SU1144046A1 - Device for determination of paramagnetic gas volume concentration - Google Patents

Abstract

A DEVICE FOR DETERMINING THE VOLUME CONCENTRATION OF PARAMAGNETIC GAS, containing a magnetic system,; In the gap. Which houses a chamber in the form of an acoustic resonator filled with the analyzed mixture and The output of which is connected to the input of the measuring path, which is different with the fact that, in order to increase the accuracy and sensitivity of the measurement, the magnetic system gap is placed An agitator concentrator made in the form of a plate made of a magnetically conductive material, normally located in relation to the power lines of the magnetic system and cut in the direction of the longitudinal axis of the resonator by a zigzag cut with a step equal to the length of the acoustic wave, (A magnetic flux transducer mounted on the jumper - , both parts of the concentrator. 4 4 :: 4 35

Description

This invention relates to analysis. substances (materials) by their magnetic properties and can be used, for example, in determining the concentration of free oxygen in the composition of flue gases

There are various devices designed to determine the concentration of free oxygen in a gaseous environment. Most preferred. These devices are based on the use of the dependence of the magnetic permeability of a gas mixture on its composition, mainly on the coitication of free oxygen in it. IS For most gas mixtures encountered in practice, magnetic permeability is proportional to the amount of free oxygen in it. This is due to the fact that oxygen, in comparison with other gases, has a pronounced paramagic properties. Thus, the concentration of free oxygen in the analyzed mixture can be determined by the value of the magnetic permeability of the next. The determination of the magnetic permeability of the gas mixture is determined by measuring one of the physical quantities uniquely related to the permeability of the test medium. These values are magnetic induction, the inductance of the solenoid, the volume of which is filled with the test mixture, is mutual inductance,. between the two placed in the test medium, and so on. 0

However, this measurement method. and the device do not have sufficient accuracy and sensitivity.

The closest to the invention is a device for determination. the volumetric concentration of paramagnetic gas containing a magnetic system, the S gap of which contains a chamber in the form of an acoustic resonator filled with the analyzed mixture and supplied with a converter — electrical oscillations into acoustic ones — connected to an alternating generator. current, and the magnetic flux transducer, the output of which is connected to the input of the measuring path,

When an acoustic stable wave is excited in the resonator, 55 modulation of the density and magnetic permeability of the gas medium under study is observed. For the magnetic permeability of the gas medium, the following expression can be written in this case:

fa ((| U-ll

2J

Ij-ftljci

(About t ov- X-sob2

where P | d, nj is the magnetic constant and relative magnetic permeability of the test gas at its normal pressure and temperature, respectively; W - depth ratio

modulations :;

L is the length of the acoustic wave;

X - coordinate of space F - frequency of acoustic

fluctuations.

Magnetic permeability modulation is accompanied by the modulation of the magnetic induction on the floor in the interpolar space of the magnetic system, i.e.

6-H ((W -) - m-co5 x-co52ffFt, (

where H is the magnetic field intensity in the static mode, i.e. in the absence of acoustic vibrations. From the expression (2) it follows that the variable component of the magnetic induction in the gap is an alternating function of the longitudinal axis of the resonator X

 . (("-) m.coS- x-co52JFt. (3)

Consequently, the total value of the variable magnetic flux of the system is also a periodic function of the X coordinate, and its maximum value does not exceed the variable magnetic flux acting within the same antinode of the acoustic wave, i.e. at

.

An increase in the sensitivity of a known gas analyzer is achieved by placing in the gap a magnetic system of a multi-electrode Hall sensor, the design, powering circuit and location of which leads to the fact that the amplitude Uy of the output signal

proportional to the sum of the absolute values of the elementary variables with respect to the currents penetrating the volume with the test gas, i.e.

    -.

