In order to enable kinetic online measurements in cell cultures during exposure to altered gravitational stimulation a new device has been constructed. The analysis principle is based on photon counting with a photomultiplier tube (PMT). The system can work in a rotating mode (clinostat principle) as well as in 1 g conditions. Biological verification was successfully performed with a Luminol-based luminescence measurement of the immune reaction of mammal macrophages. An identical methodical approach is foreseen for an ISS experiment (TRIPLE LUX). Alteration of the rotation speed of the PMT clinostat (60 and 2 rotations per minute—rpm) resulted in a speed-dependent decrease of the luminescent signal, contributing to the current discussion whether and how fast rotation of a sample around one axis perpendicular to the direction of the g-vector provides the condition of functional weightlessness or omnilateral mechano-(gravi-) stimulation.