Pitot tube measurement of airflow total pressure and static pressure air velocity to confirm the shape of a pipe device. The structure of the pitot tube, the head of hemispherical, after a double casing. Speed measuring head alignment to flow, when the head center holes ( Total pressure hole) Feelings to flow, total pressure p0, the inner tube sent to pressure gauge. Head after about 3 ~ 8 d coat evenly open a hole on the wall, Static pressure hole) , feeling coming flow static pressure p, the casing is also to pressure gauge. For incompressible flow, according to the Bernoulli equation and energy equation can be calculated Mach number, and then seek speed. But in supersonic flow, the pitot head appeared in vitro shock, total pressure hole feelings is a wave after total pressure, static pressure to flow is also difficult to measure, thus pitot no longer apply. Total pressure hole has a certain area, it is all the feelings of the stationary point near the average pressure, slightly below the total pressure, static pressure hole feelings also have certain error of static pressure, and other such as manufacturing, installation, also can have error, it should be add a correction coefficient to measure the velocity & zeta; 。 ζ Value is in commonly 0. 98-1. 05 range, in the air of known speed correction or correction of standard pitot tube and determined. Pitot tube structure is simple, easy to use and quite useful.