SU502205A1 - Eddy current device for monitoring electrically conductive products - Google Patents

Description

one

The invention relates to the field of non-destructive testing by a vortex method of electrically conductive products and can be used to control electromagnetic parameters.

Eddy current devices for monitoring electrically conductive products are known, comprising a generator configured as an amplifier with positive feedback, a parametric type sensor, and a frequency counter. A disadvantage of the known devices is the dependence of the readings of these devices on the gap between the sensor and the product, which reduces the accuracy of measurement of the parameters of the products.

In order to improve the accuracy of monitoring the electromagnetic parameters of the product, the proposed device is equipped with a phase shifter and a quadrupole with linear phase-frequency characteristic connected in series with the sensor, and the sensor is transformer-based.

FIG. 1 shows a block diagram of the proposed device; in fig. 2 - hodographs introduced by e. d. for transformer sensor; pa fpg. 3 - phase characteristic four-pole characteristic.

The device contains an amplifier 1, a phase shifter 2, a quadrupole 3 with a linear phase-frequency characteristic, a transformer sensor 4, a reference product 5, a controlled product 6, a frequency meter 7, and an initial voltage compensator 8.

Amplifier, Phaser, Compensator and

The transformer sensor is connected in cascade in series to a closed system with positive feedback. The transmission coefficient of the system in the open state at the expense of the amplifier is made larger than one (amplitude balance). The minimum possible transmission coefficient of the transformer sensor is made. The phase shifter compensates the initial phase shift, and the compensator compensates the initial voltage of the sensor. A monitored product is located in the measuring area of the sensor. The frequency meter is connected to the output of the amplifier and registers the change in frequency.

The device works as follows.

With the nominal gap value ho from the sensor to the product and the nominal thickness / of the product, the phase shift is e. d. relative to current The total phase incursion in a closed loop in the generation mode must be zero (phase balance). For this, phase shifter 2 introduces an initial phase shift (-cro). As a result, the oscillator operates at a frequency / o.

When reducing the thickness of the product to / i

phase introduced by e. d. changes to value

As a result, the phase shift of AF F1-pho appears and the generation frequency changes to the value of /. At the same time, due to the linear phase-frequency characteristic of the quadrupole, the frequency increment is directly proportional to the phase change and, accordingly, to the product parameter. As the thickness increases to / 2, the phase of the emf applied changes. to f2 and the frequency decreases to a value of / 2.

The use of a quadrupole with a linear phase-frequency characteristic allows the conversion of the product parameters that affect the phase of the input em. d. directly into the frequency, with the conversion law "phase increment-frequency increment linear.

Due to the fact that the lines of influence of the gap (hi-kg) are close to the radial straight lines, the phase and, consequently, the frequency with its change remains constant. Therefore, the proposed Device suppresses the effect of gap changes.

The proposed device can be used in all cases of thickness measurement and electromagnetic control, when useful information is contained in a change in the phase of the emf applied. and its increments for various sensors.

Claims (1)

Invention Formula An eddy current device for monitoring electrically conductive products, comprising a generator made in the form of an amplifier with a phase shifter in its positive and feedback circuits, a sensor and a frequency meter, characterized in that, in order to improve the control accuracy, it is provided with connected in series feedback with a sensor with an initial voltage compensator and a quadrupole with linear phase-frequency characteristic, and the sensor is transformer-made.