Capacitance Pressure Sensor Fault Detection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Pressure sensors used in process monitoring systems face inaccuracies and faults due to electrode damage, non-linearity, and changes in dielectric constants, which are difficult to detect and compensate for, leading to potential failures in pressure measurements.
Innovation Solution
A diagnostic system that utilizes changes in capacitance transfer functions between main and ring electrodes to detect faults and impending failures, with a microcomputer system monitoring the transfer function H, which remains constant unless a fault occurs, allowing for real-time diagnostic outputs and alerts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a deflectable diaphragm with capacitance measurement is used to measure pressure, then pressure measurement capability is provided, but measurement inaccuracies occur due to electrode damage, non-linearity, and changes in dielectric constants
Solution Approach 1:
The patent divides the capacitance measurement system into multiple independent capacitance measurements (first capacitance with first electrode, second capacitance with second electrode, third capacitance with third electrode, fourth capacitance with fourth electrode). By segmenting the measurement into multiple independent capacitance channels, the system can detect faults in individual electrodes while maintaining overall measurement capability through the remaining healthy electrodes.
Solution Approach 2:
The patent implements a diagnostic system that continuously monitors capacitance measurements and compares them against expected values to detect faults. The system provides feedback about the health status of electrodes and dielectric materials, enabling early detection of degradation trends and potential failures before they affect measurement accuracy.
2Measurement precision
If additional electrodes are added to reduce measurement inaccuracies, then measurement accuracy improves, but device complexity increases
Solution Approach 1:
The patent designs the capacitance measurement system so that the same set of electrodes and capacitance measurements serve dual purposes: (1) measuring pressure through capacitance changes, and (2) diagnosing faults by monitoring changes in capacitance values over time. This multi-functionality eliminates the need for separate diagnostic hardware, reducing overall device complexity while maintaining improved measurement accuracy.
Solution Approach 2:
The patent uses changes in capacitance values as diagnostic parameters to detect faults. By monitoring how capacitance values change over time and comparing them against baseline values, the system can detect electrode damage, non-linearity, and dielectric material degradation without adding separate sensing elements or complex diagnostic hardware.
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 system effectively detects single and simultaneous faults, reducing measurement inaccuracies and enabling early detection of potential failures, thereby maintaining the accuracy and reliability of pressure sensor readings.
Implementation Method 1
A capacitance is measured with respects to the diaphragm, with the diaphragm forming one of the capacitive plates of the capacitor. As the diaphragm is deflected due to applied pressure, the measured capacitance changes.
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A diagnostic system for a pressure sensor (56) having a cavity (132, 134) configured to receive on applied pressure is provided. The cavity (132, 134) has a first and a second wall. A deflectable diaphragm (106) is positioned in the cavity and configured to form a first and a second capacitance with the first wall and a third and a fourth capacitance with the second wall which change in response to the applied pressure. The capacitances form a first transfer function and a second transfer function. Changes in the first transfer function relative to the second transfer function are detected to provide a diagnostic output.