Spectra Precision DG613, Information Manual

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Elevation of Flat Bottom Manholes
1. When a Laser is to be set on a flat surface where the laser beam is not centered in the pipe,
use model 1230 Heavy Duty Trivet Plate and Universal Fixed Pole.
2. Using this system, the elevation of the laser beam can be set by either measuring down from a
grade offset hub outside the trench or up from the floor of the manhole to the beam.
3. The 1239 has both tenths/hundredths and cm/mm scales for setting the elevation of the beam.
1230/1237 Heavy Duty Invert Plate
The invert plates model 1230 (English) and 1237 (Metric) are one piece cast aluminum support
plates that provides automatic self-centering of the Laser in 10 in. (250 mm), 12 in. (300 mm) or
15 in. (400mm) pipe diameters. The invert plates are used along with the 1239 Universal Fixed
Pole for setups on the manhole bottom, outside of the manhole or in pipes larger than 15 in. (400
mm) diameter.
1239 Universal Fixed Pole
The 1239 Universal Fixed Pole supports a Laser at a predetermined elevation above the invert.
The 1239 may be used with the 1228 Universal Adjustable Invert Plate, the 1230/1237 Heavy
Duty Invert Plates, or the 1244 T-Bar Assembly.