Infrared Thermal Sensor Beam Thermocouple Placement
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Solution Overview
Problem
Existing thermal infrared sensors face challenges in optimizing signal-to-noise ratio (SNR) and mechanical stability, particularly in high-vacuum conditions where thermocouple thermal conductivity affects performance.
Innovation Solution
The design incorporates a membrane suspended by beams, where at least one beam lacks a thermocouple, optimizing the thermal resistance ratio between radiation/convection and conduction through the gas medium and thermocouples, with a filling factor less than 50% and pressures below 10 Pa, to enhance SNR while maintaining mechanical stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If thermocouples are placed on all beams to measure temperature difference, then measurement precision is improved, but thermal conductivity through thermocouples increases causing heat loss and reducing signal-to-noise ratio
Solution Approach 1:
The patent extracts the thermocouple from the beam structure by placing it only on the membrane surface, separating the temperature sensing function from the mechanical support function. This allows the beam to provide structural support without the parasitic thermal conduction path that thermocouples create when mounted on them, thereby reducing heat loss while maintaining measurement capability through alternative means.
Solution Approach 2:
The patent segments the functional responsibilities: the membrane structure handles temperature sensing, while the beam structure handles mechanical support. By dividing these functions into separate components rather than combining them, the patent eliminates the thermal conduction path through the beam, reducing heat loss while preserving both structural integrity and measurement capability.
2Loss of energy
If beams are made long and thin to minimize heat loss, then thermal resistance is improved, but mechanical strength deteriorates
Solution Approach 1:
The patent extracts the temperature sensing function from the beam structure and places it on the membrane surface. This allows the beam to be optimized purely for mechanical strength without the constraint of accommodating thermocouples, enabling the use of longer, thinner beam geometries that provide higher thermal resistance while maintaining sufficient mechanical strength through proper structural design.
3Measurement precision
If membrane size is maximized to increase infrared light reception, then sensitivity is improved, but heat loss through beams increases
Solution Approach 1:
The patent extracts the thermocouple from the beam and places it on the membrane surface, eliminating the thermal conduction path through the beam. This allows the membrane to be made larger for increased infrared light reception and sensitivity without proportionally increasing heat loss through the beam support structure, as the beam no longer acts as a thermal conduction path.
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 improves the SNR by approximately 3 dB without compromising mechanical stability, particularly beneficial in low-pressure environments where thermocouple thermal conductivity is significant, and allows for better heat management and sensitivity.
Implementation Method 1
a plurality of beams for suspending the membrane comprising at least one beam having a thermocouple arranged therein or thereon for measuring a temperature difference (ΔT) between the membrane and the substrate
Implementation Method 2
at least one beam having a thermocouple arranged therein or thereon for measuring a temperature difference (ΔT)
Implementation Method 3
a membrane arranged in said cavity for receiving infrared radiation (IR) through a window or aperture
Implementation Method 4
an external object (or subject) emits IR radiation, which typically enters the cavity via a window or aperture in the package, and warms up the membrane
Implementation Method 5
the thermal resistance (RT1) between the membrane and the substrate via radiation and convection and conduction through the gas medium in the cavity
Implementation Method 6
conduction through the gas medium in the cavity
Implementation Method 7
the thermal resistance (RT1) between the membrane and the substrate via radiation and convection and conduction through the gas medium in the cavity
Data Source
Figure 1(a)~1(d)
Figure 2~3
Figure 4
AI summary
An infrared thermal sensor (10) for sensing infrared radiation is disclosed. The infrared thermal sensor comprises a substrate (1) and a cap structure (2) together forming a sealed cavity (3), a membrane (4) arranged in said cavity (3) for receiving infrared radiation (IR) through a window or aperture (22) and a plurality of beams (5a, 5b, 51, 52) for suspending the membrane (4). At least one beam (51) has a thermocouple (6) arranged therein or thereon for measuring a temperature difference (ΔT) between the membrane (4) and the substrate, the plurality of beams (5a, 5b, 51, 52). Furthermore at least one beam (52) is mechanically supporting the membrane without a thermocouple being present therein or thereon.