Method for determining and/or monitoring fill level of a medium in a container
A method for determining and/or monitoring fill level of a medium in a container with a measuring device, which works according to the travel time measuring method, wherein measurement signals are transmitted toward the medium and are received, wherein from the high-frequency total measurement signal, composed by superimposing the transmitted measurement signals, the reflected wanted echo signals and the disturbance echo signals, a raw echo curve or digitized envelope curve is ascertained. The wanted echo signals and/or the disturbance echo signals in the raw echo curve or the digitized envelope curve are ascertained based on an ideal echo curve, which shows the amplitude of the echo signals of an ideal reflector as a function of the distance from the ideal reflector, and based on the ascertained wanted echo signal the fill level is determined.
1. A method for determining and/or monitoring fill level of a medium in a container with a measuring device, which works according to the travel time measuring method, comprising the steps of:
transmitting measurement signals toward the medium and reflected on a surface of the medium as wanted echo signals or on a surface of a disturbing element as disturbance echo signals and are received,
from the high-frequency total measurement signal, composed by superimposing the transmitted measurement signals, the reflected wanted echo signals and the disturbance echo signals, by a sequential sampling, a low-frequency, intermediate frequency signal is produced,
from the intermediate frequency signal at least one raw echo curve or digitized envelope curve dependent on travel time or travel distance is ascertained;
ascertaining the wanted echo signals and/or the disturbance echo signals in the raw echo curve or the digitized envelope curve based on an ideal echo curve, which shows the amplitude of the echo signals of an ideal reflector as a function of the distance from the ideal reflector; and
based on the ascertained wanted echo signal the fill level is determined.
2. The method as claimed in claim 1 , wherein:
the ideal echo curve is calculated and ascertained by means of a predetermined algorithm.
3. The method as claimed in claim 1 , wherein:
the ideal echo curve is ascertained by means of a comparison measurement with an ideal reflector and stored.
4. The method as claimed in claim 2 , wherein:
the ideal echo curve is fitted by means of an algorithm and an adaptive ideal echo curve is produced.
5. The method as claimed in claim 4 , wherein:
said adaptive ideal echo curve is shifted by the algorithm based on an offset-shifting along a logarithmic amplitude axis.
6. The method as claimed in claim 5 , wherein:
the shifting of said adaptive ideal echo curve is performed based on the algorithm based on the amplitude of the greatest echo.
7. The method as claimed in claim 5 , wherein:
the shifting of said adaptive ideal echo curve is performed based on the algorithm based on a noise level.
8. The method as claimed in claim 5 , wherein:
the shifting of said adaptive ideal echo curve is performed based on the algorithm based on setting parameters of the measuring device ( 1 ).
9. The method as claimed in claim 1 , wherein:
said adaptive ideal echo curve is adapted to changed measuring conditions, e.g. in the form of signal attenuation changes, by means of a shape adapting based on the algorithm.
10. The method as claimed in claim 9 , wherein:
the shape adapting of said adaptive ideal echo curve is performed by the algorithm by means of a monitoring of the amplitude of said wanted echo signal at different distances, respectively travel times.
11. The method as claimed in claim 9 , wherein:
the shape adapting of said adaptive ideal echo curve is performed based on the algorithm based on setting parameters of the measuring device ( 1 ).
12. The method as claimed in claim 1 , wherein:
for diagnosis of the measuring device or the measuring point and for obtaining further supplemental information concerning the application, said ideal echo curve is compared with said adaptive ideal echo curve based on the algorithm.
13. The method as claimed in claim 1 , wherein:
for diagnosis of the measuring device or the measuring point and for obtaining further supplemental information concerning the application, said ideal echo curve or the adaptive ideal echo curve is compared with the noise level based on the algorithm.