Method and arrangement for determining the absolute humidity of gases

In such a method or in such an arrangement, a laser beam is emitted within a prescribed frequency spectrum and split into a measurment beam, which passes through the gas to be investigated, and a reference beam. The intensities of these component beams and the intensity of the radiation reflected out of the gas to be investigated are measured by detectors and fed to a computer, and the absorption of the gas to be investigated is determined as a function of a comparison of the measured values of intensity in a frequency range characteristic of water, and as a function thereof the absolute humidity is determined. The measurement beam is moved cyclically in order to scan a sector of area transverse to the direction of transmission of the measurement beam with the aid of a scanner device, and the moving transmission and reflection beams are captured by detectors after exiting from the gas to be investigated, and the measured values are fed to the computer.