Power outage recovery method and apparatus for demand recorder with

Abstract

A demand recorder includes a microprocessor for receiving data pulses representative of measured events and formats the incoming data into demand intervals. After a predetermined number of demand intervals, called a collection period, the microprocessor transfers the data for more permanent storage to a solid state memory which may be removed for remote processing. The system has battery carryover during a power outage, but the microprocessor prevents data transfers to the solid state memory. At the end of a collection period in which a power outage occurred, the microprocessor transfers the current data to a secondary portion of random access memory. For subsequent demand intervals until power is restored and including any thermal recovery periods, the processor formats event data by assigning index numbers for demand intervals in order of occurrence and stores data only for those demand intervals in which power consumption was actually measured. After the system has returned to normal operation, the data temporarily stored in secondary RAM is transferred to the solid state memory and the data in primary RAM which is stored in compacted format is re-constructed into normal storage format in RAM with all intervals during which no event data was detected being zero-filled. As data is taken from primary RAM, converted into the original format and transferred to secondary RAM for storage in the solid state memory, the remaining data in primary RAM is advanced in memory, similar to the operation of a stack memory, so that as much space as possible is made available for data storage in the event of a subsequent power outage prior to the time all of the data in primary RAM is converted and stored in the solid state memory.