Types Of Adjustment In Levelling


Types Of Adjustment In Levelling

There are two types of adjustment in the leveling
1. Temporary adjustment 2. Permanent adjustment.
1. Temporary adjustment:- Temporary adjustment is performed with each setup of the instrument. In the temporary adjustment, There are main two steps.
A. Setting up the level:-
(a)(i)Fixing the instrument on the tripod:- Release the clamp screw of the instrument, hold the instrument in the right hand fix it on the tripod by running round only the lower part with the left hand, screw the instrument firmly.

(a)(ii) Leg Adjustment:-Set the instrument in the desired position and convenient height for sighting the staff. Bring all the foot screws in the center of their run. Fix any two legs into the ground and move the third leg of the tripod right or left until the instrument bubble approximately leveled.

(b). Leveling Up the Instrument:-Place the telescope parallel to two-foot screws. Turn these foot screws inward or outward until the bubble center. Turn the telescope 90 degree and turn the foot screw until bubble in the center. Repeat the process until the bubble remains center.

B. Focusing The Eye and Object Glass:-

Types- Of -Adjustment -In -Levelling

(i)Focussing The Eye piece:-A White paper kept on in front of object-glass. Move the eyepiece in and out until the crosshairs are distinctly seen.

(ii) Focussing The Object Glass. Direct the telescope towards the staff. And on looking through the eyepiece, bring the image of the staff between the two verticle hairs of the diaphragm. Adjust the objective by turning the focussing screw until the parallax is eliminated. The parallax is completely eliminated when there is no change in the staff reading.

2. Permanent Adjustment:-There are generally two permanent adjustments in any type of leveling instrument.

i. The axis of the bubble tube should be perpendicular to the verticle axis.

Test:- Set up the level on firm ground and level it carefully in the usual way. The bubble will now be central in two positions at the right angles to each other. Bring the telescope over one (third ) foot screws and turn it through 180 degrees. If the bubble remains central. The adjustment is correct.

ii. The Line of collimation parallel to the axis of the bubble tube. This method is checked and adjusted by the two peg method.

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