Gas sensing apparatus

Patent metadata

Field	Value
Publication number	US-9417207-B2
Application number	US-201214232323-A
Country	US
Kind code	B2
Filing date	Jul 9, 2012
Priority date	Jul 13, 2011
Publication date	Aug 16, 2016
Grant date	Aug 16, 2016

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).

First claim

The invention claimed is:

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.

2. Method according to claim 1 , wherein the second gas flow is unfiltered ambient air.

3. Method according to claim 1 , wherein at least one specific gas, or group of gases, or class of gases, not including the target gas, is substantially removed from both the first gas flow and the second gas flow.

4. Method according to claim 1 , wherein the first gas flow is generated by operating a controllable flow generator, and wherein the second gas flow is generated by switching off the controllable flow generator.

5. Method according to claim 1 , wherein the first gas flow is generated by operating a controllable flow generator in a first direction, and wherein the second gas flow is generated by operating the controllable flow generator in the opposite direction.

6. 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.

7. Apparatus according to claim 6 , wherein the control device is designed, in the second operational mode, to switch off the gas flow generating means to allow unfiltered ambient air to reach the target gas sensor convectively.

8. Apparatus according to claim 6 , wherein the control device is designed, in the second operational mode, to operate the gas flow generating means to generate a second gas flow in a direction opposite to the first gas flow direction.

9. Apparatus according to claim 6 , further comprising a second gas flow generating means, wherein the control device is designed, in the second operational mode, to operate the second gas flow generating means to generate a second gas flow in a direction opposite to the first gas flow direction.

10. Gas sensing apparatus according to claim 6 , further comprising a second gas filter, wherein the second gas filter is designed to remove from ambient air at least one specific gas or group of gases or class of gases, wherein the first target gas filter is designed to remove from ambient air the same gases as the second gas filter and also the target gas, and wherein in the first operational mode the sensor is downstream of the first target gas filter while in the second operational mode the sensor is downstream of the second gas filter.

11. Gas sensing apparatus according to claim 10 , further comprising a second set of target gas filter and second gas filter on opposite sides of the sensor, and further comprising controllable flow selection means for causing a gas flow to the sensor either via the first target gas filter or the corresponding second filter or via the second target gas filter or the corresponding second filter.

12. Gas sensing apparatus according to claim 6 , wherein the control device) is designed to regularly alternate between the first operational mode and the second operational mode.

13. Gas sensing apparatus according to claim 6 , wherein the target gas filter comprises a carrier structure having air passage channels, the carrier material being impregnated with an impregnant composition effective to absorb the target pollution component, and wherein, if the target pollution component is formaldehyde, the impregnant composition preferably comprises KHCO 3 , K 2 CO 3 , Trishydroxy-methyl-aminomethane, and Kformate.

14. 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.

15. Gas sensing apparatus according to claim 14 , further provided with an opening at a position downstream of the target gas filter and upstream of the second sensor, the opening being provided with a controllable closure device;
the apparatus comprising a control device for controlling the closure device;
wherein the apparatus is capable of operating in a calibration mode, in which the control device is designed to open the closure device and calculate a difference (Δ) between the two measuring signals (Smu, Smf) received from the two sensors, representing an offset between said two sensors;
and wherein the apparatus is capable of operating in a measuring mode, in which the control device is designed to close the closure device and calculate a compensated measuring output signal (SΔc) of the apparatus, representing the concentration of pollutant in the gas, according to the formula
SΔc=Smu−Smf−Δ

in which:
SΔc indicates the compensated measuring output signal;
Smu indicates the measuring output signal of the first gas sensor;
Smf indicates the measuring output signal of the second gas sensor;
Δ indicates the said difference calculated in the calibration mode.

Assignees

• Marra Johan
• Klootwijk Johan Hendrik
• Giesbers Jacobus Bernardus
• De Wild Nico Maris Adriaan
• Bulder Marcel
• Niessen Rogier Adrianus Henrica
• Van Der Linde Peter
• Koninklijke Philips Nv

Inventors

• Marra Johan
• Klootwijk Johan Hendrik
• Giesbers Jacobus Bernardus
• De Wild Nico Maris Adriaan
• Bulder Marcel
• Niessen Rogier Adrianus Henrica
• Van Der Linde Peter

Classifications

• G01N33/0006

  Calibrating gas analysers · CPC title

• G01N1/2273 Primary

  Atmospheric sampling · CPC title

• G01N27/4045

  for gases other than oxygen · CPC title

• G01N27/403 Primary

  Cells and electrode assemblies · CPC title