FMCW Radar Fill-Level Device Self-Diagnostic Method
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Solution Overview
Problem
Radar-based fill-level measuring devices face limitations in accuracy due to the inability to produce infinitesimally short microwave signal pulses, leading to reduced resolution and potential errors from disturbance signals, which can result in incorrect fill level measurements and compromised functional ability, especially in the presence of electromagnetic interference.
Innovation Solution
A method involving the production and transmission of two microwave signals with different frequency changes, where the fill level is determined from the frequency of the difference signals, and the functional ability is checked by comparing the frequency of a second difference signal to a reference frequency, indicating whether the device is functionally incapacitated.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If pulse radar method is used for fill-level measurement, then circuit implementation is simple, but measurement resolution is limited due to inability to produce infinitesimally short microwave signal pulses
Solution Approach 1:
The patent applies periodic frequency modulation to the microwave signal, where the frequency changes periodically over time (chirp signal). This periodic action allows the system to encode distance information in the frequency domain, enabling higher resolution measurements while maintaining simple circuit implementation characteristic of pulse radar methods.
2Measurement precision
If FMCW method with frequency changing microwave signals is used, then measurement resolution is improved, but disturbance signals from reflection on stirring devices cause incorrect measurements
Solution Approach 1:
The patent employs feedback mechanisms where the system continuously monitors the received signals and compares them against expected patterns. When disturbance signals are detected (such as reflections from stirring devices), the system can identify these as anomalies and either filter them out or trigger alerts, ensuring that only valid fill level measurements are processed.
Solution Approach 2:
The patent introduces signal processing intermediaries including reference signals and comparison circuits that act as mediators between the raw received signals and the final measurement output. These intermediaries help distinguish between valid echo signals from the fill level and spurious reflections from stirring devices by comparing signal characteristics against known patterns.
3Reliability
If electromagnetic disturbance radiation is present, then functional ability of the measuring device is compromised, but no built-in mechanism exists to detect or prevent this
Solution Approach 1:
The patent implements self-service functionality where the measuring device automatically monitors its own operational status and detects functional impairments caused by electromagnetic disturbances. The system performs self-diagnostics by analyzing signal characteristics and can autonomously identify when electromagnetic interference is degrading performance, enabling reliable operation through built-in fault detection capabilities.
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 method allows for regular checking of the fill-level measuring device's functional ability, ensuring safety and accuracy by distinguishing between valid and invalid echo signals, thus maintaining the required Safety Integrity Level (SIL) and preventing incorrect fill level measurements.
Implementation Method 1
radar-based fill-level measuring device, which serves for measuring the fill level of a fill substance located in a container
Implementation Method 2
a first echo signal (E1), which is produced by reflection of the first microwave signal (S1), is received
Implementation Method 3
a first difference signal (IF1) is produced by mixing the first received signal (e1) with the first electrical signal (s1)
Data Source
AI summary
A method for checking the functional ability of an FMCW-based fill-level measuring device, which serves for measuring the fill level of a fill substance located in a container, as well as to a fill-level measuring device suitable for performing this method. For checking the functional ability, a microwave signal is produced, whose frequency change differs from the frequency change of the measurement signal used during regular measurement operation. By comparing the frequency of the difference signal resulting from the microwave signal with a predetermined reference frequency, it is ascertained, whether the fill-level measuring device is functionally able. Thus, the fill-level measuring device detects, independently, whether it is functionally able, or whether an error is present, caused principally by device-internal disturbance signals. This offers, especially, a clear advantage as regards meeting safety standards for the field device.