Hall Speed Sensor
A Hall speed sensor is an active sensor that detects the change in a magnetic field through a semiconductor powered from a supply voltage. Unlike a magnetic pickup, its output amplitude does not depend on speed; it gives a clean square wave even at speeds close to zero. It is typically supplied with 5 V or 12 V.
Being active has two consequences. First, the sensor needs a three-wire cable: supply, ground and signal. Second, the output is mostly open collector and requires a pull-up resistor on the control side.
- Advantage: a reliable signal at low speed and during cranking as well. This is decisive on slow-turning shafts and in position sensing.
- Limit: since it is a semiconductor, temperature endurance is more critical than with a passive pickup; when choosing a mounting spot in the engine bay, stay away from hot surfaces.
The same physical principle is also used in position measurement: the AS5600 that reads the actuator position on the GS740-3P is likewise a contactless magnetic sensor working by the Hall effect. The difference is in the quantity measured — one gives speed, the other shaft angle. The GS740-3P's closed loop is built not on speed but on this angle measurement.
Context in which this term is used: Electronic speed and throttle control on a diesel engine