Device and method for detecting characteristics of a fluid

A method for detecting characteristics of a fluid which is to be examined, by:

• emitting several light beams from a light source, of which one of the light beams is a measurement beam, which is emitted for passage through the fluid, and another light beam is a reference beam, which is emitted for bypassing the fluid,
• driving a movable cover device, arranged downstream of the light source, into a first position, releasing the measurement beam and covering the reference beam,
• detecting the light beams, let through by the cover device, with a light detector, arranged downstream of the cover device,
• driving the movable cover device into a second position covering the measurement beam and releasing the reference beam, and detecting the light beams let through by the cover device with the light detector,
• driving the movable cover device into a third position and detecting the light beams let through by the cover device with the light detector, and in third position of the movable cover device, the light beams emitted from the light source are covered differently compared to the first position and to the second position of the movable cover device,
• wherein an output parameter of the light detector, influenced by the light beams, is different when the movable cover device is in the third position than the output parameter of the light detector when the movable cover device in the first position and in the second position, and
• comparing the output parameters of the light detector in the first position, the second position and the third position of the cover device using a processing unit arranged downstream of the light detector, for detecting a motion blockade of the cover device.