RU2463589C1 - Eddy current flaw detector for inspecting cylindrical articles - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: flaw detector has a passage eddy current converter 1, having on a circular cylindrical chassis two orthogonal two-section exciting coils 2 and 3, a circular exciting coil 4, two four-section measuring coils 5 and 7, two two-section measuring coils 6 and 8, four one-section measuring coils 9-12. The circuit with which the coils are connected comprises generators 13 and 14 of harmonic signals of close frequencies, a harmonic signal generator 15, a synchronisation circuit 16, quadrature phase changers 17 and 18, amplitude-phase detectors 19-28, integrating samplers 29-38, computing units 39 and 40, amplitude selectors 41 and 42 and an automation unit 43.

EFFECT: high reliability of inspection owing to high sensitivity to short defects.

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Description

The invention relates to non-destructive testing of longitudinally extended products such as wire, rods or pipes.

Known eddy current flaw detector (USSR author's certificate No. 1397821, IPC G01N 27/90, publ. 05/23/1988, bull. No. 19 [1]), containing a straight eddy current transducer (ETC) with a circular excitation winding placed on a circular cylindrical frame and four measuring windings, two generators, two measuring bridges, four amplitude-phase detectors, a computing unit, symmetrically arranged with respect to it, four measuring windings uniformly distributed around the circumference. Due to the presence of four measuring windings and four measuring channels in the eddy current transducer, the signal from the transverse displacement of the controlled product is extracted and adjusted in accordance with the direction of the shift of the conversion coefficients in each measuring channel, which significantly reduces the dependence of the signal on the defect on the transverse displacement of the control object, high reliability detection of short defects (for example, local lack of penetration of a weld).

The disadvantage of this flaw detector is the low reliability of detection of extended defects with a small gradient of properties in the longitudinal direction (grooves, scratches, cracks with a rounded bottom and slight differences in depth), which is also characteristic of other flaw detectors with continuous eddy current transducers.

Known eddy current flaw detector for monitoring cylindrical products (RF patent No. 2090882, IPC G01N 27/90, publ. 09/20/1997, bull. No. 26 [2]), selected as a prototype, containing a straight eddy current transducer placed on a circular cylindrical frame with two orthogonal two-section excitation windings with half-circle size and mutually opposite winding direction, the first and second four-section measuring windings with mutually opposite winding direction of adjacent sections, t s and fourth two-piece with the same direction of winding sections measuring windings, first and second harmonic generators of signals of close frequencies, the synchronization circuit, four amplitude-phase detector, four integrating sampler, a computing unit, an amplitude selector and automation unit. The sections of the first and third measuring windings are located symmetrically at the boundaries of the sections of the first field winding. The sections of the second and fourth measuring windings are located symmetrically at the boundaries of the sections of the second field winding. The outputs of the first and second generators are connected respectively to the first and second field windings, and the inputs are connected to the first output of the synchronization circuit. The signal inputs of the first and second amplitude-phase detectors are connected respectively to the first and third measuring windings, and the control inputs of these amplitude-phase detectors are connected to the output of the first generator. The signal inputs of the third and fourth amplitude-phase detectors are connected respectively to the second and fourth measuring windings, and the control inputs of these amplitude-phase detectors are connected to the output of the second generator. The signal inputs of the four integrating discretizers are connected to the outputs of the first, second, third, and fourth amplitude-phase detectors, the control inputs of these integrating discretizers are connected to the second output of the synchronization circuit, and the outputs are each with a separate input of the computing unit. The input of the amplitude selector is connected to the output of the computing unit, and its output is connected to the input of the automation unit.

The flaw detector provides high sensitivity to surface longitudinal defects, regardless of whether their depth changes in the longitudinal direction sharply or smoothly.

A disadvantage of the known device is the low sensitivity to short defects, the length of which in the longitudinal direction does not exceed the longitudinal size of the sections of the ECP.

The objective of the invention is to increase the reliability of control by increasing the sensitivity to short defects.

