SU763823A1 - Device for measuring magnetic field inductance and temperature - Google Patents

Description

The device relates to the measurement technique and can be used for the first time: induction of magnetic field and temperature, for example, in magnetic systems. A device is known that contains a measuring probe with a Hall sensor in which the temperature control of a Hall sensor is made by changing. input current 1. However, the signal used in such a device for temperature control depends on the magnetic field, which reduces the measurement accuracy. In addition, the device does not measure the temperature. The closest to the technical essence of the invention is a device comprising a Hall sensor in a heat sink, a source of DC and AC voltages, an AC bridge and a control element — a transistor. In this device, the input circuit of the sensor is connected simultaneously to one of the arms of the ac bridge and to the circuit consisting of a series-connected DC source and a transistor 2} Changing the sensor temperature causes its input resistance to change and subsequent the bridge. The converted unbalance signal of the bridge enters the base of the control transistor, which leads to a change in the DC power flowing in the input circuit of the Hall sensor, and consequently, to a change in its temperature. - However, due to the existence of the magnetoresistance effect, the change in the input resistance of the Hall sensor can be caused not only by a change in temperature, but also by a change in the magnetic field, i.e. In such a device, the temperature of the Hall sensor depends on the induction of the magnetic field, which reduces the measurement accuracy. In addition, from the principle of operation of the device, it follows that the input current of the sensor contains a constant and an alternating component, and the constant component is a function of the temperature of the medium and the magnetic field. therefore, the output of the Hall sensor also contains a constant and a variable component and depends both on the magnetic field and temperature, and the dependence on the magnetic field becomes non-linear, making it difficult to measure the magnetic field and temperature.

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

This is achieved by the fact that the device for measuring the induction of the magnetic field and temperature, containing the Hall sensor in the heat insulating casing and recording devices, is equipped with an adjustable DC source, the output of which is connected to the current electrodes, and the input to the Hall electrodes of the Hall sensor.

The Hall sensor is made of a p-type semiconductor crystal in which the point of temperature inversion of conductivity is above the upper limit of the range of measured temperatures.

FIG. 1 shows a functional diagram of the device i in FIG. 2 shows the dependence of the relative increase in the input resistance of the Hall sensor on the induction of the magnetic field.

The device contains a measuring probe 1 with a Hall sensor 2, the output electrodes 3, 4 of which are connected to the input of an adjustable source 5 of direct current. The output of the latter is connected to the input electrodes b, 7 of the Hall sensor, which are connected to the device 8 for measuring - "April", and the device 9 for measuring the current is included in the input circuit of the Hall sensor.

The operation of this device is as follows.

When the output of the regulated constant current source 5 is connected to the input electrodes b j 7 of the Hall sensor 2, a current T flows in the input circuit of the Hall sensor, and in the absence of a magnetic field, the voltage on the output electrodes 3, 4 of the Hall sensors, and hence on the input DC source is zero. When a measuring probe 1 is placed in a volume in which the magnetic field B and temperature T are to be measured, a voltage appears on the output electrodes of the Hall sensor, the value of which can be determined from the formula

 , St) 1bh,

sh

active plastigde thickness

with us Hall sensor-,. Ry (T) is the Hall constant, depending on temperature; Input Current Sensor 2

BY Hall;

at

magnetic field induction This voltage is fed to the input of an adjustable source 5 of direct current, which leads to an increase in the input current of the Hall sensor. An increase in the input current of the Hall sensor leads, firstly, to an increase in the voltage across the electrodes 3.4 and at the input of an adjustable source

direct current, which causes a further increase in the input current, and secondly, an increase in the power dissipated on the Hall sensor, which entails an increase in its temperature. Since the measured temperature is always lower than the conduction inversion temperature, the process of increasing the temperature of the active plate of the Hall sensor continues until the temperature of the active plate becomes equal to the temperature of the inversion of conductivity at which the Hall constant is zero. The voltage across the electrodes 3, 4 and at the input of the controlled constant current source 5 also becomes zero. The change in input current is stopped. If the temperature of the active plate of the 2-Hall sensor exceeds the conduction inversion temperature, a voltage of opposite sign appears at the output electrodes 3.4 and the input of the regulated DC source, which causes a decrease in the input current of the Hall sensor. The decrease in the input current of the sensor-Hall continues until the voltage at the electrodes 3.4 and at the input of the controlled constant-current source 5 becomes zero, i.e. until the temperature of the active plate of the Hall sensor becomes equal to the temperature of the inversion of conductivity. Thus, this state in which the temperature of the active plate of the Hall sensor is equal to the conduction inversion temperature is stable. The magnitude of the input current at which this state is reached depends on the temperature of the medium.

Per unit of time, the amount of heat dT is removed from the active plate of the Hall sensor

(2)

.n-;

5 where s

-the surface of the active plate;

-the coefficient of heat conduction;

dT

- temperature gradient

The distance from the active plate of the Hall sensor to the surface of measuring probe 1 is sufficiently small, and also taking the temperature on the surface of the measuring probe to coincide with the temperature of the medium, determine the temperature gradient

dT THAT

(2.)

one

dx d

where Id is the temperature of the active plate of the Hall sensor d is the distance from the surface of the active plate of the Hall sensor to the surface of the measuring probe.

Taking into account that the active plate of the Hall sensor has the shape of a parallelepiped, and also considering that the temperature gradient is constant; over the surface of the plate and determined by formula (3), it is obtained that the amount of heat removed from the entire surface of the plate per unit time

about-. Tr-t

(I

-S.

 d

On the other hand, the amount of my heat

V bX b 151

where Uj, x is the input voltage of the Hall sensor.

In the steady state, the temperature of the active plate of the Hall sensor is equal to the temperature of the inversion of conductivity, and the amount of heat withdrawn is equal to the amount of heat absorbed, where

  (6) The medium temperature is a linear function of the input power of the Hall sensor:

,, i) where f} is the coefficient.

The constants T, and can be determined experimentally for each measuring probe by calibrating it. Thus, measuring the input voltage with the help of the device 8, and using the device 9. The input current of the Hall sensor, from the formula (7) get the measured temperature value. Calculated by

measured value

and and

Xx

Bx

The input impedance of the sensor, the curve in figure 2 determine the induction of the magnetic field.

Since the conduction inversion temperature of p-type semiconductors does not depend on the magnetic field induction, due to this, the error in temperature measurement due to the magnetic field is eliminated and the temperature measurement accuracy is improved.

Claims (2)

Invention Formula A device for measuring the induction of a magnetic field and temperature, which contains a Hall sensor in a heat-insulating housing and recording devices, characterized in that, with the Purpose of improving the measurement accuracy, it is equipped with an adjustable DC source, the output of which is connected to current and Hall Electrodes Hall Sensor. 2. The device according to claim 1, which is based on the fact that the Hall sensor is made in the form of a semiconductor, p-type crystal, in which the point of temperature inversion of conductivity is above the upper limit of the range of measured temperatures. Sources of information taken into account in the examination 1. USSR author's certificate number 488168, cl. G 01 R 33/06, 1973. 2. Authors certificate of the USSR 469196, cl. G 01 R 33/06, 1973.