Planar Microwave Sensor for Pulp Thickness Measurement
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Solution Overview
Problem
Existing devices for measuring the thickness of cellulosic pulp in paper making machines face challenges due to the use of radioactive sources, inaccurate ultrasound sensors, and microwave sensors with limited penetration and thermal sensitivity, making them impractical and inefficient.
Innovation Solution
A device incorporating a planar microwave sensor with a slot-type resonant circuit using fractal or pseudo-fractal geometric patterns, integrated with a temperature sensor and A/D converter, allowing for precise thickness measurement by shifting resonance frequency based on dielectric constant, and enabling integration into the paper making machine's blades.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If GRS (Gamma Back Scattering) sensors are used to measure cellulosic pulp thickness, then measurement accuracy is improved, but the device becomes expensive and impractical due to the radioactive source
Solution Approach 1:
The patent removes the radioactive source from the measurement system entirely, extracting the harmful element while preserving the measurement function through alternative non-radioactive sensing methods
Solution Approach 2:
The invention replaces expensive radioactive sources with cheaper, non-radioactive sensor components that can be manufactured at lower cost and do not require special handling or licensing
2Ease of manufacture
If ultrasound sensors are used to measure cellulosic pulp thickness, then the device is easier to manufacture, but measurement accuracy deteriorates, especially in the paper making environment
Solution Approach 1:
The patent changes the physical parameter used for measurement from ultrasound to electromagnetic radiation (microwave), which interacts differently with the cellulosic pulp and water, providing superior accuracy in the paper making environment while maintaining manufacturing feasibility
3Quantity of substance
If microwave sensors with resonance chambers are used to measure water content, then the sensor can estimate water quantity, but the device becomes expensive, has limited penetration capacity, and cannot be integrated into the blades
Solution Approach 1:
The patent transitions from three-dimensional resonance chambers to two-dimensional planar sensor elements, enabling integration into the blade structure while maintaining measurement capability through surface-mounted or embedded configurations
Solution Approach 2:
The invention uses thin film or planar sensor structures that can be flexibly integrated into the blade geometry, replacing rigid resonance chambers with adaptable electromagnetic sensing elements that conform to the blade surface
4Quantity of substance
If microwave sensors with metal-based alloy resonance chambers are used, then water content can be measured, but thermal expansion or contraction causes frequency shifts that affect measurement accuracy
Solution Approach 1:
The patent changes the material composition of the resonance chamber from metal-based alloys to materials with low thermal expansion coefficients, such as ceramics or composite materials, thereby minimizing thermal frequency shifts and improving measurement stability
Solution Approach 2:
The invention employs composite materials for the resonance chamber structure that combine low thermal expansion properties with appropriate electromagnetic characteristics, reducing thermal sensitivity while maintaining measurement functionality
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
The device provides accurate, uniform microwave field penetration, reduced temperature sensitivity, and increased measurement accuracy, enabling effective monitoring of pulp thickness and water content, enhancing drainage efficiency and paper quality.
Implementation Method 1
measure the frequency response of a layer of material... by measuring the frequency response of the cellulosic pulp layer
Implementation Method 2
the resonance frequency which affects the response... characterized by a frequency response curve, basically centred around a resonance frequency
Implementation Method 3
The planar type sensor... generates a uniform electromagnetic field
Data Source
Figure 1
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AI summary
A device (1; 1b) for measuring the thickness of a layer of material (20) is provided with reading means (2) and control means (3) connected to the reading means (2). The reading means (2) include a microwave planar type sensor (6) and an A/D converter (8) connected to the microwave sensor (6) and arranged in proximity of the microwave sensor (6).