Tower Ruler is a kind of level ruler. Most of the early level rulers were made of wood, which was heavy and limited in length (generally 2m), so it was not convenient to carry when measuring. Later, it was gradually made of aluminum alloy and other light and high-strength materials, and adopted tower shrinkage form. It was easy to draw out when in use, and the range of single elevation measurement was greatly improved. The length was generally 5m, and it could be contracted when carrying. Because its shape was similar to tower shape, it was often called tower ruler.
As the tower ruler is made of metal, the height of all the tower rulers can reach 5m, and most of the tower rulers are used outdoors. Therefore, it is necessary to keep away from the wires to prevent electric shock accidents. When measuring river water level with tower ruler, attention should also be paid to prevent drowning.
Use of folding tower ruler
The tower ruler is mostly of rectangular drawing structure, and the snap spring pops up at each drawing section. When using, it is necessary to pay attention to whether the snap spring is in place, otherwise the measurement error will be caused. In order to facilitate observation and debate, the distance is marked with a red point above or below the number on the tower ruler. If there is a red point on the number, it means the range of 1m section, and two red points mean the range of 2m section... And so on. If the number on the tower ruler is "4", it means 4m.
Maintenance of folding tower ruler
The surface of the ruler should be kept clean to prevent damage. The bottom plate of the ruler is easy to be damaged by moisture due to water or wet mud. It should be kept dry and fixed with screws. When using the tower ruler, pay attention to the looseness of the interface and spring plate, and when pulling out the upper section of the tower ruler. Pay attention to whether the interface is secure. If it falls off and is not found, the reading will be wrong.
requirement
The leveling staff is the length standard for measuring the height difference. If there is any error in the length of the leveling staff, it will bring systematic error influence on the observation results of precision leveling. Therefore, the following requirements are put forward for the precision leveling staff:
(1) When the temperature and humidity of the air change, the length of the dividing line of the leveling rod must be kept stable or only slightly changed. In general, the dividing of precision level is painted on invar alloy belt, and invar alloy belt is stretched in the groove of wooden ruler body with a certain tensile force, so that the length of invar alloy belt will not be affected by the expansion and deformation of wooden ruler body. The number of leveling rod division is marked on the wooden ruler on both sides of invar alloy belt, as shown in Fig. 5-7 (a) and (b).
(2) The division of the leveling rod must be very correct and precise, and the accidental error and systematic error of the division should be very small. The magnitude of accidental error and systematic error of leveling rod division mainly depends on the level of division and calibration technology. At present, the accidental mean square error of precise leveling rod division is generally in the range of 8 ~ 11 M. Because the systematic error of precise leveling rod division can be corrected by the average true length per meter of leveling rod, the accidental error of division represents the comprehensive accuracy of leveling rod division.
(3) The structure of the leveling rod should be straight, and the length, bending and torsion of the ruler body are not easy to occur. Generally, the wooden body of precise leveling rod should be made of high-quality wood with special treatment. In order to avoid changing the length of the leveling rod due to the wear of the bottom of the leveling rod in use, a solid and wear-resistant metal base plate must be nailed on the bottom of the leveling rod.
In the precise leveling operation, the leveling rod shall be erected on the special ruler pad or ruler pile with certain weight. The shape of ruler pad and ruler pile is shown in Figure 5-8.
(4) A round level device shall be attached to the body of the precise level staff, so as to keep the level staff in a vertical position during operation. Generally, the ruler supporting ring should be installed on the ruler body, so that the ruler supporting person can make the leveling rod stable in the vertical position.
(5) In order to improve the alignment accuracy of leveling rod division, the form and color of leveling rod division are coordinated with the color of leveling rod. Generally, the precise leveling rod is divided by black lines, as shown in Figure 5-7. It is helpful for the accurate alignment of leveling rod division during observation by combining with the light yellow ruler.
There are two kinds of dividing values of line dividing precision leveling staff: l0 mm and 5mm. As shown in Fig. 5-7 (a), the precise leveling staff with division value of lomm has two rows of divisions. The row of division notes on the right side of the ruler from 0 to 300cm is called the basic division, the row of division notes on the left side from 300 to 600cm is called the auxiliary Division, and the reading difference between the basic division and the auxiliary division at the same height is a constant, which is called the basic auxiliary difference, usually called the ruler constant, Leveling operation can be used to check the accuracy of readings. As shown in Figure 5-7 (b), the precision level with a grid value of 5mm also has two rows of dividers, but the two rows of dividers are staggered by 5mm, so in fact, the left side is odd dividers, and the right side is even dividers, that is, the odd dividers and even dividers occupy one row respectively, without auxiliary dividers. The right side of the wooden ruler is marked with the meter number, and the left side is marked with the decimeter number. The whole mark is from 0.1 to 5.9 M. the actual division value is 5 mm, and the division mark is twice larger than the actual value. Therefore, the actual elevation difference value measured by this kind of leveling rod must be divided by 2.
The precise leveling staff with a grid value of 5mm also has an auxiliary dividing line.
The bar code level used with the digital code level is shown in Figure 5-9. Through the detector of digital code level to identify the bar code on the level, and then through digital image processing, give the reading on the level, instead of the visual reading on the level.
