Laser Fill Level Measurement Using Detuned Sampling
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Solution Overview
Problem
Current laser-based fill level measurement technologies face limitations in multi-target capability, robustness against disturbances, measurement accuracy, and cost due to high sampling rates and power consumption, making them unsuitable for level measurement in liquid media and automation technology.
Innovation Solution
A method and device using laser pulses with a defined transmission repetition frequency and sampling frequency, where the sampling frequency is generated by different frequency-generating components, allowing for multiple sub-echo curves to reconstruct an overall echo curve, reducing the number of required pulses and enabling higher measurement speed and accuracy with lower costs and power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If high sampling frequencies are used to achieve necessary measurement accuracy with pulse widths of 1-5 ns, then measurement precision is improved, but device cost and power consumption increase significantly
Solution Approach 1:
The patent employs periodic laser pulses with a repetition frequency that is intentionally detuned from an integer multiple of the sampling frequency. This periodic action with slight frequency offset creates a time-stretched effect where multiple sampling points accumulate over several pulse periods, effectively achieving high-resolution measurement without requiring excessively high sampling frequencies. The detuning creates a walking pattern where samples progressively cover the entire pulse waveform over multiple periods.
Solution Approach 2:
The patent maintains continuous measurement by overlapping multiple pulse-period sampling sequences. Instead of discrete independent measurements, the system continuously accumulates sampling points across multiple pulse periods, creating an uninterrupted measurement stream that improves both accuracy and temporal resolution while keeping sampling frequency requirements manageable.
2Productivity
If high transmission pulse rates are used to achieve fast data acquisition for moving liquid surfaces, then productivity is improved, but use of energy increases significantly
Solution Approach 1:
The system uses periodic laser pulses with optimized repetition frequency that balances measurement speed and energy consumption. By detuning the pulse repetition frequency from an exact integer multiple of the sampling frequency, the system achieves effective time-stretching that allows adequate sampling resolution at lower pulse rates, reducing the number of high-power pulses needed per measurement cycle.
Solution Approach 2:
The patent dynamically adjusts the relationship between pulse repetition frequency and sampling frequency through controlled detuning. This dynamic frequency relationship allows the system to adapt the measurement cycle duration and pulse rate to match the motion characteristics of the liquid surface, optimizing both acquisition speed and energy efficiency for different measurement conditions.
3Loss of information
If existing laser scanning systems with full-waveform scanning are used for geodata acquisition, then measurement completeness is improved, but they are too slow and expensive for level measurement applications
Solution Approach 1:
The patent implements a periodic sampling scheme where the sampling frequency is detuned from an exact multiple of the pulse repetition frequency. This creates a time-stretched representation of the complete waveform over multiple pulse periods, achieving full-waveform scanning capability at lower sampling frequencies. The periodic detuning ensures that all portions of the waveform are eventually sampled while maintaining measurement speed suitable for level monitoring.
Solution Approach 2:
The patent segments the waveform acquisition process across multiple pulse periods rather than requiring all samples within a single pulse period. By dividing the measurement into sequential segments that accumulate over several detuned periods, the system reconstructs the complete waveform information at a slower, more energy-efficient pace suitable for level measurement applications.
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 achieves high measurement speed, low component costs, low power consumption, and increased laser power, enabling accurate level measurement in liquid media while meeting safety and accuracy requirements, with a significant reduction in the number of pulses required compared to existing methods.
Implementation Method 1
emitting the laser pulses with a defined transmission repetition frequency towards the surface of the material being filled... the laser pulses are received after reflection from the surface of the material being filled
Implementation Method 2
the transit time of the laser pulse is measured using highly accurate time-to-digital converters (TDCs). The operation of these TDCs is comparable to a stopwatch: there is a start signal and a stop signal
Data Source
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AI summary
The invention relates to a method for the laser-based determination of the filling level of a filling material in a container according to a propagation time method, wherein laser pulses of a predefined pulse width (Tp) are generated, wherein the laser pulses are emitted at a defined transmission repetition frequency (? Pulse) in the direction of the surface of the filling material, wherein the defined transmission repetition frequency (? Pulse) of the laser pulses is obtained by multiplying a predefined fundamental frequency (?) by a predefined divider factor (TF), wherein the laser pulses are received after reflection at the surface of the filling material, wherein the laser pulses reflected at the surface of the filling material are sampled at a sampling frequency (?S) differing slightly from the fundamental frequency (?) in such a manner that a plurality of samples are recorded for each laser pulse and are each stored as a sub-echo curve (SEK), wherein the stored sub-echo curves (SEK) are combined after every measurement cycle to form a total echo curve (EK), and wherein the filling level is determined using the total echo curve (EK).