Dual Diaphragm Pressure Sensor with Foreign Matter Offset Cancellation
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Solution Overview
Problem
Conventional pressure sensors face accuracy deterioration due to foreign matter adhering to the diaphragm, which restricts deformation and affects pressure detection accuracy.
Innovation Solution
A pressure sensor design featuring two diaphragms with separate reference pressure chambers and a calculator to calculate an offset value from differential signals, allowing for cancellation of foreign matter influence and maintaining detection accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single diaphragm is used for pressure detection, then the device structure is simple, but detection accuracy deteriorates when foreign matter adheres to the diaphragm
Solution Approach 1:
The single diaphragm is divided into two separate diaphragms: a first diaphragm for pressure detection and a second diaphragm as a reference. This segmentation allows the system to distinguish between actual pressure changes and effects caused by foreign matter adhesion, thereby maintaining detection accuracy while managing structural complexity.
Solution Approach 2:
The system changes the operational parameters by introducing a reference diaphragm that experiences the same foreign matter effects but no actual pressure changes. By comparing the electrical parameters (resistance changes) between the two diaphragms, the system can isolate and eliminate the foreign matter influence from the measurement.
2Reliability
If a cap is disposed on the substrate to seal gauge resistors, then the gauge resistors are protected, but foreign matter can still adhere to the exposed diaphragm portion
Solution Approach 1:
The diaphragm structure is segmented into two separate diaphragms with different exposure conditions. The first diaphragm remains exposed for pressure sensing while the second diaphragm can be positioned or designed to minimize foreign matter adhesion, allowing the system to differentiate between actual pressure effects and foreign matter effects.
Solution Approach 2:
The second diaphragm acts as an intermediary reference element that experiences the same foreign matter environment as the first diaphragm but is not subjected to the measurement pressure. This intermediary allows the system to measure and compensate for foreign matter effects separately from actual pressure effects.
3Stability of the object's composition
If foreign matter adheres to the diaphragm, then the diaphragm deformation is restrained, but this leads to inaccurate pressure detection
Solution Approach 1:
The system uses the second diaphragm as a feedback reference to continuously monitor and compensate for foreign matter adhesion effects. By comparing the output signals from both diaphragms, the system can calculate the foreign matter influence and subtract it from the first diaphragm's signal, thereby maintaining accurate pressure detection despite foreign matter presence.
Solution Approach 2:
The system changes from a single-parameter measurement (one diaphragm) to a differential parameter measurement (two diaphragms). This allows the system to separate the pressure-induced deformation parameter from the foreign matter-induced deformation parameter, enabling accurate pressure measurement even when foreign matter is present.
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 effectively cancels the impact of foreign matter on pressure detection, ensuring accurate measurement by calculating differential values between detection and offset signals, thereby maintaining detection accuracy even with adhered foreign matter.
Implementation Method 1
the diaphragm is deformed in accordance with differential pressure between pressure of the measurement medium and pressure in the reference pressure chamber
Implementation Method 2
The gauge resistors provided on the diaphragm are deformed to cause variation in output voltage of the bridge circuit
Data Source
AI summary
A pressure sensor includes: a first substrate having first and second diaphragms on one surface provided by first and second recesses on another surface; first and second detecting elements on the first and second diaphragms; a second substrate providing a first reference pressure chamber with the one surface of the first substrate; a third substrate providing a second reference pressure chamber sealing the second recess; and a calculator calculating an offset value by a difference between a reference signal and an inspection signal and detecting a pressure of a measurement medium by a difference between a detection signal and the offset value. The first detecting element outputs the detection signal or the inspection signal according to a pressure difference between a first reference pressure or a reference medium pressure and a measurement medium pressure in the first recess. The second detecting element outputs the reference signal according to a difference between the first reference pressure and and a second reference pressure.