Rheometer Thermal Expansion Compensation via Linear Sensor
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Solution Overview
Problem
Rheometers face challenges in maintaining a constant measurement gap due to thermal expansion of the drive shaft, which affects the accuracy of viscosity measurements.
Innovation Solution
A rheometer equipped with a linear position sensor that uses a pair of coils and a target to measure thermal expansion, allowing for real-time adjustment of the measurement gap by processing and control electronics to maintain a constant gap between measuring objects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If thermal expansion of the drive shaft is not compensated, then the device structure remains simple, but the measurement precision deteriorates due to changes in the measurement gap
Solution Approach 1:
The patent implements a feedback mechanism where a position sensor continuously monitors the measurement gap between measuring objects and feeds this information back to the control system. The control system then automatically adjusts the drive shaft position to maintain the desired gap, compensating for thermal expansion effects in real-time without requiring complex mechanical pre-compensation structures
Solution Approach 2:
The patent replaces complex mechanical compensation structures with an electronic sensing and control system. Instead of using mechanical elements to physically compensate for thermal expansion, the system uses a position sensor to detect gap changes and an electronic controller to actuate the drive shaft, substituting mechanical complexity with electronic control
2Measurement precision
If specialized configurations are used to compensate for thermal expansion, then measurement accuracy improves, but the device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent employs a universal position sensor and control system that can compensate for thermal expansion across various rheometer geometries and configurations. The same basic sensing and control architecture works for different measuring object arrangements, eliminating the need for specialized compensation mechanisms for each configuration and simplifying manufacturing
Solution Approach 2:
The patent changes the operational parameters of the system by introducing real-time monitoring and dynamic adjustment capabilities. Instead of manufacturing specialized components with fixed compensation features, the system dynamically adjusts the drive shaft position based on actual thermal conditions, making the device easier to manufacture while maintaining measurement accuracy
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 ensures a substantially constant measurement gap is maintained across various geometries, reducing thermal expansion errors and eliminating the need for specialized configurations, thereby enhancing measurement accuracy and reliability.
Implementation Method 1
a linear position sensor comprising: a target (134) mounted to the drive shaft (128); and a pair of coils (138), wherein the linear position sensor is configured to measure thermal expansion of the drive shaft (128) based on a change in impedance of the coils (138) resulting from a displacement of the target (134) relative to the coils (138)
Implementation Method 2
the motor is a drag cup motor (126) and the coils (138) are mounted to the drag cup motor (126)
Implementation Method 3
Rotary rheometers, viscometers or viscosimeters are used to measure fluid or other properties of materials such as their viscosity by rotating, deflecting or oscillating a measuring object in a material, and measuring, for example, the torque required to rotate or deflect or oscillate the object within the material
Data Source
Figure 1A
Figure 1B
Figure 1C
AI summary
A rheometer includes a drive shaft, a drag cup motor for rotating the drive shaft, a first measuring object supported by the drive shaft, a second measuring object, a linear position sensor, and processing and control electronics. The linear position sensor includes a target (e.g., an aluminum target) mounted to the drive shaft, and a pair of coils. The linear position sensor is configured to measure thermal expansion of the drive shaft based on a change in impedance of the coils resulting from a displacement of the target relative to the coils. The processing and control electronics are in communication with the coils and are configured to adjust a position of one of the measuring objects relative to the other based on a change in impedance of the coils resulting from a displacement of the target relative to the coils, thereby to maintain a substantially constant measurement gap therebetween.