A 3D
Probe is used to determine the velocity pressure, yaw and pitch angle of the flow velocity
vector, and the temperature in a stack or duct. Yaw angle is determined directly by rotating the probe to null the pressure across a pair of symmetrically placed ports (2 & 3) on the probe head.
The pitch angle is calculated using probe specific calibration curves. From these values and a determination of stack gas density, the average axial velocity of the stack gas is calculated.
The average gas volumetric flow rate in the stack or duct is then determined from the average axial velocity.