A Hall Effect sensor is a device that detects the presence of magnetic field. It is based on the Hall Effect. The Hall Effect was discovered by Edwin hall in 1869. When current is passed through the conductor and the same conductor is placed in magnetic field perpendicular to the current flow then a voltage called the hall voltage is generated perpendicular to both the current and magnetic field. This is known as Hall Effect.
The above figure shows the Hall Effect.
When no magnetic field is applied to the current carrying thin semiconductor material(hall element) the hall voltage(Vh) is zero. When an external magnetic field is applied to the current carrying hall element perpendicular to the current flow a Lorentz force acts on the current due to which a voltage called hall voltage(Vh) is generated perpendicular to both the current and the magnetic field. This voltage is very small (in uV) and needs amplification.
The advantages of Hall effect sensors are
- Non contact operation so there is no wear and friction. Hence unlimited number of operating cycles
- High speed operation - over 100 kHz possible. Where as at high frequencies the inductive or capacitive sensor output begins to distort
- When packed immune to dust, air, water where as capacitive sensor may get triggered by dust.
- Can measure zero speed
- Wide temperature range
- Highly repeatable operation
- Capable of measuring large current
- May be affected by external interfering magnetic field
- Large temperature drift
- Large offset voltage
- Current sensing
- Power sensing
- Proximity detection
- Speed detection
