Mitsui Minings & Melting Co., Ltd.

Shinya Furuki

Kiyoshi Yamagishi

Atsushi Koike

Takayuki Takahata

Hiromitsu Miyajima

Kenichi Hiraizumi

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.

Flowmeter

A flow metering method and a flowmeter capable of providing an electric output corresponding to the metered flow rate of metered fluid by an electric circuit including a thermal type flow sensor disposed in a metering flow path and an electric output corresponding to the reference flow rate of the metered fluid by an electric circuit including a reference thermal type flow sensor disposed in a reference flow path allowing the metered flow to flow freely; the flow metering method, comprising the steps of providing a calibration curve including a reference flow calibration curve and a measurement flow calibration curve at a plurality of temperatures for reference fluid beforehand, providing the deviated amount of the temperature of the reference flow calibration curve from the reference temperature corresponding to the electric output based on the electric output corresponding to the reference flow calibration curve based on the deviated amount, and converting the temperature corrected amount to the flow value of the metered fluid based on the electric output corresponding to the metered flow rate of the metered fluid by using the measured flow rate calibration curve of the reference temperature and by allowing for the temperature corrected amount.

Flow metering method and flowmeter

A thermal flowmeter is provided with a flow rate detecting unit ( ) containing a heating element, a flow rate detecting temperature sensing element and a flow rate detecting electroconductive fin plate ( ) extending into a fluid flow passage ( ), which are disposed so as to enable heat transfer therebetween, the flow rate detecting temperature sensing element varying in electrical characteristic value in accordance with the flow of the fluid in the fluid flow passage ( ); and, a fluid temperature detecting unit ( ) containing a fluid temperature detecting temperature sensing element and a fluid temperature detecting electroconductive fin plate ( &prime;) extending into the fluid flow passage ( ), which are disposed so as to enable heat transfer therebetween, the fluid temperature detecting temperature sensing element varying in electrical characteristic value in accordance with the temperature of the fluid. The flow rate of the fluid is detected on the basis of the electrical characteristic values of the flow rate detecting and fluid temperature detecting temperature sensing elements, and a fluid discrimination is effected by determining a conductivity between the flow rate detecting and fluid temperature detecting fin plates ( &prime;). According to this thermal flowmeter, with simple constitution, discrimination of whether the fluid is the required one or not is effected so that passage of erroneous fluid can be avoided.

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Ageo, Japan

Shinya Furuki