Rheometer Guard Reduces Stray Capacitance

Solution Overview

Problem

Rheometers face challenges in measuring rheological properties due to stray capacitances between electrodes and temperature-controlled thermal conductors, which can lead to measurement errors and slow temperature response.

Innovation Solution

The implementation of a low thermal impedance guard, comprising a thermally conductive metal plate and layers of low thermal impedance conductive material and electrically insulating material, between the electrical insulator and the thermally conductive metal plate, helps mitigate stray capacitances while maintaining thermal conduction.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If the thickness of the insulator is increased to reduce stray capacitance, then measurement precision is improved, but thermal resistance increases causing slower temperature response

Engineering Contradiction:

Improvemeasurement precisionVSAvoidtemperature response

Core Design Contradiction:

Measurement precisionVSSpeed

Solution Approach 1:

The insulating structure is divided into multiple layers with different functions: a first insulating layer (ceramic or polymer) provides electrical insulation, while a second insulating layer (metal plate with conductive material) provides thermal conduction. This segmentation allows each layer to optimize for its specific function without compromising the other.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The solution uses composite material structure combining electrically insulating materials (ceramic, polymer) with thermally conductive materials (metal plate, conductive material) to create a multi-layer insulator that simultaneously provides electrical insulation and thermal conduction pathways.

Inventive Principle:

Principle #40Composite materials

2Measurement precision

If the thickness of the insulator is increased to increase thermal capacitance, then stray capacitance is reduced, but device complexity increases

Engineering Contradiction:

Improvestray capacitance reductionVSAvoiddevice complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The insulating structure is divided into multiple layers with different functions: a first insulating layer (ceramic or polymer) provides electrical insulation, while a second insulating layer (metal plate with conductive material) provides thermal conduction. This segmentation allows each layer to optimize for its specific function without compromising the other.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The solution uses composite material structure combining electrically insulating materials (ceramic, polymer) with thermally conductive materials (metal plate, conductive material) to create a multi-layer insulator that simultaneously provides electrical insulation and thermal conduction pathways.

Inventive Principle:

Principle #40Composite materials

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 effectively reduces measurement errors caused by stray capacitances and ensures a faster temperature response, thereby improving the accuracy and performance of rheological measurements.

Implementation Method 1

mitigating a source of stray capacitance from the traveling from the first and second electrodes to the thermally conductive metal plate

Methodology Applied

Scientific EffectStray capacitance: Parasitic Capacitance

Implementation Method 2

providing a desirable thermal conductance between the thermally conductive metal plate and uppermost surface of the lower geometry

Methodology Applied

Scientific EffectThermal conduction: Conduction (thermal)

Data Source

PatentUS20250180451A1Device for rheo-electric measurements having a low thermal impedance guard

Publication Date: 2025.06.05 TA INSTRUMENTS WATERS LLC

AI summary

The present disclosure describes an apparatus for performing electrical and rheology measurements of a material sample, comprising: an upper geometry; and a lower geometry. The lower geometry is stationary and the upper geometry rotates relative to the lower geometry. The lower geometry includes: a first electrode; a second electrode; and an electrical insulator for electrically isolating the first electrode from the second electrode. A thermally conductive metal plate is below the electrical insulator. A layer of low thermal impedance conductive material and a layer of electrically insulating material are between the electrical insulator and the thermally conductive metal plate.