Nikon NPL-632, Instruction Manual

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6 Checking and Adjustment
152 Field Station NPL-632 Instruction Manual
Checking the 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. The instrument constant is set by the manufacturer before the instrument is
shipped. However, to ensure the highest operational accuracy, Nikon recommends
that you check the instrument constant several times a year.
To check the instrument constant, you can either compare a correctly measured base
line with the distance measured by the EDM, or follow the procedure below.
To check the instrument constant:
1. Set up the instrument at Point P, in as flat an area as possible.
2. Set up a reflector prism at Point Q, 100 m away from Point P. Make sure that
you take the prism constant into account.
3. Measure the distance between Point P and Point Q (PQ).
4. Install a reflector prism on the tripod at Point P.
5. Set up another tripod at Point R, on the line between Point P and Point Q.
6. Transfer the NPL-632 instrument to the tripod at Point R.
7. Measure the distance from Point R to Point P (RP), and from Point R to Point
Q (RQ).
8. Compare the value of PQ to the value RP + RQ. The difference should be
within the specified range of error for the instrument (± 3 mm + 2 ppm ×
distance).
9. At 100 m distance, the error range is ± 3.2 mm. If the error is out of range,
contact your dealer.
10. Move the NPL-632 to other points on the line between Point P and Point Q.
About 100 m
P Q
P R Q