RU1793248C - Electromagnetic level gage - Google Patents

Abstract

Usage: the invention relates to Measuring technique, in particular to devices for measuring the level of liquids that convert pressure into magnet movement proportional to the measured level. The invention can be used to accurately measure the level of liquid media in all sectors of the economy. SUMMARY OF THE INVENTION: the device comprises a non-magnetic housing, magnetic fluid, an annular permanent magnet, a pressure receiving surface, a non-magnetic tube, and a transducer. The pressure-receiving surface is made in the form of a bellows membrane, an annular magnet is mounted on a non-magnetic tube, and two electromagnets are additionally installed to adjust the measuring range and adjust the zero of the level gauge. 1 ill.

Description

ate with

The invention relates to measuring technique, in particular to devices for measuring the level of fluids that convert pressure into magnet movement proportional to the level being measured. The invention can be used to accurately measure the level of liquid media in a wide range in all sectors of the economy.

A device is known that converts pressure to magnet movement, used to measure the level of liquids. contains a sealed housing, the cavity of which is divided by an elastic element connected to permanent magnets, between which the poles of the HoL sensor are located, the magnets are mounted on a frame equipped with a regulator of its position relative to the Hall sensor.

The main disadvantage of this device is the narrow range of measured

levels and low accuracy of measurements. This is due to the fact that the sensitive element in the device. is an elastic element whose sensitivity is determined by its rigidity, which cannot be compensated by the high sensitivity of the Hall sensor.

 The closest technical solution to the invention, chosen as a prototype, is a magnetic pressure transducer that converts pressure into magnetic fluid movement and comprises a non-magnetic housing, a permanent ring magnet, a non-magnetic tube, a pressure receiving surface, a magnetic fluid, and an inductive transducer.

This device has the following disadvantages: a narrow range of level measurement due to the parameters of a permanent ring magnet; low accuracy 3

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rhenium due to the lack of correction of the zero state of the device; Allows you to measure the levels of only non-aggressive media and media that are not miscible with magnetic fluid.

The aim of the invention is to increase accuracy and extend the measuring range by eliminating direct contact of the magnetic fluid with the controlled medium and adjusting the volumetric magnetic force.

This goal is achieved by the fact that in an electromagnetic level gauge containing a non-magnetic housing with a sensing element inside it in the form of a magnetic fluid, an annular permanent magnet and a transducer of displacement of the sensing element, according to the invention, the housing is equipped with a non-magnetic tube communicating with it, on the free end of which there is a transducer movement of the magnetic fluid, and the end from the housing side is captured by a permanent ring magnet made with axial magnetization, while These are a bellows fixed at the end of the housing with the possibility of interacting with the controlled medium, and two electromagnets, one of which is located on the outer surface of the nonmagnetic housing, and the second on the outer surface of the nonmagnetic tube, with the north pole of the permanent magnet pointing toward the free end of the tube. :.

The drawing shows a level gauge connected to a supply tank, a longitudinal section.

The electromagnetic level gauge contains; there is a supply tank 1 with controlled fluid 2, a pressure-receiving surface in the form of a bellows 3, body 4, tube 5, magnetic fluid 6, an annular permanent magnet 7, an electromagnet coil 8 for adjusting the level of the measured level, an electromagnet coil 9 for adjusting zero a level gauge, a transducer 10 for converting the measured level to an electrical signal, a measuring unit 11 including current control elements in the electromagnets 8 and 9, and signal measuring elements from the transducer 10 displaying the measured level on the indicator and issuing, if necessary, control signals. .

The magnet 7 has axial magnetization and is mounted on the tube 5 so that its north pole is directed from the housing 4, which ensures the retraction of the magnetic fluid 6 into the cavity of the tube 5 and eliminates

its leakage. The coil of electromagnet 8 is mounted on housing 4, and electromagnet 9 is mounted on a tube 5 next to magnet 7.

The converter 10 is connected to the tube

5, and its output is with the input of the measuring unit 11. The coils of the electromagnets 8 and 9 are connected to the outputs of the unit 11, which provide the necessary adjustable currents.

0 Housing 4 and tube 5 are made of bronze. The housing 4 is made cylindrical with an inner diameter of 20 mm, an outer one - 23 mm and a height of 50 mm. The housing 4 is equipped with a threaded connection with a flow capacity 1. Tube 5 has an inner diameter of 4 mm, an outer diameter of 7 mm and a length of 80 mm. In the upper part of the housing 4 there is an internal protrusion on which the welded bellows 3 is rigidly mounted through the seal

0 with a diameter of 18 mm, scraping corrugations 5, a thickness of 0.08 mm, made of flat corrugated annular membranes made of 36NHTYu material.

A fluid based on transformer oil with magnetite particles stabilized by oleic acid with a saturation magnetization M of 50 kA / m was used as magnetic fluid 6. Magnetic fluid fills the housing 4 and half of the tube 5 with full contact with the inner surface of the bellows 3.

The ring magnet 7 is made of barium ferrite having a field strength of

5 operating point 150 kA / m. Outside diameter

rings 20 mm, inner - 8 mm, thickness

10 mm. The ring magnet reliably inserts into

saturation of magnetic fluid 6 in the tube

5 and prevents its leakage, creating a gradient of magnetic field strength sufficient for this.

. The coil of electromagnet 8 with a length of 40 mm contains 200.0 turns, and the coil of electromagnet 9 with a length of 10 mm contains 1000 turns. Both coils are wound with PEV-1 wire with a diameter of 0.125 mm.

