Abstract: A directional device operating similar to a wind vane has a hollow vertical shaft which is journalled in a housing containing three chambers in communication. An air inlet port is located on the side of the directional vane and communicates through the hollow journalled shaft into the first chamber. A small aperture in the wall between the first and second chambers dampens the movement of the fluid flow from chamber 1 to chamber 2. A conventional baffle separates the second and third chambers and simultaneously allows fluid flow from the second to the third chamber while further damping the fluid flow to such a point that the fluid in the third chamber is substantially static. The third chamber is in communication with a differential pressure gauge which then compares the static pressure in chamber 3 with another pressure source.