Differential Pressure Sensor Common Mode Error Compensation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Differential pressure sensors face challenges in accurately measuring pressure differences at high pressures due to common mode errors caused by thermal expansion and material strain, leading to inaccurate readings, especially in harsh media environments.
Innovation Solution
The implementation of a differential pressure sensor design that includes two pressure sensing die assemblies, one to measure differential pressure and another to measure common mode error, with each die having a diaphragm and pressure-sensitive electrical elements, connected in a bridge circuit configuration to correct for common mode errors, ensuring accurate pressure readings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single pressure sensing die is used to measure differential pressure, then the device structure is simple, but common mode errors occur at high pressures leading to inaccurate readings
Solution Approach 1:
The pressure sensing function is segmented into two separate die: a first pressure sensing die for measuring differential pressure and a second pressure sensing die for measuring common mode pressure. This segmentation allows each die to specialize in specific measurement functions, improving overall measurement accuracy by isolating common mode errors from differential pressure measurements.
Solution Approach 2:
The second pressure sensing die acts as an intermediary that measures common mode pressure effects (thermal expansion, material strain) which then can be compensated for in the differential pressure measurement. This intermediary die captures the error signals that affect the primary measurement die, enabling error correction.
2Ease of manufacture
If pressure sensing die is directly attached to base plate, then manufacturing is simple, but thermal expansion and material strain cause common mode errors
Solution Approach 1:
A support structure serves as an intermediary component between the pressure sensing die and the base plate. This support structure isolates the die from direct attachment to the base plate, preventing thermal expansion and material strain from the base plate from being transmitted to the die, thereby eliminating common mode errors while maintaining manufacturing simplicity.
Solution Approach 2:
The support structure provides localized thermal isolation specifically at the die attachment point, while the rest of the system maintains its original construction. This localized intervention addresses the thermal expansion issue without requiring complete redesign of the entire assembly, preserving ease of manufacture.
3Device complexity
If electrical components are exposed to harsh media, then device structure is simple, but corrosion occurs damaging the components
Solution Approach 1:
A flexible diaphragm serves as a protective barrier that isolates the electrical components from harsh media while allowing pressure transmission. The diaphragm is positioned between the media and the electrical components, preventing direct contact and corrosion, while still enabling the pressure sensing function to operate reliably.
Solution Approach 2:
The flexible diaphragm acts as an intermediary that transmits pressure information from the harsh media environment to the protected electrical components without allowing direct contact. This intermediary layer preserves component durability while maintaining the sensing function.
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 effectively reduces common mode errors, providing accurate differential pressure measurements even at high pressures, such as 1000 psi, by isolating the sensors from strain-related errors and using a non-corrosive oil fill to protect electrical components.
Implementation Method 1
The resistive elements exhibit resistance that is proportional to the strain placed on the thinned semiconductor material forming the diaphragm
Implementation Method 2
Resistive elements are formed on the surface of the diaphragm 103. The resistive elements exhibit resistance that is proportional to the strain placed on the thinned semiconductor material
Implementation Method 3
Support structure 207 may be formed from glass or similar material which has a coefficient of thermal expansion closer to that of the silicon pressure sensing die 100 as compared to the coefficient of thermal expansion of the stainless steel making up the base plate 201. This matching of the coefficients of thermal expansion prevents exertion of forces on the die 100 not related to pressure, but rather, caused by the strain related to the dissimilar rates of expansion between the die 100 and the base plate 201.
Data Source
Figure 1~2
Figure 3A
Figure 3B~3C
AI summary
A differential pressure sensor may provide a common mode corrected differential pressure reading. The differential pressure sensor may include two pressure sensing diaphragms. The pressure sensor may be configured so that the first diaphragm measures the differential pressure between two sections of a fluid. The pressure sensor may also be configured so that the second diaphragm measures the common mode error experienced by the die at the time the differential pressure is read by the first diaphragm. Electrical connectors may be configured so that the differential pressure outputs a common mode error corrected differential pressure reading based on the readings of the first and second diaphragm.