SU1163204A1 - Vibration densimeter - Google Patents

Abstract

VIBRATION PLOTNOM containing a frequency density sensor, a temperature-frequency converter, a first multiplier, a comparison unit and a secondary device, while the outputs of the multiplier and frequency density sensor are connected to the inputs of the comparator, the output of which is connected to the secondary device and the input of the multiplier, the other input of which connected to the output of the temperature-frequency converter, which is so tachomed that, in order to improve the measurement accuracy, it is additionally equipped with a second multiplier, adder, unit of mouth constants., the frequency quad, the second multiplier is connected in series with the first, and its input is connected to the output of the comparison unit through a series-connected adder and frequency quad, the other inputs of which are connected to the outputs of the constant setting block. (L

Description

a i

4ib

The invention relates to a measurement technique, in particular, instruments for determining the density and mass flow of liquids and gases, and can be used in the chemical, petrochemical, food and other industries,

A density meter is known that contains two tubular vibration sensors having different coefficients for converting density to an oscillation frequency. To ensure that the temperatures are equal, the liquid is passed through both vibration sensors, and the temperature deviations of the sensor frequencies are subtracted in Comparison Unit 1.

The temperature error of the differential densitometer, in which the monitored medium is passed through both vibration sensors, is determined from the ratio

(t) fj-4.

"

-ui

P - 1

 W

where p is the relative error

density measurements-, - frequency ratio of vibrating data CHIKOV;

 - relative temperature coefficients of resonator frequencies, 1 / deg, ui temperature increment, deg.

Since the values of n, h and depend on the controlled density p, the full compensation of the temperature error O is provided only at one point of the measurement range f - f, for which, as follows from expression (1), n /. At the other points of the measurement range, the cL error differs from zero, which is a drawback of the instrument.

The closest in technical essence to the invention is a vibrating density meter containing a frequency density sensor, a temperature frequency converter, a multiplier, a comparator unit and a secondary device, the outputs of the multiplier and frequency density sensor being connected to the inputs of the comparator unit, the output of which is connected to the secondary device and the input of the multiplier, the other input of which is connected to the output of the temperature-frequency converter Zovatel. A decrease in the temperature error of the instrument over the entire measurement range is achieved by multiplying in the measuring circuit of the increment device f, the signal of the temperature transducer by the scale factor fc, depending in some way on the controlled density and then subtracting the obtained result l –i in the comparison unit. l, K from the output signal of the density sensor 2 1.

However, multiplication 4 | only on the scale factor fc equal to

.Kl

/ + dj

where. The standing tube 20 of the resonator is equal to the mass ratio of a unit tube length, t, to the orifice area F;

ip is the deviation of the controlled density from the initial

values (fo)

It is not possible to compensate for the subsequent subtraction of temperature error in p over the entire range of 30 measured densities.

{f-rff d rc)

at.

The aim of the invention is to improve the accuracy of the measured 1 by compensating for the temperature error associated with the dependence of the temperature coefficient of the resonator frequency Pa on the controlled density.

The goal is achieved by the fact that a vibration density meter containing a frequency density sensor, a temperature-frequency converter,

e the first multiplier, the comparison unit and the secondary device, while the outputs of the multiplier and the frequency density sensor are connected to the inputs of the comparison unit, the output of which is connected to the secondary device and to the input of the multiplier, the other input of which is connected to the output of the temperature-frequency converter, is additionally equipped with a second multiplier , adder, constant setting unit, frequency quad, the second multiplier is connected in series with the first, and its input is connected to the output of the block

comparisons through a series-connected adder and a frequency quad, to the other inputs of which the outputs of the constant setting unit are connected.

The drawing shows the block diagram of the proposed densitometer.

Frequency density sensor 1 (for example, a tubular tuning fork resonator with an excitation system) and temperature-frequency converter 2 (for example, a solid tuning fork resonator with a starting frequency subtraction and subtraction circuit) via a second multiplier 3 (for example, a controlled divider) and the first multiplier 4 are connected to the inputs of the comparison unit 5 (for example, a mixer), the output of which is connected to the secondary device 6 (for example, a digital frequency meter), to the input of the first multiplier 4 and through the series-connected frequency quad 7 (n For example, a digital-functional converter) and an adder 8 (for example, a mixer with a filter) to the input of the second multiplier 3, and the outputs of the constant setting unit 9 (for example, a frequency synthesizer) are connected to the other inputs of the Quad 7 and the adder 8 A signal / signal from the density sensor 1 from the output of block 5 is fed through the output of converter 2 through quad 7 and adder 8, in which the signal n is formed, to multiplier 3, from which output the signal 2 lf goes to smart light 4, and the signal from the output of the latter, equal to l h K, in block 5 is subtracted from the signal f

x (i) of density sensor 1, and since l p (-t) L f riK, the secondary device 6 measures the frequencies fp depending only on the density of the medium, reduced to a certain

temperature

The technical advantage of the proposed vibration densitometer is the full compensation of the temperature error over the entire measurement range, which, with accurate measurements of the mass flow rates of petroleum products, will provide significant savings.

Claims (1)

(.54) A VIBRATION DENSITY METER containing a frequency density sensor, a temperature-frequency converter, a first multiplier, a comparison unit and a secondary device, while the outputs of the multiplier and the frequency density sensor are connected to the inputs of the comparison unit, the output of which is connected to the secondary device and to the input of the multiplier , the other input of which is connected to the output of the temperature-frequency converter, characterized in that, in order to improve the measurement accuracy, it is additionally equipped with a second multiplier, adder, installation unit constants., by a frequency quadrator, the second multiplier being connected in series with the first, and its input is connected to the output of the comparison unit through a series-connected adder and frequency quadrator, to the other inputs of which the outputs of the constant setting unit are connected.