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Photometric Gas Analysis
Some gases absorb unique wavelengths (colours) of light. This property can be used to detect the concentration of a selected gas in a mixture.
A light source (usually in the ultraviolet or infrared range) is focussed through a sample cell containing a continuously flowing sample of the gas mixture to be measured and onto a detector.
Depending on application, this basic concept is applied in two different ways:
SBSW (Single beam single wave)
Used where a miniature transducer is required. The light source is electronically modulated, removing the need for a motor and rotating filters.
Benefits:
Fast response - used where real-time measurements are required, faster compared to commonly used alternative solutions, such as electrochemical techniques.
High stability and accuracy - a specially designed source and temperature control sensor.
Low maintenance requirements - quality manufacture and design.
(Gfc) Gas filter correlation
Used where extremely accurate low level measurements are required or where background gases have the potential to interfere with the measurement.
The measure and reference filters are replaced with gas filled cuvettes. The reference cuvette is filled with a sample of the gas to be measured, the measure cuvette with (typically) nitrogen. This technique is known as 'Gas Filter Correlation'.
Benefits:
Fast response - used where real-time measurements are required, faster compared to commonly used alternative solutions, such as electrochemical techniques.
High stability and accuracy - the single-beam, dual wavelength technique and gas filter correlation (Gfc) are virtually immune to obscuration of the optics. This prevents drift hence reducing calibration frequency.
Unaffected by background gases - a result of Servomex application expertise enhanced by the inherent selectivity of gas filter correlation.
Low maintenance requirements - quality manufacture and design.