SU578613A1 - Eddy current flaw detector - Google Patents

Description

I

HaoopeTeiiiie belongs to the field of non-destructive isogoganin and is intended for non-destructive testing of metal pipes, pipes and wires.

The eddy current flaw detector for controlling metal products is well-known, which is the most technical to the invention, containing a generator, a generator with a current and measuring windings of through-pass type, measured by means of flocks, placed along the product, the ammeter phase phase signal processing (SAFiS), two coincidence circuits and an automation unit ij.

The known device has a number of disadvantages associated with a low signal-to-noise ratio when detecting small defects and a sharp decrease in the reliability of the control when the noise fluctuates over a wide range caused by structural heterogeneity of the metal, internal mechanical stresses, and spatial interlaces of the product. .

The aim of the invention is to improve the measurement accuracy.

This is achieved due to the fact that the flaw detector is equipped with a series-connected squaring scheme, a bottom limiting cascade and a root extraction scheme connected between the SAFOS and the automatics unit, two detectors and four transformers, the primary windings of which are connected each with its patch sensor each first from secondary windings

all impulses are connected to their cascade, all the second windings are connected to / from the 11 ° C .. to the Ic.ibiio ii through the one-way pz of the detectors connected to the SAFiS, and the third to the gyyi. Another detector is also connected to the SAFi ..

iia phpg 1 is an electrical block diagram of a defect zone; in fig. 2 shows the placement of pass-through and overhead windings.

sensor relative to the monitored product.

The flaw detector consists of a generator 1, a sensor 2 with a current winding 2-1 and measuring differentially connected windings 2-2 and 2-3 of a through passage type, measuring coils 3, 4, 5 and 6 of the surface type, placed around the perimeter of the product; four transformers U, 8, U and 10, each of which contains one primary

7-1; i-1 y-1. 10-1 and three secondary windings: 7-2, 7-3, 7-4, 8-2, 8-3, 8-4, 9-2, 9-3, 9-4, 10-2, 10- 3, 10-4, two-stage amplifier And, 12, the cascades of which are covered by feedback for automatic adjustment of the amplifier, (not shown) amplitude detectors 13, 14, SAFOS 15, shapers 16, 17, 18, 19 pulses in amplitude and duty ratio, coincidence circuit 20, square squaring circuit 21, threshold limiter 22 from below, root extraction circuit 23, anti-percussion circuit 24 of the automation unit 25.

The flaw detector works as follows.

The signal from measuring windings 2-2 and 2–3 of the pass-through type is amplified in amplifier I, 12, detected in SAFOS 15, squared by circuit 21, limited from below by limiter 22, then using square 23, the square root is extracted from the signal. If the logic circuit 20 does not receive a signal to the non-AND 24 circuit, the signal from the defect passes to the automation unit 25. If a signal appears at the output of circuit 20, the pulse is not received at the automation unit 25. The gain of the first cascades 11 and 12 is controlled by the voltage supplied from the measuring coils 3 and 4, 5 and 6 through the amplitude detectors 13 and 14. The winding of each of the four coils 3, 4, 5 and 6 is connected to the primary winding of the corresponding transformer 7 , 8, 9 and 10. The transformer has three secondary windings, the first ones of which (7-2; 8-2; 9-2; 10-2) are interconnected in series and connected through the detector 13 to the control input of the cascade 11 ; the second windings are connected in pairs and in opposite directions (7-3; 8-3; 9-3; 10-3), and among themselves - in parallel and connected via detector 14 to the control input of the cascade 12, the third winding (7-4; 8-4; 9-4; 10-4) pulse drivers 16, 17, 18, 19 are connected to coincidence circuit 20.

The magnitude of the applied voltage of the overhead coils is directly proportional to the magnitude of the structural heterogeneity. This signal, through its successively connected windings, controls the gain of the cascade 11. The signal from the transverse movements of the product is released by counter-switching on the diametrically opposite applied coils (3 and 5; 4 and 6) and is used to suppress the effects of the movements by adjusting the gain of the cascade 12.

The effect of defects on the output signal of overhead coils is significantly weakened due to the small width of the defects. Using squaring, bottom clipping schemes and root extraction schemes, the signal-to-noise ratio is increased. Logic circuits 20 and 24 are used for

detuning from local changes along the length of the structure, when a signal occurs simultaneously in all four overlapping cages, in contrast to a defect that can cause a signal only in one (rarely two) of these

coils

Claims (1)

1. USSR author's certificate No. 376710, cl. G 01N 27/86, 1971. FIG. one