Flowmeter

Abstract

A flowmeter for achieving a fluid flow rate value by using calibration curves on the basis of the output of a detection circuit using a bridge circuit () containing as constituent resistors respective temperature sensing elements of a flow rate detector containing a heating element () and a fluid temperature detector in an indirectly heated type flow rate sensor unit. The bridge circuit () varies the circuit characteristic value in plural steps by a multiplexer () for selectively connecting the output terminal and any one of the connection terminals between the in-series connected resistors. Plural calibration curves are provided in association with the steps of the circuit characteristic value, and any one of the plural calibration curves is selected in accordance with the step of the circuit characteristic value selected by the multiplexer (). The flow rate range to be measured is set every calibration curve, and the multiplexer () is controlled in accordance with the fluid flow rate value thus achieved, and the calibration curve corresponding to the flow rate range to which the flow rate value belongs. According to this flowmeter, the flow rate can be measured with excellent precision over a board flow rate range.