| 摘要 |
A vapour eliminator and liquified gas dispensing system comprising a vessel (10) which is connected to receive liquified gas from a supply. The vessel (10) has a vapour discharge line (12) connected to the top (51) of the vessel so that vapour can be discharged. Sensing means (50) has a capacitive element (70) located in the top (51) of the vessel and which changes its capacitance in response to change in the phase of material in the vessel (10) to which the capacitive element (70) is exposed. The sensing means (50) generates phase signals in response to changes of the capacitance of the element (70) whereby the phase signals can be utilised to open or close the vapour discharge line (12) at the beginning or end of a vapour elimination operation respectively. The sensing circuit (65) may comprise an oscillator circuit (58) of which the capacitive element (70) is a component determining the frequency of the oscillator circuit, and a frequency responsive circuit (59) operative to produce an output signal in response to a predetermined change of the oscillator frequency. Alternatively, the sensing circuit (65) may comprise a bridge circuit supplied by an AC source, the capacitive element (70) being located in an arm of the bridge circuit whereby a change in reactance of the arm of the bridge within which the capacitive of element is located causes a change in the output of the bridge circuit thereby causing generation of the phase signal. Alternatively, the sensing circuit (65) may include a pulse generator (71), the characterisation of the pulse train depending on the capacitance of the element (70). |