I ll, kV-H. (U, ((U-l) .m, (4)

where K is the coefficient of proportionality;

V is the volume of the gas under study, and the arrival of a graph in the mecholar space zj. The disadvantages of the known device should include the limited sensitivity and accuracy of measurements. The sensitivity of the device is proportional to the used volume of the test gas. This volume in real & instructions is limited to the maximum allowable dimensions of the Hall sensor. As a starter, the manufacture of large-sized Hall sensors is a fairly complex task. This is due to the fact that sensitive Hall sensors are made of single crystals, the sizes of which are limited, and the economic costs of their production increase with increasing sizes of sensors. From this, a gas analyzer design is needed that would allow the use of unified sensors with unlimited acoustic chamber sizes. Moreover, the accuracy of measurements in this gaeo-analyzer is limited by a small, compared to other sensors of the magnetic field, the coefficient of transmission of the Hall sensor, and also by a much larger temperature error. It also requires the creation of gas analyzers in which efficient and cheap magnetically sensitive sensors can be used. The purpose of the invention is to increase the accuracy and sensitivity of measurements.

The goal is achieved by the fact that in the device for determining the volumetric concentration of paramagnetic gas containing a magnetic system, in the gap of which is placed a chamber in the form of an acoustic resonator, filled with the analyzed mixture and equipped with an electrical oscillation into acoustic transducer

variable tick and magnetic converter, the output of which is connected to the input of the measuring path, the magnetic concentrator is placed into the magnetic system gap, made like a plate of magnetic core of the material, norm ..: located in relation to the power line of the powerful magnetic system And cut by ii ; nti; iBJieimH longitudinal axis reconnaissance) rp zigzag slit with pitch, p; nm length: acoustic wave, with a magnetic flux transducer mounted on the bridge connecting both sides of the hub.

The acoustic resonator is made in the vice of the lengths of the hollow tube connected by a knee, the longitudinal size of which is equal to the length of an odd number of half-waves of an acoustic wave.

FIG. schematically shows the device, the structure of the flat magnetic concentrator and the image together with the magnetic system and removed from it; in fig. 2 - equivalent circuit diagram of the gas analyzer magnetic circuit.

The device contains a magnetic system 1, a chamber 2-B in the form of a resonator is placed in the form of an acoustic resonator filled with the analyzed gas flow, an electrical oscillation into acoustic transducer 3 connected to an alternator 4, a magnetic flux transducer 5 the input of the phase-sensitive amplifier 6, the input of which is connected to the generator 4 trans. The belt current, while the output of the amplifiers 6 is connected to the recording device 7. The magnetic hub of the magnetic system is also placed a magnetic hub 8, made in the form of a plate of magnetic conductive material, normally located in relation to the power lines of the magnetic system 1 and cut in the direction of the longitudinal The first axis of the resonator into two parts is a zigzag cut with a step equal to the acoustic wave (for example, made in the form of a square wave), the transducer 5 of the magnetic flux installed on the jumper connecting both Asti concentrator 8. The acoustic resonator can be made in the form of two pieces of a hollow tube connected by a knee, the longitudinal dimension of which is chosen from the ratio 2- (where k O, 1, 2, .., n, as a result of which IB of the lower part of the resonator each of its volume points, the acoustic oscillations are in antiphase with oscillations in a number of located points of the upper part of the resonator. Between the lower and upper parts of the resonator 2 there is a flat magbiti concentrator 8, made in the form of a square wave, so that the centering center is formed by two offset combs, the teeth of which alternate. The magnetic concentrator is installed in the interpolar space in such a way that the location of its teeth is at the antinodes of the acoustic wave in the resonator. In case of pre-shaking of 3 riic oscillations in acoustic in chamber 2 with the analyzed gas, the standing acoustic oscillations are established. In this case, similarly to the well-known device, in a resonator with a frequency of acoustic oscillations, the density and, accordingly, magnetic permeability (density of the analyzed gas) are modulated. Therefore, for the processes occurring in it, expressions (T) (3) are valid, taking into account that for a curved resonator, the X coordinate is the longitudinal axis of the resonator. It should be noted that the modulation of the magnetic conductivity of the medium leads not only to the modulation of the normal component of the magnetic induction, but also to the appearance of variable tangential Magnetic fluxes (along the longitudinal axis of the resonator), the amplitude and direction of which are the harmonic function of the longitudinal axis of the resonator. The increase in the sensitivity of the proposed gas analyzer is achieved by placing a magnetic magnetic field in the gap of the magnetic system normally located in relation to the power lines {magnetic system the torus, the arrangement of the teeth of which is consistent with the location of the beams of the standing acoustic wave. As a result of this design of the concentrator, a variable magnetic flux circulates in its bridge, equal to the sum of the absolute values of the elementary variable tangential flows penetrating the cavity between the tubes of the resonator. Therefore, the output voltage and o (, (x of the converter installed on the hub jumper is about | Portionally this sum and for it, by analogy with expression (4), you can write the following expression Bbixl -V -fo (lW -) -, ( 5). —The proportionality coefficient taking into account the efficiency of the construction. This conclusion can be reached by examining the equivalent circuit of the magnetic circuit section of the proposed device. The circuit contains an equivalent source of magnetic flux 9, resistances 10-13, which take into account the magnetic resistance of the gas medium in in the same acoustic wavelength (i.e., within two adjacent antiphase wave antinodes) for both sections (upper and lower) of an acoustic resonator, resistance, taking into account the magnetic resistance of the concentrator, resistance taking into account the shunting effect of the air gap between the teeth of the concentrator, and the measuring device reflecting on an equivalent circuit the relationship of the flow passing in the jumper with the readings of the measuring instrument 7. As shown earlier, in the adjacent ones. in acoustic waves, the change in time of the magnetic permeability occurs in antiphase, which causes time-varying and alternating along the longitudinal axis of the concentrator magnetic fluxes that circulate along the contour with the least magnetic resistance, i.e. The presence of a magnetic concentrator mainly through its jumper (resistance 14) and partially through shunting air gaps between its teeth (resistance 15). To increase the efficiency of the concentrator, reduce the resistance (i.e., take for a concentration of 7 .1

