A revolution counter using a magnetic bubble device and permanent magnets has been developed that can count up/down and maintain shaft revolutions without using electrical energy. It consists of a newly developed dedicated magnetic bubble chip, a pair of bias magnets, a ring magnet, a pair of coils wound around the chip, and a signal processing circuit. A multi-turn fully absolute encoder has been realized by using this counter in conjunction with an optical encoder which we also developed. It is expected that there will be numerous applications for this encoder, including use as a replacement for conventional mechanical counters.
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