Abstract: A switch is provided with the ability to diagnose its own operation and provide signals that represent the actuation of the switch and various diagnostic outputs that indicate fault conditions or potential fault conditions with regard to either the switch or related machinery. A magnetically sensitive component, such as a Hall element, is used to provide an analog output signal that is representative of the position of an actuator to which a magnet structure is rigidly attached. As the actuator moves in response to an external force, the magnet structure moves with respect to a stationary magnetically sensitive component. The analog output from the magnetically sensitive component can be used to determine the position of the switch. Based on this information, a microprocessor provides a binary output signal indicating whether the switch is actuated or deactuated.

Abstract: A monitoring device is provided for use in association with a limit switch or similar mechanically actuated device in order to permit its end of life to be predicted. The system uses nonvolatile random access memory to store a count which represents the number of occurrences of one of two alternative events. The first event is the occurrence of a number of switch actuations and the second event is the lapse of a predetermined period of time. When either of these two events occurs, a microprocessor increments a count in the nonvolatile memory unit and clears both the clock and the volatile memory parameter. When the number stored in the nonvolatile memory represents a number of actuations estimated to be appropriately equal to the total life of the switch, this condition can be signaled to a sensor bus by a communication circuit. Alternatively, a light emitting diode can be alternately energized and de-energized to represent the number of actuations having exceeded the predicted end of life total.