SU771583A1 - Device for producing magnetic field of given formula of induction in ferromagnetic specimen - Google Patents

Description

A secondary winding, one output of which is connected to the first output of the magnetizing winding, and the other connected to the first input of the differential amplifier, the second input of which is connected to the second output of the magnetizing winding.

The drawing shows a block diagram of the device.

The device comprises a series-connected master oscillator 1 and a power amplifier. 2, a ferromagnetic sample 3 under test with a magnetizing winding 4, a differential amplifier 5 covered by feedback through resistors b (P) and 7 (R2), and an additional winding 8,. located on the sample.

The device works as follows.

For the circuit formed by power amplifier 2 and magnetizing coil 4, you can write

dB

-e (t) i, r +

(one)

where .e (t) is the voltage at the output of the power amplifier; Go - output impedance of the power amplifier.

It can be seen from the drawing that if we take the value of the input resistance R, of the differential amplifier 5 sufficiently large (Rn -, (), then;..,

Kg

under the second law of Kirchhoff

(2)

  BUT; (3) Calc. I., - output voltage of the differential amplifier; U.UY, - voltage on additional and magnetizing windings.

If we ensure the amplification factor and the voltage E of the differential amplifier to satisfy the condition, then the input voltage of this amplifier must be vanishingly small, since the output voltage, kvtvUgic output from energy considerations, is always the final value . Therefore, with a sufficient degree of accuracy can be taken

id. uvi, {)

and taking into account equations (2) and (3) and get

14 1, (5)

From the expression (k) and with the fulfillment of the condition for the equality of the dynamic inductances of the magnetizing ri additional windings L (t) L (t) (which is easily done when applying an equal number of turns) the trace

1 or subject to equality

According to the first law of Kirchhoff + i, i,

|, t, -,

7) and

Define from expressions

the mask U and the substitute in equation (1), finally get

db

e (t) SWv

m at

whence it follows that the shape of the magnetic induction curve in a ferromagnetic sample is uniquely related to a given voltage at the output of the power amplifier.

Thus, due to the introduction of a differential amplifier covered by feedbacks and an additional winding, the current through the magnetizing winding through the current introduced through the elements is completely balanced, resulting in a parasitic voltage drop at the output of the power amplifier from the high-frequency components of the magnetizing current. At the same time, the specified mode does not depend on the degree of saturation of the ferromagnetic sample and is preserved in a wide range of frequencies of the magnetizing current due to the identical nature of the change in the inductive resistance of the magnetizing and additional windings.

Claims (2)

Invention Formula A device for creating a predetermined form of induction of a magnetic field in a ferromagnetic sample, containing in series a connected one. a generator, a power amplifier, loaded on a magnetizing winding, characterized in that, in order to increase the accuracy and simplify the creation of a given form of induction, a differential amplifier is included in the second, covered by both inputs by resistive feedback, and an additional winding, one output of which is connected with the first output of the magnetizing winding, and another plug into the first input of a differential amplifier, the second input of which is connected with the second output of the magnetizing winding. Information sources, taken into account in examinations1. USSR author's certificate number 336623, cl. G 01 R 33/12, 1972. 2. Chernyshev E. T. et al. Magnetic Measurements. 1969, p. 182 (prototype)