Rheometer Gravitational Compensation for Force Accuracy
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Solution Overview
Problem
Rheometers face limitations in accurately measuring small forces due to gravitational forces affecting the measurement quality, leading to increased noise and reduced sensitivity, especially when using moving coil motors where the power supply lines need to be moved, and linear drives with resilient suspensions that exhibit non-linear behavior and hysteresis effects.
Innovation Solution
Incorporating a magnetically acting linear motor with a gravitational compensation unit that uses a permanent magnet and ferromagnetic parts to counteract the weight of the moving parts, allowing for precise force measurement by canceling out gravitational forces and minimizing noise, thereby enabling higher measurement resolution and accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a moving magnet linear motor is used, then power supply lines do not need to be moved, but the weight of the moving parts increases due to the magnet
Solution Approach 1:
The patent applies gravitational compensation by introducing a counteracting force (electromagnetic force from coil 67) to balance the weight of the slider 62 and its components. This compensation system allows the use of a moving magnet motor (which provides stable power supply) while neutralizing the negative effect of increased weight through active gravitational compensation.
2Measurement precision
If the weight of moving parts is increased to provide gravitational compensation, then measurement accuracy improves, but the force required to move the actuating rod increases
Solution Approach 1:
The patent extracts the gravitational force component from the measurement by compensating for it separately. The coil 67 generates an electromagnetic force that specifically counteracts the gravitational force on the slider 62, allowing the measurement system to focus only on the sample force FS without the confounding weight component.
3Device complexity
If resilient suspension is used in linear drives, then the structure is simplified, but non-linear behavior and hysteresis effects occur
Solution Approach 1:
The patent replaces the mechanical resilient suspension system with an electromagnetic gravitational compensation system. Instead of using springs or elastic elements that exhibit non-linear behavior and hysteresis, the patent uses coil 67 to generate electromagnetic force for gravitational compensation, providing linear and predictable force characteristics.
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 solution allows for precise measurement of small forces with improved accuracy and reduced errors, as the gravitational compensation unit effectively neutralizes the weight of the moving parts, ensuring that only the force applied to the sample is measured, enhancing the overall measurement quality.
Implementation Method 1
the gravitation compensation unit (60) has a permanent magnet (63) and ferromagnetic parts (64), matched to one another in such a way that between the ferromagnetic part (64) and the permanent magnet (63) a magnetic force acts which counteracts the weight
Implementation Method 2
If the coil is energized, an electromagnetic field is created, which exerts a force on the rotor. The resulting forces are proportional to the electric current (F ~ I).
Data Source
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AI summary
The invention relates to a rheometer for determining rheometric measurement data, wherein the rheometer comprises a rotational rheometer (100) having at least units for measuring and/or adjusting the normal force (9) and/or the rotational speed of the measuring part (1a) and/or the torque exerted by or on the measuring shaft (3) and/or the deflection angle of the measuring shaft (3), wherein the measuring shaft (3) is rotatably mounted in a bearing (5), preferably in an air bearing, preferably at a predetermined height above a base (50) of the rotational rheometer (100), wherein the rotational rheometer (100) is combined with a linear DM(T)A analysis unit (200) which includes a linearly adjustable adjusting rod (3') guided in a bearing (6), preferably in an air bearing, preferably in a predetermined rotational position, and at least units for measuring the tensile and/or compressive force and/or the position and/or feed movement of the adjusting rod (3') ownsand wherein the measuring shaft (3) and the adjusting rod (3') each carry a measuring element (1a, 1b) which form a measuring gap (1) and the sample (19) to be examined, preferably viscoelastic, is introduced into the measuring gap (1) between the opposing measuring elements (1a, 1b). According to the invention, the DM(T)A analysis unit (200) comprises a linear motor (2'), in particular a magnetically actuated motor, with a stator (61) and a rotor (62), wherein the DM(T)A analysis unit (200) comprises a magnetically actuated gravitational compensation unit (60) with which the weight force of the adjusting rod (3'), the measuring element (1b) arranged on the adjusting rod (3'), the rotor (62) and optionally the components attached to the rotor (62) can be compensated.