The use of bubble level and zero calibration method
1. The reasons for the zero position error of the level meter:
Factors such as transportation, placement, vibration, temperature, wear, and adhesive aging will cause the zero position of the level meter to be inaccurate, so the correctness of the zero position indication error of the level meter should be checked before use. In the process of laboratory calibration, the correctness of the zero position is also checked first, and then the next step of calibration is performed.
2. Calibration method of zero position of level meter
There are two ways to calibrate the zero position of frame-type and strip-type level gauges: one is to check the correctness of the zero-position error on a roughly horizontal plate (or machine tool guide rail); "Calibration Specification for Level Meter" to calibrate the zero error. Now it is described as follows:
1. Check the correctness of the zero position error on a roughly horizontal flat plate (or machine tool guide rail).
After the bubbles are stable, take a reading at one end (such as the left end) and set it to zero. Then turn the spirit level 180. , still placed on the original position of the plate, usually it is advisable to place a positioning block. After the bubble is stabilized, the reading (A grid) is still at the original end (left end), and the zero indication error of the level meter is 1/2A grid. The value should meet the requirements in Table 1.
2. According to JJF1084-2002, the zero error calibration is carried out on the zero position calibrator of the level meter.
JJF1084-2002 introduced the zero error calibration method based on five different working surfaces.
The zero position error based on the working plane is introduced.
Before measurement, place the level to be calibrated with a clean (polished and cleaned) measuring surface on the workbench of the zero position calibrator of the level, close to the positioning block. After the bubble stabilizes, count o at one end of the bubble. ;Then turn the level meter 180o, put it in the original position accurately, record the reading at the other end of the bubble according to the first reading side, half of the difference between the two readings is the zero error. According to Table 1 requirements. Make a pass or fail judgment. If the zero error exceeds the allowable range in Table 1, the level meter zero adjustment mechanism (adjusting screw or nut) needs to be adjusted to reduce the zero error to within the allowable range. Do not turn the screws and nuts that are not adjusted at will. Before calibration and adjustment, the working surface of the level meter and the calibration table such as the flat plate must be wiped clean.
Adjustment Method of Level Meter Zero Position Error
1. adjustable on one side
There are two fixing screws on both sides, one end is used for fixing, and the other end is used as an adjustment mechanism. You can use a special wrench or a screwdriver to adjust the zero error of the working surface. Adjust the fastening screw, place the level on the flat plate close to the positioning block, press the left end (end A) of the bubble to read n^ after the bubble is stable, and then rotate the level 180. , placed exactly in its original position. Follow the side of the first reading and note the reading of 0n at the other end of the bubble (end B). If > , the B end is higher, adjust the screw with a wrench to move the air bubbles to the lower end by 1/2 (aB one mouthful) space. Re-test after standing still for half an hour, and adjust in the same way. After the zero error reaches the requirement, be sure to tighten the screw with a fine-tuning adjustment mechanism wrench. * After the final zero position error meets the requirements of JJF1084-2002, place it on the plate for 4 hours and measure again to judge whether it is qualified. Sometimes it is still out of tolerance, usually within 2 grids of the glass tube scale. At this time, the method used is not to move the previous adjustment screw, but to use a screwdriver to slightly rotate the screw of the fine-tuning adjustment mechanism (see Figure 3). . Place it for another 4h and re-measure. until qualified. For a fixed level without any adjustment device, if the zero position is incorrect, it can only be adjusted by grinding the measuring surface or changing the air bubble. It is only limited to spirit levels or levels with large division values and low accuracy.
