US 2015/0020587 A1Published application

Temperature Compensation Module For a Fluid Flow Transducer

AssigneeHoneywell International Inc.

InventorsAndrew Joseph Milley, Lamar Floyd Ricks, Craig Scott Becke

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Abstract

Apparatus and associated methods relate to a temperature-compensated drive for a heating element used in a micro-bridge flow sensor. In some embodiments, the heating element may be located substantially between two temperature sensors. The two temperature sensors may be convectively coupled to the heater by a fluid ambient. When the fluid ambient is flowing, one of the temperature sensors may be upstream of the heating element, and one of the temperature sensors may be downstream. The fluid may be heated by the heating unit, and this heated fluid may then flow past the downstream temperature sensor. The two temperature sensors may be used in a Wheatstone bridge configuration. In some embodiments, an output signal of the Wheatstone bridge may be indicative of a measure of fluid flow. The temperature-compensated drive for the heating element may enhance, for example, the flow meter's disturbance rejection of ambient temperature.

Claims20

Dependent claims

A Micro ElectroMechanical Systems (MEMS) die, comprising:

a heating element configured to be substantially in direct thermal coupling with a fluid ambient;
a first temperature sensor configured to be substantially in direct thermal coupling with the fluid ambient;
a second temperature sensor configured to be substantially in direct thermal coupling with the fluid ambient, wherein the heating element is located substantially between the first temperature sensor and the second temperature sensor, and wherein the heating element is convectively coupled to the first temperature sensor and the second temperature sensor via the fluid ambient;
a differential amplifier configured to receive a first signal output by the first temperature sensor and a second signal output by the second temperature sensor, the differential amplifier having an output signal indicative of a flow of the fluid ambient, wherein the signal indicative of the flow of the fluid ambient has a temperature disturbance;
and,
a heating-element bias circuit comprising a temperature-varying reference and an amplifier, the temperature-varying reference having an output connected to an input of the amplifier, and wherein the temperature-varying reference output varies in response to a substrate temperature of the MEMS die,
wherein the heating-element bias circuit provides a temperature-varying bias that substantially compensates for the temperature disturbance of the signal indicative of the flow of the fluid ambient.

4 more elements

Dependencies are inferred from the claim text.

Facts

Application: 13/943,551Filed 16 Jul 2013
Published: 22 Jan 2015
Term ends: Not estimatedThe source records don’t support an estimate.

Classification6 codes

G01F 1/698
Circuits therefor, e.g. constant-current flow meters: feedback or rebalancing circuits, e.g. self heated constant temperature flowmeters
G01F 1/6845
Structural arrangements; Mounting of elements, e.g. in relation to fluid flow: micromachined devices
G01F 1/692
Of resistive type: thin-film arrangements
G01F 1/6965
Circuits therefor, e.g. constant-current flow meters: comprising means to store calibration data for flow signal calculation or correction