SU1280330A1 - Device for measuring level of dielectric materials - Google Patents

Abstract

The invention can be used to measure, control, automatically regulate levels of bulk, lumpy and liquid materials. The purpose of the invention is to improve the noise immunity of level measurement. The alternating voltage of the sinusoidal form from the exhaust of the generator 3 enters the plates 1 and in a controlled volume bounded by the plates 1, a circular electromagnetic field is excited. If there is a controlled material between the plates 1, a bias current flows between them, the magnitude of which is larger than the bias current in air. This causes an increase in the EMF indicated in the coil 2 by an amount proportional to the polarization current. The amplifier 6 converts this EMF into a voltage whose amplitude is greater than the voltage amplitude if there is no material between the plates 1. Passing the peak detector 7, the voltage goes to the input of the integrating amplifier 8, the voltage from which goes to the input of the threshold: element 9 and at the output of the signaling unit 4, the voltage will be equal to O, indicating the presence of a controlled material. 1 hp f-ly, 6 ill. (L u ace o 00

Description

112

The invention relates to methods for measuring the level of dielectric bulk materials and liquids and can be used to measure, control, signal and automatically control the levels of bulk, lumpy and liquid materials in bunkers, tanks and other containers in the food, construction, mining, metallurgical and other industries. x industry.

The aim of the invention is to improve the noise immunity measurement

level

FIG. 1 is a diagram illustrating the principle of operation of the device; Fig. 2 shows the dependences of the amplitude value of the EMF (in relative units) at the output of the inductive sensitive element (coil) as a function of the relative excitation frequency of the electromagnetic field; on fig.Z - block diagram of the device; Fig. 4 shows voltage diagrams at the outputs of the elements of the device in the absence of a controlled material (the hopper is empty); 5 - the same, but in the presence of a controlled material (the hopper is full); Fig. 6 shows experimental dependences of the relative amplitude, for example, at the output of the amplifier as a function of the excitation frequency of the electromagnetic field for some materials.

The principle of operation of the proposed device is as follows.

In a controlled volume, bounded by plane-parallel plates 1 (figure 1), forming a capacitor,. excite the electromagnetic field by applying harmonic voltage U U Sincot to the plates, where UQ is the voltage amplitude; co - circular frequency.

An excited electromagnetic field leads to polarization of the material between the plates 1, and between them there is a bias current, the vector of which is determined by the expression

e

 with dE dPe ° dt dt

50

: -2ezi

f, ac. where to jrdE

zg

displacement current density in vacuum; Е - vector of tension

external electromagnetic floor; Re is the polarization vector;

(1) q is equivalent relative

dielectric constant; the bulk of the material.

The projection of the same displacement current on the axis 55 X, normal for the plates condensate. Taking into account the proportionality of the electric field applied to the plates of the harmonic voltage, is determined by the expression

dPe

- - current density poldt

organization.

In a dielectric in a uniform electric field, a resultant field arises, the intensity of which

h 0

0

five

EP where e (1 + ee) (2)

relative, di-. electrical permeability of diesel, trike; Eh. PdOb - dielectric

the susceptibility of a substance or the polarizability of a unit volume of a dielectric is proportional to the volume of all molecules in 1 cm; Pd is the number of molecules in,

unit of volume. оС is the polarizability coefficient of the molecule. The dielectric polarization vector is determined by the expression

R ,, „eer.

(3)

The form of an electromagnetic wave arising in this case substantially depends on the shape of the capacitance, and when it is performed in the form of a plane capacitor, the electromagnetic wave is circular, the intensity vector of the electric field coincides with the direction of wave propagation and the normal capacitor plates, and the intensity vector of the magnetic field is parallel , them.

Then from expression (1) it follows that the bias current is determined by the expression

T f f with -o t-a

S - dt

(four)

the area of the capacitor plates or the smallest of them;

equivalent relative

dielectric constant; the bulk of the material.

icx G and

ScoLI Si.n (Qt. - kx),

where k is the wave number;

X is the current coordinate. From the expression (5) it follows that the bias current depends on the relative dielectric constant Eg of the material in the controlled volume, and, therefore, to determine the material level, it is necessary to measure the bias current (for example, its amplitude).

