Sensors are very important organs of any measurement system. They collect data from the surroundings/ physical parameter and provide electrical signal as the input to the systems. Amongst wide variety of sensors operating on different sensing principles and used in different applications, position sensors play an important role in different systems. Whether it is fly-by-wire aircraft systems, drive-by-wire cars, bullet trains taking round curves, injection molding machines, packaging machines, medical equipments, and so on, position sensors finds their applications, of course in different ways.
Capacitive Position sensors
Magnetostrictive Linear Position Sensors
Eddy Current based position Sensor
Fig. 10: A Cross Sectional Diagram Showing Operation of Eddy Current Position Sensors
Fig. 11: Diagram showing Change of Coil Impedance as a Function of Distance in Eddy Currents
HEBM & Fiber-Optic Position Sensor
Fig. 12: Representational Image Explaining Working of Hall Effect Based Magnetic Position Sensors
Fig. 13: Image Shoiwng Hall Effect Based Magnetic Sensor
Optical Position Sensor
Potentiometers are often the cheapest option for position sensing, but needs physical contact with the moving target. Hall sensors are also cheap but are used in ON/OFF type of applications. It is effective only for applications where detailed position information is not required. Optical sensors have very fast response as they are non-contact type, light in weight and don’t need to counter friction. Accuracy is governed by the number of counts. More the counts, better is the accuracy. However, proper alignment and protection from harshy or dust environment is necessary. They are relatively costly. Eddy current based position sensors are moderately priced but are not preferred in applications requiring highly detailed positioning information or where large gaps exist between the sensor and the target. These can tolerate dirty environments and are good when mounted on stationary mechanical structure. LVDTs or RVDTs are priced highly but can tolerate dirty or harsh environments. They offer high accuracy, high precision as well as high sensitivity. They find applications in industrial and aerospace applications.
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