Dual Ear Canal Temperature Sensing for Core Body Accuracy
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Solution Overview
Problem
Existing technologies face challenges in obtaining accurate and reliable core body temperature measurements from the ear due to the narrow and angular ear canal, which obstructs a direct field of view for temperature sensors, and require solutions that address size, power constraints, and environmental temperature compensation.
Innovation Solution
The use of a dual-temperature sensor system positioned at specific locations within the ear canal, including a distal and proximal sensor, coupled with a heat balance equation to calculate absolute core body temperature, utilizing thermistors for low power and low cost continuous monitoring.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a handheld IR sensor is used to measure tympanic membrane temperature, then temperature measurement capability is achieved, but the narrow and angular ear canal obstructs the direct field of view from the sensor to the tympanic membrane
Solution Approach 1:
The measurement system is segmented into two functional parts: an IR sensor positioned to measure ear canal wall temperature (not directly the tympanic membrane), and a separate computational algorithm that estimates core body temperature from this indirect measurement combined with environmental temperature data. This segmentation allows measurement around the anatomical obstruction rather than requiring direct line-of-sight to the tympanic membrane.
Solution Approach 2:
The ear canal wall acts as an intermediary medium between the IR sensor and the target (core body temperature). Instead of measuring the tympanic membrane directly, the system measures the temperature of the ear canal wall which has been thermally influenced by core body temperature, and uses this intermediary measurement combined with heat transfer modeling to estimate the desired parameter.
2Reliability
If multiple temperature sensors are deployed in the ear canal to overcome field of view limitations, then measurement reliability improves, but device size and complexity increase
Solution Approach 1:
The system segments the measurement function across two sensors positioned at different locations (distal and proximal) in the ear canal, each measuring different thermal conditions. This spatial segmentation provides redundant and complementary data that improves reliability without requiring a single complex sensor system.
Solution Approach 2:
The system changes the measurement parameter from direct tympanic membrane temperature to ear canal wall temperature at multiple positions. By measuring temperature gradients and differences at different locations rather than attempting direct tympanic membrane measurement, the system achieves reliable core temperature estimation through computational thermodynamics.
3Reliability
If continuous temperature monitoring is implemented in wearable devices, then health monitoring capability is provided, but power consumption increases
Solution Approach 1:
The system replaces active heating and direct contact measurement mechanisms with passive infrared thermal sensing. The IR sensor passively detects thermal radiation from the ear canal wall without requiring external heating elements or mechanical contact, significantly reducing power consumption while enabling continuous monitoring.
Solution Approach 2:
The measurement system utilizes the body's own thermal radiation and the natural thermal properties of ear canal tissues as the measurement source. The ear canal wall's thermal characteristics serve the measurement function without requiring external energy input to the measurement process, enabling low-power continuous operation.
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 core body temperature measurement with an error of +/- 0.5°C or less, providing reliable health monitoring capabilities in wearable devices.
Implementation Method 1
The distal temperature sensor is configured to sense one or both of conductive heat and convective heat and to produce a first temperature signal
Implementation Method 2
The distal temperature sensor is configured to sense one or both of conductive heat and convective heat and to produce a first temperature signal
Implementation Method 3
The proximal temperature sensor is configured to sense one or both of conductive heat and convective heat and to produce a second temperature signal
Implementation Method 4
The proximal temperature sensor is configured to sense one or both of conductive heat and convective heat and to produce a second temperature signal
Data Source
Figure 1
Figure 2
Figure 3A~3B
AI summary
An electronic device comprises an enclosure configured for insertion into the ear canal and comprising a distal end configured to extend at least beyond a first bend of the ear canal. A distal temperature sensor is situated at a location of the enclosure that faces a tragus-side of the ear canal between the first and second bends when the enclosure is fully inserted into the ear canal. A proximal temperature sensor is situated on the enclosure at a location spaced apart from a surface of the ear canal and proximal of the distal temperature sensor in an outer ear direction when the enclosure is fully inserted into the ear canal. A processor, coupled to the distal and proximal temperature sensors and to memory, is configured to calculate an absolute core body temperature using a heat balance equation stored in the memory and the first and second temperature signals.