Process controller with power outage analysis capability

摘要

A process controller with power outage analysis capability uses a real time clock generator powered by an uninterruptible power source for providing a real time reference which is used to measure the actual duration of a process controller disabling power outage. A non-volatile memory is also powered by the uninterruptible power source and is used to store the maximum allowable outage time limit for a particular process being controlled. The clock generator is initialized at the start of the power outage by a power outage detector which provides an early warning of an imminent power outage. After the power is restored to the controller, a digital computer used in the process controller compares the actual power outage time as represented by the accumulated clock time with allowable power outage time limit stored in the memory and is arranged to provide a first process control sequence if the actual power outage time is less than the maximum allowable time and a second process control sequence if the actual power outage time is greater than the maximum allowable time.