RU2193181C2 - Device for measurement of liquid density - Google Patents

Abstract

FIELD: continuous measurement of density of petroleum products directly in reservoirs of petrol stations and oil tank centers. SUBSTANCE: method consists in converting motion of float into electrical signal. Used as converter is two-circuit self-excited oscillator whose one oscillatory circuit is just coaxial line vertically immersed in liquid under test together with float embracing it on the outside; external circular permanent magnet is secured on said float; when float is set in motion due to change in density of liquid under test, circular permanent magnet is also set in motion; this magnet is arranged inside coaxial line and is connected with shorting plunger made from non-magnetic alloy; it has sliding galvanic contact with both tubes of coaxial line. While moving, plunger shorts coaxial line at different points, thus changing its active length and consequently frequency of signal generated by oscillator depending on density of liquid. EFFECT: enhanced accuracy of measurements. 1 dwg

Description

 The invention relates to a device for measuring the density of liquids, in particular for continuous measurement of the density of petroleum products directly in the storage tanks of gas stations and tank farms.

 A device for measuring the density of a liquid is known - a densitometer containing a toroidal float immersed in liquid with an annular permanent magnet fixed on it, which together move along a vertically and coaxially located inside them cylindrical tubular body made of non-magnetic material, with a hermetically sealed lower end, inside of which a converter for linear displacement of the float into an electrical signal located in the form of a ferrite-semiconductor distributor is located [1]. Depending on the density of the measured liquid, the float moves in the vertical direction under the action of a changing buoyant force acting on it, magnetizing magnetically fixed to it with a permanent magnet one or another core of the distributor. After magnetization with a single pulse received from the counting device, the first core of the distributor, the last pulses from the clock generator begin to arrive at the last one, which sequentially move the first pulse through the elements of the distributor, magnetizing them. When the magnetization reversal of each element on the counting device receives an impulse. In the place of the distributor, which is located in the magnetic field of a permanent magnet mounted on the float, the ferrite core is magnetized by this field and closes the pulse further along the distributor. The number of pulses received at its input, counted by a counting device, is a measure of the density of a controlled fluid. The disadvantage of this device, limiting its use, is the discreteness of the parameter measurement, which is determined by the final dimensions of the magnetizable elements (ferrite core with a winding), which in turn leads to a decrease in the accuracy and resolution of the density meter, which is unacceptable, for example, at significant volumes of automobile fuel revolutions in the capacities of gas stations and tank farms.

 The aim of the invention is to improve the accuracy of measuring density.

 This is achieved by the fact that the transducer for displacing the float into an electric signal is made in the form of a double-circuit oscillator of microwave oscillations, the output of which is connected by a cable to the input of the frequency meter and one of the oscillatory circuits of which is a vertically located coaxial line, enclosed externally by the float, consisting of two coaxial pipes, made of non-magnetic metal with low resistivity, the lower ends of which are shorted by a sealing plug made of pipe material, and inside the coaxial line coaxially with it there is an internal permanent magnet of a ring shape with a shorting plunger attached to it made of a non-magnetic low-resistance alloy, which is designed to provide it with constant sliding galvanic contact with both pipes, moved coaxially with it, under the influence of the magnetic field of an external permanent magnet mounted on the float coaxial line.

 The drawing shows the proposed device.

 The device consists of a toroidal float 1, on the upper plane of which an external annular permanent magnet 2 is fixed. Inside the float 1 there is a vertically located coaxial line 3, consisting of two pipes made of non-magnetic metal with low resistivity, - the outer pipe 4 and the inner pipe 5 which are shorted from below by a sealing plug 6 made of pipe material. Inside the coaxial line 3 along the inner tube 5 there is an inner annular permanent magnet 7 with a shorting plunger 8 fixed thereon made of a non-magnetic alloy. The float 1 rests on the means of balancing the float - a spring 9, the lower end of which is attached to the plug 6. The upper end of the coaxial line 3 is connected to the microwave oscillator 10, which is connected by a power cable 11 to the power supply unit 12, and the output of the microwave oscillator 10 is connected cable 13 with the input of the frequency counter 14. The device, with the exception of the power supply 12 and the frequency counter 14, is connected to the lower end of the tubular rod 15 and lowered through the process hatch 16 into a container 17 with the measured liquid. The rod 15 at the required lowering depth is fixed by a clamp 18 mounted on the cover 19 of the hatch 16.

 The device operates as follows.

 On a tubular rod 15 through the hatch 16, a device without a power supply 12 and a frequency counter 14 is lowered into the tank 17 to the required depth. After that, the lid 19 of the hatch 16 is closed and with the help of the clamp 18 the rod is fixed at the set depth. If the container 17 is empty, then the float 1 together with the external permanent magnet 2 is in the lowest position, which is determined by the compressed spring 9. Together with the float 1, the internal permanent magnet 7 with the shorting plunger 8 fixed on it, which shorts between the internal 5 and external 4 pipes of the coaxial line 3. When the power supply unit 12 is turned on, the microwave oscillator 10 starts to generate microwave oscillations at a frequency determined mainly by the active length of the shorted coaxial oh line 3, which is one of its two oscillatory circuits. When the shorting plunger 8 is in the lowest position, the active length of the coaxial line is maximum, therefore, the frequency of the emitted microwave oscillations will be minimal. Oscillations from the output of the generator 10 via cable are fed to the input of the frequency counter 14, which can be calibrated in units of density. When the tank 17 is filled with some kind of oil product, the float 1 will begin to float, dragging the internal magnet 7 with the shorting plunger 8, until the force pushing it out, which will be the greater, the higher the density of the measured liquid, is not balanced by the resultant force, which equal to the sum of all the forces acting from top to bottom, that is, the weight of the float 1 with magnet 2, the weight of the inner magnet 7 with the shorting plunger 8, the tensile forces of the spring 9. As a result, moving up the shorting plunger 8 will reduce the active Inu coaxial line 3, which will increase the natural frequency of the generator 10, which will be noted in the readings of the frequency of oscillations 14.

 Thus, the proposed device makes it possible to increase the accuracy of measurements by replacing the discrete registration of the investigated parameter with continuous using identical sensors - floats and, in addition, the design of the device is simplified by using standard metal pipes instead of ferrite cores with windings. The proposed device can be used in many industries where accurate and continuous measurements of the density of liquid products are required.

Sourse of information
1. USSR author's certificate 397813, class G 01 N 9/10, published September 17, 73. Bulletin 37.

Claims (1)

 A device for measuring the density of a liquid containing a balanced toroidal-shaped float immersed in a liquid with an annular permanent magnet fixed to it, a means for balancing the float, a transducer for moving the float into an electric signal, characterized in that the transducer for moving the float into an electric signal is made in the form of a microwave microwave oscillator oscillations, the output of which is connected by a cable to the input of the frequency meter and one of the oscillatory circuits of which is a vert an angularly located coaxial line enclosed externally by a float, consisting of two coaxial pipes made of non-magnetic metal with low resistivity, the lower ends of which are shorted by a sealing plug made of pipe material, and inside the coaxial line it is displaced coaxially with the external magnetic field permanent magnet mounted on the float, an internal permanent magnet of a circular shape with a shorting plunger attached to it, made of non agnitnogo low resistivity alloy whose design ensures a constant sliding galvanic contact with the two pipes of the coaxial line.