Abstract: The invention relates to a method of eliminating the effect of temperature, air pressure and/or a disturbing material component or a like parameter in photometric analysis in which is generated a so-called dark signal, the passage of emitted radiation for detection being blocked at that time, a reference signal for one or more material components to be measured, said reference signal not being affected by said material component to be measured, as well as for each material component to be measured a measuring signal representing the amount of material component to be measured. According to the invention, whenever the difference between a reference signal and a measuring signal changes due to a change in any of the above parameters, there is generated a control signal which represents said parametric change and is proportional thereto, said control signal serving to change the difference between a reference signal and a dark signal in order to compensate for said parametric change.