What are Variable Reluctance Speed Sensors?

Meet the Connector: Variable Reluctance Speed Sensors

Engine speed and position sensing enhance vehicle performance and safety. Engine management, fuel efficiency, and emissions reduction all rely on the accurate measurement of rotational speed. The advancement of this technology is in line with increased demand for high-performance and eco-friendly vehicles.

Variable reluctance speed (VRS) sensors measure changes in magnetic reluctance (magnetic resistance). Their simple, rugged construction requires no external power and has no moving parts or wear mechanisms, making them useful in multiple applications. The amplitude of the signal depends on speed, air gap, geometry of target, magnetic properties of target material, and the electrical load. The sensors generate AC voltage and signal strength is dependent on speed.

VRS sensors measure the angular velocity (rotational speed) of the shafts within the transmission to determine when to shift gears. A VRS sensor can act as crankshaft position sensor, providing the angular position of the crankshaft to the electronic control unit (ECU), which allows the ECU to determine engine speed.

The DSE series variable reluctance (VR) speed sensors from TE Connectivity consist of an iron core, an inductive coil, and a permanent magnet. A ferrous pole wheel passing the sensor face changes the magnetic field strength, resulting in an AC voltage being induced in the coil.

VRS technology is valued in industrial applications as well, including automation and robotics. These sensors measure rotational speed in motors and generators to maximize performance and prevent failures, which is particularly useful where precision and reliability are essential. Real-time data on rotational speed contributes to efficiency and minimizes downtime. High-precision VRS sensors for robotics and automation are in demand for a growing number of fields, including manufacturing and logistics.

VRS is also used in aircraft engine management and navigation systems for monitoring rotational speed of aircraft engines and other components.

Honeywell Thrumold Variable Reluctance Speed (VRS) sensors from Mouser Electronics detect engine timing and transmission speed. The passive VRS sensors help improve engine combustion process efficiency. They determine the speed and position of rotating shafts in heavy-duty, off-road, and construction vehicles. A precise engine timing signal optimizes the combustion process in engine camshaft and crankshaft applications. This series features an operating temperature range of -40 °C to +150 °C.

Analog to digital

VRS sensor output is an analog signal (like a sine wave), with the frequency and amplitude proportional to the target’s velocity. An analog-to-digital converter converts the signal to a square wave that the computer sees as high (1) or low (0).

Design Notes

Construction: The sensor is made up of a permanent magnet, a ferromagnetic pole piece, and a coil of wire.

Types: Options include hermetically sealed, cryogenic, high temperature, intrinsically safe, and explosion proof. VRS sensors with ATEX and EX certification can be used in explosion-proof environments, making them safe for use in industrial and aerospace applications.

Environmental properties: VRS sensors withstand high vibration and high temperatures. They may be chemically compatible with engine oil, diesel fuel, water, engine coolant, salt spray, and trisodium phosphate cleaning solution.

Markets and Applications

Automotive, Transportation, Industrial, Mil/Aero

Heavy-duty, off-road, and construction vehicles; high performance and eco-friendly vehicles; anti-lock braking systems (ABS); precision, high-reliability industrial and manufacturing equipment, logistics, and robotics and automation; aircraft engine management and navigation systems.

Suppliers

Mouser Electronics, TTI Inc., TE Connectivity, STMicroelectronics

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