Airflow Sensor Assembly with Pneumatic Autozero for Offset Calibration

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Solution Overview

Problem

Airflow sensors in air ducts exhibit offset readings, leading to inaccurate measurements, especially at lower airflows, and these offsets can change over time, causing errors despite initial calibration.

Innovation Solution

An airflow sensor assembly with a pressure redirection device and a controller that pneumatically couples high and low pressure pickup devices to determine and adjust for offset values, allowing for periodic recalibration and providing accurate airflow measurements by subtracting the offset from the sensor readings and applying a gain value.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Extent of automation

If a pressure redirection device with solenoid is added to provide autozero function, then periodic and automatic calibration is achieved, but the device complexity increases

Engineering Contradiction:

Improveautomatic calibration capabilityVSAvoidsensor assembly complexity

Core Design Contradiction:

Extent of automationVSDevice complexity

Solution Approach 1:

The solenoid valve acts as an intermediary component that enables automatic offset calibration by periodically isolating the sensor from differential pressure. This intermediary device allows the system to perform self-calibration, achieving high automation despite the added component complexity.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The system uses pneumatic components (solenoid valve, pressure redirection device) to automatically control the calibration process. The solenoid valve pneumatically redirects pressure paths to isolate the sensor for offset measurement, providing automated calibration functionality. The pneumatic approach enables reliable automatic operation with simple control logic.

Inventive Principle:

Principle #29Pneumatics and hydraulics

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

The solution ensures accurate airflow measurements by automatically calibrating the sensor offset, reducing errors and maintaining precision over time, even at lower airflow rates.

Implementation Method 1

The pressure redirection device is pneumatically coupled to the high pressure pickup device and the low pressure pickup device

Methodology Applied

Scientific EffectPneumatics:

Implementation Method 2

a differential pressure sensor

Methodology Applied

Scientific EffectDifferential pressure sensing:

Data Source

PatentEP3896403A1Ecoair valve with pneumatic solenoid to provide autozero function for air velocity pressure sensor

Publication Date: 2021.10.20 JOHNSON CONTROLS TYCO IP HLDG LLP

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AI summary

An airflow sensor assembly for an air duct is provided. The airflow sensor assembly includes the air duct having an interior wall and an exterior wall, a high pressure pickup device, a low pressure pickup device, a pressure redirection device, and a pressure sensor. The pressure redirection device is fluidly coupled to the high pressure pickup device and the low pressure pickup device and includes a low inlet, a high inlet, and a common outlet. The pressure sensor is selectively fluidly coupled to the high pressure pickup device and the low pressure pickup device and includes a first inlet and a second inlet. The second inlet is fluidly coupled to the common outlet of the pressure redirection device.