The problem is solved due to the fact that the eddy current flaw detector for monitoring cylindrical products, as in the prototype, contains a straight eddy current transducer with two orthogonal two-section excitation windings located on a circular cylindrical frame with half-circle size and the opposite direction of winding, the first and the second four-section measuring windings with the mutually opposite direction of winding of adjacent sections, the third and fourth two-section mi with the same direction of winding sections measuring windings, first and second harmonic generators of signals of close frequencies, the synchronization circuit, four amplitude-phase detector, four integrating sampler, a computing unit, an amplitude selector and automation unit. The sections of the first and third measuring windings are located symmetrically at the boundaries of the sections of the first field winding. The sections of the second and fourth measuring windings are located symmetrically at the boundaries of the sections of the second field winding. The outputs of the first and second generators are connected respectively to the first and second field windings, and the inputs are connected to the first output of the synchronization circuit. The signal inputs of the first and second amplitude-phase detectors are connected respectively to the first and third measuring windings, and the control inputs of these amplitude-phase detectors are connected to the output of the first generator. The signal inputs of the third and fourth amplitude-phase detectors are connected respectively to the second and fourth measuring windings, and the control inputs of these amplitude-phase detectors are connected to the output of the second generator. The signal inputs of the four integrating discretizers are connected to the outputs of the first, second, third, and fourth amplitude-phase detectors, the control inputs of these integrating discretizers are connected to the second output of the synchronization circuit, and the outputs are each with a separate input of the computing unit. The input of the amplitude selector is connected to the output of the computing unit, and its output is connected to the input of the automation unit.

According to the invention, on the cylindrical frame of the eddy current transducer, a third excitation winding of a circular structure and symmetrically located relatively uniformly distributed around it fifth, sixth, seventh and eighth measuring windings with an angular size of a quarter of a circle and the same direction of winding are additionally placed. The fifth and seventh measuring windings are located symmetrically relative to the boundaries of the sections of the first field winding. The sixth and eighth measuring windings are located symmetrically with respect to the boundaries of the sections of the second field winding. The flaw detector additionally contains a third harmonic signal generator, first and second quadrature phase shifters, six amplitude-phase detectors, six integrating discretizers, a second computing unit, and a second amplitude selector. The output of the third generator is connected to the third field winding, and the input is connected to the first output of the synchronization circuit. The inputs of the first and second quadrature phase shifters are connected to the outputs of the first and second generators, respectively. The signal inputs of the fifth and sixth amplitude-phase detectors are connected respectively to the first and second measuring windings, and their control inputs are connected to the outputs of the first and second quadrature phase shifters, respectively. The signal inputs of the seventh, eighth, ninth and tenth amplitude-phase detectors are connected respectively to the fifth, sixth, seventh and eighth measuring windings, and their control inputs are connected to the output of the third generator. The signal inputs of six integrating samplers are each connected to the output of one of six amplitude-phase detectors. The control inputs of these integrating discretizers are connected to the second output of the synchronization circuit, and their outputs are each connected to a separate input of the second computing unit, the output of which is connected to the input of the second amplitude selector. The output of the second amplitude selector is connected to the second input of the automation unit.

Figure 1 shows a structural diagram of an eddy current flaw detector for monitoring cylindrical products; figure 2 - the design of the ECP; figure 3 - functional dependence of the signal of the measuring channel from the lateral displacement of the test object; figure 4 - functional dependence of the signal of the measuring channel from the defect from the lateral displacement of the control object.

The eddy current flaw detector for monitoring cylindrical products contains a straight eddy current transducer 1 (ETC) with two orthogonal two-section excitation windings 2 and 3, an excitation winding of a circular structure 4, two four-section measuring windings 5 and 7, two two-section measuring windings 6 and 8 located on a circular cylindrical frame , four single-section measuring windings 9-12, harmonic signal generators of close frequencies 13 (G1) and 14 (G2), harmonic signal generator 1 5 (G3), synchronization circuit 16 (SS), quadrature phase shifters 17 (KF1) and 18 (KF2), amplitude-phase detectors 19-28 (AFD1-AFD10), integrating discretizers 29-38 (ID1-ID10), computing units 39 (VB1) and 40 (VB2), amplitude selectors 41 (AC1) and 42 (AC2), automation unit 43 (BA).

