Abstract: An apparatus (1) including two plates (3, 4) which can be rotated in relation to each other and between which the rheological properties of a test substance (6) disposed in an intervening area (5) can be determined. At least one of the plates (3) is provided with a light inlet (2) sealed by a body (8, 10) in order to carry out an optical measurement method, e.g., infrared spectroscopy, enabling other characteristics of the test substance to be determined simultaneously. The body (8, 10) is light permeable at least in the infrared spectrum, and on its side facing the intervening area (5), the body (8, 10) terminates in a flush contour relative to the to the plate (3) in which it is provided so that undesirable interactions which might affect the measurement of the rheological properties of the test substance (6) are reliably excluded.

Abstract: An apparatus (1) including two plates (3, 4) which can be rotated in relation to each other and between which the rheological properties of a test substance (6) disposed in an intervening area (5) can be determined. At least one of the plates (3) is provided with a light inlet (2) sealed by a body (8, 10) in order to carry out an optical measurement method, e.g., infrared spectroscopy, enabling other characteristics of the test substance to be determined simultaneously. The body (8, 10) is light permeable at least in the infrared spectrum, and on its side facing the intervening area (5), the body (8, 10) terminates in a flush contour relative to the to the plate (3) in which it is provided so that undesirable interactions which might affect the measurement of the rheological properties of the test substance (6) are reliably excluded.