SU1462174A1 - Colour magnetic-television flaw detector - Google Patents

Description

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This invention relates to a magnetic field inspection of the quality of welded joints and can be used in all areas of mechanical engineering.

A magnetographic flaw detector is known, comprising a magnetic head mounted for scanning a magnetic tape with recording of the stray fields due to a defect in the welded joint, an electron-beam tube (CRT) with scanning and synchronization units. The electrical signals induced in the magnetic head come to the CRT screen and judge the quality of the welded joint from the image on the screen.

The drawback of the device is the low resolution, due to the constant attenuation of the image of the fields of defects observed on the screen of the tube.

The closest in technical essence to the invention is a color magnetic and television flaw detector containing a tape unit, a reading unit, an amplifier and a video control unit, including a series-connected video amplifier, a color unit, a color kinescope, to the cathode of which a second output video amplifier, frame and line synchronization units are connected corresponding synchronization sensors.

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In addition, the device contains a random-access memory unit for sequential accumulation of information read out line by line from the tape to subsequently form the television image of the removed information from it.

The disadvantage of the device is the low resolution and reliability of the monitoring, due to the use of a RAM block, which complicates the design of the device. In addition, any block of memory has bounds on the amount of memory defining the dynamic range of the memory device. The known device does not allow continuous viewing of the investigated area of the object.

The aim of the invention is to increase the resolution and reliability of the device,

This is achieved by the fact that a color magnetic and television flaw detector containing a tape unit, a reading unit, an amplifier and a video control unit, including a series-connected video amplifier, a color unit, a color kinescope, to the cathode of which a second output amplifier, frame synchronous It is equipped with a switch, connected to the readout unit and the frame synchronization unit, and output to the amplifier, an electronic formation unit ideo signal of the line connected by inputs to the horizontal synchronization unit and to the amplifier, and the output to the video amplifier, the reading unit is designed as a drum with a two-channel system of p-heads distributed around its circumference with displacement of the heads along its axis and This is proportional to the length of the read line.

Fig. 1 shows a block diagram of a color magnetic and television flaw detector in Fig. 2, a block diagram of one of the elements of a block for selecting chrominance signals.

A color magnetic-TV flaw detector contains a tape-carrying unit (not shown), a reading unit made in the form of a drum 1 with a two-channel system of n-head 2,

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located along its circumference with displacement of heads 2 along its axis with a spacing A of the line and spaced from each other at a distance L, proportional to the length of the read line, commensurate with the width of the investigated magnetic tape 3, transmitting the read signal through the collector pick 4, connected in series 5, an amplifier 6, an electronic unit 7 for forming a video signal of a line, a video monitoring unit 8 comprising a series-connected video amplifier 9, a color block 10, a color kinescope 11 (CRT), the second output being amplified bodies 9 are connected to the kinescope channel 11, block 12 frame and block 13 horizontal synchronization with the corresponding sensors 14 and 15 synchronization, block 7 of forming the video line signal is connected by another input to block 13 horizontal synchronization, and the output to video amplifier 9 video control unit 8, switch 5 the defectoscope is also electrically connected to the frame synchronization unit 12.

The synchronization circuit also includes a modulation disk 16 and a light emitter 17. The disk 16 is located on the axis of the drum 1 and has apertures located along its perimeter, spaced from each other at a distance proportional to the length. L lines read.

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The chromaticity unit 10 is a high-speed analog-to-code-signal converter, and each terminal amplifier of the chromaticity unit 10 contains a feedback input to which the corresponding tube electrode of the color kinescope 11 is connected.

A structural diagram of one of the elements of the chromaticity block 10 is shown in FIG. In each of the three elements (in the three primary colors: red, green, blue), the selection of the chromaticity signals contains a resistive chain of forming reference threshold voltages on resistors 18-22, voltage comparators made on operational amplifiers 23-26 and threshold logic elements NAND 27, 28 and a resistive chain to form a stepped signal 29 and 30.

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. The output of video amplifier 9 and reference voltages from a resistive chain for quantizing video signal levels are connected to the differential inputs of the operational amplifiers.

The flaw detector works as follows.

When the drum 1 rotates at a frequency of, for example, 50 revolutions per second, the magnetic reproducing heads 2 sequentially with step A run through the magnetic tape 3, reading the records along the lines depicted by dotted lines. At the moment each head 2 is incident on the test tape 3, the synchronization system issues a horizontal start trigger of the video monitor unit 8, and the rotational speed of the drum 1 determines the frame scanning frequency of the kinescope 11.

Thus, the scanning pattern of the head 2 on the tape 3 is synchronized with the movement of the electron beam on the screen of the video monitoring unit 8, playing back the information recorded on the tape line by line. In this case, the switch 5 synchronously with the frequency of rotation of the drum 1 sequentially connects to the input of the video signal forming unit 7 one or the other of the channels of the two-channel head 2, thus performing interlaced scanning. In block 7, the information signal is mixed with synchronization and illumination signals. The number of reproducible lines for a drum with a diameter of 170 mm is Z 32. (16 dual-channel heads), which corresponds to the reproduction of a television frame with a width of L 33 mm and an extension of the control zone X 64 mm.

The resolution of this visualization system determines the number of decomposition elements in a frame:

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This corresponds to the reproduction of information from an area of –1 mm, which is almost an order of magnitude larger than the area of a magnetic footprint due to a deep defect. With

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By this, taking into account that the magnetic head reacts to the sign of magnetization, the resolving power increases even more. Thus, for the simplest version (16 reproducing heads), the flaw detector provides a sufficiently high resolution.

A significant advantage of this magnetic recording system, unlike the prototype, is the ability to view a moving tape. If the tape moves 1 frame by frame length (V 64 mm / s), then the speed of the tape will be much less than the frame rate of image. Corresponding to this speed deviation of the frequency of reproduced fields:

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where p is the frame rate.

Consequently, the spectral lines of the signal spectrum occupy narrow frequency bands (spectrum expansion ± 2 Hz) and the discrete nature of the spectrum is almost preserved. The motion of the image reproduced from tape to screen will not be blurred.

To obtain information about the size of the defect detected on the screen, the video signal from the video amplifier 9 goes to block 10, the elements of which form a stepped signal that determines the reproducible color tone. The shape of the stepwise color signal is determined by the ratio of the resistances of the resistors 18-22 and 29 and 30 (Fig. 2). By color, judging the size of the defect, for example, red indicates an unacceptable defect.

A color magnetic and television flaw detector allows one to increase the resolution and reliability of a magnetic flaw detector by directly visualizing a section of magnetic tape on a television screen, and it will also allow fixing any control area on the screen for an arbitrarily long time to observe, study and measure it.

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Claims (1)

A COLOR MAGNETOTELVISION DEFECTOSCOPE containing a tape drive unit, a readout unit, an amplifier and a video control unit including a series-connected video amplifier, a color unit, a color picture tube, to the cathode of which a second video amplifier output is connected—