Abstract: Disclosed is method for determining the concentration of constituents in a fluid, such as cutting fluids or HFC fluids, using refractometry by means of a laser of a measuring device that uses the transmitted light principle, comprises specifying a peak value for the laser light received by refraction on a photodiode line using a homogeneous fluid to be transilluminated, and keeping the peak value constant despite the occurrence of disturbances by adapting one or more of the duty cycle of the laser, the current intensity for the laser, and the sensitivity of the photodiode line.

Abstract: Disclosed is a measuring apparatus for determining the concentration of constituents in a fluid, such as cooling lubricants or HFC hydraulic liquids, by refractometry, wherein the fluid present for measuring is guided through a sample chamber, which is connected to a fluid inlet and a fluid outlet and which is at least partially transparent such that the beams of a light source, for example in the form of a laser, passing through the sample chamber containing the fluid at least partially experience a refraction and can be detected by a sensor device outside the sample chamber.

Abstract: A valve device having a valve housing (4), in which a hollow valve part (6) is guided in a longitudinally movable manner, which valve part, controlled by an actuating device (8,14), in at least one open position opens the fluid path through the valve between a fluid inlet (E) and a fluid outlet (A) along a predeterminable flow path for a fluid and in a closed position, in which the valve part (6) is in contact with a valve closing part (10) from which it lifts off in the respective open position, blocks this fluid path, is characterized in that there is at least one flow guide device causing an at least partial reversal of direction in the flow path of the fluid emerging from the valve part (6) as soon as the latter assumes an open position.