Combination Absolute and Differential Pressure Transducer
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Solution Overview
Problem
Pressure-based mass flow controllers and meters face accuracy degradation at high outlet pressures due to mismatched absolute pressure transducers and increased sensitivity to outlet pressure changes, leading to reduced performance and increased costs.
Innovation Solution
A combination absolute and differential pressure transducer is used, which includes flexible corrugated metal diaphragms and micro-machined silicon elements, along with a circuit board for data storage and signal amplification, to reduce sensitivity to transducer mismatches and outlet pressure variations, while minimizing size and cost.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If separate absolute pressure transducers are used to measure upstream and downstream pressures, then the mass flow rate can be calculated, but accuracy degrades at high outlet pressures due to transducer mismatch
Solution Approach 1:
The patent combines two absolute pressure transducers into a single integrated differential pressure transducer that directly measures the pressure difference between upstream and downstream sides. This merging eliminates the mismatch errors that occur when using separate transducers, as the differential transducer measures only the pressure difference internally without being affected by absolute pressure variations or transducer calibration differences.
Solution Approach 2:
The invention extracts the differential pressure measurement function from the two separate absolute pressure transducers and implements it through a dedicated differential pressure sensing mechanism. This allows the system to directly obtain the pressure difference value without calculating it from two separate absolute pressure readings, thereby eliminating the source of measurement error.
2Measurement precision
If separate absolute pressure transducers are used, then pressure measurements can be obtained, but the system becomes more sensitive to outlet pressure changes
Solution Approach 1:
By merging the pressure measurement functions into a single differential pressure transducer, the system directly measures only the pressure difference across the flow restriction. This eliminates the harmful effect of sensitivity to outlet pressure variations, as the differential transducer is designed to be insensitive to common-mode pressure changes affecting both measurement points.
3Measurement precision
If separate absolute pressure transducers are used, then pressure data can be collected, but device complexity and cost increase
Solution Approach 1:
The patent merges two separate absolute pressure transducer components into a single differential pressure transducer unit. This reduction in component count simplifies the device structure, reduces assembly complexity, and lowers overall cost while maintaining the necessary pressure measurement functionality.
Solution Approach 2:
The differential pressure transducer performs the multi-function of measuring both upstream and downstream pressure conditions through a single device that directly outputs the pressure difference. This universal measurement capability eliminates the need for separate transducers and associated signal processing for each pressure point.
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 solution improves accuracy and reduces cost by minimizing the impact of transducer mismatches and outlet pressure changes, enhancing performance across a wide range of pressures without the need for frequent recalibration.
Implementation Method 1
flexible corrugated metal diaphragms
Implementation Method 2
micro-machined silicon elements using silicon strain gauges
Implementation Method 3
the first and second cavities are filled with a silicone-based oil
Data Source
AI summary
The disclosed embodiments include a combination absolute pressure and differential pressure transducer that includes at least a first cavity and a second cavity, at least a first pressure port and a second pressure port, a first isolation membrane exposing the first cavity to a first fluid pressure applied to the first pressure port, a second isolation membrane exposing the second cavity to a second fluid pressure applied to the second pressure port, at least one absolute pressure sense element exposed to absolute pressure in one of the first cavity and the second cavity, and at least one differential pressure sense element exposed to differential pressure between two of the first cavity and the second cavity.