Pneumatic cylinders are a low cost, simple and durable choice for many industrial applications. They form a useful part of integrated automated systems, howewver pneumatic cylinders do not provide any feedback on the position of their movement, when this is a requirement design engineers must use a position sensor. The extension or retraction status of the cylinder's piston must be detected, and an electrical signal supplied to the system controller. Pneumatic cylinder manufacturers therefore have developed a number of ways in which the position status may be detected and indicated.
Position sensors use a variety of techniques to make this determination. One method is to install inductive proximity switches or electromechanical limit switches on the outside of the cylinder. These can detect any targeted metal components on the machine's moving parts, but the installation hardware for this type of detector is expensive and complex. It also increases the physical size of the assembly overall, and is not easy to adjust. In addition, because the hardware is mounted externally it is prone to incidental impact or contact which can cause misalignments or damage. A more common and popular choice is to use magnetically actuated sensors, which detect the motion of an internal magnet set inside the cylinder on the piston. These sensors are attached to the aluminium sides of the cylinder, or alternatively into an extruded slot going into the cylinder. Magnetic-field sensors mostly detect only end-of-stroke position in either direction, but it is possible also to install multiple sensors along the entire length of a cylinder, to allow detection at several separate points.