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Decrease of an error of measurement of distance level gauge with it is frequency the modulated signal against hindrances and noise

Keywords:

B.A. Atayants – Ph.D.(Eng.), General Director of Open Company enterprise «KONTAKT-1» (Ryazan)
E-mail: skb@kontakt-1.ru
V.M. Davydochkin – Ph.D.(Eng.), Head of Department of Microwave Oven of Devices and Aerials, Open Company enterprise «KONTAKT-1» (Ryazan)
E-mail: skb@kontakt-1.ru
V.V. Ezersky – Dr.Sc.(Eng.), Professor, Department of Radio Control and Communications, Ryazan State Radio Engineering University
E-mail: ezerski@yandex.ru


At practical measurement of level of filling of industrial tanks by radio transparent substances with small reflecting ability at a processed signal necessarily there is a stirring reflexion from heterogeneity wave guide a path (WGP) and reflexion from a tank bottom. And measurements are made against additive noise. These stirring factors lead to occurrence of an essential making error of measurement of distance by level gauges with the frequency-modulated signal.
In work possibility of essential decrease in the specified error is shown. Signal processing difference frequencies on an exit of the amalgamator with use of adapted weight functions (AWF) is with that end in view used. FWF of a signal allow to operate the form of spectral density of amplitudes (SDA) so that in a point of measurement of position of a maximum of SDA of a useful signal zero of the set frequency rate of Spa of stirring signals were formed. Besides AWF allow to minimise their noise strip.
Because position of stirring reflexion from heterogeneity WGP and a tank bottom is known, and position of measured level is not known, process of optimisation of parametres AWF is iterative and watching. On the first step any is used WF (for example, Blekmana), allowing on the readout of a signal written down in memory to execute an initial estimation of distance from a level gauge to controllable level. The knowledge of this estimation provides calculation of size of demanded parametres AWF with which the next stage of processing is made. This procedure repeats until difference between again received estimation of distance and the previous estimation will not decrease less some set size. Then new measurement of a signal and its processing with the initial parametres AWF received for the previous signal is made.
By means of numerical modelling the quantitative estimation of possibilities of the offered procedure of minimisation is executed.
It is received that optimisation of parametres AWF allows to lower essentially size of an error of measurement of distance in such range of distances between a useful reflector and a stirring reflector where their permission is provided. And character of dependence of an error of measurement from the measured distance for AWF does not depend on distance to the bottom the tank. The error smoothly changes in all working range of distances. During too time for WF Blekmana (or any another WF with unchangeable parametres) is observed sharp change of size of an error in the same range of distances.
Minimisation of a noise strip allows to lower twice approximately an error of measurement against additive noise.

References:
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