US 5,965,813 AGranted

Integrated flow sensor

AssigneeIndustry Technology Research Institute

InventorsYue-Min Wan, Ching-Yi Wu

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Abstract

A flow sensor comprises a heater module, a fluid temperature sensor and a Wheatstone bridge module. In the heater module, a heater is disposed very close to a heater temperature sensor and an insulation layer electrically isolates these two elements. The heater and the heater temperature sensor are disposed together on a floating membrane positioned normally to the fluid flow. The Wheatstone bridge module regulates electric current supplied to the heater, based on a constant temperature difference between the heater and the fluid, and provides voltage information of the electric current. A microprocessor converts the voltage information into velocity of fluid to be measured. A bypass channel is designed to adjust flow impedance of the fluid. Further disclosed is a fluid temperature sensor with the same design of the heater module whereby the factor of flow direction of the fluid may be ignored.

Claims9

Dependent claims

An integrated thermal flow sensor, comprising:

a channel for a fluid to be measured to flow through;
a fluid temperature sensor to measure a temperature of said fluid;
a heater to generate thermal energy, positioned inside said channel and connectable to said fluid;
a heater temperature sensor adjacent to said heater to measure a temperature of said heater;
a power supplier to supply electric current to said fluid temperature sensor, said heater, and said heater temperature sensor;
a regulator to regulate current supplied to said heater such that a substantial difference is maintained between the temperature of said heater and the temperature of said fluid, and to generate signals representing variations of current supplied to said heater;
a calculator to calculate velocity of said fluid according to the current variation signals generated by said regulator;
an insulation layer to electrically isolate said heater and said heater temperature sensor;
and
a floating element positioned substantially normally to said channel to support said heater and said heater temperature sensor.

7 more elements

Dependencies are inferred from the claim text.

Facts

Application: 09/120,725Filed 23 Jul 1998
Granted: 12 Oct 1999
Term ends: Not estimatedThe source records don’t support an estimate.

Classification5 codes

G01F 1/692
Of resistive type: thin-film arrangements
G01F 1/6842
Structural arrangements; Mounting of elements, e.g. in relation to fluid flow: with means for influencing the fluid flow
G01F 1/6845
Structural arrangements; Mounting of elements, e.g. in relation to fluid flow: micromachined devices
G01F 1/699
Feedback or rebalancing circuits, e.g. self heated constant temperature flowmeters: by control of a separate heating or cooling element