Differential Pressure Sensor Pre-Compression Overpressure Protection
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Solution Overview
Problem
Differential pressure sensing systems face limitations in responding to and recovering from overpressure events, particularly for semiconductor-based sensors which are prone to damage and introduce systemic errors due to their brittle nature and the use of oil isolation techniques that introduce temperature and pressure hysteresis.
Innovation Solution
The differential pressure sensor is encapsulated within an independent volume of fill fluid, with a third fluid volume exerting compressive forces to maintain the sensor in a compressed state, reducing the risk of overpressure damage and incorporating temperature compensation to minimize errors from line pressure and temperature fluctuations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If semiconductor-based differential pressure sensors are used, then measurement precision is improved, but reliability deteriorates due to brittleness and sensitivity to tensile forces during overpressure events
Solution Approach 1:
The patent applies preliminary anti-action by pre-compressing the semiconductor differential pressure sensor with a bias spring and filling the chamber with a fluid at a pressure higher than atmospheric pressure. This creates a preliminary compressive stress state that counteracts the tensile forces generated during overpressure events, preventing sensor failure while maintaining measurement precision
Solution Approach 2:
The patent implements beforehand cushioning by enclosing the sensor in a fluid-filled chamber that acts as a cushioning medium. The fluid and bias spring absorb and distribute overpressure forces before they can directly impact the fragile semiconductor sensor, protecting it from damage while allowing continuous operation
2Reliability
If isolator diaphragms with fill fluid are used, then the differential pressure sensor is protected from harsh process fluids, but temperature and pressure hysteresis errors are introduced
Solution Approach 1:
The patent extracts the problematic oil isolation technique and replaces it with an alternative approach. Instead of using oil-filled isolators that cause hysteresis, the invention uses a different configuration with a fluid-filled chamber and bias spring that achieves sensor protection without introducing temperature and pressure hysteresis errors
Solution Approach 2:
The patent changes the physical parameters of the isolation system by using a fluid at controlled pressure and temperature, and by introducing a bias spring with specific mechanical properties. These parameter changes allow the system to maintain sensor protection while minimizing hysteresis effects through careful selection of fluid properties and spring characteristics
3Device complexity
If the movable diaphragm is allowed to freely engage the chamber wall during overpressure, then the sensor structure is simple, but plastic deformation occurs causing systemic errors
Solution Approach 1:
The patent applies preliminary anti-action by pre-compressing the sensor assembly with a bias spring, creating an initial compressive force that prevents the movable diaphragm from engaging the chamber wall during overpressure events. This maintains structural simplicity while preventing plastic deformation through the pre-applied counter-force
Solution Approach 2:
The patent implements beforehand cushioning by positioning the bias spring and fluid-filled chamber to cushion the sensor assembly before overpressure occurs. This cushioning system absorbs excess pressure forces, preventing diaphragm-to-wall contact and the resulting plastic deformation that would cause systemic measurement errors
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 solution enhances the robustness of differential pressure transmitters, allowing them to operate in demanding conditions and extend their lifespan by minimizing errors and maintaining the sensor in a compressive state, even during extreme pressure excursions.
Implementation Method 1
A third fluid volume surrounds the differential pressure sensor and exerts a compressive force on the sensor
Implementation Method 2
Pressure is transferred from the process fluid to the differential pressure sensor through a substantially incompressible fill fluid carried in a passageway
Implementation Method 3
The isolator diaphragms are positioned at the process fluid inlets and isolate the differential pressure sensor from the harsh process fluids being sensed
Data Source
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AI summary
A differential pressure transmitter (200; 300; 400; 500; 600; 700) includes first (210; 310) and second (212;312) process fluid inlets. A differential pressure sensor (214; 338; 518; 638) is disposed within the transmitter (200; 300; 400; 500; 600; 700) and has first and second sensor inlets. A first isolator diaphragm (230; 330) is located proximate the first process fluid inlet (210; 310) and is operably coupled to the first sensor inlet through a first fill fluid volume (334). A second isolator diaphragm (232; 332) is located proximate the second process fluid inlet (212;312) and is operably coupled to the second sensor inlet through a second fill fluid volume (336). Measurement circuitry (218) is operably coupled to the differential pressure sensor (214; 338; 518; 638) and configured to measure an electrical parameter of the sensor (214; 338; 518; 638) and provide an indication of the measured parameter. A third fluid volume (354) substantially surrounds the differential pressure sensor. The third fluid volume (354) exerts a compressive force on the differential pressure sensor (214; 338; 518; 638).