CMOS Dew Point Sensor Array for Condensation Detection
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Solution Overview
Problem
Conventional dew point sensor devices face limitations in accuracy and efficiency due to the reliance on single-point temperature measurements and limited sensitivity in detecting the onset of condensation, particularly at low humidity levels.
Innovation Solution
A dew point sensor device incorporating a semiconductor substrate with a Peltier element, temperature sensor, and an array of capacitor elements, where the electronic circuit generates binary digits to indicate capacitance changes, allowing for precise detection of dew point through comparisons at decreasing temperatures, and optionally utilizing a hydrophilic cover layer to enhance condensation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single-point temperature measurement is used to detect dew point, then the device structure is simple, but the measurement precision is insufficient
Solution Approach 1:
The patent divides the capacitor into multiple capacitor elements (e.g., 256 elements) arranged in an array on the semiconductor substrate. Each capacitor element independently measures capacitance changes, allowing the system to detect condensation onset more precisely through statistical analysis of multiple measurement points rather than relying on a single measurement location.
Solution Approach 2:
The invention transitions from single-point temperature measurement to a two-dimensional array of capacitor elements on the semiconductor substrate surface. This spatial distribution across multiple dimensions enables more accurate detection of condensation patterns and improves dew point measurement precision by capturing spatial variations in the gaseous medium.
2Measurement precision
If conventional mirror-based dew point sensors are used, then the detection principle is simple, but the sensitivity to small droplets is limited
Solution Approach 1:
The patent replaces the optical mirror-based detection system with an electrical capacitance measurement system. The capacitor elements measure changes in capacitance caused by condensation on their surfaces, substituting optical reflection principles with electrical field-based detection, which provides higher sensitivity to small droplet formation.
Solution Approach 2:
The invention utilizes changes in capacitance as the key measurement parameter instead of optical reflectance. By monitoring capacitance variations of the capacitor elements as condensation forms on their surfaces, the system achieves enhanced sensitivity to small droplets through electrical parameter changes rather than optical parameter changes.
3Reliability
If the sensor surface is made hydrophobic to prevent contamination, then contamination resistance improves, but condensation detection efficiency decreases
Solution Approach 1:
The patent applies different surface properties to different parts of the sensor system. The semiconductor substrate and capacitor elements have hydrophilic surfaces that promote condensation for efficient detection, while the device housing and non-measuring surfaces can be hydrophobic for contamination resistance. This local differentiation allows simultaneous optimization of both detection efficiency and contamination resistance.
Solution Approach 2:
The invention separates the measuring surfaces (capacitor elements) from the non-measuring surfaces (device housing, connections). The capacitor elements are designed with specific surface properties optimized for condensation detection, while other parts of the device can have different surface properties for contamination protection, allowing independent optimization of each function.
4Area of stationary object
If a large mirror is used for dew point detection, then the detection area is sufficient, but the device size increases
Solution Approach 1:
The patent transitions from a single large two-dimensional mirror surface to a three-dimensional array of multiple small capacitor elements distributed across the semiconductor substrate surface. This dimensional reorganization provides sufficient total detection area while maintaining a compact device footprint through vertical integration and miniaturization.
Solution Approach 2:
The invention divides the detection surface into multiple small capacitor elements (e.g., 256 elements) arranged in an array, replacing a single large mirror. This segmentation allows the total detection area to be distributed across multiple small units that can be integrated into a compact semiconductor device, reducing overall device volume while maintaining sufficient detection area.
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 approach significantly enhances the accuracy and speed of dew point detection, enabling the measurement of smaller droplets and reducing device size while allowing for contamination monitoring and easy regeneration.
Implementation Method 1
a Peltier element, integrated in the substrate
Implementation Method 2
The capacitor elements are arranged at a surface above the substrate, so that they can be exposed to a gaseous medium or atmosphere
Implementation Method 3
The capacitor comprises a plurality of capacitor elements each having a capacitance
Implementation Method 4
The temperature sensor is arranged in the vicinity of the capacitor, so that the temperature of the capacitor can be measured at least approximately
Data Source
AI summary
In an embodiment a method includes determining, for each capacitor element of a plurality of capacitor elements of a capacitor, an increase of a capacitance of a capacitor element caused by a decrease of a temperature of the capacitor and deriving a dew point from a temperature at which the increases of the capacitances or values corresponding to the increases of the capacitances exceed a predefined limit by generating a set of binary digits, each of the binary digits corresponding to one of the capacitor elements and indicating whether the capacitance of the capacitor element is within a predefined range, comparing sets of binary digits generated at different temperatures and determining a number of capacitor elements for which the corresponding binary digits of the sets are different and repeating the comparison for a sequence of sets generated at decreasing temperatures.