Guided Wave Radar Interface Measurement Using Segmented PED Probe
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Solution Overview
Problem
Conventional guided wave radar level gauge systems face difficulties in accurately determining substance interface levels, especially when dealing with substances like sand with low dielectric constants below substances with high dielectric constants, such as water, due to signal attenuation and the need for complex tank feed-throughs.
Innovation Solution
The system employs a power divider to split the transmit signal into two signals with different propagation characteristics, using a Partially External Dielectric (PED) transmission line probe with varying dielectric layers and shielding configurations to optimize signal coupling for different measurement depths, allowing for the identification of deep and shallow interface levels without a non-standard tank feed-through.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional guided wave radar level gauge system is used to measure substance interface levels, then the system structure is simple, but the measurement precision deteriorates when dealing with substances like sand having low dielectric constants below substances with high dielectric constants such as water
Solution Approach 1:
The transmission line probe is segmented into multiple sections with different dielectric properties. The probe includes a first section with a first dielectric material and a second section with a second dielectric material, where the different dielectric sections are configured to provide different signal coupling characteristics for measuring different substance interfaces, thereby improving measurement precision without requiring a completely complex system redesign
Solution Approach 2:
Different sections of the transmission line probe are assigned different dielectric materials with specific local qualities. The first dielectric material is optimized for coupling with certain substances while the second dielectric material is optimized for other substances, allowing the single probe to adapt its local coupling characteristics to match the specific measurement requirements at different depths and substance combinations
2Measurement precision
If a PED transmission line probe is used to improve interface level measurement, then the ability to measure interface levels improves, but there are still measurement situations where the performance is not sufficient, particularly when detecting substances with low dielectric constants below high dielectric constant substances
Solution Approach 1:
The transmission line probe is divided into multiple sections with different dielectric materials, each section being optimized for specific substance combinations. This segmentation allows the probe to adapt its coupling characteristics to match the specific measurement requirements at different depths, improving both measurement precision and adaptability to various substance combinations including challenging cases like sand below water
Solution Approach 2:
The probe utilizes different dielectric materials with varying permittivity values to change the signal coupling parameters along the probe length. By selecting dielectric materials with specific permittivity ranges, the system can optimize signal penetration and coupling for different substance interfaces, thereby enhancing adaptability to measure various substance combinations accurately
3Measurement precision
If a sensing element with multiple coaxial cables is used to measure from top and bottom of the tank, then the measurement performance for certain situations improves, but the device complexity increases due to the need for a feed-through allowing passage of multiple coaxial cables
Solution Approach 1:
The invention merges the function of multiple coaxial cables into a single transmission line probe structure. Instead of requiring separate top-down and bottom-up measurement systems with multiple cables and complex feed-throughs, the single probe integrates multiple dielectric sections that enable bidirectional measurement capability, thereby reducing device complexity while maintaining measurement precision
Solution Approach 2:
The transmission line probe is designed with universal multi-functionality to perform both top-down and bottom-up measurements using the same probe structure. The multiple dielectric sections enable the single probe to adapt its coupling characteristics for different measurement directions and substance combinations, eliminating the need for separate measurement systems and complex multi-cable feed-throughs
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 simplifies and cost-efficiently measures multiple substance interface levels by enhancing signal separation and reducing attenuation, facilitating accurate determination of interface levels without the need for complex feed-throughs, thereby improving measurement performance in challenging scenarios.
Implementation Method 1
electromagnetic signals are guided towards and into the product by a transmission line probe
Implementation Method 2
Partially External Dielectric (PED) transmission line probe with varying dielectric layers
Implementation Method 3
The electromagnetic signals are subsequently reflected at the surface of the product, and the reflected signals are received by a receiver or transceiver
Implementation Method 4
a shielding conductor spaced apart from the probe conductor and extending along at least a portion of the second transmission line probe member
Data Source
Figure 1
Figure 2A
Figure 2B
AI summary
A radar level gauge system (2) comprising: a transceiver (26); a tank feed-through (34); a power divider (36) to divide a transmit signal into a first transmit signal (ST1) and a second transmit signal (ST2); a first probe member (38) configured to guide the first transmit signal and to return a first reflection signal (SR1), said first probe member providing a first relatively large average attenuation; a second probe member (40) configured to guide said second transmit signal and to return a second reflection signal (SR2), said second probe member providing a second relatively small average attenuation; measurement signal forming circuitry for forming a measurement signal comprising a first set of echo indicators indicating reflection of said first transmit signal, and a second set of echo indicators indicating reflection of said second transmit signal; and level determining circuitry for determining a first level based on said first set of echo indicators, and a second, deeper, level based on said second set of echo indicators.