The new Yokogawa TruePeak Tunable Diode Laser Spectroscopy (TDLS) analyzers are one of the most robust process analyzers available, designed to make fast accurate measurements on near-infrared absorbing gases in harsh process environments including high temperature or pressure, environments involving corrosive gases and high particulate content typically without sample conditioning. Most applications are measured in-situ, reducing installation and maintenance costs. In addition, most measurements are rapid (5 seconds) and interference free, offering improved accuracy when compared to other process analyzers.
There is no sensor to come into contact with the process and no moving parts, providing a high MTBF (Mean Time between Failures) and a low cost of ownership. It offers a range of flexible installation options, materials of construction and features on-board diagnostics and validation methods. A unique alignment method allows adjustment without compromising the process seal. TruePeak measurement ensures accuracy even during simultaneous sample pressure, temperature, and background gas changes.
Tunable Diode Laser Spectroscopy (or TDLS) measurements are based on absorption spectroscopy. The TruePeak Analyzer operated by measuring the amount of laser light that is absorbed (lost) as it travels through the gas being measured. In the simplest form a TDLS analyzer consists of a laser that produces infrared light, optical lenses to focus the laser light through the gas to be measured and then on to a detector, the detector, and electronics that control the laser and translate the detector signal into a signal representing the gas concentration.
Gas molecules absorb light at specific wavelengths, called absorption lines. This absorption follows Beers law. TDLS Analyzers are effectively infared analyzers which obey the Beer-Lambert Law.
The TruePeak measurement integrates the area of the absorbance rather than measuring peak height or peak width value alone. This means you get a true interference free analysis.
Using a tunable diode laser as a monochromatic light source offers the benefits of sensitivity, selectivity to resolve single absorption lines, and power to overcome the effects of optically thick environments with high particulate.
Sensitivity. Application Dependant. Sub-PPM in some applications.
Selectivity. The narrow line width of the laser is able to resolve single absorption lines. This provides more choices of a particular peak to use for measurement, usually allowing one isolated peak to be used.
Power. Diode lasers have power ranging from 0.5mW to 35mW. Also, being highly coherent this allows measurement in optically thick environments (high particulate loading).
Monochromatic. No dispersive element (filter, etc.) required. Light source itself is selective.
Tunable. Wavelength can be swept across the entire absorption feature; this allows resonant (peak) and non resonant (baseline) measurement during every scan. By measuring the baseline and peak, power at the detector can fluctuate rapidly by large amounts without affecting the measurement. This is useful for high particulate applications.
