Infrared Sensor Thermal Isolation via Air Gap
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Solution Overview
Problem
Infrared thermometers face significant temperature drift and inaccuracy due to heat energy transfer from the measured object, particularly when measuring low body temperatures, leading to substantial measurement errors.
Innovation Solution
A temperature measurement head design featuring a casing, tubular conductor, cap-shaped conductor, and an air gap that isolates the infrared sensor from the heat energy, utilizing the insulation properties of air to prevent heat transfer and ensure accurate measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the infrared sensor is directly exposed to the measured object through the detection hole, then the infrared signal reception is efficient, but heat energy transfers to the sensor causing temperature drift and measurement errors
Solution Approach 1:
The patent introduces an air gap as an intermediary substance between the infrared sensor and the measured object. This air gap acts as a thermal insulator that blocks heat energy transfer from the measured object to the sensor, while still allowing infrared radiation to reach the sensor through the detection hole. The air gap is formed by the spacing between the sensor housing and the infrared sensor surface, creating a thermal barrier that eliminates the harmful heat transfer effect.
Solution Approach 2:
The patent utilizes air as an inert atmospheric medium to create an insulating environment around the infrared sensor. The air gap surrounding the sensor prevents thermal conduction and convection from the measured object, creating a thermally isolated environment for the sensor while maintaining optical transparency for infrared detection. This inert atmospheric approach effectively blocks the harmful thermal influence without interfering with the infrared measurement function.
2Ease of operation
If the sensor is inserted into the ear canal for measurement, then the measurement is convenient and fast, but the body temperature directly heats the sensor causing large temperature differences and measurement errors
Solution Approach 1:
The air gap serves as a thermal intermediary that decouples the sensor from direct thermal contact with the ear canal environment. When the thermometer is inserted into the ear canal, the air gap prevents thermal conduction from the warm ear canal walls to the sensor, maintaining the sensor at a stable temperature while still allowing the sensor to detect infrared radiation from the eardrum for accurate temperature measurement.
Solution Approach 2:
The patent segments the thermal pathways from the measured object to the sensor by introducing the air gap as a separating medium. This segmentation divides the thermal field into isolated zones, preventing the formation of a continuous thermal conduction path from the ear canal to the sensor, thereby maintaining measurement accuracy while preserving the convenience of insertion-based measurement.
3Reliability
If conventional structures are used without thermal isolation, then the device structure is simple, but temperature drift exceeds 1°C causing serious reliability issues
Solution Approach 1:
The air gap provides an effective thermal isolation mechanism with minimal structural complexity. By simply maintaining a spaced relationship between the sensor housing and the infrared sensor surface, the design achieves reliable thermal isolation without requiring complex insulation materials or multi-layer structures. This intermediary approach delivers measurement reliability while keeping the device structure simple and cost-effective.
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 air gap effectively prevents heat energy transfer, significantly improving measurement accuracy and reliability, making the thermometer more reliable and cost-effective.
Implementation Method 1
The air gap is disposed between an outer sidewall surface and a top surface of the infrared sensor and corresponding inner sidewall surface and inner bottom surface of the cap-shaped conductor and completely isolates the outer sidewall surface and the top surface of the infrared sensor from the corresponding inner sidewall surface and the inner bottom surface of the cap-shaped conductor
Implementation Method 2
a thermocouple disposed inside the sensor is configured to detect the temperature difference between an upper surface and a lower surface of the thermocouple itself. Specifically, when infrared rays from the human body are received by the upper surface of the thermocouple, the temperature of the upper surface increases. Thus, a temperature difference between the upper surface and the lower surface of the thermocouple is produced, and the thermocouple outputs a voltage signal of the temperature difference
Implementation Method 3
Infrared body temperature measurement technology has been widely applied. It adopts an infrared sensor to receive infrared rays irradiated from the human body and adopts a temperature measuring circuit module to process the infrared signals whereby obtain the body temperature
Data Source
AI summary
A temperature measurement head structure comprises a shell (14), a tube-shaped thermal conductor (13), a cap-shaped thermal conductor (12) and an infrared sensor (11). Detection holes are arranged at a front end of the shell (14) and a front end of the cap-shaped thermal conductor (12). The tube-shaped thermal conductor (13) is located inside the shell (14). A bottom surface of the infrared sensor (11) and an end portion of the tube-shaped thermal conductor (13) are closely adhered to the detection hole at the front end of the shell (14). The cap-shaped thermal conductor (12) surrounds the infrared sensor (11) and is sleeved on an external wall at the end portion of the tube-shaped thermal conductor (13). The detection hole at the front end of the cap-shaped thermal conductor (12) is located behind the detection hole at the front end of the shell (14). The temperature measurement head structure further comprises an air gap (20) formed between top and side surfaces of the infrared sensor (11) and the cap-shaped thermal conductor (12). Also provided is a clinical thermometer comprising the temperature measurement head structure. The clinical thermometer has a simple structure, and greatly improves the precision and reliability of temperature measurement.