ADA INSTRUMENTS PROF X2 Operating Manual page 13

Repeat one more time the definition of collimation axis error ( c) and calculate it's average
value. The value difference shouldn't exceed 2". If this value is more than 2" you should
do the adjustment. The procedure of correcting of collimation axis error is described below.
5. The adjustment of the place of zero (MO) of the vertical circle.
After leveling the instrument, observation should be done on the target (point) at two positions
of the circle of theodolite. The locking knob (10) of the compensator should be ON.
The place of zero is calculated according to the following formula:
Where Л and П- reading of vertical circle.
Repeat the definition of the place of zero (МО) and calculate average value. The value shouldn't exceed 2".
If this value is more than 2" you should do the adjustment in accordance with the adjustment ( c):
Focus the levelled instrument at the target and take the readings Л of the horizontal and vertical circles.
Calculate the correction with the help of following formulas:
Set the corrected report of H circle with the help of horizontal micrometer screw.
The same way, set the corrected report of V circle.
With the help of the pin or screwdriver loosen adjustment screws to overlay the reticule image with the target.
Notice! You should correct 2c first, and only then- МО
Notice! You can correct
МО=0,5 (Л-П) for theodolites with precise system of reading of vertical angles from 0°.
МО=0,5 (Л+П)-360° for theodolites with precise system of reading of vertical angles from 90°.
correction Л= Л – с for horizontal circle
correction Л= Л –
МО with the help of corrective screws under the protective cover plate (13).
МО for vertical circle
1
PROF
Fig.7
MEASUREMENT FOUNDATION
X2