US 12,480,872 B2
Method for measuring a concentration of a gas and associated apparatus
Thomas Beyer, Freiburg (DE); and Julian Edler, Emmendingen (DE)
Assigned to SICK AG, Waldkirch (DE)
Filed by SICK AG, Waldkirch (DE)
Filed on Sep. 19, 2023, as Appl. No. 18/370,034.
Claims priority of application No. 22196656 (EP), filed on Sep. 20, 2022.
Prior Publication US 2024/0094122 A1, Mar. 21, 2024
Int. Cl. G01N 21/39 (2006.01); G01J 3/433 (2006.01)
CPC G01N 21/39 (2013.01) [G01J 3/4338 (2013.01); G01N 2201/121 (2013.01); G01N 2201/1273 (2013.01)] 18 Claims
OG exemplary drawing
 
1. A method for measuring a concentration of a gas in a gas mixture, said method comprising that:
a light beam modulated in a ramp shape and/or in a step shape in its wavelength and additionally periodically modulated is transmitted from a light source into a measurement zone;
the modulated light beam passes through a light-absorbing medium in the measurement zone and is detected as reception light by a detector, wherein the reception light is converted by the detector into a detector signal;
a derivative signal is determined based on the detector signal by performing a transformation of the detector signal into the frequency range wherein an evaluation of the detector signal transformed into the frequency range is performed for an n-fold of the frequency of the modulated light beam in order to obtain the derivative signal; and
at least two measurement values of a phase of the derivative signal are determined and a correction function is calculated based on the determined measurement values of the phase of the derivative signal in order to correct the derivative signal with the correction function.