Fast Humidity Sensor Calibration Using Low Thermal Mass Structure
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Capacitive humidity sensors face challenges in achieving accurate zero point humidity calibration due to slow response times, leading to inaccuracies in dry capacitance measurements and temperature dependence changes over time.
Innovation Solution
A humidity sensor structure with a low thermal mass active sensing area and separate heating resistor allows for fast thermal response, enabling precise dry capacitance measurement and autocalibration, eliminating the need for separate temperature measurement elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If heatable elements like resistors are used for calibration, then zero point humidity measurement value can be obtained, but the response time is too slow to achieve real zero point humidity calibration
Solution Approach 1:
The sensor structure is segmented into a separate active sensing area with low thermal mass and a larger sensor frame, allowing the sensing region to respond quickly to temperature changes during calibration while the frame provides structural support and housing for electronics
Solution Approach 2:
The patent changes the thermal parameters of the sensing area by reducing its thermal mass through miniaturization and using materials with appropriate thermal properties, enabling the sensing region to reach thermal equilibrium rapidly during calibration cycles
2Measurement precision
If separate temperature measurement elements are added for accurate temperature measurement during heating, then temperature measurement accuracy is improved, but device complexity increases
Solution Approach 1:
The sensor structure is designed to perform multiple functions: the active sensing area serves both as the humidity sensing element and as the temperature measurement region during calibration, while the heating resistor provides both calibration heating and temperature control, eliminating the need for separate dedicated components
Solution Approach 2:
The patent merges the temperature measurement function into the existing sensor structure by utilizing the thermal response of the active sensing area itself, combining what would traditionally be separate functions (temperature sensing and humidity sensing) into an integrated system
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 fast and accurate dry capacitance measurement, reducing response times by 20 times compared to humidity response times, allowing for precise calibration and drift compensation.
Implementation Method 1
a humidity sensor structure (22) with a low thermal mass active sensing area and separate heating resistor
Implementation Method 2
an active sensor (22) including a humidity measurement capacitor (9)
Implementation Method 3
The capacitor 9, temperature measurement 8 and heating elements 7 are placed so that they can considered to be an island 22 on low thermal conducting self-sustaining film 14
Implementation Method 4
temperature sensor 8
Data Source
Figure 1~2
Figure 3~4
AI summary
According to an example aspect of the present invention, there is provided a sensor structure (19) formed on a substrate (12) comprising a sensor frame (21), comprising electric contacts (1-6) for sensors, an active sensor (22) within the sensor frame (21) comprising at least a capacitive humidity sensor (9). In accordance with the invention the active sensor (22) is connected to the sensor frame (23) only by a thin thermally isolating layer (14) supporting the active sensor (22), the thermally isolating layer (14) including electric contacts from the sensor frame (21).