The output of the generator 13 (G1) is connected to the input of the quadrature phase shifter 17 (KF1) and the field winding 2. The output of the generator 14 (G2) is connected to the input of the quadrature phase shifter 18 (KF2) and the field winding 3. The output of generator 15 (G3) is connected to the field winding 4. The inputs of the generators 13-15 (G1-G3) are connected to the first output of the synchronization circuit 16 (CC). The signal inputs of the amplitude-phase detectors 19-22 (AFD1-AFD4) are connected respectively to the measuring windings 5-8. The signal inputs of the amplitude-phase detectors 25-28 (AFD7-AFD10) are connected respectively to the measuring windings 9-12. The signal inputs of the amplitude-phase detectors 23 (AFD5) and 24 (AFD6) are connected respectively to the measuring windings 5 and 7. The control inputs of the amplitude-phase detectors 19 (AFD1) and 20 (AFD2) are connected to the output of the generator 13 (G1). The control inputs of the amplitude-phase detectors 21 (AFD3) and 22 (AFD4) are connected to the output of the generator 14 (G2). The control inputs of the amplitude-phase detectors 23 (AFD5) and 24 (AFD6) are connected respectively to the outputs of the quadrature phase shifters 17 (KF1) and 18 (KF2). The control inputs of the amplitude-phase detectors 25-28 (AFD7-AFD10) are connected to the output of the generator 15 (G3). The outputs of the amplitude-phase detectors 19-28 (AFD1-AFD10) are connected respectively to the inputs of the integrating discretizers 29-38 (ID1-ID10), the control inputs of which are connected to the second output of the synchronization circuit 16 (CC). The outputs of the integrating discretizers 29-32 (ID1-ID4) are each connected to a separate input of the computing unit 39 (VB1). The outputs of the integrating discretizers 33-38 (ID5-ID10) are each connected to a separate input of the computing unit 40 (WB2). The outputs of the computing units 39 (WB1) and 40 (WB2) are connected respectively to the inputs of the amplitude selectors 41 (AC1) and 42 (AC2), the outputs of which are each connected to a separate input of the automation unit 43 (BA).

Figure 2 shows the design of the passage eddy current transducer 1 (ECP) of the flaw detector. For clarity, the windings are conventionally spaced along the longitudinal axis Z, but in reality all windings are aligned in the longitudinal direction. The sections of the two-section field windings 2 and 3 have a half circle size and a mutually opposite direction of winding. Single-section measuring windings 9-12 with an angular size of a quarter of a circle and the same direction of the winding are uniformly distributed around the circumference and are located symmetrically relative to the circular field winding 4. The measuring windings 9 and 10 are located symmetrically relative to the boundaries of the sections of the field winding 2, the measuring windings 11 and 12 are located symmetrically relative to the boundaries of the sections of the field winding 3. Four-section measuring windings 5 and 7 have a mutually opposite direction of winding adjacent sec s, and the two-section measuring coils 6 and 8 - the same winding direction. The size of the sections of the measuring windings 5-8 in azimuth is not as fundamental as in the case of field windings 2, 3 and measuring windings 9-12, and lies in the range of 30-40 ° for four-section and 55-70 ° for two-section windings, which ensures acceptable uniformity of sensitivity at any azimuth of the defect and high linearity of the HTP hodograph from lateral displacements of the controlled product. The sections of the measuring windings 5 and 6 are located symmetrically at the boundaries of the sections of the exciting winding 2, the sections of the measuring windings 7 and 8 are located symmetrically at the boundaries of the sections of the exciting winding 3.

The flaw detector is installed either directly on the production line of pipes, rods or wire, or on a special control line. In both cases, the linear movement of the controlled products through the eddy current transducer 1 (ECP) of the flaw detector in the direction of the Z axis is ensured (Fig. 2).

Flaw detector works as follows. Generators 13-15 (G1-G3) produce harmonic voltages with frequencies f ₁ , f ₂ and f ₃ . The generators are synchronized by circuit 16 (SS), due to which the frequency differences are kept stable

f ₂ -f ₁ = Δf and f ₃ -f ₁ = k · Δf,

where k is an integer.

In this case, various options for synchronizing the frequencies of the generators are possible. For example, such when the synchronization circuit contains a rectangular pulse generator of the reference frequency f ₀ , and generators 13-15 (G1-G3) incorporate frequency dividers respectively in

m (n-1), mn, n (n-1) times,

where m and n are integers.

The generators also include selective circuits for extracting the first harmonics of rectangular signals. The frequencies of the output voltages of the generators 13-15 (G1-G3) are equal, respectively

f ₁ = f ₀ / m · n;

f ₂ = f ₀ / m (n-1);

f ₃ = f ₀ / n (n-1).

