Product Introduction: The variable optical path transmission immersion probe can be used for online measurement of liquid absorption rate. The optical path of this probe with an outer diameter of 1/2 inch can be set by the user within the range of 0.5mm to 20mm, making it extremely versatile for high or low absorption liquids. As long as the probe tip is immersed in the liquid, the measurement can be carried out. The light from the light source can be coupled into a fiber bundle consisting of 6 fibers through a standard connector, and then transmitted all the way to the end of the probe, where it is reflected by a diffuse white material through a user-defined physical gap of 0.25-10mm. The reflected light enters the seventh detection fiber, which conducts the detected data into the spectrometer through a connector. In order to maximize the detection efficiency of the probe, the detection fiber at the end of the probe is placed in the middle of the illumination fiber. All fiber bundles are installed in a flexible stainless steel sleeve. The fiber bundle is divided into two parts in the metal part of the probe, and connected to the spectrometer and light source through a one meter long fiber.