SU721781A1 - Arrangement for measuring magnetic field intensity - Google Patents

Description

The invention relates to the field of electromagnetic engineering and is intended to measure magnetic tape in magnetic recording apparatus. Magnetic intensity measuring devices are known that contain a ferrosonde probe, the secondary windings of which are connected to phase discriminators 1. The closest technical entity to this invention is a device comprising a ferromagnetic core with primary and secondary windings, a time interval meter consisting of a spring, an AND element, the output of which is connected to a counter, and the first input The outputs of which are connected to the control inputs of the counter 2. A disadvantage of the known devices is low measurement accuracy. The purpose of the invention is to improve the measurement accuracy. The goal is achieved by the fact that the device contains primary and secondary windings, a time interval meter, which is connected from a counter, an element, the output of which is connected to the counter, and the first input is connected to a pulse generator, two elements NOT, the outputs of which are connected o. The control inputs of the meter are equipped with three triggers, an additional element and, an additional element NOT and a triangular current generator, the output of which is connected to the primary winding of the core, the secondary winding of which is connected to separate inputs of the first trigger, separate outputs of the first trigger are connected by combining the elements NOT, the counting input of the second trigger and the counting input of the third trigger are connected to the corresponding separate outputs of the first trigger, the output of the second trigger pogo connected to the counting input of the third trigger, the output is supplemented by the even element of the cut; the additional element is NOT with the installation input of the first trigger FIG. 1 shows a functional diagram of the proposed device; on

FIG. 2 - time diagram of his work.

The device consists of triggers 1, 2, 3, counter 4, element

5 and the pulse generator 6, the Converter 7 is connected to a triangular current generator 8, the outputs of the converter 7 are connected to the trigger inputs 1, the outputs of which are connected through the terminals 9 and 10 to the inputs of the counter 4. The counting input of the counter 4 is connected to the output of the And 5 element, whose inputs connected to the generator 6 and the output of the trigger 2. Element And 11 inputs connected

the input of the element NO 9 and the output of the trigger 3, and the output with the element NO 12, the output of which is also connected to the input of the element NO 9. The operation of the device is as follows. At the initial moment, all the triggers 1, 2, 3 and counter 4 are reset. Element I 5 is closed, does not allow pulses from generator 6 to the counter. The first positive pulse received at the first input of trigger 1 from converter 7, trigger 1 is thrown, flips trigger 2, and through element 9 sets meter 4 to direct count. In this case, the trigger 2 through the element And 5 allows the passage of pulses from the generator

6 on the counter 4.

A positive impulse arriving at the left input of trigger 1 (corresponds to a negative impulse 2, in Fig. 2) flips triggers 1 and 3. At the same time, trigger 1 through the element NOT 10 sets counter 4 to the inverse position.

In the counter, from the number of pulses transmitted to it during time T, (Fig. 2), the number of pulses transmitted during time T is subtracted. The next positive impulse received at the right input of trigger 1 transfers it and also trigger 2, which closes the element I 5 and prohibits the passage of pulses from the generator b to the counter 4. In addition, the element 12 is torn off and the trigger 1 is reset.

The transducer core 7 made of a ferromagnetic material with a rectangular hysteresis loop with primary and secondary windings wound on it is placed in a measured flux magnetic field, and the intensity of this field must be less in absolute value than the coercive force of the H. core. After the core is placed in the measured field, the magnetic state of the core is characterized, for example, by a point M on the hysteresis loop. When a triangular-shaped current is transmitted through the primary winding, it creates a variable intensity H (t), the amplitude of which H is chosen to be larger than 2H, the core will re-magnetize along a dynamic hysteresis loop, while in the secondary winding sharp pulses of great steepness and short duration will appear celebrating moments of equality:

H (t) - HO and H (t) + HO.

Moreover, these two points will correspond to pulses of opposite polarity, but identical in other characteristics. The duration of these pulses is due to the finite steepness of the vertical sections of the hysteresis loop and the reactive properties of the output circuit. Between pulses, the core is saturated, and the voltage in the secondary winding is zero.

FIG. 2 accept the following notation:

HQ is the intensity of the magnetic field being measured,

H. - coercive force of the core,

H is the amplitude of the exciting alternating magnetic field.

4Vj.A6

e s- jj j-pulse EMF arising

in the secondary winding, C, Cj, are the intervals between pulses of opposite polarity, 1, Chg. phase of the moments of comparison

those. moments when H (t) + HO. As can be seen from FIG. 2 Tt

rt-,

 ,

0 where

From here 2D.

From consideration of the adjacent triangles of the ODE and UEC it follows:

§ gdeoah ,,

AE IHJ-H,

from where

U, .T | Hc1-But

From consideration of similar triangles GNF and GLR it follows: GF C.R NF L.R where C.

and T | Ns.Ns r-4 IHJ

from where

 -Vt I-raj c o-l "clHo)

Itl

t -t ZA4-J.H,

those. at a constant frequency and amplitude of the field exciting field, the difference in the intervals between the pulses of one polarity and the opposite polarity between them is directly proportional to the intensity of the measured field.

Claims (2)

1. USSR Author's Certificate No. 140230, cl. G 01 R 33/00, 1961. 2. Phobrikant V.A. Fundamentals of Theory 0 building measuring bodies of relay protection and automation, Energie, 1968, p. 104-109 (prototype). Tr G, (rig 2