axis, wherein the piezoelectric material is also pyroelectric. The sensor block has in an axial direction axial ends and in lateral directions perpendicular to the axial direction lateral side faces. The sensor electrodes are adapted for capturing a shear mode sensor signal. The sensor element further comprises a discharge guard adapted to locally alter and/or rearrange charges so as to counteract pyroelectric displacement charges on the lateral side faces of the sensor block.