Topcon GPT-7500 Series, Instruction Manual

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3 STANDARD MEASUREMENT MODE
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Precautions for Use of Non-prism long mode
GPT-7500 series made non-prism measurement possible to reach the distance that had never been
achieved before.
In the non-prism long mode, the following attentions need to be paid because the farther the target
object be, the weaker the reflection from the target and the larger the beam diameter become.
1) Measurement Time
In the non-prism long mode, the measuring time largely depends on a distance to the target object
and the color (or reflectance) of the object. Especially when the measurement distance is far, or
when the reflectance of the measured surface is low, measuring time will become longer.
2) Beam Diameter
Beam diameter becomes large in the long distance. Try to bring as much beam as possible to the
measured surface.
If the beam is not lased rightly as in the cases below, may cause incorrect measurement.
In such cases, collimate the position where the beam is not fallen besides the measured surface,
set measurement distance range ( Chapter 3.2.3 “Setting Measurement distance range of Non-
prism long mode” .).
3) Cutoff during Measurement
While in the Non-prism long mode, you had better use the instrument in the place where the light
path may not be cut off by cars or people. You may not be able to collect accurate figures if it is often
cut off.
4) Re-measuring
When the reflectance of the measured surface drastically changes as in the case of looking quickly
from the white object to the black object, or when the distance to the object changes a lot, you may
face a temporary suspension. If you cannot measure even after a while, press [MEAS] or [MODE]
key to restart measurement.
(e.g.1) the beam also reaches the wall either before or behind the object
(e.g.2) the beam reaches the wall behind due to the size of the object
(e.g.3) the beam is thrown on the ground before the object