The analyzer being programmed to derive, from the velocity measurement made within the single chamber, {HEAD ~ information} relating to {TAIL ~ the level} of the gaseous substance to be monitored 
relating to
The analyzer being programmed to derive , from the velocity measurement made within the single chamber , { HEAD ~ information } relating to { TAIL ~ the level } of the gaseous substance to be monitored
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH