Optical Gas Sensor Segmented Enclosure Design

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Solution Overview

Problem

Existing optical gas sensing apparatuses face challenges in maintaining accuracy due to small variations in fluid composition outside the measurement path and the need for explosion-proof housings, which can be bulky and cause optical disturbances, requiring thick lenses and costly purging gases.

Innovation Solution

A spectroscopic gas sensing apparatus with a smaller explosion-proof enclosure for the light transmitting element, separating the electronics and sensing components, allowing a thinner light transmitting element and a constant gas composition along the light path, reducing optical disturbances and eliminating the need for costly purging gases.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a traditional explosion-proof housing is used to enclose the laser transmitter and receiver, then safety is improved, but the housing becomes bulky and causes optical disturbances requiring thick lenses

Engineering Contradiction:
Improveexplosion-proof safetyVSAvoidhousing volume
Core Design Contradiction:
ReliabilityVSVolume of moving object

Solution Approach 1:

The patent divides the traditional single explosion-proof housing into two separate enclosures: a first explosion-proof enclosure for the laser transmitter and a second explosion-proof enclosure for the laser receiver and electronics. This segmentation reduces the volume of each individual housing while maintaining overall safety, and eliminates the need for thick light transmitting elements by separating the optical path from the bulky housing structure.

Inventive Principle:
Principle #1Segmentation

2Reliability

If a traditional explosion-proof housing is used, then safety is improved, but optical disturbances increase requiring costly purging gases

Engineering Contradiction:
Improveexplosion-proof safetyVSAvoidpurging gas cost
Core Design Contradiction:
ReliabilityVSLoss of substance

Solution Approach 1:

By segmenting the housing into two separate enclosures with dedicated optical paths, the patent eliminates the need for purging gases that would otherwise be required to maintain optical quality in a single large housing. The separation allows each enclosure to be optimized independently, removing the substance loss associated with purging gases.

Inventive Principle:
Principle #1Segmentation

3Device complexity

If the light path is exposed to ambient gas composition variations, then device complexity is reduced, but measurement accuracy deteriorates

Engineering Contradiction:
Improveenclosure structureVSAvoidgas composition measurement accuracy
Core Design Contradiction:
Device complexityVSMeasurement precision

Solution Approach 1:

The patent uses segmentation to create a controlled optical path environment within the two separate enclosures, isolating the measurement path from ambient gas composition variations. This allows high measurement precision to be achieved without excessive device complexity by localizing the controlled environment only where needed for the optical path.

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 design enhances optical performance by using a thinner light transmitting element and maintaining a constant gas composition, improving measurement accuracy and reducing the risk of explosions while adhering to explosion-proof standards.

Implementation Method 1

Gas absorption spectroscopy generally measures the presence and/or concentration of a species of interest in a gas sample by passing a light beam through the sample and detecting the absorption at wavelengths of a particular spectral absorption feature of the species of interest

Methodology Applied
Scientific EffectAbsorption spectroscopy: Absorption Spectroscopy

Implementation Method 2

Light from the laser transmitter is directed towards gas in a target zone, reflected from a reflector, and received back at the laser receiver

Methodology Applied
Scientific EffectLight reflection: Reflection

Data Source

PatentEP3198261B1Optical gas sensing apparatus with explosion-proof enclosure
Publication Date: 2019.08.21 ROSEMOUNT INC
  • EP3198261B1 patent drawingFigure 1
  • EP3198261B1 patent drawingFigure 2

AI summary

An optical gas sensing apparatus (100) includes an explosion-rated device electronics enclosure (104). An explosion-rated sensing enclosure (108) has a light transmitting element (116) to allow light to pass out of and into the sensing enclosure. The sensing enclosure (108) is operably coupled to the explosion-rated device electronics enclosure (104) by a feed-through (122). In one aspect, an internal volume of the sensing enclosure (108) is less than or equal to about one fiftieth of the volume of the explosion-rated device electronics enclosure (104). In another aspect, the thickness of the light transmitting element (116) is less than or equal to about 3 millimeters. A light source (110) is disposed within the sensing enclosure (108) and is operably coupled to the device electronics (102). A detector (111) is disposed within the sensing enclosure (108) and is also operably coupled to the device electronics (102).