What is the fine-grained topic of the following text: Convenience, safety and long life of field device: a rotary encoder with fist size can measure the interval from several Mu to several hundred meters, n stations, only need to deal with the question of the safety device of a rotary encoder (Changchun encoder), can prevent many near switches, photoelectric switches in the field mechanical device trouble, simple It was doubtful that he was hit and damaged by high temperature and water vapor. Only return the topic.
The fine-grained topic of the text is: Safety and durability of rotary encoders in field devices.