Microwave Sensor Dirt Layer Compensation
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Solution Overview
Problem
Microwave sensors used to measure flowable substances, such as sewage sludge, face significant errors due to dirt build-up, leading to inaccurate process control and economic losses, as the dirt layers alter the relative dielectric constants and affect the measurement of the substance's properties.
Innovation Solution
The apparatus employs multiple microwave sensor elements arranged in a configuration that calculates effective distances and differences in time of flight, independent of dirt layer thickness, using transmitter-receiver pairs to eliminate the impact of dirt layers on measurement results, and a signal processing unit to determine the desired properties of the flowable substance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If microwave sensor elements are placed in contact with flowable substance for measurement, then measurement capability is achieved, but dirt build-up on sensor elements causes measurement errors
Solution Approach 1:
The system uses at least three sensor elements arranged in multiple transmitter-receiver pairs to create multiple measurement paths. By segmenting the measurement into multiple independent paths and calculating differences in time of flight between these paths, the system can eliminate the common-mode effect of dirt layers that accumulate on all sensor elements, thereby maintaining measurement precision despite dirt build-up.
Solution Approach 2:
The patent introduces an intermediary calculation method that uses the difference in time of flight between multiple measurement paths as an intermediate parameter. This intermediate parameter (difference in time of flight) is independent of the absolute dirt layer thickness, allowing the system to derive the desired property of the flowable substance while eliminating the harmful effect of dirt accumulation.
2Measurement precision
If multiple transmitter-receiver pairs are used to eliminate dirt layer effects, then measurement accuracy improves, but device complexity increases
Solution Approach 1:
The system divides the measurement function into multiple transmitter-receiver pairs, where each pair provides an independent measurement path. This segmentation allows the use of simple individual sensor elements while achieving complex measurement objectives through the combination of multiple paths and differential calculation of time of flight differences.
Solution Approach 2:
The sensor elements serve multiple functions: they act as both transmitters and receivers in different pairs, and each sensor element participates in multiple measurement paths. This multi-functionality reduces the need for additional specialized components, thereby limiting the increase in device complexity while still achieving improved measurement accuracy.
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 significantly reduces or eliminates measurement errors caused by dirt layers, providing more accurate results for process control and reducing economic losses by improving the accuracy of consistency and solid content measurements in flowable substances.
Implementation Method 1
at least three microwave sensor elements (100, 102, 104) which are arranged at separate locations in a measurement chamber (106) in contact with the flowable substance (108)
Implementation Method 2
calculates effective distances and differences in time of flight
Implementation Method 3
the effect of the layered dirt on the microwave sensor elements may cause an error of up to tens of percentages to a measurement result
Data Source
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AI summary
An apparatus for measuring flowable substance which comprises at least three microwave sensor elements (100, 02, 104) arranged at separate locations in a measurement chamber (106) in contact with the flowable substance (108). The sensor elements (100, 102, 104) operate as at least two transmitter-receiver pairs (110, 12), which transmit and receive microwave radiation via at last two paths of different lengths, through layers of dirt (114, 116, 118) on the sensor elements (100, 102, 104) and the flowable substance (108)for eliminating an effect of dirt layers (114, 116, 118) on the sensor elements (100, 02, 104) from the measurement result.A signal processing unit (120) comprises a controller which is configured to control feed of at least one substance which has an effect on the measured value of the flowable substance (108) to the chamber (106) on the basis of the measured value of the desired property of the flowable substance (108).