Fresenius Medical Care 4008 E Technical Manual page 472

Speed and rotational direction monitoring unit
A slotted disc is attached to the drive shaft of the syringe holder for monitoring the speed and the
direction of rotation. This slotted disc penetrates the range of the optical sensor, where it
generates a specific light-dark pattern.
The optical sensor converts this pattern into corresponding voltage levels.
The slotted disc is divided in three sections of 120 degrees each, each of them having the same
window configuration:
20-degree opening, 20-degree tie, 40-degree opening, 40-degree tie.
The division of the disc in two sections leads to the following speed-related pattern:
20° 40° 60° 80° 100°
In the opposite direction of rotation, the pattern is as follows:
20° 40° 60° 80° 100°
These patterns are evaluated by the software, so that a stop of the shaft is recognized not later
than after 20°, because an L/H level or an H/L level respectively must be achieved after the
corresponding period of time, if the shaft is rotating.
After a 80-degree rotation, an error in the direction of rotation of the shaft is recognized.
Fresenius Medical Care
120° 140° 160° 180°
120° 140° 160° 180°
8-175
4008 4/09.03 (TM)
8.19.2 Circuit diagram and component layout diagram
P.C.B. LP 950 Control board (HEP)
8-176
Fresenius Medical Care 4008 4/09.03 (TM)
P.C.B. LP 950
Component layout diagram