Wireless Position Switches And Command Devices

R. Stahl's new 8074 F series position switches and 8040 F series command devices are completely wireless solutions for radio signal communication. Requiring neither signal lines nor external energy supply connections, the units can be freely installed in zone 1, 2, 21, or 22 hazardous areas. Users therefore need not worry about any wiring when e.g. retrofitting the command devices into difficult-to-access machines or plants. Since there is no need to route cables around or over joints or bearings, the switches are particularly suitable for reporting positions from movable machine parts. The switching signals are transmitted on the license-free SDR band at 868 MHz. Up to 300 m maximum radio range outdoors and a 30 m range within buildings ensure that receiving units can usually be placed within safe areas. Otherwise, R. STAHL can equip these with flameproof enclosures. The Ex switching devices generate the energy required for sending data telegrams by means of an integrated induction generator: when the switching element is actuated, the kinetic energy of the switching process is electrodynamically harvested, and immediately used to feed the radio module. In contrast to battery-supplied wireless switches, these self-supporting units do not need any regular servicing to remain fully functional.