Hall Devices

HALL DEVICES

The device which uses the hall effect for its application is known as Hall device.

There are three types of Hall devices.

They are

(a) Gauss Meter

(b) Electronic Multiplier

(c) Electronic Wattmeter

(a) Gauss Meter

The Hall voltage for a given hall element; RH and t are constant. The current I through Hall element is also kept constant.

This principle is used in Gauss meter. It is used for measuring magnetic field. (Fig. 3.19)

The variation of Hall voltage with magnetic field is shown. in fig. 3.20. The voltmeter which is used to measure VH can be directly calibrated in terms of Gauss. The graph can be also used to measure any unknown magnetic fields.

(b) Electronic Multipliers

From Hall effect, we have

Since RH and t are constant for an element

VH ∝ BzI1

But, the magnetic field Bz is proportional to current (I2) through the coil.

i.e., Bz ∝ I2 

⸫ VH ∝ I1 I2

i.e., VH is a measure of the product of two currents. This is the basic principle used in analog electronic multipliers. The fig. 3.21 shows the circuit diagram for electronic multiplier.

(c) Electronic Wattmeter

Hall effect is used to measure electrical power dissipated in a load. The instrument used to measure the power in a circuit using Hall effect principle is known as Hall effect - Watt meter.

S is Hall effect sample. It is placed in a magnetic field Bz produced by the load current IL passing through the coils CC as shown in fig. 3.22.

The voltage across the load VL the load drives the current through the sample. R is a series resistance which is >> than the resistance of the sample and that of the load. Also Iy << IL.

If 't' thickness of the sample, then the measured Hall voltage

This is the electric power dissipated by the load. The voltmeter that measures VH can be calibrated to read power directly.

Metal Semiconductor (MS) Contact

Metal-Semiconductor (MS) contact plays a very important role in the present day electronic devices and Integrated Circuit (IC) technology.

When a metal and a semiconductor are brought into contact, there are two types of junctions formed depending on the work functions of the metal and semiconductor.

Types of Metal - Semiconductor junction

Work Function: Energy required to raise the electrons from the metal or the semiconductor to the vacuum level.