Trimble S - Block diagram; High angle accuracy instruments (0,5” & 1”)

Chapter 3
Theory of Operation
P/N 57150002, Revision 5.0 3 - 39 Trimble S, VX, SPS & RTS Service Manual
F
Fig. 3-38 Coarse and fine code of the angle disc
The information from the CMOS image sensors is sent to the processor board for calculation and
conversion into an angle.
Block diagram
Fig. 3-39 Angle unit block diagram
To make the absolute encoder robust and less sensitive to eccentric mounting errors two CMOS
detectors are positioned with 180 separation at the disk to read the tracks (coarse and fine code). The
final angle value is calculated as the mean value of these two readings and first order errors with same
size but different signs will be eliminated.
High angle accuracy instruments (0,5” & 1”)
Instruments with 0,5” & 1” angle accuracy includes a pre calibrated Horizontal Turning Unit. As long
as the Horizontal Turning Unit is kept together and the parts, SRC board with magnets / Angle disc /
MSB board are not removed the high angle accuracy is still valid.
Even if the parts are removed accidentally and assembled together the Horizontal Turning Unit needs
to be calibrated to achieve the high angle accuracy.
The calibration of the Horizontal Turning Unit is made in the factory.
Fine code
Coarse code
CMOS
Detector
Angle disc
MSB board
Angle unit
IPC
board
Angles
Servo
unit
CU