Chapter 3
Theory of Operation
P/N 57150002, Revision 5.0 3 - 37 Trimble S, VX, SPS & RTS Service Manual
F
Function description
Mechanically the angle unit is located as a fully integrated part inside the servo motor housing. The
motor protects the angle glass disc form dirt and dust. The centre unit, angle disc assembly contains
the optical glass disc. The angle board contains laser transmitter and image area detectors (CMOS
detectors), the angle board also includes the servo motor winding. All together this design creates a
rugged and accurate absolute encoder measuring angles with an accuracy of 0.2 mgon at a rate of
1000 Hz. The angle sensor is designed not only for displaying and storing angle data but also to
support the servo system with fast angle information. Final angle data calculations are made in the
IPC board.
Fig. 3-36 Horizontal angle system parts
Angle disc
A mechanical centre unit holds a glass disc with optical encoder pattern and a mirror. By using two
separate tracks a uniform accuracy and resolution around the circle is obtained. Both tracks are
illuminated with a single laser light source and projected on a CMOS image area sensor. By using
one common sensor for both tracks usual alignment problems are eliminated. The design will be
compact and less parts have to be assembled.
The function of the disc assembly is the same for both horizontal and vertical sensor but the
mechanical axis is different due to how the disc is mounted.
MSB board incl. motor winding
Includes a LED and a detector, CMOS image area sensor.
The angle board is the same for both vertical and horizontal sensor and includes the motor winding.
Angle disc
MSB board incl.
motor winding
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