Humidity Sensor Shielding in Physical-Quantity Detection Devices
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Solution Overview
Problem
The integration of humidity and pressure sensors on a semiconductor substrate in existing air flow rate sensors makes them susceptible to water droplet and dust adherence, leading to inaccurate measurements and variations in characteristics.
Innovation Solution
The design of a physical-quantity detection device with separate sub-passages for each sensor element, where the humidity sensor is shielded by pressure sensors, reducing the likelihood of water droplet and dust adherence and maintaining high measurement accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If humidity sensor and pressure sensor are integrally formed on semiconductor substrate, then device integration is improved, but water droplet and dust adherence to sensors increases
Solution Approach 1:
The patent divides the sensor housing into separate measurement chambers - a first measurement chamber for the humidity sensor and a second measurement chamber for the pressure sensor. This segmentation physically separates the sensors into different spatial zones, preventing water droplets and dust from simultaneously accessing both sensors while maintaining integrated functionality on the semiconductor substrate.
Solution Approach 2:
The patent introduces a flow rate sensor element as an intermediary component positioned in the air flow path between the air intake and the measurement chambers. This element acts as a protective barrier that disrupts direct water droplet and dust access to the humidity and pressure sensors while allowing air flow measurement to continue.
2Measurement precision
If sensors are exposed to air flow for measurement, then detection capability is improved, but contaminant adherence to sensors increases
Solution Approach 1:
The patent segments the air flow measurement function from the physical sensor exposure by creating separate measurement chambers. The humidity sensor and pressure sensor are housed in isolated chambers that are indirectly exposed to air flow through controlled openings, rather than being directly in the main air stream. This allows detection capability while reducing contaminant adherence.
Solution Approach 2:
The flow rate sensor element serves as an intermediary that mediates between the air flow and the sensors. It is positioned to intercept water droplets and dust particles in the air flow path, preventing them from reaching the measurement chambers containing the humidity and pressure sensors, while still enabling accurate detection of air flow characteristics.
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 configuration effectively reduces water and dust adherence to the humidity sensor, enhancing detection accuracy and stability, while minimizing the impact of contaminants on measurement results.
Implementation Method 1
a flow rate sensor element that measures an air flow rate
Implementation Method 2
a humidity sensor element that measures humidity
Implementation Method 3
a pressure sensor element that measures air pressure
Data Source
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AI summary
In order to improve sensor characteristics and minimize variation in said characteristics, a pressure sensor is positioned upstream of a humidity sensor so as to help prevent water from contacting the humidity sensor and dust from adhering to the humidity sensor. This physical-quantity detection device 300 is characterized by having a detection unit 422 that detects humidity, a detection unit 421 that detects pressure, a circuit board 400 that has an electronic circuit that processes detection signals, and a housing 302 that accommodates the circuit board 400. The physical-quantity detection device 300 is also characterized in that the detection units 422, 421 are laid out on the surface of the circuit board 400 in a straight line in the direction in which a gas being measured flows, with the detection unit 421 that detects pressure positioned upstream of the detection unit 422 that detects humidity.