Using the adjusting elements of the block 11, the current in the electromagnet 8 can be regulated within 0-40 mA and create

0 magnetic field directed against the floor of the magnetic fluid b. The current in electromagnet 9 can vary between 0-25 mA and create a field that agrees or disagrees with the magnetic field of ring magnet 7. The cores of electromagnets 8 and 9 are magnetic fluid itself. As the converter 10, a conventional differential transformer sensor is used.

The proposed level gauge reacts to a change in the level in the supply tank 1, i.e. pressure drop. From the basic hydrostatic equation, the pressure drop is determined by

Ar pgh,

(1)

about

where AR is the pressure drop at the liquid point at a depth h ;. p g is the gravity of the liquid. Magnetic fluid is distinguished from common fluids by the presence of a volumetric glittal flooded M VH. therefore, expression (1) for our case has the following form:

AP / 9gh- // 0M VH,

(2)

where ju0 is the magnetic permeability of the vacuum; ; | | M - magnetization of magnetic liquid CTk

VH is the gradient of the magnetic field strength in the liquid.

Taking into account that the volumetric magnetic force significantly exceeds the gravity of the used volume of the magnetic fluid, then its value can be neglected, and expression (2) will have the form:

 DR ft0M VH. (3)

| It can be seen from this expression that, by varying the gradient of the magnetic field strength, it is possible to widely vary the range of the measured level of the controlled liquid 2 in the tank 1.

, The proposed electromagnetic level | measure works as follows,

 If there is no liquid 2 in the container 1, there is no pressure on the magnetic liquid 6 through the surface of the bellows 3, which is firmly held by the magnet 7 in the tube 5 to zero. In this case, the transducer 10 provides a signal corresponding to the zero liquid level 2 to the measuring unit 11. If, for some reason (for some reason, the transducer gives a signal indicating the presence of a liquid level 2 in an empty tank 1, then the current is changed using the control element of the unit 11, and if necessary, its direction in electromagnet 9 and zero is corrected by micromotion of the magnetic fluid liquid in the tube 5 interacting with the transducer 10.

When the container 1 is filled with liquid 2, a pressure differential is formed, which acts on the magnetic fluid 6 through the receiving surface of the bellows 3. Under pressure, which is directed against the bulk magnetic force, the magnetic fluid 6 is forced out of the housing 4

5 into the tube 5. Micro-displacement under pressure of the magnetic fluid b in the housing 4 is proportional to the level of the measured liquid 2 causes micro-displacement of the magnetic fluid in the tube 5, but 5 times

0 larger due to the difference in the diameters of the housing 4 and the tube 5, which ensures high sensitivity of the level gauge. Moving with the magnetic fluid 6 in the tube 5 interacts with the transducer 10,

5 which gives a signal proportional to the measured level to block 11.

With a decrease in the controlled level of liquid 2, the pressure acting on the magnetic liquid 6 also decreases under

0 the action of buoyant bulk magnetic force magnetic fluid b of. the cavity of the tube 5 moves into the cavity of the housing 4 and the transducer 10 provides a signal to the measuring unit 11 corresponding to the new lower liquid level 2.

It can be seen from expression (3) that the upper limit of the measured level is determined by the magnitude of the gradient of the magnetic field strength. For example, in the absence of the field of the electromagnet 8, the limit of the measured level is determined by the field of the ring magnet 7, which provides in the magnetic fluid VH equal to 2-106 A / m2, therefore

5 according to expression (3)

DR 1.26-10 b-50-103-2-106 1,2b-105Pa.

Since 10J Pz is approximately equal to a pressure of 1 atm., For water the upper limit of the measured level is 12.6 m.

By increasing the magnetic field strength of the electromagnet 8, it is possible to reduce the values of the magnetic field gradient 5 and to adjust the upper limit of the level measurement in the direction of its decrease.

Since the volume of magnetic fluid 6 in the housing 4 is 30 times greater than the volume of fluid in the cavity of the tube 5, to provide the same buoyant volumetric magnetic force in the fluid 6 of the housing 4, it is sufficient to obtain a magnetic field strength gradient that is 30 times less than

5 of the tube cavity 5. Therefore, the current control range used in electromagnet 8 provides a wide range of measured levels - from 10 cm to 12.6 m. Moreover, the lower limit of the measurement range is reached at a current of 38 mA in electromagnet 8, i.e. not at peak current.

The accuracy of measurements of the upper levels in the entire range is not lower than ± 0.5%, which is 2–4 times higher than that of the well-known, widely used level gauges.

Installation as a receptive surface of the bellows 3 in contact with the magFormula and taking a look

An electromagnetic level gauge comprising a non-magnetic housing with a sensing element inside it in the form of a magnetic fluid, an annular permanent magnet, and a displacement transducer of the sensitive element, and so on. that, in order to increase accuracy and expand the measuring range, the housing is equipped with a non-magnetic tube communicating with it, at the free end of which a transducer with liquid is installed; b, it allows to further increase the accuracy of measurements, since it has a linear elastic characteristic.

All this indicates the achievement of the objective of the invention with great positive effect. g

magnetic fluid, and the end from the side of the case is covered by a permanent ring magnet made with axial magnetization, while a bellows is introduced, fixed at the end of the case with the ability to interact with the controlled environment, and two electromagnets, one of which is located on the outer surface of the non-magnetic case, and the second, on the outer surface of the nonmagnetic tube, with the north pole of the permanent magnet pointing toward the free end of the tube. V: .. ;;,: