Patent ID: 9683926
Date: 2017-06-20
CPC Classifications: G01N

Claim:
1. An exhaust gas sampling method using an exhaust gas sampling apparatus, the exhaust gas sampling apparatus including a constant volume sampling part that is configured to sample mixed gas that is controlled to have a constant flow rate, wherein the constant volume sampling part comprises a main flow path that is connected with an exhaust gas flow path through which exhaust gas flows and a diluent gas flow path through which diluent gas flows, and intended to flow the mixed gas that is a mixture of the exhaust gas and the diluent gas, a constant flow rate mechanism that is provided in the main flow path, and configured to control a flow rate of the mixed gas flowing through the main flow path to the constant flow rate and enable the constant flow rate to be changed, wherein the constant flow rate mechanism includes a plurality of flow rate adjusting parts that respectively have different flow rates and are connected mutually in parallel, and a switching mechanism that switches to at least one of the plurality of flow rate adjusting parts to flow the mixed gas, a sampling flow path that is connected to the main flow path to sample the mixed gas that is controlled to have the constant flow rate, and a moisture detecting part that is provided on an upstream side of the constant flow rate mechanism to detect moisture in the mixed gas or the diluent gas, the method comprising: on a basis of a moisture detected value obtained by the moisture detecting part, operating the switching mechanism to switch to at least one of the plurality of flow rate adjusting parts to flow the mixed gas and to adjust a dilution ratio of the exhaust gas, wherein before an exhaust gas sampling measurement the dilution ratio is adjusted by gradually increasing or decreasing the dilution ratio to make the moisture detected value closer to a predetermined reference value, and after the adjustment of the dilution ratio, the exhaust gas sampling measurement is started.