An instrument for optically measuring at least one property of a test medium, includes a light source for emission of light, a light management unit for guiding the light onto and/or into and through a detection space in the test medium, a light detection unit for detecting a fraction of the light scattered, reflected or transmitted by the test medium, a power management unit, and a data management unit. The instrument further includes or is coupled to a power source via a source wiring. The power management unit distributes energy from the power source via a buffer wiring to the light source, and via a further wiring to the light detection unit and the data management unit. The data management unit exchanges measurement data via signal wiring with the light detection unit with a receiving unit. The instrument is adapted to be operated in a potentially hazardous environment.