The operating principle of the pneumatic comparator is, when the air under constant pressure is discharged through two openings. If one of the holes is kept uniform, the pressure will change according to the size of the other. In the diagram below, the pipe 1 is connected to an air supply and through restriction jets 2 to the pipe 11 which is immersed in water in a deep vessel open to the atmosphere. The air flow in the pipe 1 increases in the pipe 11 and maintains a fixed head of H-water and extra air outlets as bubbles. The air from the pipe 11 flows through the control stream 3 and finally exits through the metering jet at 6 ° C.
The pressure in the control jet tube b / n 3 and the jet calculation 6 will depend on the size of the orifice in 6 which is controlled by the distance b / n of the measuring table and the face and is reproduced by the height of a liquid in the manometer tube8. The scale 9 also adjusts that a head difference h specifies changes in the extended space d several hundred times. The main advantages of this comparator is, easy to operate, inexpensive, independent of constant pressure, free from mechanical wear and magnification is up to 10,000 times.
Thus, it is a comparator and types of comparators that includes mechanical, optical, Reed type, electric and pneumatic comparators.