SU448405A1 - Device for measuring magnetic field - Google Patents

Description

(54) DEVICE J. MEASUREMENTS OF THE MAGNETIC FIELD

The invention is intended to measure constant and immediately changing magnetic fields.

A known circuit of a magnetic field meter with automatic stabilization of the conversion slope, comprising a Hall sensor with a controlled source of pigments, a measuring amplifier, a selective filter, a correction circuit, an error signal amplifier, a synchronous detector of a low-pass filter and a test signal generator, in which to stabilize the slope the amplitude ha; characteristics; a harmonic test signal is used.

However, in such a scheme, the conversion coefficient of the generating coil of the test signal depends on the magnetic permeability of the ferromagnetic environment. For example, when measuring the field in a vazor electromagnet), which affects the measurement accuracy.

The aim of the invention is to improve the measurement accuracy,

This goal in the proposed device is achieved by additionally introducing, into the circuit of the measuring coil, magnetically coupled to the generator coil. The signal of this coil, which carries information about the magnetic permeability of the medium, after an appropriate conversion, is used to compensate for the disturbing effect.

Figure 1 shows the block diagram of the proposed device; in fig. - structural scheme; on fig.Z time diagrams ..

The device contains a Hall sensor I, a measuring amplifier 2, a controlled power supply 3, a generator 4 with sinusoidal voltage, a generator coil 5, a reference resistor 6, a selective filter 7, and a correction circuit. mismatch amplifier 9, I 10 synchronous detector with 1-frequency filter and measuring pin II. The Hall clock is affected by the jointly measured Hz field and the test signal BO field, created by the test signal generator, consisting of the sinusoidal voltage generator 4 and the generator coil 5 connected in series with the reference resistor 6, the test signal frequency is chosen high enough (several hundred hertz). Since the measured field is constant or slowly varying: the signal, the spectra of the trial and measured fields are different. The Hall sensor is powered by a controlled direct current source 3. The component of the output signal C of the measuring amplifier, proportional to the 6sq field that is being smoked, is measured by a recording device, and the voltage VQ, proportional to the field of the test signal, is selected by a filter 7, tuned to the frequency of the test signal. the required dynamic properties of the system, a passive correction circuit 8 is introduced into the circuit, the output signal t / 3 of which is compared with the voltage and o. proportional; excitation current of the generator coil. The resultant comparison of the error signal lA-Uj-Ui after amplification by amplifier Y and detected by the synchronous detector 10, controlled by the test signal generator, is supplied as a voltage of 1 / b to the input of the controlled current source 3. The amplitude response of the conversion is stabilized by automatically adjusting the magnitude of the current In of the Hall sensor power is proportional to the deviation of the conversion coefficient of the measurement path from the specified value. In order to block the disturbing effect caused by the influence of the ferromagnetic environment, a meter was introduced into the circuit on a coil magnetically coupled to the generator, forming an air transformer with the latter. Structurally, the air transformer is made in the form of a cylindrical coil, uniformly wound on the frame with a double wire B, the average section of which is located the Hall Hall. These elements are an integral part of the measuring probe. The signal (Jo of the measuring coil associated with the current G of the generator; rhotor coil and perturbation: the expression | 1. ,,. CiOiiGi and ЛО i where, is the relative magnetic permeability of the medium; Jio is the magnetic constant; 5, is the cross-sectional area and coil length; ti / jU / g - the number of turns of the generating coil and measuring coil, respectively, is compared with a voltage UQ proportional to the excitation current of the generating coil. The selected error signal L {/ o (; - V is pulled up from the output voltage (/ X sensor Hall, also containing yush1uyu Qy,, proportional. The tuning of the pattern consists in leveling the voltages Ul and U (in the absence of a Ferromagnetic medium) by adjusting the resistor 6. Then, in the presence of a ferromagnetic medium, the component of the input signal of the measuring amplifier is proportional to the disturbing effect, will be almost zero. To determine the conditions for compensating the disturbance, consider the block diagram shown in FIG. 3, where, / (o, / {v are the transfer functions and the transducer coefficients chaps The remaining designations are the same. The signal acting at the input of the measuring amplifier will be the ratio (, l} io) Io,, Ao1o C 1o Le (vV, (; f; J-vi / 2}. From which it follows that in order to achieve absolute invariance (independence.) (/ from the perturbation. E- it is necessary and sufficiently-1 in person that the transfer function would .te be identically zero, i.e. U 0. Then the compensation condition will be fulfilled, i.e. the conversion factors of the measuring coil and the Hall sensor

should be equal

PREVIEWING PICTURES A magnetic field POLY measurement that contains a Hall switch with a controlled pacing source, a measuring amplifier, a selective filter, a correction loop, an error signal amplifier, a synchronous detector with a low-pass filter, and an alternating current source loaded on the sequential center J

A standard resistor and a generator coil, distinguishing it with the fact that, in order to improve the measurement accuracy, it is equipped with a second coil connected with a generator coil, which is turned on by connecting the generator coil with the reference resistor and the input coil

clamp measuring amplifier, and the Hall electrode of the Hall sensor is connected to the second contact of the reference resistor.

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