The dissertation covered the task to develop the regulation of a light chopper and infrared source of light for a measuring system, which is used in the infrared spectrophotometry.

The light chopper, which is consisting of an electric motor and a sector disk, is used to synchronously interrupt an infrared ray of light to a reference signal. The regulation of the light chopper was realized with the help of the phase locked loop (PLL) technology. We worked out a system of two into one another working PLL circles, which ensure that the phase deviation between the reference signal and the actual signal never becomes larger than 4?. Two light barriers on the chopper disk, which permits an exact detection of the rotational disk speed and phase position, guarantee this.

For the regulation of the infrared source of light we had to develop a measuring element, which measured the light intensity, also the control circuit to drive the filament and the choice and dimensioning of a suitable controller. For the measuring device we were given a pyroelectric element, which opposite a photodiode, exhibited so many disadvantages that we decided to take the photodiode. We have chosen the technology of pulse width modulation for the control circuit of the filament. Considering the fact that we were switching currents up to 2A this seemed us to be the best solution. For the controller we have chosen a PI-Type. The system himself has a very slow-acting behaviour and does not need a fast controller and we also wanted to reach a zero static error.