It is a u-shaped glass tube 1 and 2, with a scale 3 in the middle of the u-shaped tube, the zero of the reading is in the center of the scale, and the tube is filled with liquid to the zero. Tube l is connected to the measured medium through the joint, and tube 2 is connected to the atmosphere. When the pressure of the measured medium is greater than atmospheric pressure Pd, the working liquid level in tube 1 drops, while the working liquid level in tube 2 rises until the pressure generated by h in the height of difference between the two liquid levels is balanced with the pressure measured.
It is difficult to guarantee that the diameters of the two tubes are exactly the same in the u-tube pressure gauge. Therefore, when determining the height h of the liquid column, the liquid level height of the two tubes must be read at the same time.
The u-tube manometer is usually measured in a range of 0 ~ + / -800 mm water column or millimeter mercury column, with a precision of 1 level. It can measure pressure, vacuum degree, differential pressure and standard deviation pressure of the check flowmeter. Its characteristic is the zero mark is in the center of the scale plate, need not adjust zero before using, liquid column height must read twice.
