Ultrasonic testers, not for medical purposes; scientific, nautical, surveying, photographic, cinematographic, optical, weighing, measuring, signalling, checking, life-saving and teaching apparatus and instruments, namely, gas measurement and analysis devices for the determination of gas sound speed, velocity of gas, molecular weight, temperature, pressure, and density with respect to flowrate, gas chromatography, mass spectroscopy, volume correction and conversion devices and gas datalogging;...