SU143908A1 - Method of compensation of parasitic emf induced in the hall emf sensor circuit - Google Patents

Description

As is known, the output voltage of the sensor e. d. The Hall is proportional to the product of the control current / to the intensity of the magnetic field I, which can be expressed as:

where: K. is the transmission coefficient and R., is the input resistance of the sensor.

However, in an alternating magnetic field, the parasitic electromotive force, induced in the circuit elements and consisting of two components, is added to this useful output voltage.

One of these components, AE, is induced directly in the output circuit of the sensor (in the circuit of the Hall electrodes), the other is obtained as follows. A parasitic O is induced in the control current circuit. d. Ej., Causing the flow of a parasitic current A / in the current circuit, and:

where - total resistance of the current circuit.

The interaction of the parasitic current A / s with the intensity of the field H leads to the appearance on the Hall electrodes of the second component of the parasitic e. d. s, equal to kR,., H / (K, - coefficient) and having a double frequency with respect to the frequency of the magnetic field. Thus, the sensor is e. d. Hall in an alternating magnetic field

U ...- KR, .HI. (1)

d /

No. 143908- 2, the intensity I, when a current flows in a current circuit, yields a voltage that differs from formula (1), namely:

. U ,, KRs, H () + E, (2)

Compensation of both of these parasitic e. d. is carried out, in accordance with the invention, by counter-coupling of the current electrodes of two sensors e. d. Hall, penetrated by the same magnetic flux, using to adjust the potentiometer connected in parallel to the current input, the slider of which is connected to the common current point.

The drawing shows a circuit diagram of a device for implementing the method. The circuit includes two sensors e. d. Halls placed in a magnetic field close to each other and penetrated by the same magnetic flux. The current and hall electrodes of both sensors are connected respectively in opposite.

The digits 2, 3, 4, and 1, 2, 3, 4 denote electrodes of the same polarity for both sensors; the arrows indicate the directions of the control currents / j and / 2 of both sensors and parasitic currents A / 1 and D / 2, induced by a magnetic field of N.

According to the scheme, we can write:

. K. I (L + DL) + Af. ,, - / с. . (- l -t- DL) - D - ,,, (3)

where Rgjfi and / z 2 are the input resistances of both sensors; and q 2 parasitic e. D. s, induced in the output circuits of these sensors and having a magnetic field frequency; / Ci, Kz - coefficients.

As follows from this equality, in order to eliminate interference, it is necessary to provide two conditions:

A / 1 KZ-RSXZ l. (L)

BUT/; / C.-..1

I, 1 A E ,,. (5)

Since these two sensors / d, / (2, / ".vi and .2 are constant values, to satisfy condition (4), it is necessary that D / 1 LA / 2. This condition is fulfilled with the help of potentiometer P, included parallel to the input of the sensor system. The slider of this potentiometer is connected to the common point of the current sensor circuits.

The second condition is easily ensured by observing the identical wiring of the connecting conductors from the Hall electrodes of both sensors, for which the latter are placed closely behind each other. The conductors extending from the electrodes / and / are twisted bifilically, and the conductors from electrodes 2 and 2 are interconnected. The resistors R and Rz are used for tuning when the Hall electrodes are non-equipotential.

Subject invention

Method of compensation of parasitic e. D. s, induced in the sensor circuit e. D. from the Hall, placed in an alternating magnetic field, by counter-switching on the Hall electrodes, characterized in that, in order to compensate for parasitic electrons. with the frequency of the magnetic field and the double frequency of the magnetic field, the current electrodes of the two sensors e. d. Halls penetrated by the same magnetic flux are connected in opposite directions, and the adjustment is made by a potentiometer connected in parallel with the current input, the slider of which is connected to the common current point.