Infrared Sensor Temperature Compensation via Segmented Thermocouples
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Solution Overview
Problem
Traditional infrared temperature sensors face accuracy issues due to parasitic signals and offset errors from environmental and detector housing contributions, which are not completely eliminated by existing compensation methods.
Innovation Solution
An infrared sensor design with a cap covering a substrate, featuring active and passive thermocouple sensing elements connected in parallel, with adjustable connection modules to control sensitivity and offset, allowing for precise temperature measurement by isolating and subtracting parasitic contributions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a passive secondary detector is added to compensate for offset, then measurement accuracy is improved, but device complexity increases
Solution Approach 1:
The sensor is divided into two independent sensing elements: an active primary detector that receives IR radiation from the object of interest, and a passive secondary detector that receives only parasitic radiation from the housing and environment. This segmentation allows each detector to specialize in detecting specific radiation sources, enabling effective offset compensation while maintaining structural clarity
Solution Approach 2:
The passive secondary detector acts as an intermediary that specifically measures the parasitic offset signal generated by the detector housing and environment. By isolating and measuring this offset component separately, the system can subtract it from the total signal to obtain accurate temperature measurements without requiring complex shielding or isolation structures
2Object-affected harmful factors
If thermocouples are thermally isolated from the housing, then parasitic signal reception is reduced, but sensitivity to external radiation decreases
Solution Approach 1:
The sensor employs different thermal coupling configurations for different sensing elements: the active primary detector maintains good thermal isolation from the housing to minimize parasitic signal reception, while the passive secondary detector is thermally coupled to the housing to maximize its reception of parasitic radiation. This localized differentiation of thermal properties allows each detector to optimize its function without compromising the other
Solution Approach 2:
The parasitic radiation that normally degrades measurement accuracy is converted into a useful signal by the passive secondary detector. This detector specifically receives the parasitic radiation from the housing and environment, transforming the harmful offset signal into a measurable quantity that can be subtracted from the total signal to recover the true temperature information
3Temperature
If the reference temperature increases due to environmental conditions, then offset is created, but measurement range is extended
Solution Approach 1:
The passive secondary detector provides real-time feedback on the offset signal generated by housing and environmental temperature variations. This offset measurement is continuously subtracted from the active detector signal, creating a feedback loop that dynamically compensates for reference temperature changes and maintains measurement accuracy across varying environmental conditions
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 solution effectively reduces sensor offset and enhances sensitivity control, leading to improved accuracy in temperature measurement by isolating and compensating for parasitic signals, resulting in a more reliable temperature reading.
Implementation Method 1
The difference of temperature between the sensing element and a reference produces a readable electrical voltage signal
Implementation Method 2
The sensing element may for example be a radiation absorbing membrane. The heating results in a temperature change.
Implementation Method 3
The shielding cap is typically thermally isolated from the sensing element, for instance by leaving a spatial gap of air or vacuum between the cap and the sensing element. The IR radiation is then collected by the sensing element
Data Source
AI summary
An infrared sensor (400) comprises a first sensing element (410), comprising a set of N thermocouples (412) on the substrate whose hot junctions may receive radiation from a source external to the sensor; a second sensing element (420) comprising a set of N thermocouples (422) on the substrate whose hot junctions may not receive radiation from a source external to the sensor; first and second connection modules (307, 306) for connecting a number N1, N2 of thermocouples of the first or second sensing element (410), respectively; and connecting means for connecting an output of the first connection module (307) of the first sensing element (410) with an output of the second connection module (306) of the second sensing element (420), and an output (407, 408) for outputting the combined outputs of the sensing elements as a measure of the temperature.