Radar Level Gauge Wait State Signal Comparison
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Solution Overview
Problem
Radar level gauges face challenges in detecting the surface echo in tanks, especially with solids having non-horizontal surfaces or liquids with turbulence or foam, leading to temporary undetectable echoes, which can result in false alarms and a 'blind' measurement period during conventional wait states.
Innovation Solution
The radar level gauge enters a wait state by storing the tank signal and comparing subsequent signals to determine if the surface has moved, deferring alarms until significant changes occur, allowing for prolonged periods of undetectable echoes without raising false alarms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional wait state is used when no surface echo is detected, then false alarms are avoided during temporary undetectability, but the level gauge becomes blind and cannot detect surface movement during the wait period
Solution Approach 1:
The patent stores the last valid tank signal before entering wait state as a reference. During the wait state, the system continuously compares new tank signals against this stored reference to detect any changes in the tank environment or surface position, even when surface echo is undetectable. This preliminary reference establishment enables the system to maintain situational awareness without requiring active surface echo detection.
2Reliability
If the wait state time period is extended to allow for prolonged undetectable surfaces, then false alarms are reduced, but the level gauge remains blind for longer periods and security is compromised
Solution Approach 1:
The patent implements continuous feedback during the wait state by comparing each new tank signal against the stored reference signal. When the comparison detects a difference exceeding a threshold, the system immediately exits the wait state and raises an alarm. This feedback mechanism eliminates the need for extended wait periods by providing real-time monitoring of tank conditions, thus maintaining both reliability and rapid response capability.
3Speed
If the wait state time period is kept short to maintain security, then surface movement can be detected quickly, but false alarms are triggered during normal temporary undetectability periods
Solution Approach 1:
By pre-storing a valid tank signal as reference before the wait state begins, the system establishes a baseline for normal tank conditions. During the wait state, comparisons against this reference can be performed immediately without delay, enabling fast detection of actual surface movements while filtering out temporary undetectability events that do not produce signal differences.
4Reliability
If continuous monitoring is performed during wait state to maintain security, then surface movement is detected, but the system complexity and processing requirements increase
Solution Approach 1:
The patent extracts only the essential comparison function needed for security monitoring during wait state, separating it from full surface echo detection. By comparing tank signals against a stored reference and checking for threshold exceedances, the system achieves continuous security monitoring with minimal processing requirements, avoiding the complexity of attempting to detect surface echoes during periods when they are inherently undetectable.
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 prolongs the time before unnecessary alarms are triggered, maintaining security by ensuring the surface has not moved, even if undetectable for hours or days, and allows for quick resumption of measurements when the surface becomes detectable again.
Implementation Method 1
transceiver circuitry configured to obtain a tank signal by combining an electromagnetic transmit signal and an electromagnetic return signal caused by a reflection of the transmit signal in the tank
Data Source
Figure 1a
Figure 1b
Figure 2
AI summary
A radar level gauge for determining a process variable of product in a tank, having processing circuitry configured to process a tank signal and, when no surface echo can be identified, enter a wait state. The wait state includes a) storing the tank signal in memory, b) obtaining a wait state tank signal, c) comparing the wait state tank signal with the stored tank signal to determine a tank signal difference measure, d) repeating steps b) and c) until the tank signal difference measure is greater than a predefined threshold, e) processing the wait state tank signal to identify a surface echo, and f) when no surface echo can be identified in the wait state tank signal, setting an alarm. By storing the tank signal when the wait state is entered, it is therefore possible to defer an alarm until the tank signal deviates from this stored tank signal.