Gas density metering in ultrasonic gas flowmeters using impedance measurements and chemometrics

Measurements using ultrasonic transducers confirm that the density of the gaseous medium can be predicted from impedance measurements on the same transducers. Tests were performed with the following gases under different pressure: SF₆, N₂, He, and air. These gases were selected to achieve a large span of densities. Using chemometric techniques can circumvent any possible dual sensitivity of the transducers on temperature and density. Sensitivity analysis of the transducers as a function of density is also performed and compared with experimental results. The densitometer under discussion uses impedance variation as an intermediate variable. Impedance variations can be converted to variations in frequency. Finally, the scenario of ultrasonic mass flowmetering is discussed with plausible models for realising computer integrated mass measurements using ultrasonic transducers in dual mode, viz. Contra-propagating transit time and impedance modes.