A flame ionisation detector for measuring fluctuating concentration

Describes modifications that can be made to a flame ionisation detector to enable it to provide continuous measurements of fluctuating concentration in turbulent flows. The flame chamber of the FID is placed in the flow and samples sucked into it along a fairly short, narrow bore tube. An analysis is presented of the effect of the sampling tube on the frequency response of the probe. A simple electrometer amplifier with a suitable frequency response and sensitivity for use with the probe is described. The particular application discussed is the wind tunnel modelling of plume dispersion.