AAI's TDL-506 oxygen analyzer features a tunable diode laser

AAI presents a cost-effective solution for users' oxygen monitoring needs, the TDL-506. Harnessing the potential of surface-emitting laser technology, this system is built to produce accurate, fast and stable oxygen measurements in volatile process streams.

The TDL-506 is named for its core component, the tunable diode laser. The ability to emit high-intensity light at a specific wavelength is critical for monitoring the sharp, isolated absorbance peaks that are characteristic of diatomic oxygen. The vertical-cavity surface-emitting laser (VCSEL) housed in the TDL-506 provides this ability. The system is constructed specifically to monitor the R-branch of the oxygen A-band at 760 nm, minimizing interference and optimizing detection resolution.

The laser diode is a semiconductor device that converts electrical current into coherent, monochromatic light. The light emitted from the diode is all of one specific wavelength, and all waves are in phase with one another. The spectroscopic value of employing a laser as an optical pump is that all light passing through the sample is of the same, highly precise wavelength, enabling the system to monitor sample absorbance at one extremely well-defined spectral region. For a component such as oxygen, with very sharp and narrow absorbance peaks, the capacity for isolating these high-absorbance lines is critical for monitoring component concentration.

In the TDL-506, the VCSEL is tuned using current to the exact wavelength that coincides with the absorption A-band of oxygen (around 760 nm). This sharp wavelength selectivity minimizes interference from other stream components, and the fast scan time allows the analyzer to enhance the signal-to-noise ratio.

Engineered to account for flow rate variations, dramatic pressure/temperature fluctuations, stream pollutants and other harsh process realities, AAI's close-coupled sampling procedure ensures greater accuracy and maintenance-free performance than systems relying on cross-spec or extraction sampling.

The TDL-506 is close-coupled to a chimney and measures directly on the stack. The probe draws a continuous sample from the process stream into the flow cell via a membrane that filters out interfering particles. Unlike cross-spec analyzers that measure across the pipeline, the TDL-506 can be regularly zeroed to ensure accurate concentration readings over the long term.

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