Capacitive Pressure Sensors With Shields for Drift Compensation
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Solution Overview
Problem
Conventional pressure sensors experience unpredictable and device-specific drift due to contamination, leading to measurement errors that require replacement, as the drift cannot be reliably predicted at the time of manufacturing.
Innovation Solution
The pressure sensors incorporate a contamination shield to reduce contamination on the diaphragm, measure and predict drift rates, and compensate for temperature-induced errors by using temperature sensors and measurement circuitry to adjust pressure measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional pressure sensors are used without drift compensation, then the device complexity is low, but the measurement precision deteriorates over time due to contamination-induced drift
Solution Approach 1:
The contamination shield is pre-installed in the pressure sensor to prevent contamination before it can affect the diaphragm. This preliminary protective action maintains measurement precision over time without requiring complex post-contamination compensation mechanisms, thus resolving the contradiction between measurement precision and device complexity
Solution Approach 2:
The contamination shield acts as an intermediary component between the contaminant source and the diaphragm. It physically intercepts contaminants and prevents them from reaching the sensitive measurement elements, thereby maintaining measurement accuracy while adding only moderate structural complexity
2Measurement precision
If drift compensation mechanisms are added to pressure sensors, then measurement precision is improved, but the device complexity increases
Solution Approach 1:
The harmful drift effect is extracted and isolated from the main measurement system by using a separate contamination shield component. This allows the core pressure sensing mechanism to remain relatively simple while the shield handles the contamination issue independently, resolving the contradiction between precision improvement and complexity increase
3Reliability
If contamination shield is added to reduce drift, then reliability is improved, but device complexity increases
Solution Approach 1:
The contamination shield provides beforehand cushioning protection to the diaphragm by intercepting contaminants before they can cause damage or drift. This prior protective measure enhances sensor reliability and longevity while adding a single structural component, effectively resolving the contradiction between reliability improvement and device complexity
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 measurement errors over time by minimizing contamination and accurately predicting and compensating for drift, thereby extending the sensor's longevity and reliability.
Implementation Method 1
an electrode separated from the diaphragm by a gap to form a capacitance between the electrode and the diaphragm; measurement circuitry configured to determine a pressure in the measured pressure cavity based on the capacitance
Implementation Method 2
measure and predict drift rates, and compensate for temperature-induced errors by using temperature sensors and measurement circuitry to adjust pressure measurements
Data Source
AI summary
Disclosed example pressure sensors include: a first body defining a reference pressure cavity; a second body defining a measured pressure cavity and having an inlet configured to receive a fluid; a diaphragm between the reference pressure cavity and the measured pressure cavity; an electrode separated from the diaphragm by a gap to form a capacitance between the electrode and the diaphragm; measurement circuitry configured to determine a pressure in the measured pressure cavity based on the capacitance; and a contamination shield configured to reduce contamination on a first face of the diaphragm, the contamination shield including: a first portion configured to obstruct a direct path between the inlet and the diaphragm; and a second portion configured to occupy volume within the measured pressure cavity.