Fill Level Measurement Using Phase-Frequency Distribution
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Solution Overview
Problem
Existing filling level measurement devices face limitations in accuracy due to random fluctuations in time offsets during phase difference measurement between transmitted and received signals, which affect the determination of the filling level.
Innovation Solution
The method involves forming a cross-correlation of the phase-frequency distribution with a reference distribution and determining the fill-level propagation time using the propagation time of a maximum from the cross-correlation, while filtering frequency values using a mean value filter to stabilize the phase frequency distribution and improve measurement accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If phase difference measurement is used to improve measurement accuracy, then measurement precision is improved, but random fluctuations in time offsets occur affecting determination accuracy
Solution Approach 1:
The patent applies preliminary action by forming a phase frequency distribution from multiple measured phase differences before determining the final filling level. This pre-processing step collects and analyzes multiple measurements to identify the most probable phase difference, compensating for random time offset fluctuations and providing a more reliable basis for measurement.
Solution Approach 2:
The patent implements feedback by using the phase frequency distribution to identify the most probable phase difference through peak detection. The system continuously monitors phase differences, builds the frequency distribution, and uses the identified peak to correct and refine the measurement, creating a feedback loop that improves measurement reliability.
2Measurement precision
If cross-correlation with reference distribution is performed to compensate for time offsets, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent uses preliminary action by pre-forming a reference phase frequency distribution from initial measurements or calibration data. This reference distribution is stored and later used for cross-correlation with new measurements, enabling the system to compensate for time offsets without performing complex real-time calculations during actual measurement.
Solution Approach 2:
The patent applies copying by creating a reference phase frequency distribution that represents the ideal or calibrated state. This reference copy is then compared with actual measurements through cross-correlation, allowing the system to identify deviations and compensate for them without needing to recreate the entire analysis process from scratch.
3Measurement precision
If mean value filtering is applied to stabilize phase frequency distribution, then measurement precision is improved, but processing time increases
Solution Approach 1:
The patent applies partial action by using a mean value filter with a specific window size that balances filtering effectiveness with processing speed. Instead of filtering all historical data, the system uses a predetermined number of recent measurements to calculate the mean, providing sufficient stabilization while limiting the computational burden and processing time.
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 enhances the accuracy of filling level measurement by compensating for random fluctuations in time offsets, leading to more precise determination of the filling level.
Implementation Method 1
signal pulses of a predetermined frequency are sent into the container by means of a transmitter and receiver device with a predetermined repetition frequency, and the signal components of which are reflected back in the container towards the transmitter and receiver device are received as a received signal after a transit time dependent on the distance traveled by the received signal
Implementation Method 2
an auxiliary signal is derived from the received signal over a predetermined transit time range, representing amplitude and phase information of the received signal contained in the received signal as a function of the associated transit time
Data Source
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AI summary
The invention relates to a fill level measuring method and to a measuring device for carrying out the method, in which signal pulses of a predefined frequency (fs) are sent into a container (1) in successive measuring cycles and in each case by means of a transmitting and receiving unit (7, 7') at a predefined repetition frequency (fr), and the signal components (R) thereof that are reflected back in the direction of the transmitting and receiving unit (7, 7') in the container are received as a received signal (E) after a propagation time (t) that depends on the distance said signal components have covered, by means of which received signal the fill level (L) is measured while taking into account a phase angle that is physically induced by the fill level (L) to be measured between the transmitted and received signals (S, E) in that, in each measuring cycle, by using the received signal (E), an auxiliary signal (ZF, ZA) reproducing an item of amplitude and phase information about the received signal (E) contained in the received signal (E) is derived as a function of the associated propagation time (t), by using the auxiliary signal (ZF), a propagation time (t) of a single component reflected on the surface of the filling material (9) is determined as basic propagation time (tG), propagation times (t,) of zero crossings of the auxiliary signal (ZF, H) are determined, by using propagation times (t,) of the zero crossings of the auxiliary signals (ZF, H) that are current and were determined in a plurality of preceding measurement cycles, a phase-frequency distribution (N(t)) is derived as a function of the propagation time (t), which indicate frequencies with which zero crossings occurred in the associated auxiliary signals (ZF, H) at the respective propagation times (t), a propagation time (tNV) of a maximum (NVmax) from the frequency distribution (N(t) lying closest to the basic propagation time (tG) is determined as the fill level propagation time (tL), and the fill level (L) is determined by using the fill level propagation time (tL).