A metering device for introducing liquid reducing agent into an exhaust gas pipe. A filtered sheet is displayed to the user, where the filtered sheet is obtained by applying the first filter to the unfiltered sheet. Further, a sample reservoir for injecting a sample therein is formed as a through hole on the sample introduction flow path at a position different from that of the loading buffer reservoir. The buffer controller can be set in a mode to receive any MOD size data and includes a first channel with a FIFO for receiving incoming data via a first interface.