Abstract: The invention relates to a device and a method for the continuous optical determination of the fill level of liquids in a liquid tank of a vehicle or airplane which have a refractive index of at least 1.33 at room temperature and at a wavelength of 589 nm. The device has an elongate measurement channel (3) which can be arranged on or in a liquid tank. A light emitting means (8, 8?) is arranged such that light (13, 14) emitted by the light emitting means (8, 8?) is introduced into the measurement channel (3). A detector arrangement (12, 8?) is arranged such that light (10) emitted into the measurement channel (3) by the light emitting means (8, 8?) is incident on the detector arrangement (12, 8?). The wall (15) which defines the measurement channel (3) is designed such that the reflection coefficient for light of the predetermined wavelength or from the predetermined wavelength range is at least 70%, at least for an angle of incidence up to a predetermined limit angle.

Abstract: The present subject matter relates to the continuous optical determination of the fill level of liquids in a liquid tank of a vehicle or airplane which have a refractive index of at least 1.33 at room temperature and at a wavelength of 589 nm. A device embodiment has an elongate measurement channel in which the liquid in the tank can enter the channel and form a liquid column. A light emitting means is arranged to introduce light into the channel and pass at least partly through the liquid column Light emitted into the channel is incident on a detector arrangement after passing through at least a part of the liquid column. The wall defining the channel is designed to provide a reflection coefficient of at least 70% at the wall in the region of the liquid column at least for an angle of incidence up to a predetermined limit angle.