SU905890A1 - Magnetometer - Google Patents

Description

The invention relates to a measurement technique and is intended, in particular, for measuring magnetic fields.

A magnetometer is known that contains a series-connected generator, a thin-film magnetic sensor, a detector connected in the frequency discriminator circuit, a DC amplifier, and a recording device 1,

The disadvantage of this technical solution is the need to use a DC amplifier with a large gain factor and a large dynamic range. This is due to the slight modulation of the magnetic permeability of the film by the measured magnetic field. The use of a dc amplifier results in a LOW measurement accuracy due to flicker noise, which transits at low frequencies into drift.

The closest to this technical solution is a device containing a generator with two thin-film sensors connected to its output with oppositely oriented easy magnetization axes (EMA) connected to two amplitude detectors, respectively, each of whose outputs are connected to an input from a DC amplifier through a separating chain consisting of a series-connected resistor and a capacitor. The output of the DC amplifier is connected to

JQ recording device 2.

A disadvantage of this device is the low measurement accuracy due to the use of a DC amplifier due to its inherent zero drift and large

15 level of own noise, inversely proportional to the frequency (1 / f) where f is the frequency, n 1, 2 ... k,

The purpose of the invention is to improve the measurement accuracy.

20 This goal is achieved by the fact that a magnetometer containing a generator, to the output of which are connected in series the exciting windings of two thin-film sensors with oppositely oriented axes of easy magnetization, two amplitude detectors, measuring winding of each of the thin-film sensors

30 is connected to the input of the corresponding amplitude detector, to the output of each of which is connected a separating chain consisting of a series-connected chopper and a capacitor, and a recording device, two varicaps, a high-frequency amplifier, a balanced detector and a phase shifter are inserted, and the cathode of the first varicap is connected to the input the first amplitude detector, and the anode of the second varicap is connected to the input of the amplitude detector, the anode of the first varicap through the resistor of the second separating circuit is connected to you the second amplitude detector, and the second varicap cathode through the resistor of the first separator chain is connected to the output of the first amplitude detector; the output of each separator chain is connected to the input of the high frequency amplifier, the output of which is connected to the recording device and the second input of the balanced detector through the phase shifter connected to the output of the generator.

The drawings depict a functional magnetometer circuit.

The magnetometer contains a generator

Ic connected to its output by thin-film sensors 2 and 3 with oppositely oriented axes of easy magnetization (EMA), each of which has a stimulating

and, the measuring winding, the amplitude detectors 6 and 7, at the output of the detector 6 is connected a separator chain consisting of series-connected resistor b and a capacitor 9, and the output line of the detector 7 includes a separator chain consisting of series-connected resistor 10 and a capacitor 11 and a recording device 12. Two varicaps 13 and 14 are inserted into the device, amplifier 15 is of high frequency, balanced detector 1 and phase shifter 17. In this case, the cathode of varicap 13 is connected to the input of amplitude detector 6, and the anode of varicap 14 is connected toetektora varicap 7. The anode 13 is connected to a point of the resistor compound, and a capacitor 10

II at the output of the detector 7, and the cathode of the varicap .14 to the connection point of the resistor 8 and the capacitor 9 at the output of the amplitude detector 6. The output of each of the dividing chains is connected to the input of the amplifier

15 is high frequency, and the output of amplifier 15 via a ba; a 1 sans detector 16, the control input of which is connected to the output device 12 via a phase shifter 17, is connected to the output of generator 1.

The magnetometer works as follows.

The measured magnetic field, for example, a sinusoidal, acts on thin-film sensors 2 and 3 with oppositely oriented easy magnetization axes (EMA) and changes their own inductances (magnetic permeability of films), which leads to modulation of the high-frequency voltage of the generator 1 at the sensor output 2 and 3. The high-frequency voltage induced by the measured field induced in the measuring winding of the sensor 2 is detected by an amplitude detector 6, and the voltage at the output of the sensor 3 is detected by the detector 7. Herewith The constant components of the output signal of the detectors b and 7 have opposite signs, and the variable components of the detected voltages are synphas, since. The EMA of the film of one of the sensors 2 and 3 is located in the direction of the measured floor, and the EMA of the second - towards it. In other words, when g increases the inductance of one of the sensors 2 and 3, the inductance of the other decreases. The constant components of the detected voltages pass through resistors 8 and 10 and determine the operating points of the varicaps 13 and 14, relative to which their capacitances change under the action of the variable components of the output voltages of the detectors 6 and 7.

Since the sensors 2 and 3 and the varicaps 13 and 14 form a contour that represents a four-shouldered bridge, the equilibrium condition of this bridge can be written as

H

C-Vi

Vi (1)

and lrt where

respectively, the inductances of sensors 2 and 3; and soo. - capacity varicap 13

And 14 at a zero measured field or conditionally accepted as zero.

0 If the condition of the balance of the bridge is ensured with a zero-measured magnetic field, the signal of the generator 1 at the output of the bridge (input of the high-frequency amplifier 15) is absent. Under the action of the measured floor balance of the bridge HapytaaeTCH. This state is analytically recorded as well as 4YC i.L VifuCv,

where the corresponding increments of inductances of sensors 2 and 3; and BOS (- - relevant

 increments of capacities

14 and 13.

varicap

As follows from expression (2), a change in the capacitances of varicaps 13 and 14, synchronously with a changed magnetic field, increases the imbalance of the bridge, therefore, the magnitude of the signal, which with a small measured field is proportional to the magnitude of the latter. The modulated field measuring signal of the master oscillator 1 from the bridge output is fed to the input of a power frequency amplifier 15, the output of which is fed to the input of a balanced detector 16. To satisfy the linear detection condition, the control input to the control input of the balanced detector 16 from the generator 1 output is fed through a phase shifter 17. carrier voltage. The voltage from the output of the balanced detector. 16 enters the recording device 12.

In the proposed magnetometer, by using varicaps, a preliminary parametric amplification of the signal of thin-film sensors is carried out, and therefore an increase in the signal-to-noise ratio is achieved at the input of the high-frequency amplifier. The use of a high frequency amplifier in one's own way eliminates the zero drift inherent in the known due to the presence of a dc amplifier, as well as its flicker noise. The magnetometer operates in a wide frequency band, including zero frequencies (O - 10 kHz). The large signal-to-noise ratio allows the use of a magnetometer not only to study various magnetic phenomena, but also as a magnetic active antenna.

Claims (2)

Invention Formula A magnetometer containing a generator to the output of which is connected series-connected excitation windings of two thin-film sensors with oppositely oriented axes of a light magnetizer: vania, two amplitude detectors, the measuring winding of each of the thin-film sensors is connected to the input of the corresponding amplitude detector, to the output of each of which is a separating chain consisting of a series-connected resistor and a capacitor, and a recording device, characterized in that, in order to improve the measurement accuracy, two varicaps are introduced into it . 5 a HIGH frequency amplifier, a balanced detector and a phase shifter, with the first varicap cathode connected to the first amplitude detector input, and the second varicap anode connected to the second amplitude detector input, the first varicap anode connected to the second amplitude detector through the resistor of the second separation circuit, and the cathode the second varicap through the resistor first 5 separator chain is connected to the output of the first amplitude detector, the output of each separating chain is connected to the input of the high-frequency amplifier, the output of which is through 0, the balanced detector is connected to a recording device, and the second input of the balanced detector is connected to the generator output via a phase shifter. Information sources, 5 taken into account in the examination 1. US patent No. 341072, cl. 32443, 1967.  . 2. Bader C.D., Renzi C.S. IEEE i Transaction of Magnetics VMAG - 10, 0 1974, W 3, p. 524 - 527.