Sensata - BEI Sensors 01091-006Product Attribute Attribute Value Pulse Per Revolution 1024 PPR Overview Model HS20 is a compact, rugged hollow shaft encoder designed with harsh environments in mind. This optical encoder can be used where lighter duty encoders are not suitable or cost effective. The compact design makes it easy to incorporate into tight installations and it is well sealed to stand up to dust, dirt, and splashing liquids SIL3 PLe incremental encoders.