Dumpy Level | Uses of Dumpy Level | Dumpy Level Calibration
What is a Dumpy Level?
Dumpy level is an optical instrument used to establish and checkpoints in the same horizontal plane or surface. The tube is also used to measure horizontal levels. It consisting a telescope firmly secured into adjusting screws.
Mostly leveling kit contains:
- Level head or Level Machine
- Level staff or dry board.
It has different side views of the level head, which consists of various components, namely:
A telescope is used to observe the distant object through the line of sight provided by its arrangement.
The eyepiece is used by the observer’s eye to view the distant object. It contains a magnifying glass, which magnify the observing image and also the crosshairs of the diaphragm
It is used to cite a staff in line before focusing.
The focusing screw is used to adjust the focus for crosshairs and the image clarity
It is used for protecting object lens from direct contact with sunlight
They are provided to regulate the tribe rack position and hence the instrument can be leveled, which is known by observing the bubble tube the tribe rack plates can be lowered or raised using foot screws.
The position of the tribe rack is said to be correct when the bubble in the bubble tube is at center
It is based plate, which is rest on tripod but level, machine and tripod can be fixed here by Level screw
It is provided to check the level of the instrument. The instrument is said to be in perfect position when it is at the center or middle of the tube
It shows the degree to rotate the telescope to a particular degree.
It is used to make very slow movements in the horizontal circle.
Components of tripod
Various components of tripod-like;
- Expansion link
- Solids trap
- Tripod knob
- Aluminum frame
- Fixed dip
Different uses of Level Machine
- It is used to determine the height of a particular point
- To determine differences in height between points.
- It also used for drawing contours on the land
- For also setting out level and inclined surfaces for construction it uses.
How to Set Up a Dumpy Level./ How to use dumpy level
It involves some well-defined operations, which are required to be carried out in proper sequence.
At each set up of a level instrument temporary adjustment is required to be carried out prior to any staff observation. The temporary adjustment of a dumpy level consists of setting, leveling, and focusing.
The tripod stand is set up at a convenient height, having it’s head horizontal through our estimation.
The instrument is then fixed on the head by rotating the lower part of the instrument with the right hand and holding firmly the upper part with the left hand.
Now the bull’s-eye bubble or, say circular bubble is brought nearer to the center by adjusting the tripod legs.
It is done to make the vertical axis of the instrument truly vertical. It is achieved by carrying out the following steps.
- The first step is the level tube is brought parallel to any two off the foot screws. By rotating the upper part of the instrument, the bubble is brought to the center of the level to Barrow dating the foot screws, either in war door out war direction.
- Then the telescope is brought over the third foot screw again by rotating the upper part of the instrument, it has to be 90 degrees to the parallels crew.
- The bubble is then again brought to the center of the level to Barrow dating the third foot screw either inward or outward.
- By rotating the upper part of the instrument through 180 degrees, the level tube is brought parallel to the first 2 ft screws in reverse order.
- The bubble will remain in the center of the instrument is in permanent adjustment
It is required to be done in order to form an image through the objective lens at the plane of the diaphragm and to view the clear image of the object through the eyepiece.
This is being carried out by removing parallax by proper focusing of objective and eyepiece.
For focusing the eyepiece, the telescope is first pointed towards the sky, Then the ring of eyepieces turned either in or out until the crosshairs are seen sharp and distinct.
Focusing on my peace depends on the vision of the observer and thus required whenever there is a change in the observer
For focusing the objective, the telescope is first pointed towards the object, Then the focus is crew is turned until the image of the object appears clear and sharp, and there is no relative movement between the image and the crosshairs.
This is required to be done before taking any observation.
Instruments specifications of Leveling Staff
- Approximately leveling accuracy is 1.6 millimeter to 30 m
- Magnification off object glasses, usually 26X
- Machines working ranges generally 75 m to 100M
- Weight of machine is 1 to 2 kg
Precautions when Using Leveling Staff
- For using the level in the machine some care should be taken by the user.
- The staff can be difficult to study in high winds, but you do need to keep it vertical and still.
- Use standard sizes of staff as put requirement.
- But ensure the size of the level staff matches with the pit depth.
- Pull out the staff sections one at a time carefully
- After completion, clean each section and close the staff
- Protects from sunshine, rain and weather when not in use or even during lunch breaks
- Put the instrument into the case in correct position.
- The instrument is calibrated, ensure proper handling.
- Calibration can be disturbed with vibrations from a moving vehicle, dropping on the floor, mishandling etcetera.
- Ensure tripod is folded back
- While carrying ensure instrument cases kept on the seat and not on the vehicle floor.
Taking Measurements for Dumpy Level.
A level staff is also called the staff rod or a leveling rod. It indicates a level difference of five millimeters.
Understanding a Leveling Staff
Generally, a telescopes three hairs;
- Upper stadia Hair
- Middle stadia Hair and
- Lower stadia Hair
In the staff, middle hair shows a Reduced Level (RL) as readings in the staff increase in value as height or level increases. Generally, the staffs are available in 3,4 and 5 m in length, but you have to choose to depend upon the depth of footings.
The staffs with and thickness is 75 and 18 millimeters accordingly and it is available in wooden and aluminum but prefer to use aluminum staff
In level staff, each meter is divided into 200 divisions of five millimeters. The readings are marked on the right side with black or red figures, but you can get a perfect reading by focusing and adjusting the telescope through the tangents screw.
To measure horizontal distance staff can be also used in auto level machine, the scale of difference of upper and lower hair is designed in such manner that it says one centimeter is equal to 1 m.( 1cm=1M) Here is an example;
Upper and lower hairs = 0.280 and 0.220 m,
Difference between two hairs = 0.28 -0.220 = 0.6 m
Convert 0.6 m to centimeter, 100cm x 0.06 = 6 centimeter.
Therefore, the horizontal distance is 6.0 m.