torus material with a higher magnetic permeability) and provide a minimum magnetic permeability of the gaps between the teeth of the hub. For this purpose it is possible to fill these gaps with a non-magnetic electrically conductive material, the magnetic permeability of which for an alternating magnetic field is less than unity. A considerable factor in increasing the efficiency of a concentrator is the calculation and selection of optimal sizes and configuration of the concentrator teeth. Using a resonator in the form of two tubes connected by a U-shaped. the knee, the length of which is a multiple of the odd one, to the number of acoustic half-: waves, allows, as can be seen from the equivalent circuit, to double the coefficient of 40468

conversion unit of the device. Two resonators can also be located in the gap of the magnetic system (one for the reference medium). In this case, 5 a differential measurement method is implemented that minimizes the effect of destabilizing factors. i tori ..

In the proposed device, there are no restrictions of the working volume with gas, since a magnetic concentrator is easy to carry with a different number of teeth, and, consequently, it is possible to integrate magnetic

5 flows from a large working volume with gas. The device is technologically advanced, reliable and possesses a higher quality than the known device - accuracy and sensitivity.

Claims (1)

2. USSR author's certificate on application No. 2536372/25, cl. G 01 N 27/72, 1977 (prototype). '(54) (57) A DEVICE FOR DETERMINING THE VOLUME CONCENTRATION OF PARAMAGNETIC GAS, containing a magnetic system, in the gap of which is placed a chamber in the form of an acoustic resonator filled with the analyzed mixture and equipped with a transducer of electrical vibrations into acoustic ones connected to an alternating current generator and a transducer magnetic flux, the output of which is connected to the input of the measuring path, characterized in that, in order to increase the accuracy and sensitivity of the measurement, a magnet pleasing concentrator, configured as a plate of magnetically permeable material, normally located in relation to the lines of force of the magnetic system and a slit in the direction of the longitudinal axis of the resonator zigzag cut with 'pitch equal to the length of the acoustic wave, the said transmitter of the magnetic flux is mounted on the _lintel} connecting both parts hub .