Load Cell With Common Covering for Humidity Compensation
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Solution Overview
Problem
Existing load cells with strain gauges suffer from reduced accuracy in humidity compensation due to discrepancies in humidity conditions between the sensor location and strain gauge location, exacerbated by mechanical protection layers that further distort the humidity dependence of the weight measurement signal.
Innovation Solution
A load cell design where both the strain gauges and the measuring sensor are covered by a common covering layer, ensuring they experience the same humidity conditions, with the sensor and strain gauges made of the same material to enhance accuracy, and optionally integrated into the strain gauge production process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the sensor is glued to a surface located away from the strain gauges, then the sensor can be easily installed, but the humidity at the sensor location differs from the humidity at the strain gauge location, reducing the accuracy of the humidity compensation
Solution Approach 1:
The patent merges the sensor and strain gauges onto the same carrier foil, ensuring they are in immediate proximity and experience identical humidity conditions. This integration eliminates the humidity gradient problem that occurs when sensors are installed separately on distant surfaces, thereby resolving the contradiction between ease of installation and measurement precision.
Solution Approach 2:
The carrier foil serves as an intermediary substrate that simultaneously supports both the strain gauges and the sensor. By using this common carrier, the patent ensures that both components are exposed to the same environmental humidity conditions, enabling accurate humidity compensation while maintaining easy installation through the integrated structure.
2Strength
If the strain gauges have a covering layer as mechanical protection, then the strain gauges are protected from damage, but the accuracy of the humidity compensation is further reduced due to influence of the covering layer on the humidity conditions at the strain gauges
Solution Approach 1:
The patent applies a single common covering layer that protects both the strain gauges and the sensor simultaneously. Since both components are on the same carrier foil and under the same covering layer, they experience identical humidity conditions, allowing the sensor to accurately compensate for humidity effects on the strain gauge measurements while both remain mechanically protected.
Solution Approach 2:
The covering layer is designed with specific local properties - it provides mechanical protection while being sufficiently permeable or thin to allow humidity penetration. This local quality optimization ensures that both protected components (strain gauges and sensor) experience the same controlled humidity environment, resolving the contradiction between protection and measurement accuracy.
3Ease of manufacture
If the measuring grids and the sensor are made of the same material, then the production costs are reduced through integrated manufacturing, but the sensor may be more sensitive to humidity variations
Solution Approach 1:
The patent integrates the sensor and strain gauges onto the same carrier foil using the same material (e.g., constantan or NiCr compounds), enabling simultaneous manufacturing through the same processes. This merging approach reduces production costs and ensures identical material properties for both components, while the close proximity and common covering layer ensure they experience the same humidity conditions, maintaining reliability through accurate compensation.
Solution Approach 2:
The patent uses homogeneous material for both the strain gauge measuring grids and the sensor, ensuring consistent material properties and response characteristics. This homogeneity simplifies manufacturing and ensures that both components react similarly to humidity, allowing the sensor to effectively compensate for humidity effects on the strain gauge measurements.
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 achieves precise humidity compensation of the weight measurement signal by minimizing humidity distortions, improving accuracy and reducing temporary falsifications.
Implementation Method 1
a plurality of strain gauges mounted on the spring body and connected to a Wheatstone measuring bridge or as part thereof for generating a weight measurement signal corresponding to an acting weight
Implementation Method 2
a measuring sensor mounted in particular on the spring body for compensating for a humidity dependence of the weight measurement signal generated by the strain gauges
Data Source
Figure 1
Figure 2~3
AI summary
The invention relates to a load cell for a scale, comprising a spring body, a plurality of strain gauges mounted on the spring body and connected to a Wheatstone measuring bridge or as part thereof for generating a weight measurement signal corresponding to an acting weight, a covering layer for the strain gauges as mechanical protection, and a measuring sensor for compensating for a humidity dependence of the weight measurement signal generated by the strain gauges, wherein the covering layer covers both the strain gauges and the measuring sensor.