Frequency difference

Δf = f / mn (n-1) and k = m-n + 1.

The difference frequency signal Δf can be obtained by successively dividing the frequency f ₀ by m, n and (n-1). This signal from the second output of the synchronization circuit 16 (SS) is fed to the control inputs of the integrating discretizers 29-38 (ID1-ID10) and is used to process the signals of the eddy current transducer 1 (ETC). The output signals of the generators 13-15 (G1-G3) are fed to the excitation windings of the ECP 2-4. The currents of these windings create a magnetic field in the ECP control zone with three harmonic orthogonal spatial components of the frequencies f ₁ , f ₂ and f ₃ . The three-frequency excitation magnetic field induces eddy currents of three frequencies in the controlled product. Used measuring coil 5 and 6, for measuring the magnetic field of eddy currents frequency f ₂ for measuring the magnetic field of eddy currents frequency f ₁ - measuring coils 7 and 8, for measuring the magnetic field of eddy currents frequency f ₃ - measuring coil 9-12. Due to the corresponding directions of the winding sections of the exciting and measuring windings and their relative position (figure 2) in the absence of the product in the control zone of the ECP and when the axis of the product placed in the control zone coincides with the longitudinal axis of the through eddy current transducer 1 (ECP), the initial and introduced emfs of the measuring windings the frequencies of the measured magnetic field are absent. This property of the ETC used in the proposed eddy current flaw detector makes the latter insensitive to such interfering factors as a change in diameter and electromagnetic properties to the extent acceptable for a suitable product. The emf of the frequency of the measured magnetic field in the measuring windings appears when the eddy currents induced in the product are broken if there is a defect, radial displacement (for windings 5-8) or skew (for windings 5-12) of the controlled product relative to the longitudinal axis of the eddy current transducer 1 ( ECP). To separate these effects, amplitude-phase signal processing is used. For this, the flaw detector has ten identical measuring channels, each consisting of a series-connected amplitude-phase detector 19-28 (AFD1-AFD10) and an integrating sampler 29-38 (ID1-ID10). Channels, which include amplitude-phase detectors 19-22 (AFD1-AFD4), are designed to isolate signals from extended defects. Channels, which include amplitude-phase detectors 25-28 (AFD7-AFD10), are designed to isolate signals from short defects. Channels, which include amplitude-phase detectors 23 (AFD5) and 24 (AFD6), are designed to extract signals from the lateral displacements of the controlled product along the Y and X axes, respectively. The amplitude-phase detectors are synchronous with the corresponding control frequency f ₁ , f ₂ or f _{3 the} detection of the voltage of the measuring windings of the ECP, and the integrating discretizers average the output signals of the amplitude-phase detectors for a time T = 1 / Δf specified by the output signal of the synchronization circuit 16 (CC). Circuit integrating discretizers are made similarly used in the prototype device [2]. The frequency response of the measuring path with a reference frequency f _i has zeros at frequencies different from f _i by a multiple of Δf. In this case, the signal from the defect with the carrier frequency f _{i is} passed through the measuring path almost without distortion, and the modulated signals of the other two frequencies present at the input of the same path are attenuated by more than an order of magnitude. It is also important that slowly varying signals of these frequencies (unbalance voltage drift, signals from bias) are completely suppressed by the measuring path even at very close frequencies f ₁ , f ₂ and f ₃ . As a result of such processing of signals at the outputs of the samplers 29 (ID1), 30 (ID2), 33 (ID5), signals are proportional to the amplitudes of the introduced frequency voltages f _i , and at the outputs of the samplers 31 (ID3), 32 (ID4), 34 (ID6) ) - frequency f ₂ , at the outputs of the sampling devices 35-38 (ID7-ID10) - frequency f _3.

