THERMAL FLOWMETER

摘要

PROBLEM TO BE SOLVED: To provide a thermal flowmeter that can, even if a gap is disposed to form a diaphragm in a flow rate detecting element, restrain a drop in measurement precision due to deformation of the diaphragm and contamination of its rear side.SOLUTION: A thermal flowmeter comprising a sub-passage for allowing measurement object gas let in from a main passage to flow and a flow rate detecting element for measuring the flow rate of the measurement object gas by transmitting heat to the measurement object gas flowing in the sub-passage is provided with at least a circuit package 400 including a flow rate detecting element 602. A gap 674 is formed in the rear face of the flow rate detecting element 602 to enable a diaphragm 672 to be formed in a flow rate detecting area 437 of the flow rate detecting element 602. The gap 674 is a sealed space kept lower in pressure than the atmosphere.