The Thrumold Series VRS (Variable Reluctance Speed) sensors are designed to detect engine timing and transmission speed by determining the speed and position of rotating shafts in heavy-duty, off-road, and construction vehicles, providing information to help improve engine combustion process efficiency. These passive VRS sensors are simple, rugged devices that do not require an external voltage source for operation. A permanent magnet in the sensor establishes a fixed magnetic field.
The approach and passing of a ferrous metal target near the sensor’s pole piece (sensing area) changes the flux of the magnetic field, dynamically changing its strength. This change in magnetic field strength induces a current into a coil winding which is attached to the output terminals.