Rotational Rheometer Thermal Expansion Compensation

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Solution Overview

Problem

Rotational rheometers face challenges in maintaining the accuracy of the measurement gap thickness, which affects viscosity calculations due to thermal expansion and mechanical warping, leading to measurement errors and temperature drift issues.

Innovation Solution

A rotational rheometer with a contactless position sensor system that directly measures the distance between measurement parts, using a temperature sensor to compensate for thermal changes and adjust the gap thickness, ensuring stability and accuracy by monitoring the readjustment rate and comparing it to predetermined thresholds before commencing measurements.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If the measurement gap thickness is maintained using conventional position sensors, then the measurement can proceed, but thermal expansion and mechanical warping cause measurement errors and temperature drift

Engineering Contradiction:

Improvemeasurement gap thickness accuracyVSAvoidmeasurement stability under thermal conditions

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent replaces conventional contact-based mechanical position sensors with a capacitive distance sensor system. This substitution eliminates mechanical contact that causes wear and thermal expansion issues, using instead an electrical field-based measurement approach that is not affected by thermal conditions in the same way, thereby improving measurement precision and reliability simultaneously

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent implements a feedback control system where the capacitive distance sensor continuously monitors the measurement gap thickness, and the control unit automatically adjusts the measurement gap to compensate for thermal expansion and mechanical warping. This closed-loop feedback ensures that the measurement gap remains constant despite temperature changes, resolving the contradiction between measurement precision and reliability

Inventive Principle:

Principle #23Feedback

2Measurement precision

If the measurement gap is readjusted frequently to maintain constant thickness, then measurement accuracy improves, but measurement time increases

Engineering Contradiction:

Improveviscosity measurement accuracyVSAvoidtime required for gap readjustment

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

The patent implements continuous monitoring of the measurement gap thickness using the capacitive distance sensor during the entire measurement process. This allows for real-time detection of gap changes and immediate compensation, eliminating the need for frequent interruptive readjustments. The continuous action maintains measurement accuracy while minimizing time loss by only making adjustments when necessary

Inventive Principle:

Principle #20Continuity of useful action

Solution Approach 2:

The control unit automatically performs gap compensation based on sensor feedback without requiring manual intervention. The system serves itself by detecting gap changes and autonomously adjusting the measurement gap, thereby maintaining precision while reducing the time overhead associated with manual readjustment procedures

Inventive Principle:

Principle #25Self-service

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 approach enhances the accuracy of viscosity measurements by maintaining a constant measurement gap, reducing errors caused by thermal expansion and mechanical warping, and ensures that the system is stable before recording rheological parameters, thereby improving the reliability of the results.

Implementation Method 1

use of a contactless position sensor, by means of which measurement values are established for the changing thickness of the measurement gap

Methodology Applied

Scientific EffectCapacitive sensing: Capacitance

Implementation Method 2

thermal expansion and mechanical warping

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Data Source

PatentUS8904852B2Method for establishing rheometric parameters of samples and rotational rheometer

Publication Date: 2014.12.09 ANTON PAAR GMBH

AI summary

A method establishes rheometric parameters of samples using a rotational rheometer. A thickness of a measurement gap delimited by measurement parts is measured by a measuring unit and a predetermined thickness value is adjusted, readjusted or kept constant when the measurement temperature is changed or set to a predetermined measurement temperature setpoint value. Accordingly, starting at a time at which at least one region of a measurement part has reached the predetermined measurement temperature, measurement values to be established, more particularly continuously, at predetermined measurement times and/or for predetermined time intervals delimited by predetermined measurement times, for the changing thickness of the measurement gap and/or for the rate of change in thickness or readjustment of thickness, and for the measurement of the rheological parameters only to be commenced once these measurement values have dropped below a specific predetermined threshold.