Fluid Flow Sensor With Segmented Bridge Circuit
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Solution Overview
Problem
Existing fluid flow sensors face challenges in accurately measuring fluid flow, especially under turbulent conditions, due to complex designs and the need for multiple thermal sensitive resistors, which can complicate measurements and reduce reliability.
Innovation Solution
A fluid flow sensor design featuring only two thermal sensitive resistors on a substrate with a comb-tooth shaped heating resistor, and additional resistors on a printed circuit board forming a bridge circuit, allowing for reliable measurements in turbulent flows with a simplified structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If four thermal sensitive resistors are disposed on the substrate to form a bridge circuit, then measurement reliability is improved, but device complexity increases
Solution Approach 1:
The patent divides the bridge circuit into two parts: two thermal sensitive resistors are disposed on the substrate for direct thermal coupling with the fluid flow, while the other two resistors are disposed on a separate printed circuit board. This segmentation reduces the complexity on the substrate while maintaining the complete bridge circuit functionality for reliable measurement.
Solution Approach 2:
The printed circuit board acts as an intermediary element, carrying two of the bridge circuit resistors and electrically connecting them to the substrate-based resistors. This intermediary structure allows the bridge circuit to function reliably without requiring all four resistors to be mounted on the substrate, thus reducing device complexity.
2Measurement precision
If multiple resistor trace portions are used in thermal sensitive resistors, then measurement precision for turbulent flow is improved, but manufacturing complexity increases
Solution Approach 1:
The thermal sensitive resistors incorporate first resistor trace portions running parallel to the flow direction and second resistor trace portions running perpendicular to the flow direction. This local differentiation in trace orientation allows the sensor to capture temperature variations from different flow directions, improving measurement precision for turbulent flows while maintaining a relatively simple manufacturing process.
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 design provides improved measuring properties for turbulent fluid flows while maintaining a simple and reliable measurement process, even under operational conditions where some resistors remain thermally non-sensitive.
Implementation Method 1
a heating resistor (11) being disposed on the sensing surface (23) of the substrate (10)
Implementation Method 2
thermal sensitive resistors (12, 13) being disposed on the sensing surface (23) of the substrate (10)
Data Source
Figure 1~2
Figure 3
AI summary
Fluid flow sensor comprising a substrate (10) providing a sensing surface (23) that can be brought into direct or indirect contact with a fluid to measured; further comprising a heating resistor (11) disposed on the sensing surface (23) of the substrate (10); further comprising thermal sensitive resistors (12, 13) disposed on the sensing surface (23) of the substrate (10), wherein a first thermal sensitive resistor (12) is located at an adjacent upstream side of the heating resistor (11) and a second thermal sensitive resistor (13) is located at an adjacent downstream side of the heating resistor (11) in a flow direction of the fluid to measured, wherein each of the thermal sensitive resistors (12, 13) comprises first resistor trace portions (14) running parallel to the flow direction of the fluid to measured and second resistor trace portions (15) running perpendicular to the flow direction of the fluid to measured, and wherein the first resistor trace portions (14) and the second resistor trace portions (15) of the first thermal sensitive resistor (12) and of the second thermal sensitive resistor (13) provide for each of the thermal sensitive resistors (12, 13) square-shaped and spiral-like thermal sensitive resistor sections (16); further comprising an electronic circuit to determine a flow rate of the fluid to measured based on signals provided by the thermal sensitive resistors (12, 13). On the upstream side of the heating resistor (11) and on the downstream side of the heating resistor (11) there is located each one thermal sensitive resistor (12, 13). The two thermal sensitive resistors (12, 13) disposed on the substrate (10) configure together with resistors provided on a printed circuit board a bridge circuit, wherein the printed circuit board provides the electronic circuit. The resistor trace portions (14, 15) of each thermal sensitive resistor (12, 13) provide for each of said thermal sensitive resistors (12, 13) three square-shaped and spiral-like thermal sensitive resistor sections (16) being positioned immediately side-by-side in the direction perpendicular to the flow direction of the fluid to measured. (Fig. 1)