Oxygen monitoring

The Applied Analytics TDL-506 oxygen monitoring system uses surface-emitting laser technology to produce accurate, fast and stable oxygen measurements in even the most 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. Rugged and power efficient, the vertical-cavity surface-emitting laser (VCSEL) housed in the TDL-506 provides this ability. This system is constructed specifically to monitor the R-branch of the oxygen A-band at 760 nm, minimising interference and optimising detection resolution.

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 minimises interference from other stream components and the fast scan time allows the analyser to enhance the signal-to-noise ratio.

Any analyser is only as competent as the design of its sampling mechanism. Engineered to account for flow rate variations, dramatic pressure/temperature fluctuations, stream pollutants and other harsh process realities, the TDL-506’s close-coupled sampling 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 analysers which measure across the pipeline, the TDL-506 can be regularly zeroed to ensure accurate concentration readings over the long term. The method also steers clear of the pitfalls of extraction sampling, where the sample is dried, cleaned and inevitably diluted before measurement.