| 摘要 |
PURPOSE: To attain simple and highly reliable measurements by calculating the filling level of a liquid from the propagation delay time of a container bottom signal obtained by radiation of a microwave signal, the actual distance to a bottom, and the permittivity and permeability of the liquid. CONSTITUTION: Microwave signals are radiated toward a liquid surface 3 and the bottom 6 of a container 2 via an antenna 4 to obtain a liquid-level signal r1 and a bottom signal r2 . The height of the liquid surface 3 is calculated from the propagation delay time of the signal r1 . The ratio of the apparent distance hs to the actual distance (h) to the bottom, that is calculated from the propagation delay time of the signal r2 , becomes equal to the ratio of the apparent filling height ls to the actual filling height I of the liquid 1 to be calculated, which corresponds to the ratio of propagation speed C1 in a space of a distance (d) to propagation speed Cf1 in the liquid 1 and equals the root of the product of the permittivityεr and permeabilityμr of the liquid 1. Therefore, the filling height I of the liquid 1 can be calculated directly by calculating time distance (d) using the formula: Ia /I=(hs -d)/(h-d)=C1 /Cf1 =(εrμr )<1/2> . |
