Magnetic field sensors are actuated by magnetic fields. They detect the postion of pistons in pneumatic cylinders. Magnetic fields permeate non-magnetizable metals. The sensor is thus able to detect a permanent magnet attached to the piston through the aluminium cylinder wall. Magnetic-inductive permaprox sensors made by TURCK operate on a patented function principle. They detect permanent magnets of various field strengths reliably, operate completely wear-free and are short-circuit protected. In addition, we also offer a weld-proof version for welding applications.