Cleaning system for probe unit

Self-cleaning probe for use in optical measurements in a flow containing a known liquid, the probe comprising a measuring cell defining a passage for the liquid to be measured to pass through, the probe including minimum a first and second optical interface on opposite sides of the passage, both being in communication with the known liquid, the probe comprising at least one optical light source emitting an optical signal and a detector for receiving an optical signal having propagated partly or fully through the liquid flow from the first to the second interface,

• wherein the optical interfaces are mechanically and acoustically coupled to each other and are acoustically coupled to at least one acoustic transducer connected to a power source, adapted to produce vibrations in the frequency range of 5 kHz-1 MHz, the vibrations being substantially perpendicular to the plane of the interfaces and the acoustic energy of the vibrations of the optical interfaces exceeding the cavitation threshold in the known liquid, so as to remove deposits on the optical interfaces.