Chapter 3
Theory of Operation
Trimble S, VX, SPS & RTS Service Manual3 - 66 P/N 57150002, Revision 5.0
F
Function description - Measuring principle
Fig. 3-60 Light pulse path
The time for the transmitted signal to travel to the target and back again, has to be determined with
very high accuracy. Patented signal processing techniques are used to process 25000 laser pulses per
second to achieve the required accuracy.
This unique technique lifts up the target signal through the noise and ensures that an accurate distance
can be obtained for long distances and very weak target signals.
Function description
Measuring sequence, overview:
1. Transmitting light pulse
2. Receiving light pulse
3. Measure time difference between transmitted and received pulses
4. Calculate distance to target
5. The calculation of the distance is made from the known formula:
Distance = speed x time / 2
Speed, the speed of light is know, 300 000 km/s.
Time, the time is measured between the transmitted (reference pulse) and received pulse.
Distance, halved to get the distance one way to the target.
Functional diagram
When transmitting the light pulse a part of this pulse is returned into the receiver diode via a piece of
glass. This pulse is known as the reference pulse. The reference pulse will later be compared with the
target pulse to find out the distance to the target.
OR
Light pulse
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