SU652479A1 - Device for detecting cracks in ferromagnetic tape - Google Patents

Description

(54) DEVICE FOR DETERMINING CRACKS IN A FERROMAGNETIC TAPE

a signal, a coincidence circuit, to one input of which one of the drivers is connected, and a recording unit, the stroke of which is connected to the output of the coincidence circuit 3.

The disadvantage of the device is its low noise immunity.

The purpose of the invention is to improve the noise immunity of the device, in particular, from the effects of impulse noise.

This goal is achieved in that the device is equipped with two detectors, one of which is connected between the direct output of the amplifier and the input of the first driver, and the second one connected to the inverse output of the amplifier and the input of the second driver, and a delay line connected between the output of the second driver and the second input of the matching circuit.

FIG. 1 shows a schematic of the device; FIG. 2 - diagrams of device signals.

The device contains a permanent magnet 1, magnetizing the magnetic material along the axis of movement of the controlled sample (not shown in the drawing), and erasing the anomalously magnetized areas in the region of the indi vidual converter 2. The converter 2 is a coil located on a U-shaped ferromagnetic core , oriented also along the axis of motion of the test sample, paraphase amplifier 3, two detectors 4 and 5, two shaper 6 and 7 signals, line 8 under the junction circuit 9, coincidence and block 10 register ation.

The device works as follows ... /. .

Magnet 1 is placed above the product. A converter 2 is located between its poles, the coil of which is co-. is connected to the input of amplifier 3, to the inverting input of which a circuit is connected from the first detector 4 and the first driver 6 connected to the first input of circuit 9, and jc to the direct output circuit from the second detector 5, second driver 7 and delay line 8 connected to the second the input of circuit 9, the output of which is connected to the input of block 10. When a defect appears in the zone of converter 2, its signal will turn out in its catuid. This signal at the output of the receiving coil is shaped. bipolar pulse (Fig. 2a), the amplitude of which depends on the size of the crack. It is amplified by amplifier 3, at the outputs of which paraphase signals appear (Fig. 2b), which are detected by detectors 4 and 5 (Fig. 2b and are formed by square drivers 6 and 7 (Fig. 2d). Signal c the direct output of amplifier 3 is delayed in the delay line 8 at which it overlaps with an inverted negative pulse (Fig. 2e). Then both signals go to the inputs of circuit 9 and from its output to block 1O (Fig. 2e) the device selects from all possible signals only bipolar, in which the first imp Only positive and the second negative and the next after an interval of time less than or equal to the delay.

Thus, the device does not respond to single impulse noise, regardless of their polarity, since they will pass through only one of the two channels and will not cause circuit 9 to operate.

In the case of the arrival of the bipolar roomHs, it will trigger the circuit 9 only if the time interval between the pulses of this interference is less than or equal to the length of the rear axis in the delay line 8 and the first pulse is positive polarity. The coincidence of these conditions is powerful, that is, the device has a higher noise immunity from impulse noise of both polarities.

Claims (3)

1. Rail flaw detection, M., All-Union Publishing and Printing Association MPS, 1963, p. 130131, FIG. one. 2. USSR author's certificate No. 544904, cl. in O1N 27/82, 1974. 3. USSR author's certificate number 336588, class, in 01Р4 27/86, 197О.