| 摘要 |
PURPOSE:To enable accurate detection of a liquid surface of a liquefied gas with a simple construction by using a metal cylindrical double coaxial pipe as line of reflected wave and moreover, a mixer as high frequency element to measure a phase difference. CONSTITUTION:A directional coupler 11 connected to an output end of a high frequency oscillator 9 for outputting a single frequency branches a signal (high frequency) of a main line to be inputted into a mixer 17. The signal serves as reference signal in the detection of a phase difference. The high frequency not branched is inputted into a cylindrical double coaxial pipe 15 mounted in a tank 3 for storing a liquid 5 via a circulator 13, reflected on the surface of a float 25 floating on a liquid surface 7 between an inner tube 19 and an outer tube 21 and returns to the circulator 13 to be inputted into the mixer 17 being branched. As a DC output voltage from the mixer 17 varies with the vertical shift of the liquid surface 7 (float 25),the position of the liquid surface 7 can be detected by measuring a DC voltage. In other words, the DC output voltage is applied to a waveform conversion circuit 29 to convert a sine wave output to a linear output. By measuring the output with a voltometer 27, the liquid 7 level is read directly. |
