SU883826A1 - Device for magnetic noise measuring - Google Patents

Description

(54) DEVICE FOR MEASURING MAGNETIC NOISES

The invention relates to the technique and measurement of electromagnetic parameters of ferromagnetic materials and can be used in the measurement of magnetic noise. A device for investigating losses in ferromagnetic materials is known, in which an inductor with a measured ferromagnet and a variable capacitor constitute a parallel oscillating circuit. In addition, the device has a sinusoidal voltage generator, which serves as the source of the reference signal, with which the noise of the contour containing the measured ferromagnet Clj is compared. However, this device, due to the presence of an external oscillator, is complex and cumbersome. In addition, the use of a sinusoidal voltage generator as a reference signal in noise measurement leads to an additional error in measuring spectral density or magnetic noise coefficient due to the need to determine the effective noise bandwidth of a measuring device. The aim of the invention is to improve the measurement. The goal is achieved by the fact that a device for measuring magnetic noise containing a parallel oscillating circuit consisting of a variable capacitor and inductance coil with a ferromagnet, an inductance without a ferromagnet and a reference circuit are inserted parallel to the circuit, and in series with the reference circuit and inductance coil with ferromagnet entered two keys. FIG. 1 shows the structure of the device; in fig. 2 is equivalent to the noise scheme of the device when measuring the magnetic noise of a coil with a ferromagnet; Fig. 3 is equivalent to the noise scheme of the device when measuring the thermal noise of the reference circuit, equivalent and measurable. Device Sfig. l) contains a variable capacitor 1, an inductance coil 2 with a measured ferromagnet, an inductance coil 3 without a ferromagnet, a reference circuit 4, equivalent to measuring capacitive 2: a ferromagnet coil 2 and having only thermal noise, a key 5 for connecting a coil 2 to the measuring circuit , a switch 6 for connecting a four-stage circuit 4; As switches 5 and 6, contact groups of a polarized relay can be used. When the switch 5 is closed and the switch b is open, the device at a resonant frequency can be represented by an equivalent noise circuit (FIG. 2), on which are indicated the equivalent conductance 7 of the circuit consisting of a capacitor 1 and a coil 3 at a frequency equal to frequency, generator 8 noise thermal conductivity 7, component 9 of the total conductivity of coil 2 is active, generator 10 noise current of the total noise of coil 2 At the output of the device, noise voltage will act and the average square of which is tg9tRe (Y)

where ig is the noise current of thermal noise

generator 8;

g is equivalent to the conductance of the circuit at the resonant frequency;

Re (Y) is the magnitude of the active component 9.

If at the closed key 6 and the open key 5, the device will have the same resonant frequency and quality factor as in the previous mode, then its sound properties can be described using the equivalent noise circuit Sfg.C), where. the total conductance 1 of the reference circuit 4 and the noise current noise thermal current generator of the reference circuit 4 are indicated. In this case, the device will have a noise voltage Ug of thermal noise proviJu4. . (5) y p, Pg.

Noise spectral density on. prj magnetic noise Sz; and its sinfulness can be written as

s; - kTJ | Re (Y) (2yg- |); (c)

1-V / fHeH / W

As follows from the description of the operation of the device, the measurement of magnetic noise is produced by. comparing the noise of inductor 2 with a ferromagnet with a thermal capacity of 7 and conductivity 11 of the equivalent circuit 4, the average square of which is the total conductivity of the deformable circuit 4; Re (y) is an active component of the total conductivity of this-, the long chain 4; i is the noise current of thermal conduction noise; Using the definition of the noise factor of the two-terminal circuit and expressing the noise currents through the corresponding values of noise conducted by us, we get 9e CY) 9 e + Re CY) From G-1 () 1. fc. In case of equal Re (Y) and d, which can be accomplished by adjusting the connection of the circuit with coil 2 and circuit 4 with the help of capacitive elements, the quadratic indicator at the output of the whole meter i. gga will give readings about. , 11, - and / oTodal relative error of the noise ratio of coil 2

noise equivalent circuit 4, alternately connected to a parallel circuit that does not contain a ferromagnet. In this case, external sources of reference signals are not required, and the error due to the accuracy of determining the effective noise bandwidth of the meter is eliminated.

The device can be used to measure the electrical noise of any linear and nonlinear two-terminal network with a positive conductivity value Re (Y).

The use of new elements of an inductance coil without a ferromagnet and an equivalent circuit makes it possible to eliminate external generators of reference signals, which simplify the device, reduce the cost of its operation, and increase the accuracy of measuring noise and noises. The introduction of new elements will expand the field of application of the device and eliminate the need to develop a number of devices for measuring the noise of various bipolar structures.

Claims (1)

Invention Formula f An apparatus for measuring magnetic noise, comprising a parallel crimping circuit consisting of a variable capacitor and an inductance coil with a ferromagnet, characterized in that, in order to improve the measurement accuracy, an inductor without a ferromagnet and a reference circuit are inserted parallel to the circuit and a coil inductance with a ferromagnet introduced two keys. Sources of information taken into account in the examination . N. Btttet, H, LUtgemeier, Uber spontane zeitliche schwankungen der Magnet isterung eines Ferromagnetikums. Zettschrift fur angewandte Physik, 1963, Bd 15, N 6, S.476-480