Gas Analyzer and Method for Measuring Nitrogen Oxides in an Exhaust Gas

A gas analyzer for measuring nitrogen oxides in an exhaust gas comprising:

• an oxidation device comprising an ozone generator for generating ozone from oxygen and configured to treat the exhaust gas with the ozone to convert nitrogen monoxide within the exhaust gas into nitrogen dioxide;
• a first light-emitting diode which emits with a central wavelength of between 350 nm and 500 nm;
• a second light-emitting diode which emits with a central wavelength of between 250 nm and 265 nm;
• a measuring chamber through which the treated exhaust gas flows and light from the first light-emitting diode and light from the second light-emitting diode pass;
• a detector which detects the light from the first light-emitting diode and the light from the second light-emitting diode after said light passes through the measuring chamber and which generates a detector signal with a first signal component resulting from the light from the first light-emitting diode and a second signal component resulting from the light from the second light-emitting diode;
• an evaluation device which ascertains nitrogen dioxide concentration in the treated exhaust gas in the measuring chamber from the first signal component and outputs said concentration as the nitrogen oxide concentration in the exhaust gas and ascertains ozone concentration in the exhaust gas in the measuring chamber from the second signal component;
• and
• a regulating device which controls the ozone generator and obtains the ascertained ozone concentration as an actual value to regulate said concentration to a pre-specified setpoint value.