Differential Pressure Airflow Measurement Without Long Ducts

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Solution Overview

Problem

Existing air flow measurement methods are either costly, complex to install, or limited in their ability to accurately measure air flow without requiring long ducts, necessitating a solution that balances accuracy with reduced costs and installation complexity.

Innovation Solution

An air flow measurement system utilizing digital processing to convert differential pressure measurements from both sides of a partial obstruction into flow values, with features like low pass filtering and zero offset compensation, and an inlet extension to reduce wind interference, allowing for accurate air flow measurement without expensive equipment.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If hot wire anemometers are used to measure air flow without requiring long ducts, then measurement capability is improved, but cost and installation complexity increase significantly

Engineering Contradiction:

Improveair flow measurement capabilityVSAvoidinstallation complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent replaces complex mechanical measurement systems (hot wire anemometers requiring precise temperature sensing and controlled heating) with a simpler differential pressure measurement system using a partial obstruction and pressure sensors. This substitution maintains measurement capability while dramatically reducing installation complexity and cost.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent employs inexpensive differential pressure sensors and a simple partial obstruction structure instead of expensive hot wire anemometers. The measurement arrangement uses readily available components that can be installed without specialized equipment or extensive calibration procedures.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

2Device complexity

If spring-biased door arrangements are used to measure air flow, then cost is reduced, but calibration complexity and installation procedures increase

Engineering Contradiction:

ImprovecostVSAvoidinstallation procedures

Core Design Contradiction:

Device complexityVSEase of manufacture

Solution Approach 1:

The patent replaces the mechanical spring-biased door system with an electronic differential pressure measurement system. Instead of measuring door position angle, the system directly measures pressure differential across a partial obstruction, eliminating the need for complex calibration of mechanical components and simplifying installation procedures.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Measurement precision

If traditional air flow measurement tubes are placed in long ductwork, then measurement accuracy is improved, but applicability is reduced when long ducts are not available

Engineering Contradiction:

Improvemeasurement accuracyVSAvoidapplicability without long ducts

Core Design Contradiction:

Measurement precisionVSAdaptability or versatility

Solution Approach 1:

The patent introduces a partial obstruction that segments the air flow path, creating measurable pressure differentials on either side of the obstruction. This segmentation allows accurate measurement without requiring long duct lengths, as the pressure differential is generated locally at the obstruction point rather than requiring extended ductwork for measurement tube placement.

Inventive Principle:

Principle #1Segmentation

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

This solution provides accurate air flow measurements while reducing costs and installation complexity, effectively addressing the limitations of prior methods by using digital processing and a partial obstruction to measure pressure differentials, and an inlet extension to minimize wind effects.

Implementation Method 1

a source of measurement values is operable to generate measurement values representative of a difference in pressure from air obtained on a first side of an obstruction and air obtained on a second side of the obstruction

Methodology Applied

Scientific EffectPressure differential measurement: Pressure Gradient

Implementation Method 2

The processing unit is configured to perform low pass filtering on the measurement values

Methodology Applied

Scientific EffectLow pass filtering: Filter (electronic)

Implementation Method 3

an inlet extension to reduce wind interference

Methodology Applied

Scientific EffectWind shielding: Wind

Data Source

PatentUS8006571B2Air flow measurement

Publication Date: 2011.08.30 SIEMENS INDUSTRY INC

AI summary

An arrangement for measuring air flow includes a source of measurement values and a processing unit. The source of measurement values is operable to generate measurement values representative of a difference in pressure from air obtained on a first side of an obstruction and air obtained on a second side of the obstruction. The processing unit is configured to, in one case, convert any negative measurement values of the measurement values to a less negative value. The processing unit is further configured to perform low pass filtering on the measurement values and convert the filtered measurement values to a flow value.