System and method for multi-gas sensing at several operating temperatures
A system and a method for multi-gas sensing using dielectric excitation of a single sensing material at multiple operating temperatures. By measuring dielectric excitation responses of the gas sensing material, enhanced multi-gas differentiation and differentiation can be achieved using fewer operating temperatures than would be used by the same MOS gas sensing material configured to perform multi-gas differentiation based on resistance responses alone. The disclosed gas sensors and gas sensing techniques enable improved response linearity, improved dynamic range, and reduced computational resource consumption for multi-gas quantitation relative to traditional resistance-based gas sensing methods. Present embodiments unexpectedly demonstrate MOS-based gas sensors that can differentiate between different gases using responses collected using at least two different operating temperatures, wherein this differentiation is superior in the differentiation between different gases and in baseline stability, as compared to the resistance response of the same gas sensing material at more than two operating temperatures.
1 . A gas sensor system for multi-gas analysis of a fluid sample, comprising:
a gas sensing element configured to operate at multiple temperatures and to contact the fluid sample;
a heating element coupled to the gas sensing element and configured to heat the gas sensing element;
a heater controller operatively coupled to the heating element and configured to control the heating element to heat the gas sensing element to each of the multiple temperatures while the gas sensing element contacts the fluid sample;
a measurement circuit operatively coupled to the gas sensing element and configured to provide dielectric excitation to, and to measure dielectric excitation responses of, the gas sensing element while the gas sensing element is heated to each of the multiple temperatures and contacts the fluid sample, wherein the measured dielectric excitation responses provide enhanced differentiation between at least two gases and improved response linearity to the at least two gases in the fluid sample as compared to resistance responses of the gas sensing element when contacting the fluid sample at each of the multiple temperatures; and
a data processing unit, comprising:
a memory configured to store program instructions; and
an on-board data processor communicatively coupled to the memory and the measurement circuit, wherein the on-board data processor is programmed to execute the program instructions to receive, from the measurement circuit, the dielectric excitation responses of the gas sensing element at each of the multiple temperatures while the gas sensing element contacts the fluid sample in real-time.
2 . The gas sensor system of claim 1 , wherein the on-board data processor is configured to select at least two of the dielectric excitation responses of the gas sensing element at each of the multiple temperatures to differentiate the at least two gases in the fluid sample.
3 . The gas sensor system of claim 2 , wherein the at least two selected dielectric excitation responses are impedance responses of the gas sensing element at each of the multiple temperatures.
4 . The gas sensor system of claim 2 , wherein the at least two selected dielectric excitation responses are not resistance responses.
5 . The gas sensor system of claim 2 , wherein the on-board data processor is configured to differentiate the at least two gases by determining respective classifications, respective concentrations, or a combination thereof, of the at least two gases in the fluid sample based on the at least two selected dielectric excitation responses of the gas sensing element at each of the multiple temperatures.
6 . The gas sensor system of claim 1 , wherein the measurement circuit is configured to measure the dielectric excitation responses of the gas sensing element at multiple pre-selected frequencies at each of the multiple temperatures.
7 . The gas sensor system of claim 6 , wherein, at each pre-selected frequency and at each of the multiple temperatures, the measurement circuit is configured to measure dielectric excitation responses of the gas sensing element that are correlated with concentrations of a particular gas of a plurality of gases in the fluid sample.
8 . The gas sensor system of claim 1 , wherein the gas sensing element comprises:
a substrate, wherein the heating element is coupled to the substrate;
a single sensing material disposed on the substrate and configured to contact the fluid sample; and
electrodes coupled to the single sensing material and electrically coupled to the measurement circuit, wherein the electrodes are configured to apply, to the single sensing material, the dielectric excitation provided by the measurement circuit, and wherein the measurement circuit is configured to measure the dielectric excitation responses of the single sensing material at each of the multiple temperatures via the electrodes.
9 . The gas sensor system of claim 8 , wherein the single sensing material is a semiconducting metal oxide material.
10 . The gas sensor system of claim 1 , wherein the multiple temperatures comprise at least two different temperatures.
11 . The gas sensor system of claim 1 , wherein the at least two gases in the fluid sample comprises at least two analyte gases or at least one analyte gas and at least one interfering gas.