Fluid Sensor Fracture Detection Circuit
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Solution Overview
Problem
Existing fluid sensors, such as hot film air mass sensors, often crack or fracture at the transition between the sensor diaphragm and chip body due to thermal and mechanical stresses, leading to unreliable measurements and safety concerns in applications like fuel cells and hydrogen detection.
Innovation Solution
The implementation of printed conductors on the sensor diaphragm, specifically designed as fracture detection elements in a serpentine or meander pattern across the transition area, allows for reliable detection of cracks and fractures independent of the sensor's primary functionality, using a fracture detection circuit that compares resistance changes to a threshold value.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a thin sensor diaphragm is used to detect gas concentration, then measurement sensitivity is improved, but the sensor becomes more susceptible to cracking and fracturing at the transition to the chip body
Solution Approach 1:
The patent divides the sensor structure into distinct functional zones: a thin sensor diaphragm for measurement and a thicker chip body for structural support. The transition area is specifically designed with increased thickness to prevent cracks while maintaining the thin diaphragm's measurement sensitivity.
Solution Approach 2:
The patent applies different structural properties to different regions of the sensor chip. The sensor diaphragm area maintains thin thickness for sensitivity, while the transition area and chip body have increased thickness for mechanical strength. This local variation in structural quality resolves the contradiction between sensitivity and reliability.
2Adaptability or versatility
If thermal and mechanical stresses are present in the transition area, then the sensor can detect gas concentration changes, but cracks and fractures occur reducing sensor reliability
Solution Approach 1:
The patent designs the transition area with increased thickness and structural reinforcement before cracks can occur. This preventive design cushions against thermal and mechanical stresses that would otherwise cause fracturing, allowing the sensor to withstand operational stresses without failing.
Solution Approach 2:
The patent employs a composite structural design where the sensor chip integrates regions of different thickness and material properties. The transition area acts as a stress-absorbing composite structure that accommodates thermal and mechanical stresses while protecting the thin sensor diaphragm from cracking.
3Ease of operation
If fractures occur in the sensor diaphragm edge area, then complete sensor failure may occur, but the sensor continues to generate corrupted signals making error detection difficult
Solution Approach 1:
The patent incorporates a fracture detection device that continuously monitors the structural integrity of the sensor diaphragm. When a crack is detected, the system provides feedback to indicate sensor degradation, allowing for timely replacement before complete failure occurs. This feedback mechanism resolves the contradiction by maintaining signal generation while alerting operators to reliability issues.
Solution Approach 2:
The patent introduces a fracture detection device as an intermediary monitoring system that independently assesses sensor integrity. This mediator detects cracks before they cause complete sensor failure, providing early warning while the sensor continues to function, thus resolving the contradiction between continuous operation and signal accuracy.
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 enables efficient detection of cracks and fractures, preventing complete sensor failure and ensuring reliable operation even when cracks do not disrupt the primary measurement signals, thereby enhancing safety in critical applications.
Implementation Method 1
Typically, at least one heating resistor is situated on the sensor diaphragm
Implementation Method 2
the heating resistor being surrounded by one or more temperature measuring resistors (temperature sensors). The temperature distribution in an air stream passing across the diaphragm changes, which may in turn be detected by the temperature measuring resistors
Implementation Method 3
A sensing principle is based on the varying thermal capacity and/or thermal conductivity of the different fluid components... the detection of hydrogen in an air-hydrogen mixture makes use of the fact that hydrogen has a higher thermal conductivity than air
Data Source
AI summary
A fluid sensor may be used for detecting fluid media, in particular hydrogen. The fluid sensor includes a sensor chip having a chip surface, which has a measuring surface and a body surface. Printed conductors of a central sensor circuit having at least one heating element and at least one temperature sensor are provided on the measuring surface. Furthermore, the fluid sensor has one additional fracture detection element and one fracture detection circuit situated on the sensor chip. The fracture detection circuit is designed for detecting fractures and/or cracks in and/or on the sensor chip, in particular in the area of a boundary between the measuring surface and body surface.