A liquid sensor includes a light receiver configured to receive light. The light receiver is attachable to an outside of an accommodation unit into which a liquid is introduced and which has translucency. The light receiver receives light that has passed through the liquid in the accommodation unit or light reflected by the liquid, and outputs a signal related to a physical quantity of the liquid.

An incubation cassette for reducing liquid evaporation from wells of a microplate with a frame for receiving a microplate with wells, the frame having a central first opening surrounded by an inner wall, the dimensions are designed for inserting a microplate, and the frame having an outer wall that runs essentially parallel to the inner wall and which is attached to the inner wall connects so that a liquid reservoir surrounding the first central opening for receiving a liquid is formed by the two walls and the intermediate base is disclosed. The incubation cassette also includes a float provided in the liquid reservoir that can be brought into fluid contact with the liquid held in the liquid reservoir in such a way that the float is in relation to the liquid level of the liquid in the liquid reservoir absorbed liquid experiences buoyancy.