Patent ID: 7058532

Claim:
A flowmeter having an indirectly heated type flow rate sensor unit in which a flow rate detector containing a heating element and a temperature sensing element for flow rate detection is joined to a heat transfer member for flow rate detection, a fluid flow rate value being achieved with calibration curves on the basis of the output of a detection circuit using a bridge circuit containing the temperature sensing element for flow rate detection as a constituent resistor, characterized in that said bridge circuit includes circuit characteristic value variation driving means for varying the circuit characteristic value thereof in plural steps, plural calibration curves are provided in association with the respective steps of the circuit characteristic value, any one of the plural calibration curves is selected in conformity with the step of the circuit characteristic value selected by said circuit characteristic value variation driving means, a fluid flow rate range to be measured is set every calibration curve, the overall measurement flow rate range is covered by the plural fluid flow rate ranges, and said circuit characteristic value variation driving means is controlled in accordance with the fluid flow rate value achieved to use one of the calibration curves corresponding to the flow rate range to which the flow rate value belongs.