Immersion probe having variable path length

Abstract

An immersion probe () for the quantitative and/or qualitative analysis of a fluid (F), e.g., a liquid or a gas, using light which is guided through the fluid (F) along a light path (L), comprising a measuring head () suitable for immersion in the fluid, having an input light guide () for the light guided to the fluid (F), which input light guide can be connected to a light source, and an output light guide () for the light guided out of the fluid (F), which output light guide can be connected to a detector, a first and a second optical window, the mutually facing faces of which are in contact with the fluid, and at least one light deflection device (), which is arranged in the light path of the light exiting the input light guide () and entering the output light guide () and deflects the light coming from the input light guide () through the first optical window into the fluid and deflects the light coming from the fluid to the output light guide (). The immersion probe is characterized in that the first and the second optical window () are arranged with respect to each other in a wedge shape, and their surfaces (,) pointing toward the interior of the V face the fluid (F) to be analyzed, the at least one light deflection device () and the optical windows () being able to move back and forth relative to each other substantially in the direction of the opening of the V.