On-site installation is convenient, safe, and long-lived: a fist-sized rotary encoder can measure distances from a few μ to several hundreds of meters, with n stations. As long as the safety installation problem of a rotary encoder is solved, it can be avoided Many proximity switches and photoelectric switches are troublesome to be mechanically installed on site, and are easily damaged by high temperature and moisture. Because it is a photoelectric code disc, there is no mechanical loss, as long as the installation position is accurate, its service life is often very long.