US 2014/0174154 A1 · GAS SENSING APAPRATUS

Abstract

A method of selectively sensing the concentration of a target gas in polluted ambient air comprises the steps of: —providing a target gas sensor (220) sensitive to the target gas; —providing a first gas flow derived from the ambient air, from which first flow the target gas is substantially removed; —providing a second gas flow derived from the ambient air, substantially comprising the same target gas concentration as the ambient air; —exposing the target gas sensor to the first gas flow during a first time interval, and obtaining from the sensor a first output signal (Smf); —exposing the target gas sensor to the second gas flow during a second time interval not overlapping with the first time interval, and obtaining a second output signal (Smu); —calculating the difference (SΔ) between the first and the second output signals; calculating the concentration of the target gas from the calculated signal difference (SΔ).

Claims15

Dependent claims

Method of determining the concentration of a target gas in ambient air, the method comprising the steps of:

providing a target gas sensor that is sensitive to at least the target gas;
providing a first gas flow derived from the ambient air, the target gas being substantially removed from the first gas flow;
providing a second gas flow derived from the ambient air, substantially without removing the target gas;
exposing the target gas sensor to the first gas flow, and obtaining from the target gas sensor a first sensor signal (Smf);
exposing the target gas sensor to the second gas flow, and obtaining from the target gas sensor a second sensor signal (Smu);
determining the concentration of the target gas from the first sensor signal and the second sensor signal.

3 more elements

Gas sensing apparatus for determining the concentration of a target gas in ambient air, the apparatus comprising:

at least one target gas sensor and a target gas filter;
at least one controllable gas flow generating means for generating a gas flow derived from the ambient air;
a control device for controlling the gas flow generating means and receiving measuring output signals from the target gas sensor;
the apparatus being able to selectively operate in at least two different operational modes;
wherein the control device is designed, in a first operational mode, to control the gas flow generating means to generate a first gas flow through the target gas filter to the target gas sensor, with the target gas sensor being downstream with respect to the target gas filter;
wherein the control device is designed, in a second operational mode, to allow a second gas flow to reach the target gas sensor, the second gas flow comprising the target gas in the same concentration as in the ambient air;
wherein the control device is designed to receive a first sensor output signal Smf from the target gas sensor in the first operational mode, and to receive a second sensor output signal Smu from the target gas sensor in the second operational mode, wherein the control device (240) is designed to determine the concentration of the target gas in the ambient air from the first sensor output signal Smf and the second sensor output signal Smu.

4 more elements

Gas sensing apparatus for determining the concentration of a target gas in ambient air, the apparatus comprising:

a series arrangement of a target gas filter and two gas sensors on opposite sides of the target gas filter, wherein a first gas sensor is arranged upstream of the target gas filter for providing a measuring output signal (Smu) relating to unfiltered ambient gas and a second gas sensor is arranged downstream of the target gas filter for providing a measuring output signal (Smf) relating to filtered ambient gas;
a calculating device receiving the measuring output signals from the gas sensors;
wherein the calculating device is designed to calculate a difference signal (SΔ=Smu−Smf) between the said two measuring output signals and to derive from said difference signal the concentration of the target gas in the ambient air.

Dependencies are inferred from the claim text.

Gas sensing apapratus

Life of this patent

Gas sensing apapratus

Life of this patent

Abstract

Claims15