The invention presents a differential pressure type emission flow rate measuring method and apparatus and an emission measuring system using the same apparatus, capable of correcting measuring error occurring due to pulsation appropriately and enhancing the measuring precision of flow rate when measuring the flow rate of emission having pulsation.
The invention, in measuring the flow rate of an emission exhausted from an engine, determines an accurate flow rate in spite of pulsation by using a differential pressure type flowmeter as the flowmeter, resolving the detected differential pressure signal by frequency, and correcting by using a correction coefficient predetermined depending on each frequency obtained by frequency resolution.