Thermal Fluid Sensor Failure Detection via Cooling Rate Analysis
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Solution Overview
Problem
Conventional thermal fluid sensors struggle to differentiate between changes in fluid flow and sensor output variations caused by foreign matter adhesion, leading to erroneous detections and limited application to clean air or inert gases.
Innovation Solution
A thermal fluid sensing apparatus with a fluid sensor that detects temperature distribution, a falling time counting unit, and a failure determining unit to differentiate between normal and faulty sensor outputs based on the falling time of the signal after heating cessation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a thermal fluid sensor is used to detect fluid flow, then the sensor can provide cost-effective detection, but the sensor output varies due to foreign matter adhesion causing erroneous detections
Solution Approach 1:
The patent applies preliminary action by performing a failure determination process before actual fluid flow measurement. The system pre-heats the heater unit, measures the cooling characteristic (falling time) of the detection unit, and determines whether foreign matter has adhered to the sensor surface. This preliminary check ensures that subsequent measurements are not affected by foreign matter contamination, thereby maintaining detection accuracy while keeping the sensor cost-effective.
2Adaptability or versatility
If the sensor operates in contact with various fluids, then the applicability is expanded, but foreign matter adhesion causes sensor output variation that cannot be differentiated from actual flow changes
Solution Approach 1:
The patent implements feedback by continuously monitoring the cooling characteristic of the detection unit and comparing it against reference values. The falling time counting unit measures how long it takes for the detection unit temperature to decrease after heater cessation, and the failure determining unit compares this measured falling time with a predetermined reference falling time. This feedback mechanism allows the system to automatically detect foreign matter adhesion and adjust or flag measurements accordingly, maintaining precision across diverse fluid applications.
Solution Approach 2:
The sensor performs self-diagnosis by using its own thermal characteristics to detect foreign matter contamination. The detection unit's cooling rate serves as an intrinsic indicator of sensor cleanliness, eliminating the need for external calibration or separate contamination sensors. This self-service approach enables the sensor to maintain measurement precision across various fluid types by autonomously identifying and compensating for foreign matter adhesion effects.
3Reliability
If conventional failure detection techniques are used, then membrane breakage can be detected, but adhesion of foreign matter causing sensor output variation is not detected
Solution Approach 1:
The patent changes the detection parameter from structural integrity (membrane breakage) to thermal characteristic (cooling rate). Instead of measuring whether the membrane is intact, the system measures the falling time of the detection unit temperature after heater cessation. Foreign matter adhesion alters the thermal mass and heat transfer characteristics, changing the cooling rate. This parameter change enables detection of foreign matter adhesion while maintaining the ability to detect membrane failures, thereby expanding detection coverage.
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
Enables accurate detection of failures due to foreign matter adhesion, expanding the sensor's applicability beyond clean air or inert gases and preventing erroneous detections, while maintaining cost-effectiveness.
Implementation Method 1
a fluid sensor configured to detect a temperature distribution on a detection surface caused by heating
Implementation Method 2
a falling time counting unit configured to count a falling time of the signal value after stopping the heating
Data Source
AI summary
A fluid sensing apparatus includes a fluid sensor configured to detect a temperature distribution on a detection surface caused by heating, and output a signal value corresponding to a flow of a fluid; a falling time counting unit configured to count a falling time of the signal value after stopping the heating; and a failure determining unit configured to perform failure determination based on the falling time.