SU572702A1 - Eddy-current method of meausuring parameters of conductive articles - Google Patents

Description

one

The invention relates to the field of non-destructive testing of materials and products, and more specifically to methods for measuring the parameters of electrically conductive products by an eddy current method.

Known methods for the eddy current monitoring of the parameters of electrically conductive products consist in that the product is placed in the high frequency field of the eddy current converter containing one or more current and one measuring coil, form the resulting voltage by summing the high frequency voltage of the measuring coil with the same voltage reference voltage, There are two independent components of the resulting voltage, for example, phase and amplitude, which are used as informative signals. and, in order to obtain signals that are weakly dependent on the magnitude of the interfering parameters, they are subjected to further hardware processing 1.

A disadvantage that impedes the implementation of known methods and increases the instrumental error of measurements is the need to use phase-sensitive devices in their implementation, which must have high accuracy and stability over a wide range of amplitudes and frequencies of their output signals.

A known method for the eddy current monitoring of the parameters of electrically conductive products is that the product is placed in the high frequency field of the eddy current converter and vectorially summarizes the voltage of the converter with the reference voltage of the same frequency, isolating the active and reactive components that are used as informative 2J signals. This method is closest to the one proposed.

The disadvantage of this method is the complexity of implementation, lack of accuracy and reliability of control.

According to the proposed method for measuring accuracy, the voltage of the transducer is summed vectorially with the second reference voltage of the same frequency, which does not coincide with the first one in amplitude and phase simultaneously, and the stresses corresponding to the amplitudes of the resulting voltages are obtained, and use them as information signals.

The possibility of using the obtained directions as informative signals is due to the fact that they are independent functions of the controlled parameters. If in rectangular coordinates

(ReUBH, / mt / hn) DESCRIBE THREE (ReifeH,

JmUm), (ReUoi, / nit / oi). (Rc.L / nz, / mt / oa) respectively, the coordinates of the ends: the voltage vector of the transducer bpp, the first, i / oi and the second i / 02 of the reference voltages, then we can write

1: (-) + (- WH) (1)

Ul (RJJ ,, RJJ, Y + (tJJo - (2)

where Uz are, respectively, the amplitudes of the first and second resulting stresses.

Equations (1) and (2) are independent, unless the reference voltages Uoi and 02 do not coincide with each other in both amplitude and phase. And since the coordinates of the endVector of the voltage on the converter (DeOvp, Jm. (JBs) are independent functions of the parameters of the monitored electrically conductive product, the amplitudes of the voltages Ui and Us. Are also independent functions of the same parameters and could be used as informative signals. The use of the amplitudes of the two resulting voltages as informative signals — formed in the described manner — greatly simplifies its implementation, since it does not require the use of phase-sensitive devices a (phase meters, the isolation device and reactive components) operating in a wide range of variation of the amplitudes of the input signals. This advantage is particularly noticeable in devices with adjustable or switchable depending on the monitored parameters changing frequency range power converter.

FIG. 1 shows voltage diagrams on the converter, the reference and resulting voltages when the specific conductivity a changes in the material of the product and the gap L; in fig. 2 - functional device diagram.

The application of the described method allows solving this problem by simpler means without the use of phase-sensitive detectors. To do this, it is necessary to choose the reference voltages L / oi and Uoz (Fig. 1) so that their difference vector t / oi-Uoz will have angles equal to 45 ° with the real and imaginary axes, and the difference of squares of amplitudes of the resulting diagrams accuracy to constant terms will be proportional to the sum of the active and reactive components of the applied voltage. Indeed, subtracting (1) from (2), we get:

  2R, UB ,, (ReUoi-I Uo2) + 2 / mt / BH (/ mf 01 / mf / 02) + t / o - (3),

Where;

t / 0 () 2 - (/ mf / Ol) 2 + () - (et / Ol) 2

depends on the amplitudes and phases of the reference voltage, i.e., if ReUoi is ReUo2 mUoi-ImUoz (which is the case when the difference vector Uoi and Uoz makes an angle of 45 ° with the coordinate axes) This subtraction of the squares, the amplitudes of the resulting voltages, is equivalent to the summation of the active and reactive components of the input voltage of the converter. At the same time, there is no need to use phase-sensitive detectors, which undoubtedly simplifies the implementation and provides an increase in the measurement accuracy by reducing the instrumental error.

A device that implements the method contains a vortex current converter 1 and blocks 2 and

3 formations of the reference voltages, the inputs of which are connected to the output of the high-frequency generator 4, and the outputs of the formation units are connected to the inputs of two quadratic amplitude detectors 5 and 6, the inputs of which are connected in series with each other and with the output of the converter, and the outputs are connected to the amplitude detectors 7, 8 whose output signals are functions of the active and reactive components

applied voltage of the converter and, therefore, independent among themselves functions of parameters of the controlled product.

Formula of invention

The eddy current method of measuring the parameters of electrically conductive products, consisting in

that the product is placed in the high-frequency field of an eddy-current converter and vectorially summing the voltage of the converter with a reference voltage of the same frequency, characterized in that, in order to improve the measurement accuracy, the voltage of the converter is vectorially summed with the second reference voltage of the same frequency, not coinciding with the first one in amplitude and phase simultaneously, the voltages corresponding to the amplitudes of the resulting resulting voltages are selected and used as information signals.

Sources of information taken into account in the examination

1. Rubin B.D. and others. Electromagnetic control methods, M., 1969, p. 221-227.

2. The author's certificate number 257114, class, G 01B 7/10, 1968., ...

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