High-quality separation of the signals caused by each component of the magnetic field, allows you to effectively apply in each channel, designed to isolate signals from defects, the amplitude-phase detuning from the influence of radial displacements and distortions. The displacement lines on the complex plane of the EHP of the proposed device for each frequency component are close to some straight lines that have an angle with defect lines of the order of 45-80 ° with an optimally selected generalized control parameter. The detuning from the influence of offsets and distortions in each channel is made by adjusting the phase shifts of the measured voltages relative to the reference voltages of the amplitude-phase detectors. As a result of this, the signals caused by displacements and distortions are attenuated by measuring channels designed to isolate signals from defects by several tens of times. In contrast to the channels for extracting signals from defects, the reference voltages of the amplitude-phase detectors 23 (AFD5) and 24 (AFD6) in the channels for extracting signals from biases coincide with the phases of the signals from biases in the measuring windings 5 and 7. This is achieved by changing the phases of the output voltage of the generators used as reference, 90 ° quadrature phase shifters 17 (KF1) and 18 (KF2). At the output of the integrating sampler 33 (ID5), a signal is allocated associated with the value of the transverse displacement along the Y axis, and at the output of the integrating sampler 34 (ID6) - with the value of the transverse displacement along the X axis. Figure 3 shows the dependence of the output voltage of the integrating sampler 33 (ID5) U ₃₃ on the magnitude of the lateral displacement Y. The dependence of the output voltage of the integrating sampler 34 (ID6) U ₃₄ on X is of the same nature.

The amplitudes of signals from a defect in each channel for separating signals from defects depend not only on the geometry of the defect (depth, disclosure, orientation), but also on the azimuth of the location on the surface of the product. For independence of the amplitude of the total signal from the azimuth of the extended defect in the computing unit 39 (VB1), by analogy with the prototype device [2], pairwise algebraic summation of the output signals of blocks 29-32 (ID1-ID4) U ₂₉ , U ₃₂ and U ₃₀ , U ₃₁ , and then vector summation of the voltages (U ₂₉ + U ₃₂ ) and (U ₃₀ + U ₃₁ ). The output voltage of the computing unit 39 (VB1)

almost independent of the azimuth of the defect. Another positive feature of such an ETH signal processing algorithm is that in this case the interference signal is significantly attenuated due to a possible violation of the optimal detuning condition from bias due to a change in the electrophysical properties of the controlled product and violation of the perpendicularity of the detuning direction and the bias line. The output level of the computing unit 39 (WB1) is controlled by an amplitude selector 41 (AC1), the logical signal “1” at the output of which appears when the set threshold corresponding to the minimum detectable defect is exceeded. When "1" appears at the output of the amplitude selector 41 (AC1), the control unit 43 (BA) connected to it gives a control signal to actuators (not shown).

For independence of the amplitude of the total signal from the azimuth of a short defect, as well as the weakening of its dependence on the transverse displacements of the controlled product in computing unit 40 (VB2), by analogy with the analog device [1], algebraic summation of the output signals of integrating discretizers 35-38 (ID7-ID10 ) U ₃₅ , U ₃₆ , U ₃₇ , U ₃₈ with coefficients s ₁ , s ₂ , s ₃ , s ₄ , respectively, calculated in the computing unit 40 (WB2) depending on the values of the output signals of the integrating discretizers 33 (ID5) and 34 ( ID6) measurement channels of the transverse displacement of the product. The necessity of using correction factors when summing signals from short defects is caused by a significantly greater dependence on lateral displacements of the controlled product than in the case of signals from extended defects. Figure 4 shows the nature of the dependence of the output signals on the defect of the integrating discretizers 35 (ID7) and 36 (ID8) U ₃₅ and U ₃₆ on the value of the lateral displacement Y. These dependences can be represented by functions

U ₃₅ = F ₁ · Y · U _N1 and U ₃₆ = F ₂ · Y · U _N2 ,

where U _N1 U _N2 - signals from a defect in the corresponding channels in the absence of bias (Y = 0);

F ₁ and F ₂ are functions that describe the dependence on the signal offset from the defect.

The transformation function of the channel for measuring the displacement along the Y axis (Fig.3) can be represented as follows:

U ₃₃ = F ₃ · Y,

where F ₃ is a function that describes the dependence of the output signal of the measuring channel from the lateral displacement.

As a result of the substitution of the quantity Y = U ₃₃ / F ₃ determined from this expression into the previous expressions, we obtain the signal values from the defect independent of the offset:

U _N1 = F ₃ U ₃₅ / F ₁ U ₃₃ and U _N2 = F ₃ U ₃₆ / F ₂ U ₃₃ .

And thus the correction factors

s ₁ = F ₃ / F ₁ U ₃₃ and s ₂ = F ₃ / F ₂ U ₃₃ .

