A flow-through measuring cell having one inlet opening for entry of the fluid, and one outlet opening for exit of the fluid. A single measurement space is located between the inlet opening and outlet opening. A radiation measurement region is provided for measuring the interaction of the fluid in the measuring cell with electromagnetic radiation from outside the measuring cell. The radiation measurement region is bordered by two opposite windows of which one is intended for inlet and the other for exit of the electromagnetic radiation. The measuring cell has a positioning range with several operating positions with a different distance A, A′ between the windows into which the measuring cell can be set without rotation.