A magnetic bubble device for revolution counters

A magnetic bubble device (MBD) for revolution counters used for servomotors has been developed. This sensor was designed to count 32487 revolutions with only a 152 bit memory. A magnetic garnet film was chosen so that a wide propagation margin was achieved. The thickness of the film was also optimized so that the bubbles were stretched at a high bias field. The thickness of SiO/sub 2/ was chosen to obtain a wide pulse width. The developed MBD achieved wide margins as follows: propagation margin and stretch margin were 25, 24 Oe respectively in the bias field direction, and pulse width margin was 5.6 /spl mu/sec.