Optoelectronic Position Sensor for Electromagnetic Weighing Cell
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Solution Overview
Problem
Existing electromagnetic force compensation balances face challenges in maintaining accurate and reproducible zero position, particularly under varying temperature and humidity conditions, leading to temperature hysteresis and the need for extensive aging processes.
Innovation Solution
An optoelectronic position sensor with a light emitter and receiver mounted directly on carrier elements, attached to a monolithic base part with minimal connecting locations, using grooved drive studs for secure attachment and materials with matched thermal expansion coefficients to minimize hysteresis and aging, ensuring linear and reproducible sensor signal deflection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the light emitter and light receiver are mounted on the base part with multiple connecting locations, then the mounting stability is improved, but the temperature hysteresis and zero point drift increase due to differential thermal expansion
Solution Approach 1:
The patent extracts the light emitter and light receiver from direct mounting on the base part, instead mounting them on a carrier element that is integrated with the base part as a monolithic structure. This eliminates the intermediate connecting locations that cause differential thermal expansion, thereby maintaining mounting stability while preventing zero position drift.
Solution Approach 2:
The patent merges the carrier element with the base part to form a monolithic structure, eliminating the interface between separate components. This integration ensures that both the light emitter/receiver mounting and the base part undergo identical thermal expansion, preventing relative position changes and zero point drift while maintaining structural stability.
2Measurement precision
If extensive aging processes are applied to stabilize the zero point, then the measurement accuracy is improved, but the manufacturing time and cost increase
Solution Approach 1:
The patent implements preliminary action by designing the optoelectronic position sensor with a monolithic carrier element and base part structure from the beginning, which inherently prevents temperature hysteresis and zero point drift. This preliminary design choice eliminates the need for extensive aging processes to stabilize the zero point, as the structure is inherently stable from manufacturing completion.
3Measurement precision
If the sensor signal deflection is made linear across the entire measurement range, then the measurement accuracy is improved, but the device complexity increases
Solution Approach 1:
The patent applies local quality by ensuring that the critical measurement point (zero position) has optimal linearity and accuracy through the monolithic carrier element design. The shutter vane geometry and optical path are specifically optimized at the zero point to achieve high linearity without requiring complex adjustments across the entire measurement range, thus maintaining simplicity while improving precision where it matters most.
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 configuration enhances the accuracy and reproducibility of the zero position, reduces temperature hysteresis, and shortens the aging process, maintaining sensitivity and stability across ambient temperature and humidity changes.
Implementation Method 1
An optoelectronic position sensor, whose sensor signal is representative of the displacement of the interlinked movable parts of the balance from a zero position... typically includes a light emitter and a light receiver which are mounted on the base part with an interstitial space between them, and further includes a shutter vane which extends through the interstice and participates in the displacement travel of the movable parts
Implementation Method 2
the shutter vane and the movable parts of the balance that are connected to it are returned to their zero position by the electromagnetic force that is acting between the coil and the permanent magnet
Implementation Method 3
The signal of the position sensor is sent to a closed-loop controller which, in response, regulates the compensation current in such a way that the shutter vane and the movable parts of the balance that are connected to it are returned to their zero position by the electromagnetic force
Data Source
AI summary
A weighing cell based on the principle of electromagnetic force compensation. A permanent magnet system is mounted on a base part and includes an air gap within which is suspended a coil that is connected to a load receiver through a force-transmitting mechanism. The coil carries an electrical compensation current when the weighing cell is in operation. An optoelectronic position sensor is also included, and its signal corresponds to the deflection of the coil from a zero position which occurs as a result of placing a load on the load receiver. A closed-loop controller regulates the compensation current in response to the sensor signal in such a way that the coil and the load receiver that is connected to it are returned to their zero position by the electromagnetic force that is acting between the coil and the permanent magnet.