Trimble S - Search for external (reflected) pulse - scanning; Measuring external (reflected) pulse; Output - calculation of distance; EDM offset and DR offset

Chapter 3
Theory of Operation
Trimble S, VX, SPS & RTS Service Manual3 - 68 P/N 57150002, Revision 5.0
F
The coarse measurement only identifies strong signals. A coarse measurement is always made in
reflector mode.
Search for external (reflected) pulse - scanning
If the external signal is not strong enough to be detected by the coarse measurement the measurement
must start with finding the external pulse by scanning.
Measuring external (reflected) pulse
Measurement is initiated by pressing A/M. Measurement continuous until required STD deviation is
reached or a break command is issued (by pressing the A/M or STD button). If it is not reached, the
achieved STD deviation and the available distance is displayed.
Output - calculation of distance
The processor measures the time difference between the reference and external signal and calculates
the distance. The distance is sent to the processor board.
EDM offset and DR offset
The Trimble S6 DR300+ / DR PLUS instrument has one offset when measuring in EDM mode (to
reflector) and another offset when measuring in DR mode (to DR target). This offsets are measured
in Offset determination in PASS.
EDM offset
Determination to three prisms between 10 - 100 meters and verification to one prism between 10 -
100 meters. Totally four prisms.
DR offset
Determination to two DR targets between 15 - 50 meter and verification to one DR target between 15
- 50 meter. Totally three DR targets.
Short distance correction
The distance unit is compensated for a short distance correction. The correction is highest at close
range and is eliminated after 12 meter. The correction is made at the same time in offset determination
software in PASS. A measurement to a DR target between 2,4 - 2,6 meter is made and the
compensation is calculated. Totally one DR target.
Difference between DR mode and reflector mode
The difference between the two modes is that in reflector mode the greywedge close a little bit to only
make it possible for signals from a prism to pass through into the receiver diode, i.e. the greywedge
work as a filter and will only let strong signals such as signals from prisms through.