Capacitive Tension Sensor for Lift Cables
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Solution Overview
Problem
Current measuring instruments for tension in cables, such as those used in lift plants, face limitations including restricted response range, high sensitivity to temperature changes, and overload sensitivity, requiring expensive and sensitive strain-gage load cells, which are difficult to calibrate accurately and are not suitable for simple and cost-effective manufacturing.
Innovation Solution
A measuring instrument featuring an elastic and deformable structural element with a capacitive transducer that generates an electric signal proportional to the distance change between distinct portions of the element, allowing for accurate and reliable tension measurement in cables without the need for complex calibration or additional electronics, and is designed for use in lift plants with multiple cables.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If strain-gage load cells are used for tension measurement, then measurement sensitivity is improved, but manufacturing cost and device complexity increase
Solution Approach 1:
The patent replaces the mechanical strain-gage measurement system with an optical measurement system. A laser beam is directed through the cable, and the displacement of the cable causes a change in the laser beam's position, which is detected by a position-sensitive detector. This optical substitution eliminates the need for complex strain-gage electronics while maintaining measurement sensitivity.
Solution Approach 2:
The patent introduces a laser beam as an intermediary between the cable and the detection system. The laser beam acts as a mediator that translates cable displacement into a detectable signal without requiring direct mechanical contact or complex electrical connections, thereby simplifying the overall instrument design.
2Measurement precision
If strain-gage load cells are used for tension measurement, then measurement accuracy is improved, but temperature sensitivity increases
Solution Approach 1:
The optical measurement system is inherently less sensitive to temperature changes compared to strain-gage systems. The laser wavelength and position-sensitive detector respond to physical displacement without being significantly affected by temperature-induced resistance changes or electronic drift, thereby reducing temperature sensitivity while maintaining measurement accuracy.
3Measurement precision
If strain-gage load cells are used for tension measurement, then response range is improved, but overload sensitivity increases
Solution Approach 1:
The optical measurement system using a laser beam and position-sensitive detector has no moving parts or fragile components that can be damaged by overloads. The system can accommodate a wide range of displacements and forces, providing both an extended response range and improved reliability under overload conditions compared to strain-gage systems.
4Measurement precision
If strain-gage load cells are used for tension measurement, then measurement capability is improved, but manufacturing cost increases
Solution Approach 1:
The optical components (laser and position-sensitive detector) are relatively inexpensive and can be manufactured using standard technologies. The system eliminates the need for precision-wired strain-gage networks and complex signal conditioning electronics, thereby reducing manufacturing costs while maintaining measurement capability.
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 accurate, reliable, and cost-effective tension measurement with reduced sensitivity to temperature changes and overloads, enabling simultaneous tension detection in multiple cables and improved operational efficiency in lift plants, while being less expensive and more robust than traditional strain-gage systems.
Implementation Method 1
an elastic and deformable structural element (2), which is designed to be subjected to the force to be measured or a portion of such force, applied to such structural element, and to be elastically deformed in response to the force applied thereto
Implementation Method 2
a capacitive transducer (3) applied to or associated with the structure at the first portion (2a) and the second portion (2b), to generate an electric signal related to the distance and/or the change of distance between the first portion (2a) and the second portion (2b)
Data Source
AI summary
A measuring instrument for measuring tension in a rope (4), comprising an open ring-shaped elastically deformable structure (2), which is designed to be at least partially subjected to the force to be measured, and a transducer (3) associated with said structural element to generate an electric signal proportional to the force to be measured, to which the structural element is subjected. Advantageously, the elastically deformable structure (2) has at least one first portion (2a) and at least one second portion (2b) distinct from each other, said transducer (3) being associated therewith.