Gas sensing apparatus

摘要

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).

主权项

1. 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.