Wearable Thermopile Core Temperature Sensing
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Solution Overview
Problem
Wearable electronic devices face challenges in accurately measuring core body temperature due to variable device and environmental temperatures, requiring non-invasive methods that account for changing conditions.
Innovation Solution
A wearable electronic device with a thin film thermopile having a cold junction bonded to the logic board and a hot junction bonded to the rear cover, using a heat flux correction factor to calculate core temperature based on temperature differences, minimizing heat flux and avoiding drift errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a wearable device measures temperature directly, then the measurement is non-invasive and convenient, but the measurement accuracy deteriorates due to variable device and environmental temperatures
Solution Approach 1:
The patent introduces a thermopile as an intermediary device between the user's body and the measurement system. The thermopile includes a hot junction that contacts the user's body through the rear cover and a cold junction that contacts the logic board, measuring the temperature difference between these two points. This intermediary approach allows the system to account for environmental and device temperature variations by measuring the differential temperature, thereby maintaining measurement accuracy while preserving non-invasive convenience.
Solution Approach 2:
The patent changes the measurement parameter from absolute temperature to temperature difference. Instead of measuring the absolute body temperature directly, the system measures the temperature difference (ΔT) between the hot junction (contacting the body) and the cold junction (contacting the logic board). This parameter transformation allows the system to eliminate the effect of environmental temperature variations and device heating, as these affect both junctions equally and cancel out in the differential measurement.
2Adaptability or versatility
If the device operates in variable environmental conditions, then the device is versatile and wearable, but the temperature measurement reliability deteriorates
Solution Approach 1:
The thermopile acts as a mediator that isolates the measurement from environmental variations. By measuring the temperature difference between the hot junction (exposed to body heat) and the cold junction (isolated on the logic board), the system creates a reference measurement that is insensitive to ambient temperature changes. This allows the device to maintain reliable temperature measurements across diverse environmental conditions while preserving wearable versatility.
Solution Approach 2:
The system uses the measured temperature difference as feedback to compensate for environmental variations. The processor receives the temperature difference signal from the thermopile and uses it to calculate the user's body temperature, automatically adjusting for the effects of environmental conditions and device heating. This feedback mechanism ensures consistent measurement reliability regardless of external conditions.
3Power
If the device components generate heat, then the device is functional and operational, but the temperature measurement accuracy deteriorates due to heat flux and drift errors
Solution Approach 1:
The thermopile serves as an intermediary that measures the temperature difference between the heat-generating logic board (cold junction) and the user's body (hot junction). By positioning the cold junction on the logic board, the system actually measures the temperature rise caused by device heating, and this measurement is used to compensate for the heat flux effects. The differential measurement approach isolates the body temperature signal from the device heating interference.
Solution Approach 2:
The patent converts the harmful effect of device-generated heat into a beneficial measurement reference. The heat generated by the logic board and other components creates a measurable temperature difference that is captured by the cold junction of the thermopile. This temperature difference serves as a reference that allows the system to calculate and compensate for heat flux effects, thereby converting the previously harmful thermal interference into a useful calibration signal that improves measurement accuracy.
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 accurate, non-invasive core body temperature measurement by accounting for environmental and device temperature variations, providing a compact and reliable solution for wearable devices.
Implementation Method 1
A wearable electronic device with a thin film thermopile having a cold junction bonded to the logic board and a hot junction bonded to the rear cover
Implementation Method 2
The temperature sensor includes a thin film thermopile... sensing a temperature difference between the first junction and the second junction
Implementation Method 3
The hot junction is bonded via a thermal epoxy
Data Source
AI summary
An electronic device includes a housing defining an internal volume, a front opening, and a rear opening. The electronic device can include a display component disposed at the front opening and a rear cover disposed at the rear opening. A logic board can be disposed in the internal volume. The device can also include a thin film thermopile including a cold junction bonded to the logic board and a hot junction bonded to the rear cover.