Method and apparatus for intelligent airflow sensors

Inventors

Forbes, Charles E. • Coifman, Robert E.

Assignees

Respiratory Sciences Inc

Abstract

A sensor capable of detecting both airflow in spirometry and a full range of sound frequencies is provided. The airflow sensor includes a movable flap with one or more integrated strain gauges for measuring displacement and vibration. The sensor may be a bidirectional elastic flap airflow sensor that is capable of providing data needed for both spirometry and auscultation measurements. The sensor is provided in connection with a software module that analyzes sensor output waveforms and provides for correction functions that correct for certain non-linear response functions of the flap. The correction functions are also suitable for non-medical fluid flow metering applications. Additional devices may also be affixed to the flap, such as sensors for the ambient level of various chemicals, sensors for temperature, sensors for humidity and microphones.

Core Innovation

The invention relates to a fluid flow sensing system in which fluid passes through a housing chamber and causes a flap to move when the fluid passes thereover. A sensor coupled to the flap generates an output signal when the flap moves and is configured to sense a displacement of the movable flap in at least two directions. A determining unit receives the sensor output signal and determines flow rate data associated with the fluid from the sensed displacements.

The system includes a correction unit that receives the flow rate data and applies a correction function to correct a non-linear response of the flap. The non-linear response is described as an exponential decay of the flap response, and the correction function corrects the exponential decay. In another implementation, the non-linear response is described as baseline drift of the flap response, and the correction function corrects for the baseline drift.

The correction function is applied to compensate for the flap non-linearity using an empirically determined correction function. In particular sensor implementations, the sensor is a piezoresistive sensor and the determining unit includes voltage conversion, amplification, conversion into a digital output signal, and a calculation unit to determine air flow rate from the digital output signal. In another implementation, the determining and correction units are provided as software modules within a general-purpose computer coupled to the sensor.

Claims Coverage

The independent claims cover a fluid flow sensing system and methods for determining flow rate from a flap-displacement sensor, with correction of flap non-linear responses using defined correction functions. Across the independent claims, the inventive features include at least two-direction displacement sensing, flow-rate determination, and correction of exponential-decay or baseline-drift non-linearities, with further independent coverage for software implementation, piezoresistive signal processing, and machine-readable instructions.

Across the independent claims, flow rate data is determined from a displacement sensor coupled to a movable flap within a chamber, with the sensor sensing displacement in at least two directions. A correction unit applies a correction function to correct flap non-linear response, including exponential-decay correction and baseline-drift correction, with further independent coverage of empirically determined correction functions, piezoresistive signal processing to derive air flow rate, and determination/correction implemented as software modules or via machine-readable executable instructions.

Stated Advantages

Documented Applications