A magnetically coupled low-cost high-speed shaft position digitizer

Abstract

The outputs of many precision devices occur as shaft rotations. When the position of such a shaft must be determined to an accuracy beyond the reach of analog instruments, or when the data has to be processed by digital equipment, an analog to digital conversion must be made. It is nearly always desirable and often essential that the digitizer present no appreciable mechanical load to the shaft under measurement. A further requirement which often must be met is that readings be taken on the fly. That is, positional information may be called for when the shaft is in motion at speeds that may vary from zero to many hundreds of rpm.