Flow rate measuring method and flowmeter, flow rate measuring section package used for them and flow rate measuring unit using them, and piping leakage inspection device using flowmeter

摘要

Measurements are obtained by a computing unit based on an output Vh from an indirectly-heated constant-temperature controlling flow rate measuring section (16) and an output Vout from a two-constant-point temperature difference detecting flow rate measuring sections (18a, 18b). In the flow rate measuring section (16), a heating element (163) is feedback-controlled based on a detected temperature by a heat sensing element (162) to obtain an output Vh based on the feedback-controlled condition. An output Vout is obtained from flow rate measuring sections (18a, 18b) based on the detected temperature difference between a heat sensing element (182) disposed on the liquid-flow-direction upstream side of the flow rate measuring section (16) and a temperature sensing element disposed on the downstream side. A computing unit outputs as a measurement a flow rate obtained based on the output Vh in a flow rate region where a flow rate is larger than a predetermined boundary flow rate, and outputs as a measurement a flow rate obtained based on the output Vout in a flow rate region where it is less than a boundary flow rate. Accordingly, a flow rate is measured with good precision and sensitivity over a wide flow rate range from a trace-amount flow rate region to a comparatively large flow rate region.