Editorial Feature

Input Shaft in Automation - Turbine Speed Sensor

A turbine speed sensor, also termed an input speed sensor, is used for measuring the performance of the turbine by evaluating transmission performance and other components of the turbine. It also detects the rotation speed of the turbine, which shows the input revolution of the transaxle. The electronic transmission control detects the shift timing of the gears and controls the engine torque and hydraulic pressure based on various conditions.

This sensor operates based on various operating principles that include Hall effect, magnetoresistive and inductive to detect turbine performance without making contact with the rotary movement of phonic or toothed wheels.

It provides a digital frequency output signal for the Hall effect, magnetoresistive sensors, or a sinusoidal wave for the inductive type of sensors.

Working Principle

A typical turbine speed sensor consists of a coil wrapped around a permanent magnet. When a ferromagnetic material such as a turbine passes the sensor, the magnetic field is interrupted.

As a result, an AC voltage is generated, and the amplitude of this voltage and frequency depends on the speed of the turbine. The amplitude of this voltage also depends on the air gap, which is the distance between the sensor and the turbine.

The voltage gradually reduces as the air gap increases, and the voltage increases as the air gap decreases.

As the amplitude depends on both speed and air gap, it is important to set the air gap correctly while measuring the lower speeds. The AC voltage from the sensor can be processed again to obtain the digital output.


The turbine speed sensor is used to measure the speed of crankshaft, camshaft, gear tooth and turbine speed of a jet engine.

Other major applications of turbine speed sensors include:

  • Differential gears
  • Transmissions
  • Pumps and racks.

Products on the Market

Some of the turbine speed sensors currently available in the market are listed below:

Woodward Magnetic Pick-ups

Magnetic pick-ups developed by Woodward are speed sensors that detect the speed of an engine or turbine.

As the each gear tooth passes through the magnetic pick-ups, the gear interrupts the magnetic field in order to develop alternating voltage. The frequency of this voltage is converted into a signal to accurately determine the speed of engine or turbine.

Hall Effect Speed Sensors

Electronica Engineering’s Hall Effect Speed Sensors features optional internal pull-up resistor for 12 or 24 Vdc, adjustable fastening and 3 wires inductive sensors.

It is applicable to railway, industrial, earth-moving machinery, agricultural, military and automotive fields.

Sources and Further Reading

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