Can anyone explain in laymans terms how a Pitot tube measures air pressure in a ventilation duct.

I would appreciate it if those who don't know would leave it to those who do know to answer, and not ask why or what it is. :thumbsup:

Is this of any help owdlad, or have you already seen it and as confused as me?

http://images.google.co.uk/imgres?imgurl=http://www.grc.nasa.gov/WWW/K-12/airplane/Images/pitot.gif&imgrefurl=http://www.grc.nasa.gov/WWW/K-12/airplane/pitot.html&h=466&w=619&sz=13&tbnid=G3W8OBHhYGIJ:&tbnh=100&tbnw=133&start=2&prev=/images%3Fq%3Dpitot%2Btube%26hl%3Den%26lr%3D

No thanks anyway this is for an aircraft and doesnt apply to the pressure inside a air ventilation duct.

The principle is the same for aircraft and ventilation duct. The pitot tube is used to measure both the static and flow pressure of a fluid.

The static pressure is a pressure reading taken perpendicular to the flow

The flow pressure is a reading taken pointing in to the flow, where, because of the speed of the fluid, the pressure will be higher than the static pressure.

The difference between these two pressures is then used to calculate the speed of the fluid using this (http://www.airflow.com/techtop/fulleqn.gif) equation.

So pitots measure flow/speed by detecting the difference in pressure between measurements taken into the flow (higher) and of the flow(lower)

Thanks Guys :thumbsup: The information was for my Daughter (don't ask why) and you have just won me some Brownie points.

I told her I didn't know but knew some men who would, and as usual you lot have come up smelling of roses :clap: :clap: :clap: :clap:

You never know owdlad,....the lass might be thinking of buying you one for your birthday.