Similarly, taking into account the same nature of the dependence of the signals on the displacements X and Y, determine the correction factors

s ₃ = F ₃ / F ₁ U ₃₄ and s ₄ = F ₃ / F ₂ U ₃₄ .

The functional dependences of F ₁ , F ₂ and F ₃ on the magnitude of the lateral displacement are determined, as a rule, experimentally and are set in the computing unit 40 (WB2) tabularly or approximated by analytical expressions. The output voltage of the computing unit 40 (WB2)

U ₄₀ = s ₁ U ₃₅ + s ₂ U ₃₆ + s ₃ U ₃₇ + s ₄ U ₃₈

practically does not depend on the azimuth of the defect and little depends on the lateral displacement of the controlled product. The output level of the computing unit 40 (WB2) is controlled by an amplitude selector 42 (AC2), the logical signal "1" at the output of which appears when the set threshold corresponding to the minimum detectable defect is exceeded. When "1" appears at the output of the amplitude selector 42 (AC2), the control unit 43 (BA) connected to it gives a control signal to the actuators.

The use of the proposed eddy current flaw detector for monitoring steel rods and pipes provides an increase in sensitivity to short defects and a high reliability of control for the presence of both long and short defects.

Claims (1)

Eddy current flaw detector for monitoring cylindrical products, containing a straight eddy current transducer with first (2) and second (3) orthogonal two-section excitation windings placed on a circular cylindrical frame with half-circle size and mutually opposite winding direction, first (5) and second (7) ) four-section measuring windings with a mutually opposite direction of winding adjacent sections, the third (6) and fourth (8) two-section with the same direction of winding section measuring windings, and the sections of the first (5) and third (6) measuring windings are located symmetrically at the boundaries of the sections of the first (2) field windings, the sections of the second (7) and fourth (8) measuring windings are located symmetrically at the borders of the sections of the second (3) field windings, first and second generators of harmonic signals of close frequencies, the outputs of which are connected respectively to the first (2) and second (3) field windings, a synchronization circuit, the first output of which is connected to the inputs of the generators, the first and second amplitude-phases detectors, the signal inputs of which are connected respectively to the first (5) and third (6) measuring windings, and the control inputs are connected to the output of the first generator, the third and fourth amplitude-phase detectors, the signal inputs of which are connected respectively to the second (7) and fourth (8) measuring windings, and the control inputs are connected to the output of the second generator, four integrating discretizers, the signal inputs of which are connected to the outputs of the first, second, third, and fourth amplitude-phase of the second detectors, the control inputs of integrating discretizers are connected to the second output of the synchronization circuit, and their outputs are each connected to a separate input of the computing unit, an amplitude selector whose input is connected to the output of the computing unit, and the output is connected to the input of the automation unit, characterized in that on the cylindrical the eddy-current transducer frame additionally contains the third (4) excitation winding of a circular structure and symmetrically located relative to it uniformly distributed around fifth (9), sixth (11), seventh (10) and eighth (12) measuring windings with an angular size of a quarter of a circle and the same direction of winding, and the fifth (9) and seventh (10) measuring windings are located symmetrically relative to the boundaries of the sections the first (2) field winding, the sixth (11) and eighth (12) measuring windings are located symmetrically relative to the boundaries of the sections of the second (3) field winding, the flaw detector further comprises a third harmonic signal generator, the output of which is connected to the third (4) field winding the input is connected to the first output of the synchronization circuit, the first and second quadrature phase shifters, the inputs of which are connected to the outputs of the first and second generators, respectively, the fifth and sixth amplitude-phase detectors, the signal inputs of which are connected respectively to the first (5) and second (7 ) by measuring windings, and the control inputs are connected to the outputs of the first and second quadrature phase shifters, respectively, the seventh, eighth, ninth and tenth amplitude-phase detectors, the signal inputs of which are connected respectively Actually with the fifth (9), sixth (11), seventh (10) and eighth (12) measuring windings, and their control inputs are connected to the output of the third generator, six integrating discretizers, the signal inputs of which are connected to the outputs of the fifth, sixth, seventh , eighth, ninth and tenth amplitude-phase detectors, the control inputs of these integrating discretizers are connected to the second output of the synchronization circuit, and their outputs are each connected to a separate input of the second computing unit, the output of the second computing unit is connected to the input of the second amplitude selector, the output of which is connected to the second input of the automation unit.

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