Adaptive Echo Filtering for Transit Time Level Measurement
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Solution Overview
Problem
Existing fill level measurement methods using transit time measurement face challenges in unequivocally identifying useful echoes, leading to measurement errors due to interference echoes and the formation of 'ghost echoes' during rapidly changing filling levels, which can result in incorrect level determination and potential safety issues.
Innovation Solution
The method employs a transit time measurement approach with a pre-processing technique that divides the echo function or envelope into multiple filter areas, applying different filter parameters to each area to adaptively suppress interference and artefact echoes, ensuring accurate identification of the useful echo signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If static echo search algorithms are used to identify the useful echo, then the evaluation process is simplified, but measurement errors occur due to interference echoes and ghost echoes during rapidly changing filling levels
Solution Approach 1:
The echo function is divided into multiple filter areas (first filter area around the useful echo position, second filter area for interference echoes, third filter area for other echoes). Each area is processed with different filter parameters, allowing selective suppression of interference while preserving the useful echo signal.
Solution Approach 2:
Different filter parameters are applied to different filter areas based on their local characteristics. The first filter area uses parameters optimized for the useful echo, while the second and third areas use parameters designed to suppress interference echoes and ghost echoes respectively.
2Device complexity
If uniform filter parameters are applied to the entire echo function, then the device complexity is reduced, but interference echoes and ghost echoes cannot be effectively suppressed
Solution Approach 1:
The echo function is segmented into distinct filter areas with different characteristics. This segmentation enables the application of tailored filter parameters to each area, improving the suppression of interference echoes and ghost echoes while maintaining manageable system complexity.
Solution Approach 2:
Different filter parameters are assigned to different filter areas. The filter parameters are changed according to the local characteristics of each filter area, allowing optimal suppression of various types of echoes in their respective regions while maintaining overall system reliability.
3Reliability
If strong filtering is applied to suppress interference echoes, then measurement reliability is improved, but ghost echoes are formed during rapidly changing filling levels
Solution Approach 1:
The filtering process is segmented into different areas with different filtering strengths. The second filter area applies stronger filtering to suppress interference echoes, while the first filter area uses gentler filtering to avoid creating ghost echoes during rapid level changes.
Solution Approach 2:
The filtering strength is adjusted locally for each filter area based on the expected echo characteristics. This local quality approach allows strong filtering where interference echoes are present without creating ghost echoes in areas where the useful echo is located.
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 enhances measurement reliability and availability, particularly in challenging situations, by reducing errors and allowing for flexible evaluation through adaptive filtering, thereby preventing incorrect level determinations and ensuring accurate fill level monitoring.
Implementation Method 1
These level gauges send a periodic transmission signal in the microwave or ultrasonic range by means of a transmission/reception element in the direction of the surface of a filling and receive the reflected echo signals after a distance-dependent transit time
Implementation Method 2
receive the reflected echo signals after a distance-dependent transit time
Implementation Method 3
in which the microwaves are guided along a waveguide in the direction of the filling material reflected on the surface of the product due to the jump in impedance there
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
The present invention relates to a method for determining and monitoring the level of a medium in a container by means of a field device according to a runtime measurement method, wherein transmission signals are emitted in the direction of the medium and reflection signals are received, wherein the received reflection signals are captured as echo signals in an echo function or envelope curve dependent on the runtime or run distance, wherein an echo search algorithm is used to determine at least one useful echo signal in the echo function or envelope curve, wherein the echo function or envelope curve is preprocessed by means of at least one filter with filter parameters, wherein at least one first filter range with a first width is predefined at the position of the useful echo signal in the echo function or envelope curve and thus at least three filter ranges are formed in the echo function or envelope curve.