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Adaptive minimization of the error of measurement the distances, the caused dispersion, in frequency level gauges with weight averaging difference of frequency

Keywords:

V.M. Davidochkin – Ph. D. (Eng.), Head of Department, Open Company enterprise «KONTAKT-1» (Ryazan). E-mail: skb@kontakt-1.ru V.V. Ezerskiy – Dr. Sc. (Eng.), Professor, Ryazan State Radio Engineering University. E-mail: ezerski@yandex.ru


At measurement of level of filling of industrial tanks by means of level gauges with it is frequency modulated (FM) a signal in a mea-suring path there is a wave guide. Level measurement can be made directly in a wave guide or it can be used as the lengthening device, and measurement is made in free space behind a wave guide. Wave guide presence brings features in the processed signal, consisting in occurrence of parasitic frequency modulation (PFM) a signal difference frequencies (SDF) at linear law FM of the transmitter. PFM arises owing to dispersion presence in a wave guide. PFM leads non-uniform arrangements of zero SDF in the modulation period that causes occurrence of an additional error at use of a weight method of averaging difference frequencies. In work the quantitative estimation of an additional error is executed and is shown that its size essentially exceeds requirements of practical applications of level gauges. For elimination of influence of a dispersion on result of measurement of level it is offered to spend correction of the form of used weight function (WF). Such correction of an equivalent to nonlinear change of time scale used WF. At carrying out of measurements in a wave guide form correction is made unitary on the known cross-section sizes of a wave guide and parametres FM. At distance measurement in free space a level gauge with wave guide lengthening necessary correction of form WF depends on a parity of the measured distance and length of a wave guide. Therefore for elimination of influence of a dispersion the iterative algorithm consisting in consecutive specification of necessary correcting function on the basis of the measured distance from the aerial to a surface of a controllable material is offered. Such specification is made until difference of current result of measurement from the previous decreases less some in advance set size. The estimation of possibilities of the offered algorithm on decrease in an error of measurement of the frequency caused by presence of a dispersion is executed. It is received that at adaptive minimisation of influence of parasitic frequency modulation in both cases the error caused by dispersion influence completely disappears.
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