ABSTRACT
Osaka Gas Company has applied the correlation between the density and calorific value of natural gas to indirect continuous measurement of calorific value. Measurement is made by transforming the shades of interference fringes induced by the difference of refractive indices between standard gas and sample gas into electrical signals. Calorific value control and monitoring of send-out town gas is dependent on the existence of continuous measuring equipment with high reproducibility of measurement and speed of response. The simplest, most sensitive, and most precise method of measuring the difference in refractive indices of gases is to use an optical interferometer. Portable densitometers for inflammable gases by interferometry are compact, light, and very precise, and have been in service for decades. Gas densitometers can measure, continuously and indirectly, the calorific value of natural gas, can accurately control the calorific value of send-out town gas and can accurately monitor process gas.
