Several technologies exist to provide position feedback or data of a cylinder’s position. Linear position sensors convert the position into a proportional analog or digital signal.
LVITs—Linear Variable Inductive Transducers—are contactless position sensing devices, with sensing ranges up to 30 inches or more. Most designs feature an inductive probe surrounded by a conductive tube. This is attached to the moving object to make the reading.
Hall-Effect Transducers use a magnet that communicates with the Hall chips, which then give an output to the internally built microprocessor. The output from the microprocessor is converted to a signal required by the user interface such as voltage, current, PWM or digital output.
An example of Hall-effect linear position sensing technology from Rota Engineering
Using Hall-effect technology on linear position sensors allows manufacturers to make small, compact designs that can be mounted internally or externally to a cylinder. Hall-effect technology is well suited to mobile applications as it is highly resistive to shock and vibration. It is used commonly on steering and depth applications.
LVDTs or Linear Variable-Distance Transducers are durable and resist shock and vibration while offering high repeatability. These absolute linear position/displacement transducers convert a linear displacement into an analog electrical signal. Their design includes transformer coils wound around non-magnetic coils.
Magnetostrictive Transducers measure the distance between a position magnet attached to the component in motion and the head-end of a sensing rod that is attached to axis to be measured. An electronics module sends an analog or digital position reading to a controller or other receiving device.
Linear Encoders are available with resistive, capacitive, optical or magnetic sensing with incremental or absolute position sensing to accurately determine the stroke of the cylinder.
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