The included angle between the collimation axis of the level and the level axis in the vertical direction is called I angle. The formula for angle I is I = Δ·ρ／ s. S is the ruler distance, P is the second value corresponding to radian, Δ Is the absolute value of the height difference.
Inspection method for I angle of level:
1. Stand the instrument in the middle of two points 50 meters away from the front and back of the flat place, fine level the level, then drain the water ruler at the front and rear AB points, record the reading A1B1, and then move the instrument to point a for about two meters. If a1-b1 is not equal to A2-B2, the instrument needs to be corrected.
2. Then we start to calibrate the instrument, use an Allen wrench or tighten the calibration screw to make the scale mark adjust to the correct reading. B2 = a2 - (a1-b1), and then repeat the above steps until the error is less than the specification value of the instrument. （ShuiZhunYiiJiaoJianYanFangFa）