Resistance Temperature Detector Layer for Miniaturized Fire Sensor
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Solution Overview
Problem
Miniaturized fire sensing devices using metal oxide semiconductor (MOS) resistive sensing materials face issues with accurate temperature measurement due to electro-migration and low temperature coefficients of resistivity, leading to erroneous fire indications and unreliable heater measurements.
Innovation Solution
The implementation of a resistance temperature detector layer, such as chromium titanium oxide, positioned between the heater and sensing layer, allows for controlled temperature measurement and differentiation between resistance changes caused by temperature and gas environment changes, using a thermocouple or semi-conductive materials like silicon-based layers to provide accurate temperature control and shielding from electrical interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a platinum heating element is used to heat the sensing material, then the sensitivity of the sensor is optimized, but electro-migration from the temperature sensor may disable or destroy the heater, leading to unreliable temperature measurement
Solution Approach 1:
A dedicated temperature sensor layer is introduced as an intermediary component between the heater and the sensing material. This separate temperature sensing element does not suffer from electro-migration issues that affect the heater material, allowing reliable temperature measurement without compromising heater integrity or sensitivity.
Solution Approach 2:
The device is segmented into functionally independent layers: a heater layer for heating, a separate temperature sensor layer for temperature measurement, and a sensing material layer for gas detection. This segmentation allows each component to be optimized for its specific function without interfering with others, resolving the conflict between heater reliability and temperature measurement accuracy.
2Use of energy by moving object
If the sensing area is miniaturized to operate under low power levels, then power consumption is reduced, but temperature changes occur quickly making measurement unreliable
Solution Approach 1:
The separate temperature sensor layer acts as a dedicated intermediary that continuously monitors temperature in the miniaturized sensing area. This dedicated sensor can capture rapid temperature changes in the small area without the measurement reliability issues that would occur with shared heater-sensing structures, enabling accurate temperature tracking during low-power operation.
3Device complexity
If the heater layer has conducting legs extending away from the central portion, then the device structure is simplified, but the heater layer has only a portion of its resistance in the area proximate to the sensing material, making temperature measurement inaccurate
Solution Approach 1:
The heater structure is segmented into conducting legs for electrical connection and a central heated zone for sensing. The temperature sensor layer is positioned to specifically monitor the central zone temperature, separating the measurement function from the heating structure and eliminating the inaccuracy caused by resistance distribution in extended legs.
Solution Approach 2:
A dedicated temperature sensor layer serves as an intermediary that directly monitors the temperature in the central heated zone proximate to the sensing material. This separate measurement system accurately captures the relevant temperature without being affected by the resistance distribution in the conducting legs.
4Measurement precision
If a resistance temperature detector layer is added to enable accurate temperature measurement, then temperature control is improved, but the device complexity increases
Solution Approach 1:
The temperature detector layer is merged with the heater and sensing material layers into a single integrated structure. All layers are positioned in close proximity on the same substrate, sharing common support structures and electrical connections, which minimizes the increase in device complexity while achieving accurate temperature measurement and control.
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 reliable temperature measurement and control, reducing false fire indications by distinguishing between temperature and gas-induced resistance changes, ensuring repeatable conditions and improved manufacturability, while maintaining low power consumption and compact design.
Implementation Method 1
these heaters have low temperature coefficients of resistivity and, therefore, monitoring the heater's resistivity to determine temperature of the sensor may be problematic
Implementation Method 2
In order to heat the material, such devices typically utilize a platinum heating element
Implementation Method 3
The sensor can be fabricated from materials that interact with the gases such that some of the gases produced can change the resistance of the material forming the sensor
Data Source
AI summary
The present disclosure includes sensing device embodiments. One sensing device includes a heater layer, a resistance detector layer, constructed and arranged to indicate a temperature value based upon a correlation to a detected resistance value, an electrode layer, and a sensing layer.