There are two types of intra-mineral air pressure measuring instruments, one for determining absolute pressure and the other for measuring relative pressure. First, the determination of absolute pressure Absolute pressure is the atmospheric pressure at the point of measurement, which is zero pressure for absolute vacuum. Determination of mercury barometer instrument has two kinds and empty cassette pressure gauge, a barometer can read both the atmospheric pressure measured point directly from the instrument dial. Second, the determination of relative pressure Relative pressure, also called differential pressure, refers to the difference between atmospheric pressures at two points in the wind. Measuring instruments are: (1) U-shaped differential pressure gauge The U-shaped differential pressure gauge is a commonly used instrument for measuring the differential pressure. Two U-shaped glass tubes are respectively connected to the two skin tubes at two ends, and are led to two points where the pressure difference needs to be measured. The height difference between the two tubes in the U-shaped tube is the pressure difference between the two points, and the unit of the pressure difference is expressed by the mmH 2 O column. (two) tilting differential pressure gauge The structure of the tilting differential pressure gauge is shown in Fig. 1. Figure 1 Tilt differential pressure gauge (a) shape; (b) structure; (c) three-way cock internal hole opening and closing 1- bottom plate; 2-container; 3-glass tube; 4-plastic tube; 5--injection hole screw; 6-way three-way cock; 7-three-energy cock seat; 8-zero adjustment screw; 9-curved bracket; 10-level bubble; 11-leveling screw; 12-rubber tube When using a tilting differential pressure gauge to measure the differential pressure, place the tilting pressure measuring tube at the desired tilt angle, adjust the instrument to the level, and adjust the three-way cock to the pressure measuring position (as shown in c in Figure 1). Remove the joint of the rubber tube and the three-way cock, and gently suck with the mouth to tilt the liquid on the measuring tube to the top of the measuring tube, and eliminate the bubble accumulated in the instrument, and repeat it several times. Turn the zero adjustment knob to adjust the liquid level of the inclined pipe to zero position, turn the three-way cock to the pressure measurement position, connect the rubber tube to the “+†end and place it on the high pressure point, and connect the rubber tube to the “-†end. Placed at the low pressure point, the liquid pipe rising length of the inclined pipe is adjusted by the near inclination coefficient. (3) Pitot tube Pitot tube is a double-layered metal tube, the structure shown in FIG. The pitot tube can be used to measure the pressure difference between the two points with a U-shaped tube or a tilt differential pressure gauge. Figure 2 Pitot tube Culture Paper,Cultural Paper,Custom Paper,White Printer Paper CHINAPAPER-ONLINE(SUZHOU) E-COMMERCE CO. LTD , https://www.chinapaper-online.com