The deviation from isokinetic sampling is calculated with a relationship that is independent of the gas density, that is of the O2, CO2 and water vapour contents and of the gas temperature.
The pictures show the two types of probe head that now have a total pressure tube. The dynamic pressure is measured as the difference between the total pressure and the static pressure on the outside of the probe head. The gas velocity therefore does not affect the sensitivity of the null-pressure control, and the control is accurate even at low velocities.
Control in a wind tunnel
The graphs show how the velocity in a wind tunnel was changed in steps between 4 and 10 m/s while the null-pressure control with the AMV-02 motor valve keeps the sampling isokinetic. The measured deviation from isokinetic sampling is stable across the whole velocity range, and the motor valve restores isokinetic sampling quickly after each step.
The probe is part of our range for dust sampling. Contact us for more information.