Passive Magnetic Speed Pickups

Passive Magnetic Speed sensors are simple, rugged devices that don’t require any external power to operate. A permanent magnet in the sensor establishes a fixed magnetic field and passing a ferrous metal target (gear) near the sensor’s pole piece (sensing area) changes the flux lines 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 pickups output terminals. The output signal of the sensor is an ac voltage that varies in amplitude and wave frequency as the speed of the monitored device changes, and is usually expressed in peak to peak voltage (Vp-p).

One complete waveform (cycle) occurs as each target passes the sensor’s pole piece. If a standard gear were used as a target, this output signal would resemble a sine wave if viewed on an oscilloscope.

High Output sensors are designed for use in applications where higher output voltages are needed. They perform best at low to medium speeds with medium to high impedance loads. Front-End Sealed versions are available for use where the sensor is exposed to fluids, lubricants or adverse environmental conditions.

The TS300 self-powered digital governor is designed to control an API-611, single valve, general purpose steam turbine driving a mechanical load. For applications where 24 vdc power is not available the TS300 can be operated in self-powered mode; where the power used to run all of the TS300 electronics is generated from two speed probes. The TS300 also makes use of a back-up battery, providing power when the turbine is stopped or operating at low RPM in the self-powered configuration. The TS300 can also be used for simple turbine applications where 24vdc power is available.


  • Engine RPM (revolutions per minute) measurement on aircraft, automobiles, boats, buses, trucks and rail vehicles
  • Process speed measurement on food, textile, paper, woodworking, printing, agriculture, and pharmaceutical industry machinery
  • Motor speed measurement of electrical generating equipment
  • Speed measurement of pumps, blowers, mixers, exhaust and ventilating fans
  • Flow measurement on turbine meters
  • Gear speed measurement


  • Self-powered for remote / isolated applications
  • Direct conversion of speed to output frequency
  • Simple installation, No moving parts
  • Designed for use over a wide range of speeds
  • Adaptable to a wide variety of configurations
  • Customized VRS products for unique speed sensing applications
  • Housing materials/styles: stainless steel threaded or smooth
  • Output voltages: 8 Vp-p to 190 Vp-p

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