Castell has introduced an AS-i compatible motor safety relay that can monitor practically all electric motors and variable speed drives (VSDs). The DIN rail mounted CMM200 monitors a motor's back-EMF to detect whether it is safely at rest or in motion, with dual processors simultaneously checking the state of the motor and the condition of the relay itself. Any interference from VSDs is filtered internally by the unit.The unit has two independent channels, which monitor separate windings of the motor. Only when both channels have detected zero speed will the normally open, forcibly guided safety output terminals become closed. If the system suffers any fault, such as sensor cable discontinuity or a processor failure, it will revert to a fail-safe condition.