Flex Circuit Interface for Load Cell Strain Gauges
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Solution Overview
Problem
Load cells used in weighing equipment are susceptible to environmental conditions such as shock and vibration, leading to accuracy issues and requiring costly maintenance, despite advancements like the Weigh-Bar design.
Innovation Solution
A measurement assembly for load cells employing a flex circuit as an interface member to connect strain gauges without wires, positioning them to measure compression and tension forces directly, and completing a Wheatstone bridge circuit for accurate weight calculations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional load cells are used with wires connecting strain gauges, then the structure is simple and easy to manufacture, but the load cells are susceptible to environmental conditions such as shock and vibration, leading to accuracy issues and requiring costly maintenance
Solution Approach 1:
The patent merges the strain gauge mounting function and the electrical connection function into a single integrated flex circuit interface. The flex circuit serves both as the mechanical interface for mounting strain gauges and as the electrical conduit for signal transmission, eliminating the need for separate wire connections and improving reliability under shock and vibration while maintaining manufacturing simplicity
Solution Approach 2:
The patent employs a flex circuit (flexible printed circuit) as the interface member, which uses a flexible substrate with conductive traces to connect strain gauges. This flexible film structure is inherently more resistant to shock and vibration damage compared to rigid wire connections, thereby improving reliability without significantly increasing device complexity
2Reliability
If strain gauges are positioned on outside surfaces of the load cell body, then the manufacturing process is simple and costs are reduced, but the load cell remains susceptible to environmental conditions impacting accuracy
Solution Approach 1:
The flex circuit integrates the mounting interface and electrical connection functions, allowing strain gauges to be mounted on outside surfaces while providing protected signal transmission paths through the flexible circuit substrate, thus maintaining manufacturing simplicity while improving environmental resistance
Solution Approach 2:
The flexible substrate of the flex circuit protects the electrical connections between strain gauges mounted on outside surfaces, shielding them from environmental damage while maintaining the simplicity of external mounting and reducing manufacturing complexity compared to hermetic sealing
3Reliability
If a complex vacuum-type hermetic seal is used to protect load cells, then accuracy under environmental conditions is improved, but manufacturing costs and device complexity increase significantly
Solution Approach 1:
The flex circuit uses its flexible substrate as a protective barrier for electrical connections, providing environmental protection through a simple flexible film rather than complex hermetic sealing, thus improving reliability while maintaining low device complexity and manufacturing cost
Solution Approach 2:
The patent extracts the protection function from complex hermetic sealing and implements it through the inherent properties of the flex circuit substrate, which naturally protects electrical connections through its flexible, durable construction, simplifying the overall device structure
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 design enhances the performance and reliability of load cells, reduces production costs, and minimizes the impact of environmental factors on accuracy.
Implementation Method 1
A measurement assembly for a load cell includes a bar having a supported end, an unsupported end and a sensor holding portion disposed between the supported end and the unsupported end. The measurement assembly includes a plurality of electronic sensors including a first strain gauge pair and a second strain gauge pair configured to be disposed along the sensor holding portion of the bar. An interface member directly connects the electronic sensors for completing a Wheatstone bridge
Implementation Method 2
A strain gauge is a well known device that can be used to measure the strain being exerted on an object. In particular, for example, a strain gauge may be attached to a stressed section of a scale platform to determine the amount of force or strain exerted on the corresponding section.
Data Source
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AI summary
A load cell may include a bar having a supported end, an unsupported end and a sensor holding portion disposed between the supported end and the unsupported end. The load cell may further include a plurality of electronic sensors including a first strain gauge pair and a second strain gauge pair disposed along the sensor holding portion. The load cell may further include an interface member directly connecting the electronic sensors for weight calculation responsive to application of a load to the unsupported end. In some cases, the interface member may include a flex circuit.