US 11,892,396 B2
Gas sensor with two switchable filters and method for operating such a gas sensor
Håkon Sagberg, Oslo (NO); Britta Greenberg-Fismen, Oslo (NO); and Thor Christian Hobæk, Oslo (NO)
Assigned to Dräger Safety AG & Co. KGaA, Lübeck (DE)
Appl. No. 17/312,843
Filed by Dräger Safety AG & Co. KGaA, Lübeck (DE)
PCT Filed Dec. 12, 2019, PCT No. PCT/EP2019/084863
§ 371(c)(1), (2) Date Jun. 10, 2021,
PCT Pub. No. WO2020/120663, PCT Pub. Date Jun. 18, 2020.
Claims priority of application No. 1820293 (GB), filed on Dec. 13, 2018.
Prior Publication US 2022/0042903 A1, Feb. 10, 2022
Int. Cl. G01N 21/15 (2006.01); G01N 21/31 (2006.01); G01N 33/00 (2006.01)
CPC G01N 21/15 (2013.01) [G01N 21/31 (2013.01); G01N 33/0029 (2013.01); G01N 2021/158 (2013.01)] 15 Claims
OG exemplary drawing
 
1. A gas sensor configured and arranged to detect at least one target gas, wherein the gas sensor comprises
a light source configured and arranged to emit light,
a measurement volume,
a detector configured and arranged to receive light, and
an adaptable filter system,
wherein the measurement volume and the adaptable filter system are disposed in a light path between the light source and the detector,
wherein the adaptable filter system comprises a first optical filter and a second optical filter,
wherein the first filter is operable to switch between
a first reference state in which the first filter passes light according to a first reference wavelength profile and
a first measurement state in which the first filter passes light according to a first measurement wavelength profile,
wherein the second filter is operable, independently of the first filter, to switch between
a second reference state in which the second filter passes light according to a second reference wavelength profile and
a second measurement state in which the second filter passes light according to a second measurement wavelength profile,
wherein the first reference wavelength profile is different from the second reference wavelength profile, the adaptable filter system thereby being switchable between at least four different composite states, the composite states comprising:
a first composite state in which the first filter is in the first reference state and the second filter is in the second reference state,
a second composite state in which the first filter is in the first reference state and the second filter is in the second measurement state,
a third composite state in which the first filter is in the first measurement state and the second filter is in the second reference state, and
a fourth composite state in which the first filter is in the first measurement state and the second filter is in the second measurement state,
wherein the gas sensor is configured to switch the adaptable filter system between at least three of the composite states,
wherein the detector is configured and arranged to generate one respective detector signal corresponding to light received by the detector for every one of the at least three of the composite states used, and
wherein the gas sensor is configured to determine a presence of a contaminant other than the target gas in the light path between the light source and the detector by comparing with each other the respective detector signals generated during the at least three of the composite states.