DE2640082C2 - Circuit for temperature compensation of a Hall generator - Google Patents

Description

45

The invention relates to a circuit for temperature compensation a Hall generator according to the preamble of claim 1.

Such circuits are described in US-PS 30 08 083. Instead of the older practice of switching the compensator in the circuit of the current controlling the Hall generator, here the compensator is provided in the load circuit. The Hall voltage supplied by the Hall generator is therefore applied to it. The compensator is given in the Hall generators described in the US-PS by a temperature-dependent electrical resistance. This can be parallel to the load operated with the Hall voltage and should then have a positive temperature coefficient TK . However, it can also be in series with the load and must then be selected so that the TC of its electrical resistance is negative.

However, there are cases in which this type of compensation for the influence of temperature is not sufficient. This is especially true when the semiconductor body of the Hall generator consists of InAs. Hall generators made from InAs have a low temperature dependency of approx. -0.1% per ⁰ C. Since the resistance of the generator has a positive temperature coefficient of approx. 0.2% per "C, temperature compensation is not possible in any of the ways described in US Pat. No. 30 08 083.

It is therefore the object of the invention to create a circuit of the type mentioned at the outset that can also be used in low temperature dependence of the material of the semiconductor body an exact temperature compensation enables

This task is in accordance with the invention in a circuit according to the preamble of claim 1 solved by the features specified in its characterizing part

In the circuit according to the invention, the control current of the Hall generator is dependent on the temperature-related increase in resistance to the extent that the decrease in sensitivity by the control current increase is compensated. The circuit is in the case that the semiconductor body of the Hall generator is formed by an InAs crystal designed in such a way that it represents a negative resistance, in other words a falling resistance Has current-voltage characteristics so that when the voltage falls through the circuit, an increased Electricity flows

An embodiment of a circuit according to the invention is shown in the figure. It is on the case designed that the ring generator consists of InAs

The basic principle of the circuit in the exemplary embodiment is a bridge circuit acted upon by the control voltage source Qu, which supplies a constant voltage, with the Hall generator HG in one bridge branch, with adjustable resistors, i.e. potentiometers, in the other bridge branch and the amplifier OP in the zero branch. The values given for the resistors are matched to the commercially available type TC 21 of Hall generators.

The Hall generator is in series with the two resistors 1 and 2 at the voltage source Qu. At the non-inverting input of the operational amplifier OP is the voltage that drops across resistor 1 and the Hall generator HG (switching point A). The inverting input of the operational amplifier OP is at the switching point of the voltage divider, which is formed from the resistors 3 and 4 and the potentiometer 4a and which is finely variable via the setting resistor 4a. The output of the operational amplifier OP (switching point C) \ ri is conductively connected via the setting resistor 5 to the inverting input and via the resistor 6 to the switching point A on the Hall generator HG.

For the operation of an InAs Hall generator of the type TC 21 the following equipment was chosen:

Resistance 1 = 5.6 Ohm,

Resistance 2 = 82 ohms.

Resistance 3 = 82 ohms.

Resistor 4 = 950 ohms,

Resistor 6 = 1 kiloohm,

Setting resistor 4a = 100 Ohm potentiometer,

Setting resistor 5 = 10 kiloohm potentiometer,

Operational amplifier OP type TBA 221,

Qu = 12 volts.

The circuit shown in the figure works like this. that the resistance increase in the Hall generator

HG resulting voltage increase at the Hall generator HG is amplified. This voltage allows an additional current to flow through the Hall generator HG through the resistor 6 between points A and C , which causes the compensation sought

Before starting the circuit is at low temperature and known magnetic field acting on the semiconductor body of the Hall generator HG with the potentiometer 4a the zero point of the amplifier circuit so eings that the resistor 6 between points A and C is de-energized, which is z. B. can determine with the help of a Muhizets. Changes to the potentiometer 5 now have no effect on the output voltage Uh add.

Then, while maintaining the magnetic field (calibration field), a high temperature is brought into effect on the Hall generator HG and - now by adjusting the potentiometer 5 - the same value of the Hali voltage Uh is set that was previously adjusted at the lower temperature using the first potentiometer 4a .

If the lower calibration temperature is denoted by T _{u and} the higher calibration temperature is T ₂ , then rsan has to carry out the following points of the calibration process before commissioning:

1. HaHgenerator // Bring G to temperature Ti;
2. Connect Multizet to points A and C of the circuit shown in the drawing;

3. Adjust potentiometer 4a so that voltage appears on the Multizet, i.e. resistor 6 has become de-energized or switching points A and

ίο C are at the same potential;

4. If the magnetic Eljh field H is exactly known, measure and record the output value of the Hall voltage Uh;

5. Increase the temperature of the Hall generator HG is to the value Ti and, with the calibration field H maintained, use potentiometer 5 to adjust the Hall voltage Uh supplied by the Hall generator HG so that the value of Uh determined under number 5 appears again.

With the choice of the two calibration temperatures T ₁ and T ₂ , the compensation range is fixed. Large or small temperature ranges are recorded accordingly selecting the adjustment points

1 sheet of drawings

Claims (3)

Patent claims: 1. A circuit for temperature compensation of a Hall generator with a semiconductor crystal in which a temperature dependency of the Hall effect in the semiconductor crystal compensating compensator is provided, which is controlled by the voltage drop of the electric current flowing through the semiconductor crystal, characterized in that to form the [compensator parallel to the Hall generator ( HG) and two fixed resistors (1,2) connected in series with it, a voltage divider consisting of two series-connected fixed resistors (3,4) and a potentiometer (4a) is connected that is connected in parallel to the voltage divider and the series connection of the Hall generator (HG) and the two connected in series with it fixed resistors (1,2), the voltage source drive current to the Hall generator (HG) providing (Qu) is set such that the fixed resistor lying between the Hall generator (HG), and a 'in series with it (2 ) located switch point A with the non-inverting input e Ines operational amplifier (OP) is connected, that the voltage divider (3, 4, 4a) lying parallel to the Hall generator (HG ) and the other fixed resistor (4) as well as the potentiometer (4a) of this voltage divider are also connected switching point B is connected to the inverting input of the operational amplifier (OP) and that finally the output of the operational amplifier (OP) via cn further potentiometer (5) to the switching point B as well as about ei ^ n additional fixed resistor (6) to the switching point A is connected 2. Circuit according to claim 1, characterized in that the semiconductor body of the Hall generator (HG) consists of InAs. 3. Circuit according to one of claims 1 or 2, characterized in that a device generating a magnetic calibration field is provided at the location of the semiconductor body of the Hall generator (HG)