| 摘要 |
<p>©7 A gas analyzer for determining the concentration of the oxides of nitrogen in a sample gas, particularly exhaust from an internal combustion engine, comprises a sample chamber (11) and a reference chamber (12). Concentric tubes (14, 15) deliver to the sample chamber (11) sample gas together with ozone (03) which reacts with the NO in the sample gas to produce chemiluminescence. A planar sample photodiode (21) is disposed adjacent the sample chamber (11) to produce a sample signal representative of the total photoemissivity of the sample gas. A reference photodiode (22) is disposed adjacent to the reference chamber to provide a reference signal representative of the dark current of the photodiodes and the background photoemissivity of the sample gas. A circuit substracts the reference signal from the sample signal to produce an output representative of the concentration of the oxides of nitrogen in the sample gas. Dilution air is mixed with the sample gas either in the instrument with a viscous metering technique (101-104) or in a sample probe (66), mounted in the exhaust of the engine, with a sonic metering technique. In other embodiments, a single sample photodiode is used to measure the chemiluminescent reaction and determine the oxide of nitrogen content of the sample gas.</p> |
