Instruction manual

4-6
4
CHECKING AND ADJUSTMENT
4-5 Instrument Constant
The instrument constant is a numerical value used to automatically correct
for the displacement between the mechanical and electrical centers when
measuring distances. Although this adjustment was made at the time of
delivery, it is recommended that the constant be checked several times a
year to ensure the highest operational accuracy. Checks can be performed
by either comparing a correctly measured base line with the distance as
measured by the EDM, or by using the following procedure.
(1) Perform the check on as flat an area as possible. Set up the
DTM-350/330 at Point P, with the reflector prism 100m away at Point
Q (taking the prism constant into account).
(2) Measure the distance between Points P and Q and note it for future
reference.
(3) Set up another tripod between the two, at Point R, and transfer the
DTM-350/330 to it. Install a reflector prism back on the tripod at Point
P.
PQ
RPQ
About 100m