DEVICE FOR MEASURING THE LEVEL OF A LIQUID IN A VESSEL

摘要

The present invention relates to a device for measuring the level of a liquid in a vessel, wherein said device includes a laser, a photo-detector for receiving the laser beam reflected by the surface of the liquid as well as a laser beam-focusing member that consists of a lens located between the laser and the surface of the liquid. The ratio between the lens focal distance FL and the minimal distance hmin between said lens and the surface of the liquid is defined by the relation FL/hmin = 0.1 DIVIDED 0.2. The laser, the photo-detector and the lens are sealed apart from the vessel cavity using a planar diaphragm made of optical glass. The plane of the diaphragm is oriented at an angle not exceeding 90 DEG relative to the extreme ray, on the photo-detector side, of the laser beam which scattered after crossing said lens. The diaphragm is further fitted with a heating member.