Prior art patent document published EP 0 709 656 A2 discloses a valve with an integrated level gauge for pressurized gas. It comprises a body to be mounted on a gas container, like gas cylinder, a gas passage extending through the body from a gas inlet to a gas outlet. A capacitive gauge is mounted to the body on an inner side of the body, in contact with the pressurized gas when mounted on the container. The capacitive gauge comprises a tubular electrode and a central electrode extending coaxially through the tubular electrode. The tubular electrode comprises apertures permitting the liquefied gas to also occupy the radial space between the two electrodes, playing the role of a dielectric element of a capacitor. The level of liquefied gas in the container which is therefore also between the two electrodes, determines the average permittivity between the two electrodes and therefore the capacitance of the capacitor. The body comprises an electrical lead that is electrically connected to the central electrode and that extends through the body until an electronic unit that is attached to the body. This document does not however provide any details of how the electrical lead is mounted in a gas tight fashion on the body.
Prior art patent document published WO 2013/182649 A2 discloses a capacitive level gauge for a container of pressurized and liquefied gas. The gauge comprises a tubular electrode and a central electrode extending inside the tubular one. The upper extremity of a central electrode support is fixed to the body of the gauge via gasket. This latter has a beveled shape conforming to a corresponding beveled bore in the body. The beveled bore widens upwardly. The gasket is therefore inserted into the bore on an outer side of the body, i.e. a side of the body that is outside of the container when the gauge is mounted thereon. A nut is screwed on the body so as to compress the gasket axially downwardly, resulting in compressive forces against the central electrode support due to the beveled shape of the gasket and the bore. An electrical wire extends from the upper extremity of the central electrode through the nut until an electrical circuit that is fixed to the body. This teaching is interesting in that it provides an interesting solution for ensuring a gas tight connection between the inner and outer sides of the body of the gauge. It requires however the central electrode support to extend deep into the body in order to fit in the gasket. The positioning of the central electrode support must therefore be carefully done for guaranteeing the expected gas tight connection. The central electrode support is therefore usually mounted first on the body, the central electrode, the external tubular electrode and the electric circuit are then mounted afterwards.
Prior art patent document published WO 98/31077 discloses a modular level gauge that comprises an explosion proof connector and a probe mounted on the connector. The connector comprises a body with a through central passageway and an electrical connection pin extending through the passage. Explosion proof potting material is filled in the passage between the body and the pin so as to provide a gas tight explosion proof barrier. The pin provides two opposite shoulder sections in contact with the potting material so as presumably to avoid any risk of axial relative movement between the pin and the potting material. The probe comprises a single electrode that is electrically connected with the pin by insertion of the pin into a hole in the upper end of the probe. The probe can therefore serve as first electrode of a capacitive gauge, the walls of the container or another distinct probe serving as second electrode of the capacitive gauge. The probe is a conductive cylinder that can be easily coupled to or uncoupled from the connector by means of a modular coupler. The ability of the probe to be easily mounted to, and dismounted from, the connector is quite interesting. The probe is however of the single electrode type. In addition, this teaching fails to provide examples of potting material that can be used.