Segmented TDR Moisture Probe for Bulk Material Measurement
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Solution Overview
Problem
Existing moisture and conductivity measurement devices, such as planar moisture sensors and TDR probes, face challenges when measuring heterogeneous materials like corn cobs or wood chips, as they can interfere with the flow behavior and are prone to mechanical damage, leading to inaccurate measurements and potential breakage.
Innovation Solution
A break-resistant device with a measurement probe consisting of a conductive rod and a non-conductive rod, fastened to the container wall, uses a TDR method to determine moisture and conductivity, featuring a flexible glass fiber carrier and thin-walled conductive tube for mechanical stability and a coaxial cable for signal transmission, allowing for accurate measurements in large volumes without interfering with the medium's flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If rod probes with thick rods and small spacing are used, then measurement capability is improved, but the medium flow behavior is significantly interfered with and clumping occurs
Solution Approach 1:
The measurement probe is segmented into multiple thin rods instead of using a single thick rod or few thick rods. This segmentation reduces the total surface area blocking medium flow while maintaining multiple measurement points, thereby reducing interference with medium flow behavior and preventing clumping.
Solution Approach 2:
The diameter of the rods is reduced from thick to thin, changing the geometric parameter of the probe. This parameter change decreases the resistance to medium flow and eliminates clumping while still providing sufficient measurement capability through multiple thin rods arranged in a specific configuration.
2Measurement precision
If rod probes with thick rods are used, then measurement capability is improved, but the rods may bend during filling due to strong mechanical loading
Solution Approach 1:
The probe structure is divided into multiple thin rods rather than using fewer thick rods. Each thin rod has higher flexural strength relative to its size and is less prone to bending under mechanical loading during filling operations, while the collective arrangement maintains measurement capability.
Solution Approach 2:
The rods are made from composite materials or coated with protective layers that enhance mechanical strength and resistance to bending. This allows the rods to withstand strong mechanical loading during filling without deforming, while maintaining their measurement functionality.
3Measurement precision
If planar moisture sensors are used, then measurement capability is provided, but deposits or water film form on the sensing element surface reducing measurement accuracy
Solution Approach 1:
The sensing elements are extracted from direct contact with the medium surface. Instead of placing planar sensors where the medium touches them directly, the measurement is performed through the rod structures that are either insulated or positioned to measure field properties without direct medium contact, preventing deposit formation and water film accumulation.
Solution Approach 2:
An intermediary structure (insulation layer, protective coating, or field transmission medium) is introduced between the sensing element and the medium. This intermediary prevents direct contact that would cause deposits or water films, while still allowing the measurement field to interact with the medium for accurate moisture detection.
4Measurement precision
If planar moisture sensors with direct medium contact are used, then measurement is enabled, but the medium is not located between measurement lines but above them limiting measuring field size
Solution Approach 1:
The measurement approach transitions from a planar two-dimensional configuration to a three-dimensional arrangement using vertical rod structures. This dimensional change allows the measurement field to extend vertically through the medium depth, significantly increasing the effective measuring field area and enabling measurement of heterogeneous materials throughout the bulk volume.
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 and reliable moisture and conductivity measurements for bulk heterogeneous materials and low-density media, maintaining measurement accuracy and resistance to extreme mechanical loads, reducing the risk of damage and interference with the medium's flow.
Implementation Method 1
A break-resistant device with a measurement probe consisting of a conductive rod and a non-conductive rod, fastened to the container wall, uses a TDR method to determine moisture and conductivity
Data Source
AI summary
The invention includes a device for determining the moisture or conductivity of a medium in a container. A measurement probe is plunged into the medium and consists of a conductive material, a conductive rod, and a first feed-through component designed such that the conductive rod can be fastened to an electrically conductive wall or holder. A rod of a non-conductive material and a second feed-through component are provided, where the non-conductive rod can be fastened to the wall, the conductive rod and the non-conductive rod are dimensioned and oriented that the measurement probe is oriented parallel to the longitudinal axis of the container and a signal-processing unit designed such that high-frequency measurement signals are conducted via the measurement line to the measurement probe and that the moisture or the conductivity of the medium is determined by means of a TDR method.