Platinum Temperature Sensor Element Centered Heating
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Solution Overview
Problem
Conventional air-flow sensors face issues with fluctuating resistance due to turbulence and varying heat release, leading to inaccurate temperature measurements, especially when the heat-generating point is not centered, causing instability and requiring complex adjustments.
Innovation Solution
A platinum temperature sensor element with a meander-shaped heating part positioned at the center, surrounded by a protective film on an insulating substrate, maintaining a square-columnar shape with balanced dimensions to stabilize heat release and minimize turbulence, thus reducing resistance fluctuations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the sensor element is downsized to reduce heat capacity and improve response speed, then the thermal responsiveness is improved, but the element becomes more sensitive to air flow turbulence and installation angle variations
Solution Approach 1:
The sensor element is designed with a cylindrical shape and a specific aspect ratio (length to diameter between 0.5 and 2.0), which minimizes the variation in projected area as the element rotates. This curved, symmetric geometry ensures that air flow patterns remain consistent regardless of installation angle, thereby maintaining measurement reliability while allowing the element to be downsized for faster thermal response.
2Ease of manufacture
If the heat-generating point is positioned off-center to simplify manufacturing, then the manufacturing process is simplified, but heat release to lead wires varies causing improper temperature output
Solution Approach 1:
The heating wire is positioned asymmetrically within the cylindrical element, specifically at an eccentricity (e) that is 0.05 to 0.5 times the diameter (d). This controlled asymmetry allows the heat-generating point to be offset from the geometric center while still maintaining stable heat release characteristics. The specific eccentricity range ensures that the heating wire remains sufficiently distant from the lead wire connection points, preventing excessive heat transfer to the lead wires and maintaining accurate temperature output.
3Reliability
If the winding pitch is stabilized in winding-type elements, then resistance fluctuation is reduced, but the manufacturing complexity increases
Solution Approach 1:
The patent replaces the complex mechanical winding process with a simpler linear positioning method. Instead of winding a wire around a ceramic pipe with controlled pitch, the heating wire is positioned linearly along the cylindrical element at a specified eccentricity. This substitution of the mechanical winding system with a linear positioning system achieves stable resistance characteristics while significantly reducing manufacturing complexity.
4Reliability
If the projected area of the element varies with installation angle, then the air current around the element fluctuates, but changing the cross-sectional shape affects manufacturing
Solution Approach 1:
The sensor element employs a cylindrical cross-section rather than a rectangular or irregular shape. This curved, rotationally symmetric geometry ensures that the projected area remains constant regardless of the installation angle. The cylindrical shape is straightforward to manufacture using standard ceramic forming techniques, thus maintaining ease of manufacturing while achieving consistent air flow measurement characteristics.
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 provides stable and accurate air-flow measurements by minimizing heat release variations and turbulence, allowing for precise detection of air intake and reducing the need for complex adjustments, even when installed at varying angles.
Implementation Method 1
a hot type (also called a hot wire type) that utilizes change in resistance of a heated wire as a result of current flowing through a platinum element (platinum hot wire) so as to increase the temperature through self-heating
Implementation Method 2
losing heat as the air hits its heating portion
Implementation Method 3
a protective film that is formed on a top side of the insulating substrate to cover the pattern, the paired electrodes, and top surfaces of joined regions of the lead wires to the paired electrodes
Data Source
AI summary
Internal electrodes, a protective film, and protective films covering the top parts of internal electrode sides of lead wires are formed on a top surface of a substrate of a temperature sensor element, thereby making the overall shape a quadrangular prism and the transverse cross-section nearly a square even at any portion in the axial direction. A heating part of the temperature sensor element is provided near the center along the length, the height, and the width of the element, thereby preventing deviation of heat generation and stabilizing heat release to the lead wires. This allows the temperature sensor element to suppress fluctuation in detected temperatures due to mounting angle.