| 摘要 |
A method and apparatus for measuring the relative density of a gas. The apparatus includes a chamber to which a gas in question, for example natural gas, is supplied through an inlet and leaves through an outlet. The speed of sound SoS at ambient temperature is measured using any suitable method such as electronic control and a calculating device and an ultra-sound emitter and an ultra-sound receiver. The ambient temperature Ta is observed by a temperature sensor, and a thermal conductivity sensor measures the thermal conductivity of the gas at two different temperatures above the ambient temperature. One value ThCH of the thermal conductivity is measured at 70° C. above ambient and the other value ThCL of the thermal conductivity is measured at 50° C. above ambient. The control calculates the relative density RD of the gas according to the formula RD=g.ThCH+h.ThCL+i.SoS+j.Ta+k..Ta<2>+l where (g, h, i, j, k and l) are constants. |
