Hardware and software improvements to a paced data acquisition system for turbomachines

Abstract

Modification of the phase lock loop synchronizing circuits and of the method of input/output communication used in a synchronized data sampling system, are reported. A device known as PACER which used an analog phase lock loop for synchronization and produced a non linear set of synchronizing pulses, was modified to use a CMOS digital phase lock loop, resulting in a linear set of pulses. The associated programming which controlled the data acquisition process and sequencing, was changed to use the direct memory access feature of the system computer. This enabled data, from high response pressure transducers mounted in a turbomachine, to be taken once every rotor revolution rather than once every ten revolutions. A user's manual for paced data acquisition is included.