To measure the bias current, a bias current conversion of} 5 is used in the EMF, for which an inductive sensing element in the form of a coil is placed in the field between the plates, the plane of the coils (Fig. 1) is parallel to the plane of the plates 1. The magnetic field, generated by the bias current at an equal distance from some elementary tube 3 (Fig. 1) of the current, can be determined on the basis of the law of the total current 25 when integrated along a contour that includes the bias current tube with an area of dS and density and turn

, Н if - If- Sin (.. t-kx),

(6)

where d is the distance between the plates 1 and the total intensity of the magnetic

the field interacting with coil 2, 35 where T / i is a constant dielectric can be determined by the expression

dielectric susceptibility; with

 Sin (cot - kx). (7)

2d

In this case, in expressions (6) and (7), it is taken into account that d ", where i is the wavelength, and, therefore, at a fixed time, the value of the intensity H between the plates 1 can be considered constant.

From the expression (7) it follows that the EMF E; at the output of the loop is equal to

P.egC / UoSin (cJt-k)

E; - --- p, H-S2d

 S and „Sincot, (8)

where W is the absolute magnetic permeability of the material, for non-magnetic materials the magnetic constant U (j.

0330

10} 5 20 25

From the expression (8) it follows that the value of the EMF of the coil at constant sizes of the capacitor formed by the plates 1 and the frequency of the supply voltage unambiguously depends on the equivalent dielectric constant of the material d.

Since a capacitor (formed by plates 1, is a conservative system, external bodies and electromagnetic fields do not act on the electromagnetic field inside it, and thus external electromagnetic fields do not affect the level of EMF induced in the form of a coil, which causes high noise immunity The proposed level measurement device.

Since the value of the relative dielectric constant of the dielectric depends on the frequency of the external electromagnetic field, there is a well-defined zone of excitation frequency of the electromagnetic field, in which the use of the proposed device is advisable.

Taking into account the fact that the dielectric susceptibility of a dielectric depends on the frequency co, then with cosine-like dependence of the form

ES, 9C.Cos, (9)

where T / i is a constant dielectric

;). 27 (1- -) susceptibility of the dielectric; with

with „

the angle between the dipole axis and the vector of the external electric field intensity; SOR - natural frequency

Dipole oscillations

the EMF value EJ at the output of coil 2 is written as

E. 5-, 27 (1- §;) cj

R

G3

2d 1 + ed „Soz 27 (1-tg)

&) „

Uq sinut

(ten)

five

Ja

(eleven)

and the amplitude value e; in relative units - in the form

JlIll2 "Cos 27 (H {;) 27 (1-y)

0

where j is c- relative value

excitation frequency of the electromagnetic field.

in expression (11), for the basic value of the emf, the accepted value

L | G. I I G |

S

b

(by 2d

Figure 2 shows the dependences e d (y) calculated by expression (11) for different values of the ESD parameter, from which it follows that the dependences e; d f (y) are extreme and that there is a frequency range (in particular , frequency f), in which the values of e, d are maximum and which should be chosen as a working one.

The device contains a radiator of an electromagnetic field, made in the form of two. plane-parallel plates 1 (FIG. 3), between which an inductive sensing element is placed, made in the form of a coil 2. A frequency generator 3 is connected to the plates 1; and coil 2 is connected to the first input of conversion unit 4, to the second input of which bus 5 of the reference voltage is connected.

In addition, an amplifier 6, a peak detector 7, an integrating amplifier 8 with two-sided limitation, and a threshold element 9 are installed in the conversion unit 4, the input element of the amplifier 6 is connected to the coil 2, and the output through the peak detector 7 is connected to the first input of the integrating amplifier 8 , the second input of which is connected to the bus 5 of the reference voltage, and the output is connected to the input of the relay amplifier 9.

The amplifier 6 can be made on the basis of the operational amplifier 10 with resistors 11-13; peak detector 7 - on the diode 14 and the capacitor 15; an integrating amplifier 8 with two-sided limitation — on an operational amplifier 16 with resistors 17–19, a capacitor 20 and zener diodes 21 and 22, and a threshold element 9 — on an indirect radio amplifier 23 with resistors 24 and 25 and a diode 26.

The device works as follows.

The alternating voltage of a sinusoidal form from the code of the generator 3 enters the plates 1 forming a capacitor, and in a controlled volume bounded by the plates 1 a circular electromagnetic field is excited.

ten

12-803306

In the absence of a controlled

the material in the field of the capacitor formed by the plates 1, between them flows a bias current in the air, 5 the value of which practically does not differ from the magnitude of the bias current in a vacuum. The bias current excites a magnetic field that induces a sinusoidal EMF in coil 2, and the amplitude of this EMF at a constant voltage amplitude at the output of generator 3 is determined only by the bias current in air.

