Hall Sensors

In 1879, Edwin H. Hall (1855-1938), an american
physicist, discovered this effect. The electrons of the current
flowing in an electrical conductor are diverted from their normal
direct path by an outer magnetic field perpendicular to their
motion. Due to the so-called Lorentz force, a potential difference
(the Hall voltage) is created, proportional to the field strength of
the magnetic field and to the current. Silicon is used almost
exclusively as a basic material for the technical implementation
of magnetic field sensors, as the Hall-effect is most pronounced
in semiconductors. In modern Hall-effect sensor devices, the
magnetic field sensitive Hall element is combined with the signal
processing on a single silicon chip. Three different types of
sensor architecture are available today:
- Digital switches
- Linear sensors
- Direct angle sensors

Hall switches:
The simplest application is to use the sensor as a “digital switch“.
The magnetic field strength is measured and compared with a
fixed threshold level predefined or programmable in the sensor.
As soon as this value is exceeded (switching point) the switching
state at the output of the sensor changes and the output transistor
is switched on or off. Two types of switches are available:
3-wire version with an open-drain output or 2-wire versions with
current-coded output.

Linear Hall Sensors:
Linear Hall Sensors differ from the switches as follows:
Depending on the magnetic field, the output does not have a
discrete switching state, but provides a signal proportional to the
magnetic field strength.
This output signal can be delivered as an analog output voltage,
a pulse-width-modulated signal (PWM) or even as a modern bus
protocol (Lin, SENT).

Direct angle sensors:
New types of Hall-effect sensors do not measure the absolute
magnetic field anymore. So-called direct angle sensors capture
the field vector by measuring sine and cosine components of
the magnetic field. This is possible due to the new 3D-HAL
technology from Micronas. Vertical Hall plates measure the
magnetic field components in the chip plane and not the
components perpendicular to the chip surface. These kind of
sensors provide angular and position information directly via an
output signal proportional to the measured angle or position.