Chapter 3
Theory of Operation
P/N 57150002, Revision 5.0 3 - 73 Trimble S, VX, SPS & RTS Service Manual
F
Distance unit - High Precision / DR Standard / DR
The EDM High Precision / DR Standard / DR is a direct reflecting distance meter based on the phase
shift method. An optical transmitter transmits a modulated light beam to the target. The optical
receiver detects the returning light reflected from the target. The EDM High Precision / DR Standard
/ DR measures the phase difference between transmitted and received light and calculate the distance.
Location of EDM High Precision / DR Standard / DR distance unit
Fig. 3-66 Location of EDM High Precision / DR Standard / DR (coloured)
Technical Specifications
See Data Sheet.
Function description
The purpose of the distance unit is to measure the distance to a target with the use of an infrared (IR)
or visible light beam. This is achieved in the following steps:
• Transmitting of an IR signal.
• Receiving of the reflected IR signal.
• Determine the phase difference between the transmitted and the received signals.
• Upon the phase difference, calculate the distance to the target.
The calculation of the distance is made from the known formula:
Distance = speed x time
• Speed, the speed of light is known 300 000 km/s.
• Time, the time is measured by the phase difference of received signal and reference signal
Greywedge
Transmitter
Receiver
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