SU1663522A1 - Device for reproducing magnetogram for magnetic-tape testing - Google Patents

Abstract

The invention relates to magnetic tape detection and can be used when reading the magnetograms in the process of quality control of products. The aim of the invention is to increase the sensitivity and accuracy of control when playing magnetograms by increasing the permissible read speed of the magnetic head and correcting the shape of the read signal. The goal is achieved in parallel with integrating the signal by the integrator 3, taken from converter 1, is differentiated by block 7, and then the signals received after integration and differentiation are mixed in antiphase in mixer 4, while the phase of one of the signals is corrected by a phase shifter 8. The resulting signal is displayed on the video monitoring unit 5 displaying information. 3 il.

Description

ABOUT

about

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figure 1

The invention relates to magnetic flaw detection and can be used when reading magnetograms in the process of quality control of products from ferromagnetic materials.

The aim of the invention is to increase the sensitivity and accuracy of the control when playing the magnetograms by correcting the waveform read by the induction magnetic head by repeated differentiation.

Figure 1 shows the block diagram of the proposed device; figure 2 - topography of the magnetic field recorded on the tape, and the electrical signal generated by the induction magnetic head for line-by-line reading; Figs. 3 are graphs of signals at the input and output of the blocks of the device, explaining the signal reproduction correction.

The device contains series-connected magnetically sensitive transducer 1 of induction type, amplifier 2, integrator 3, mixer 4 and information display unit 5, series high-pass filter 6, an input connected to the output of the magnetic-sensitive converter, a differentiation unit 7 and a phase shifter 8, output connected to the second input of the mixer.

The device works as follows.

A signal is read from the magnetic carrier (not shown) using the induction type converter 1 (Fig. 2). obtained in the process of product control. The read signal after amplification by the amplifier 2 is integrated by the integrator 3 and fed to one of the inputs of the mixer 4. In parallel with the integration of the signal taken from the induction converter 1, it is differentiated. This allows you to select the high frequency component of the information signal using a high pass filter 6, and then restore the original information. After integration by integrator 3 and differentiation by block 7, the signals are mixed in mixer 4 with opposite phases, while the phase shift of one of the mixed signals is controlled by the phase shifter 8. After mixing the signals in mixer 4, information is fed to the screen of the video monitor of the display unit 5 to determine availability and evaluation magnitude of the defect.

Figure 2, and shows a graph of the magnetic field In (X), recorded in the form of a magician

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nitograms on magnetic tape in the zone of a defective welded joint. Two characteristic sizes are indicated: A is the width of the weld, and a is the size of the magnetic field perturbed by the defect. Figure 2, b also shows a graph of the electric signal f (t) (ideal, without taking into account distortions) produced by the induction magnetic head when reading the magnetogram section line by line.

The source information signal f (t) can be represented as a sum of low-frequency and high-frequency components:

f (t) f (t) + gH (t), (1)

m-1 where f (t) At sp e Pv - low frequency

positing;

sp e |

- high frequency

gM (t):

Inl 2m

constituting.

The output of converter 1 is

Mtl-dfWo. d m

-ar - pre-amplifier output

2c gain factor K is obtained

K, (,).

At the output of integrator 3,

K-Kvf (t) "KKvf (t), since the integration of the high-frequency component greatly reduces the signal

(/ elnn dt y and for large n because of the n in the denominator get 0).

Here is the integration / integrator

3 and the differentiation of the dmM signal in the converter is not reduced due to the blockage of the amplitude-frequency characteristic of the converter at frequencies entering the dm.

The output of the high pass filter 6 remains d

dt

9m (g)

since the low frequencies entering into f (t). do not pass

At the output of the differentiation unit 7, a signal is received

9m,

which is proportional to gw (t), i.e.

-N2 a% gM (t).

At the output of the phase shifter 8 (with a phase shift of 180 °) receive

N2ftЈgM (t). (2)

Mixer 4 adds the components (1) and (2) with a certain ratio of amplitudes 2, i.e. get

KKif (t) + K2N2 QJ§ dm (1) (t) + gM (t) f (t), 5

which corresponds to the initial type of magnetization f (t).

The proposed device allows to improve the performance of the magnetographic control due to the high tolerance of the reading speed by the induction converter, as well as the sensitivity and accuracy due to the shape correction from the gnap read by the induction head during its integration.

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Claims (1)

Claims The device for reproducing magnetograms at magnetic recording flaw detection, containing a magnetically sensitive transducer and integrator connected in series, as well as an information display unit, characterized in that, in order to increase the sensitivity and accuracy of reproduction of the recording on the display unit, to the integrator output, and the output to the information display unit, and in series by a high-pass filter, the input m connected to the output transducer unit, and differentiating the phase shifter output is connected to the second input of the mixer. (pus. 2 df df d f d f figs Jfffldt j