Zero Heat Flux Temperature Sensor Feedback Control
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Solution Overview
Problem
Existing temperature sensing devices for measuring core body temperature are not accurate enough, particularly in clinical settings, due to heat flux issues caused by thermal insulation and temperature gradients, leading to inaccurate skin temperature readings.
Innovation Solution
A zero heat flux temperature sensing device with a thermal insulator and heat flux modulators that control temperature differences to minimize heat flux, ensuring more uniform temperature distribution and accurate core body temperature measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a thermal insulator is used in the temperature sensing device, then the heat flux from the contact area towards the top of the device is reduced, but the temperature gradient inside the device increases and measurement accuracy deteriorates
Solution Approach 1:
The patent employs feedback control by using the temperature difference measured between the first and second temperature sensors to control the heating element. The heating element is activated to compensate for the temperature drop caused by the thermal insulator, creating a closed-loop system that maintains measurement accuracy while preserving the thermal insulation benefits.
Solution Approach 2:
The patent changes the thermal conductivity parameter of the middle section dynamically. By introducing a heating element that can be activated based on the measured temperature difference, the system adjusts the thermal properties of the device in response to operating conditions, allowing optimization between heat flux reduction and measurement accuracy.
2Measurement precision
If the temperature sensing device is positioned against the skin of the body, then core body temperature can be measured, but the skin temperature below the device becomes warmer due to local insulating effect
Solution Approach 1:
The patent divides the temperature sensing device into distinct functional sections: a first section for measuring skin temperature, a middle section with thermal insulator and heating element for compensating temperature gradients, and a second section for measuring temperature at the top. This segmentation allows each part to perform its specific function independently, managing the thermal effects locally without compromising overall measurement accuracy.
3Measurement precision
If the heating element is activated to eliminate temperature difference, then heat flux through the device is reduced, but device complexity increases
Solution Approach 1:
The heating element serves multiple functions: it compensates for the temperature drop caused by the thermal insulator, maintains the temperature gradient necessary for accurate measurement, and can be controlled based on feedback from the temperature sensors. This multi-functionality justifies the added complexity by providing both measurement and active thermal management capabilities.
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
The device achieves more accurate core body temperature measurements by reducing heat flux and temperature gradients, thereby improving the reliability of temperature readings.
Implementation Method 1
a thermal insulator, a second temperature sensor and a heating element... the thermal insulator creates a significant step in this gradient
Implementation Method 2
there will be a decreasing temperature gradient in the sensing device in the direction away from the contact area between the temperature sensing device and the skin
Implementation Method 3
The heating element will be heated until the measured temperature difference between the first temperature sensor and the second temperature sensor will become very small and substantially equal to zero
Data Source
AI summary
The invention relates to a zero heat flux temperature sensing device (100) for sensing a core body temperature of an object (113). The zero heat flux temperature sensing device (100) comprises a layer (107), a first temperature gradient sensor (105), a first heat flux modulator (103) and a heat flux modulator controller (102). The layer (107) has an opposing first side (112) and second side (108). In use the first side (112) is nearest to the object (113). The layer (107) is for obtaining a first temperature difference over the layer (107) in response to a first heat flux in a first direction from the first side (112) to the second side (108). The first temperature gradient sensor (105) senses at the first side (112) of the layer (107) a second temperature difference in a second direction. The second direction extends from a first border of the first side (112) towards a second border of the first side (112). The first heat flux modulator (103) is arranged at the first side (112) of the layer (107) and is constructed to change a second heat flux in a second direction at the first side (112) of the layer (107) in order to influence the second temperature difference. The heat flux modulator controller (102) controls the first heat flux modulator (103) on basis of the sensed second temperature difference in order to decrease an absolute value of the second temperature difference. The effect of the measures according to the invention is that the zero heat flux temperature sensing device (100) senses the core body temperature of the object (113) more accurately.