FLOW RATE MEASURING METHOD AND FLOW METER

摘要

PROBLEM TO BE SOLVED: To provide a flow meter which can measure a flow rate with little measuring error even in a case that thermal property of fluid varies based on a change of fluid composition. SOLUTION: The flow meter is provided with a measuring flow rate detecting circuit which includes a thermal sensor 10 that is arranged in a measuring passage which makes fluid flowing being accompanied by introducing and leading of fluid to a case, and a referential flow rate detecting circuit which is arranged in the case and includes a thermal flow rate sensor 11 that is arranged in a referential passage so that the fluid can freely flow. A CPU converts to a flow rate value using a calibration line on referential fluid in a flow rate converting circuit based on a compensated output corresponding value that is obtained by compensating a measuring flow rate based on a referential flow rate corresponding value, from the measuring flow rate corresponding value that is obtained in a measuring flow rate detecting circuit based on the thermal interaction between fluid and a flow rate sensor 10 in a measuring passage and the referential flow rate corresponding value that is obtained in a referential flow rate detecting circuit based on the thermal interaction between fluid and a flow rate sensor 11 in a referential passage.