The voltage induced in coil 2 is fed to the first input of the signaling unit 4, i.e. to the input of the amplifier 6, made on the basis of the operational amplifier 10 with resistors 11-13 and having a high input resistance. Amplifier 6 converts the input emf (emf at the output of coil 2) into output voltage U ((Fig.4) with practically no current consumption from coil 2, which eliminates the influence of the electromagnetic field produced by the current in coil 2 on the magnetic field, generated by bias current.

f5

20

25

30 Voltage U | The amplifier 6 is fed to the input of the peak detector 7, made on a diode 14 and a capacitor 15, in which it is converted into a detected (straightened and smoothed) voltage Uj (Fig. 4). The voltage Ug is fed to the first input of the integrating amplifier 8 with two-sided limitation, the second input of which (i.e., the second input of the sig-40 lysis unit 4) receives the reference voltage U of the positive polarity voltage from the reference voltage bus 5. The level of the reference voltage is determined by the level

45 of the voltage U at the output of the peak detector 7 and is equal to its absolute value (or slightly more) in the absence of controlled material between the plates 1. The voltage from the bus voltage 5 of the reference voltage is formed by any device known in electrical engineering (FIG. 3 not shown).

Integrating amplifier 8 with two-party limiting can be made on the basis of operational amplifier 16, resistors 17-19 with capacitor 20 and zener diodes 21 and 22 in the negative reverse circuit

Voltage U | An amplifier 6 is supplied to the peak-detector input 7, performed on a diode 14 and a capacitor 15, which is converted into a detected (straightened and smoothed) voltage Uj (Fig. 4). The voltage Ug is fed to the first input of the integrating amplifier 8 with two-sided limitation, to the second input of which (i.e., the second input of the sigializing unit 4) receives the reference voltage U of the positive polarity voltage from the reference voltage bus 5. The level of the reference voltage is determined by the level

voltage U at the output of peak detector 7 and is equal to its absolute value (or slightly more) in the absence of controlled material between the plates 1. The voltage is generated from the bus 5 of the reference voltage by any device known in electrical engineering (in FIG. shown).

The integrating amplifier 8 with two-sided limitation can be made on the basis of the operational amplifier 16, resistors 17-19 with capacitor 20 and zener diodes 21 and 22 in the negative reverse circuit

In connection with the operational amplifier 16, cht provides a two-sided limitation of the output voltage U of the operational amplifier 16 (integrating amplifier 8) at a level determined by the voltage stabilizing the zener diodes 21 and 22, and eliminates the deep saturation of the operational amplifier 16.

Thus, in the case under consideration (Fig. 4), the output of the integrating amplifier 8 produces a negative polarity U4, which is fed to the input of the threshold element 9 made on the operational amplifier 23 with resistors 24 and 25 and a diode 26 in the negative reverse circuit connection of the operational amplifier 23, excluding the formation of a negative polarity voltage at the output of the relay amplifier 9. Consequently, when voltage threshold element 9 arrives at the input 1) 4; negative polarity, at its output (i.e., the output of the signaling unit 4), a positive voltage U, different from zero, is generated, which signals the absence of controlled material between the plates 1 (the hopper is empty).

In the presence of a controlled material between the plates 1 between them flows a bias current defined by

both by the bias current in the air and by the polarization current of the material being monitored. The magnitude of the bias current in this case is greater than the magnitude of the bias current in air (i.e., in the absence of a controlled material between the plates 1). This causes an increase in the emf induced in coil 2 by an amount proportional to the polarization current. The amplifier 6 converts this emf to voltage U, (figure 5), the amplitude of which is greater than the voltage amplitude U, (figure 1) in the case when there is no controlled material between the plates 1. The voltage rectified and smoothed by the peak detector 7 and, in the form of voltage U-, whose level exceeds the level of the reference voltage in absolute terms and on the bus 5 of the reference voltage (figure 5), goes to the first input of the integrating amplifier 8, at the output of which a voltage and a positive polarity is formed, which, arriving at the input of the threshold

element 9, switches it, and at the output of amplifier 9 (i.e., at the output of the signaling unit 4), the voltage U (figure 5) takes a zero value, signaling the presence of a controlled material between the plates 1 (the hopper is full). "

The presence in the device of an integrating amplifier 8 together with a peak, a detector 7, eliminates the repeated triggers of the threshold element 9 caused by fluctuations in the amplitude of the voltage U when the bunker is filled (and the space between the plate 1) due to the filtering properties of the integrating amplifier 8 (Fig .5, the initial part of the diagram, for example, SRI).

