Patent ID: 8440466

Claim:
A parameter setting method that is applied to a nitrogen oxide analyzer including a reactor in which an ozone-containing gas and a sample gas containing nitrogen oxide continuously introduced in a time-series order are mixed and the mixed gas is passed out through an output port, and a photo detector that detects a light intensity of chemiluminescence caused by the mixing, wherein the concentration of nitrogen oxide in the sample gas can be calculated based on the light intensity detected by the photo detector, the method comprising: producing a steady state by flowing a reference sample gas whose nitrogen oxide concentration is kept constant and a reference ozone gas whose ozone concentration is known at a constant flow rate instead of the sample gas and the ozone-containing gas respectively and by making the pressure in the reactor constant; gradually changing the ozone concentration alone in the steady state; obtaining a specific ozone concentration as being an ozone concentration in case that a change amount of the light intensity corresponding to the change of the ozone concentration becomes less than or equal to a predetermined minute amount; calculating a value that specifies a chemiluminscent response time constant intrinsic to the reactor and that determines a velocity of a response between nitrogen oxide and ozone based on the specific ozone concentration; and setting a relationship of parameters that determines an average resident time of the sample gas in the reactor so that the luminescence response is generated almost only in the reactor even though the ozone concentration of the ozone-containing gas changes within a predetermined range based on the value, wherein the parameters include the cubic volume of the reactor, the pressure in the reactor, the flow rate of the sample gas introduced into the reactor, and the flow rate of the ozone-containing gas introduced into the reactor.