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Purpose of a Speed Sensor

The purpose of any speed sensor machine is to detect the speed of an object, usually a transport vehicle. Different speed sensor technologies are used for different kinds of transport vehicle based on the medium it operates. Examples are buses, cars, ships, submarines, and aircraft.

We all need speed in life otherwise we will not be able to reach anywhere on time. This implies to various machines too. Machines have been innovated to ease our life, they have specific work to do. Since work is directly proportionate to the speed or velocity, hence to make any machine work, speed is required. And to measure speed we need Speed Sensors and various technologies for them to work.

passive wheel speed sensor

passive wheel speed sensor

  • Speed Sensors and their various principles

Speed sensing and speed calculations are based on many different methods. A single principle may not be suitable to take care of various speed sensor problems; hence different principles have been invented. Some of the common principles are mentioned below.

  • Wheel speed sensors: these type of speed sensors are also called vehicle speed sensors (VSS) or tachometer. They read the speed of the wheel while rotating and thus provides the current speed of the vehicle.
  • Pitot tubes based sensors: they are mainly used by the aircrafts to measure their flying speeds. They consist of two tubes which measure the pressure exerted by the movement of the flight and therefore provide the speed.
  • Speedometers: originally invented by Charles Babbage, this measures the speed of vehicle as well as displays the result. It is fitted in the vehicle itself. Speedometers used in boat, ships or submarines are called Pit log. The one which is used in aircraft is called airspeed indicators. Speed sensor locations vary according to the machine and its size and mass.
  • Radar Doppler speed sensors: these are based on Doppler’s effect and measure the speed based on the echo produced by radar signals while moving closer or away from the target object. The speed is measured with the help of the according frequencies produced by these echoes.
  • Lidar based speed sensors use remote sensing technologies that measure the distance by illuminating a target with the help of laser and analyzing the reflected light. This type of sensing is commonly used for seismology, archaeology, geomorphology, atmospheric physics, remote sensing and contour mapping.
  • Laser surface velocimeters measure velocity and length of moving surfaces. They also use laser Doppler principle and measure by evaluating the light scattered back by the object. They are widely used in quality control and other processes in industrial based factories.
  • Piezoelectric based sensors use the piezoelectric effect and measure changes in acceleration, pressure, temperature, force, strain and convert them to  electrical charge.


  • Speed Sensors: based on different technologies

Speed sensors are based on various technologies. This is because not all machines are alike and input and output may differ for different purposes. Each technology is based on different applications and its requirements may cater to different speed sensoring problems. The speed sensor`s transmission will also vary according to the vehicle, its uses and the technology suitable for it.

  1. Hall Effect Zero Speed Sensors give zero speed sensing and are found in both oriented and non-oriented types of models (e.g. this one). The target object can be ferrous like gear or sprocket or even magnetic.
  2. Variable Reluctance Speed Sensors can easily sense any ferrous metal in their target area and is suitable for various specifications and different environments. It is passive in nature and can work even if not connected to power circuit or amplifiers.
  3. RF (Eddy Current) Speed Sensors can sense non ferrous metals too. Metals like aluminum and stainless steel can also be sensed. It’s an active device and therefore requires coupling with a signal or power circuit.

Various speed sensing technologies have given a new dimension to different ways of locomotion. This has made our life easier and faster. In the near future many new technologies will be invented which will help us to reach the next level. Researchers and scientists have already invented many machines which use these speed sensing technologies to derive various other information.

More Information about Speed Sensors:

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