Bubble tube: To determine the sensitivity of a dumpy level

Aim:

This lab activity aims to determine the sensitivity of the bubble tube at a dumpy level.

Theory:

A dumpy level, commonly used in surveying and construction, is an optical level that measures height differences and angles. It comprises a telescope mounted on a tripod and leveling is achieved by using a bubble tube.

The bubble tube is a cylindrical glass tube filled with liquid and a small air bubble. When the level is placed on a surface, the bubble moves toward the highest point. The sensitivity the is determined by the diameter of the tube and the viscosity of the liquid inside it.

Apparatus & Materials required: Bubble tube

• Dumpy level
• Measuring tape
• Tripod Stand
• Plumb-bob
• Two pegs
• Spirit level
• A4 size paper
• Pen/pencil

Procedure:

1. Set up the tripod stand on a level surface.
2. Fix the dumpy level onto the tripod stand and adjust the height of the telescope to the comfortable eye level.
3. Place the spirit level on the base of the dumpy level and level the tripod stand by adjusting the legs.
4. Fix two pegs on the ground in a straight line at a distance of about 20 meters apart.
5. Fix a plumb-bob on each peg to make sure they are vertical.
6. Place the dumpy level in between the two pegs with the telescope facing towards one of the pegs.
7. Look through the telescope and focus it on the top of the peg.
8. Adjust the bubble tube by using the leveling screws until the bubble is centered.
9. Record the reading of the level staff held vertically on the peg at the same point where the plumb-bob is hanging.
10. Move the dumpy level towards the other peg and repeat the process of leveling the and recording the reading of the level staff.
11. Repeat the process for several times to get an average reading for each peg.
12. Calculate the difference in height between the two pegs by subtracting the reading of the level staff on the second peg from the reading on the first peg.
13. Calculate the sensitivity of the by dividing the difference in height by the number of divisions on the bubble tube.

Results: of bubble tube

After experimenting, the height of the first peg from the ground was 1.25m, while the height of the second peg from the ground was 1.45m.

We calculated the difference in size between the two pegs to be 0.20m and determined the number of divisions on the tube to be 20.

To determine the sensitivity of the tube, we divided the difference in height by the number of divisions on the bubble, resulting in a sensitivity of 0.01m per division.

These results are important as they help in understanding the precision and accuracy of the dumpy level‘s measurements.

Precautions: bubble tube

1. To avoid any errors in the readings, ensure that the surface on which the tripod stands is level.
2. To prevent any movement, firmly fix the pegs on the ground.
3. Use the plumb-bob to ensure that the pegs are vertical.
4. Properly focus the telescope to avoid any parallax errors.
5. Handle the bubble tube carefully to avoid any damage.

Conclusion:

This lab activity has helped in determining the sensitivity of the at a dumpy level. The sensitivity of the bubble is an important parameter that affects the accuracy of the readings taken by the dumpy level. By knowing the sensitivity of thtube,

one can determine the precision of the measurements taken by the dumpy level. This lab activity can be,

Horizontal Measurement angle by repetition method