MEMS Thermopile Orientation for Internal Temperature Measurement
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Solution Overview
Problem
Existing internal temperature measuring apparatuses face challenges in accurately measuring core body temperature due to high heat resistance and heat capacity, leading to poor responsiveness and increased error from heat flow sources outside the measurement object.
Innovation Solution
The apparatus employs a MEMS device with first and second thermopiles oriented in the same direction relative to their cold and hot junctions, integrated with a package having high heat conductive units and a printed circuit board, to calculate internal temperature with reduced susceptibility to heat flow from external sources.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a heat insulator having a large heat resistance and large heat capacity is used, then measurement accuracy is improved, but responsiveness deteriorates (long time required to obtain stable measurement result)
Solution Approach 1:
The patent divides the measurement system into two separate measurement paths: one for measuring temperature difference (using the MEMS chip with thermopile) and another for measuring reference temperature (using a separate temperature sensor). This segmentation allows each component to be optimized for its specific function, enabling the MEMS chip to be small and responsive while the reference temperature measurement can use more stable components.
Solution Approach 2:
The patent introduces a base as an intermediary component that thermally connects the measurement object to the MEMS chip while providing thermal isolation from external heat sources. The base acts as a mediator that transfers heat from the measurement object to the sensor while blocking heat flow from the environment, thus improving responsiveness without sacrificing accuracy.
2Speed
If a MEMS chip is used to measure temperature difference, then responsiveness is improved, but measurement accuracy deteriorates due to easy generation of estimated error from heat flow from external heat sources
Solution Approach 1:
The patent converts the harmful effect of external heat flow into a beneficial measurement mechanism. By orienting the thermopile's cold junctions in the same direction, the patent causes temperature gradients from external heat sources to affect both cold junctions equally, creating equal errors that cancel out in the differential measurement. This transforms the harmful thermal interference into a self-canceling effect.
Solution Approach 2:
The patent employs asymmetric orientation of the thermopile structure where both cold junctions are oriented in the same direction relative to the hot junctions. This asymmetric configuration is specifically designed to make the sensor equally sensitive to external heat flow from one direction, ensuring that thermal interference affects both measurement paths symmetrically and can be eliminated through differential calculation.
3Speed
If the MEMS chip size is reduced to 2 mm to 3 mm square, then heat resistance and heat capacity decrease improving responsiveness, but susceptibility to heat flow from external heat sources increases
Solution Approach 1:
The patent extracts the temperature sensing function from the MEMS chip by separating the thermopile (which measures temperature difference) from the reference temperature sensor. This extraction allows the MEMS chip to be miniaturized for responsiveness while the reference temperature measurement can be performed by a separate component that is less susceptible to external heat flow interference.
Solution Approach 2:
The base serves as a thermal intermediary that isolates the miniaturized MEMS chip from external heat sources while maintaining thermal contact with the measurement object. This intermediary structure protects the small sensor from harmful thermal interference while preserving its responsive 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 enhances measurement accuracy and responsiveness by minimizing estimated errors caused by heat flow from external sources, allowing for precise internal temperature calculation.
Implementation Method 1
a first thermopile configured to measure the first temperature difference and a second thermopile configured to measure the second temperature difference
Data Source
AI summary
An internal temperature measuring apparatus includes a base and a MEMS device disposed on the base. The MEMS device includes a top face and a support. The top face includes a first thermopile configured to measure a first temperature difference used to calculate an internal temperature and a second thermopile configured to measure a second temperature difference used to calculate the internal temperature together with the first temperature difference. An orientation in which a cold junction of each thermocouple constituting the first thermopile is viewed from a hot junction coincides with an orientation in which a cold junction of each thermocouple constituting the second thermopile is viewed from a hot junction.