公开(公告)号：DE3174069D1

公开(公告)日：1986-04-17

申请号：DE3174069

申请日：1981-10-20

Applicant: IBM

Inventor： COX GERALD LEON ,  MADDOX RANDALL ADRIAN

IPC: G01D5/36 ,  G01D5/249 ,  G01D11/24 ,  H03M1/00 ,  H03M1/24 ,  G01D5/245

Abstract: A field replaceable encoder including a slotted housing (20) having a pair of passages (21, 22) therethrough essentially perpendicular to the longitudinal axis of the housing, is attachable to the frame (9) of a machine having a rotatable shaft (11) to which the encoder is to be mounted. Attached to the housing is an accurate stationary mask (50), the mask having slits (51, 52) which are aligned with the passages in the housing. The mask includes an accurately dimensioned aperture (53) for locating the mask, and thus the housing, on a bearing (12) on the rotatably mounted shaft. A pair of light sources (# 5, 36) and a pair of light detectors (41, 42) are mounted on opposite sides of the housing aligned with the passages and slits in the mask. A hub (65), to which is attached a rotating disc (60), is connected to the rotating shaft, the disc being mounted in the slotted housing so that interdigitated opaque and transparent portions (61, 62) align with the slits of the mask, and thus the light sources and light detectors.