The selection of the operating frequency of the 0 3 generator is made experimentally. Figure 6 presents the experimental dependence of the relative amplitude UAI

p and At voltages o --- at the output of force (8

5 bodies 6 from the frequency f of the generator 3, where Ufli is the amplitude value of the voltage U (; id, d is the amplitude value Uj for air (in the absence of material between the plates 1). In FIG.

0 denotes: curve 1 — J F (f) dependence for air, curve 2 — for grinded wheat, curve 3 — for ground fireclay. From the curves shown in Fig.6, it follows that the most efficient operation of the device in the frequency range of 80-100 kHz.

Claims (2)

11280330 The invention relates to methods for measuring the level of dielectric bulk materials and liquids and can be used to measure, control, signal and automatically control the levels of bulk, lumpy and liquid materials in bins, tanks and other containers in food, construction, mining, metallurgical and other industries - 0 lx industry. The aim of the invention is to improve the noise immunity of level measurement. Figure 1 is a diagram illustrating the principle of operation of the device; Fig. 2 shows the dependences of the amplitude value of the EMF (in relative units) at the output of the inductive sensitive element (coil) as a function of the relative frequency of the excitation of the electromagnetic field; on fig.Z - block diagram of the device; Fig. 4 shows voltage diagrams at the outputs of the elements of the device in the absence of a controlled material (the hopper is empty); Fig.5to same, but in the presence of a controlled material (the hopper is full); Fig. 6 shows experimental dependences of the relative amplitude of the voltage at the output of the amplifier as a function of the excitation frequency of the electromagnetic field for some materials. The principle of operation of the proposed device is as follows. 35 In a controlled volume, bounded by plane-parallel plates 1 (figure 1), forming a capacitor,. excite the electromagnetic field by applying harmonic voltage U U Sincot to the plates, where UQ is the voltage amplitude; co - circular frequency. An excited electromagnetic field leads to polarization of the material between the plates 1, and between them there is a bias current, the vector of which is determined by the expression with dE dPe (1) q ° dt dt f, ac. where to j is the displacement current density in vacuum; Е - vector of external electromagnetic field intensity; Re is the polarization vector; Before this, there is a problem in the field of the electric locomotive where it is: -255 X, and the three class is the current density of the polarization. In a dielectric, which is in a single electric field, an ulti- mating field arises, the intensity of the EP (1 + EE) is relative, di-. electrical permeability of diesel, trike; Ae. SdAb — the dielectric susceptibility of a substance or the polarizability of a unit dielectric volume is proportional to the volume of all molecules in 1 cm; Pd is the number of molecules per unit volume. оС is the polarizability coefficient of the molecule. The polarization vector of the dielectric is determined by the expression P ,, „eer. The form of the electromagnetic wave that arises in this case significantly depends on the shape of the capacitance, and when executed as a flat capacitor, the electromagnetic wave is steep, the intensity vector of the field field coincides with the wave propagation pressure and is small in the capacitor plates, and the torus of the magnetic field intensity is parallel to it. . Then from expression (1) it follows that the bias current is determined by the expression S T f f dt с -о t-a S is the area of the capacitor plates or the smallest of them; ezi is the equivalent relative dielectric constant; the bulk of the material. The projection of the same displacement current on the axis is normal for the plates of condensate. taking into account the proportionality of the electric field to the harmonic voltage applied to the cuts, it is followed by the expression icx Г and ScoLI Si.n (Qt. - kx), where k is the wave number; X is the current coordinate. From expression (5) it follows that the bias current depends on the relative dielectric constant Eg of the material in the controlled volume, and therefore, to determine the material level, it is necessary to measure the magnitude of the bias current (for example, its amplitude). To measure the bias current, the bias current is converted into an electromotive force, for which an inductive sensing element in the form of a coil is placed in the field between the plates, the plane of the coils (Fig. 1) is parallel to the plane of the plates 1. The intensity of the magnetic field created by the bias current is equal to the distance from some elementary tube 3 (FIG. 1) of the current can be determined on the basis of the law of total current when integrating along the contour, including the elementary tube of the displacement current with an area of dS and density and coil, H if - If - Sin ( ..t-kx), where d is the distance between the plates and the total strength of the magnetic field interacting with coil 2, 35 where it can be determined from the expression Sin (cot - kx). (7) In this case, in expressions (6) and (7), it was taken into account that d%, where i is the wavelength, and, therefore, at a fixed time, the value of the intensity H between the plates 1 can be considered constant. From the expression (7) it follows that the EMF E; at the output of the coil is equal to Р .egC / UoSin (cJt-k) Е; - --- p, H-S2d S and „Sincot, (8) where W is the absolute magnetic permeability of the material, for non-magnetic materials the magnetic constant U ( j. 12 (5);). It is known where 0 From expression (8) it follows that the value of the EMF of the coil at constant sizes of the capacitor formed by the plates 1 and the frequency of the supply voltage is uniquely dependent on the equivalent dielectric constant of the material d. Since a capacitor (formed by plates 1, is a conservative system, external bodies and electromagnetic fields do not act on the electromagnetic field inside it, and thus external electromagnetic fields do not affect the level of EMF induced in the form of a coil, which causes high noise immunity of the proposed level measurement device. Since the value of the relative dielectric constant of the dielectric depends on the frequency of the external electromagnetic field, there is a well-defined area excitation frequency of the electromagnetic field, in which the application of the proposed device is advisable. Considering that the dielectric susceptibility of a dielectric depends on the frequency of co, then with the cosine dependence of the type of ES, 9 C. Co, T / i is the constant dielectric susceptibility of the dielectric; - -) the angle between the dipole axis and the vector of the external electric field intensity; Соr - the natural frequency of the oscillations of the dipole, the emf emission EJ at the output of the coil 2 sat in the form, 27 (1 - §;) cj (1- tg) meaning of e; in relative terms, in the form JlIll2 Cos 27 (H {;) 27 (1-у) -ts-, is the relative value of the excitation frequency of the electromagnetic field. in expression (11) for the base value of the emf, the accepted value is L | G. I I G | Figure 2 shows the dependences of u (y) calculated by expression (11) for different values of the ESD parameter, from which it follows that the dependences e; d f (y) are extreme and that there is a range of frequencies (in particular , frequency f), in which the values of e, d are maximum and which should be chosen as a working one. The device contains a radiator of an electromagnetic field, made in the form of two. a plane-parallel plate 1 (Fig. 3), between which an inductive sensing element is placed, made in the form of a coil 2. A frequency generator 3 is connected to the plates 1; and coil 2 is connected to the first input of conversion unit 4, the second input of which is connected to bus 5 of the reference voltage. In addition, an amplifier 6, a pic detector 7, an integrating amplifier 8 with two-sided limitation, and a threshold element 9 are installed in the conversion unit 4, the input of amplifier 6 is connected to coil 2, and the output through peak detector 7 is connected to the first input of integrating amplifier 8, the second input of which is connected to the bus 5 of the reference voltage, and the output to the input of the relay amplifier 9. The amplifier 6 can be made on the basis of the operational amplifier 10 with resistors 11-13; peak detector 7 on diode 14 and capacitor 15; integrating amplifier 8 with two-sided limitation — on the operating force of the body 16 with resistors 17–19, capacitor 20 and zener diodes 21 and 22; threshold element 9 — on an operadion amplifier 23 with resistors 24 and 25 and a diode 26. The device operates as follows. The alternating voltage of a sinusoidal form from the code of the generator 3 enters the plates 1 forming a capacitor, and in a controlled volume bounded by the plates 1 a circular electromagnetic field is excited. 1 06 In the absence of a controlled material in the field of a capacitor formed by plates 1, a bias current flows in the air between them, the value of which practically does not differ from the magnitude of the bias current in a vacuum. The bias current excites a magnetic field that induces a sinusoidal EMF in coil 2, and the amplitude of this EMF at a constant voltage amplitude at the output of generator 3 is determined only by the bias current in air. The voltage induced in coil 2 is fed to the first input of the signaling unit 4, i.e. to the input of the amplifier 6, made on the basis of the operational amplifier 10 with resistors 11-13 and having a high input resistance. Amplifier 6 converts the input emf (emf at the output of coil 2) into output voltage U ((Fig.4) with practically no current consumption from coil 2, which eliminates the influence of the electromagnetic field produced by the current in coil 2 on the magnetic field, the bias current generated. The voltage U | from the extrude of amplifier 6 is fed to the input of peak detector 7, made on diode 14 and capacitor 15, which is converted into detected (straightened and smoothed) voltage Uj (Fig. 4). Voltage Ug is fed to the first input of the integrated amplifier 8 with two An external restriction, to the second input of which (i.e., to the second input of the sigializing unit 4), receives a reference voltage U of positive polarity from the reference voltage bus 5. The level of the reference voltage is determined by the voltage level U at the output peak detector 7 and equal to its absolute value (or slightly more) in the absence of controlled material between plates 1. The voltage is generated from the reference voltage bus 5 by any device known in electrical engineering (not shown in FIG. 3) . The integrating amplifier 8 with two-sided limitation can be made on the basis of the operational amplifier 16, resistors 17-19 with a capacitor 20 and zener diodes 21 and 22 in the negative feedback circuit of the operational amplifier 16, which provides a two-sided limitation of the output voltage U of the operational amplifier 16 (integrating amplifier 8) at the level determined by the voltage stabilizing the Zener diodes 21 and 22, and eliminates the deep saturation of the operational amplifier 16. Thus, in the case under consideration (Fig. 4) During the integrating amplifier 8, a negative polarity voltage U4 is formed, which is fed to the input of the threshold element 9 made on the operational amplifier 23 with resistors 24 and 25, and a diode 26 in the negative feedback circuit of the operational amplifier 23, which eliminates the formation of the output of the relay amplifier 9 negative polarity voltages. Therefore, when a threshold element 9 of voltage 1) 4 arrives at the input; negative polarity, at its output (i.e., the output of the signaling unit 4), a positive voltage U, different from zero, is generated, which signals the absence of controlled material between the plates 1 (the hopper is empty). If there is a controlled material between the plates 1, a bias current flows between them, determined by both the bias current in the air and the polarization current of the material being monitored. The magnitude of the bias current in this case is greater than the magnitude of the bias current in air (i.e., in the absence of a controlled material between the plates 1). This causes an increase in the emf induced in coil 2 by an amount proportional to the polarization current. The amplifier 6 converts this emf to voltage U, (figure 5), the amplitude of which is greater than the voltage amplitude U, (figure 1) in the case when there is no controlled material between the plates 1. The voltage rectified and smoothed by the peak detector 7 and, in the form of voltage U-, whose level exceeds the level of the reference voltage in absolute terms and on the bus 5 of the reference voltage (figure 5), goes to the first input of the integrating amplifier 8, at the output of which a voltage is formed and a positive polarity, which, when it enters the input of the threshold element 9, switches it, and at the output of the amplifier 9 (i.e. at the output of the signaling unit 4), the voltage U (figure 5) assumes zero value signaled by the presence of a controlled mate The rial between the plates 1 (the hopper is full). "The presence of the integrating amplifier 8 in conjunction with the peak, the detector 7, eliminates the repeated operation of the threshold element 9 caused by the amplitude fluctuations of the voltage U when the hopper is filled (and the space between the plates 1) an account of the filtering properties of the integrating amplifier 8 (Fig. 5, the initial part of the voltage diagram). The selection of the operating frequency of generator 3 is made experimentally. Figure 6 shows the experimental dependences of the relative amplitude UAI p and At voltage o --- at the output of amplifier 6 on frequency f of generator 3, where Ufli is the amplitude value of voltage U (; i; i, d) the amplitude value Uj for air (for the absence of material between the plates 1) .Figure 6 denotes: curve 1 - dependence JF (f) for air, curve 2 - for grinded millet, curve 3 for ground chamotte. From the curves shown in figure 6, it follows that the most effective operation of the device is in the frequency range of 80-100 kHz. Formula 1 invention To measure the level of dielectric materials, containing a frequency generator, connected to an electromagnetic field emitter, a sensitive inductive element connected to the first input of a conversion unit, characterized in that, in order to increase the noise immunity, the electromagnetic field emitter is made in the form of two plane-parallel plates, and sensitive the inductive element is made in the form of a coil and is placed between the Llastins so that the axial line of the coil is perpendicular to the plane of the plates, while the second od Lok transformations coupled to bus reference voltage. 2. The device according to A.1, about tl and h. This is due to the fact that an amplifier, a peak detector, an integrating amplifier with a two-sided limitation and a threshold element are inserted into the conversion unit, and the amplifier input is connected to the sensitive element, and 1280330 the amplifier output is connected through a peak detector to the first input of the integrating amplifier, the second input of which is connected to the reference voltage bus, and the output 5 of the connection to the input of the threshold element tSh rSchR t tt t and, g , - F1AB.6