Midac - Model V-Series -FTIR-based Moisture Analyzers System

• Low ppb detection of moisture in corrosive gases
• Complete immunity to the effects of atmospheric background moisture
• Rapid response and equilibration
• Multiple compound capability
• Transportable

MIDAC has delivered systems for on-line and R&D applications which have demonstrated lower detection limits of less than 10 ppb for H2O in matrices of HCl, HBr, and NF3. These results are attained in real-time with measurement intervals shorter than one-minute.

MIDAC has delivered systems for on-line and R&D applications which have demonstrated lower detection limits of less than 10 ppb for H2O in matrices of HCl, HBr, and NF3. These results are attained in real-time with measurement intervals shorter than one-minute.

FTIR is a proven technology for measuring moisture in corrosive gases. The traditional approach, however, has relied on purging the instrument with dry nitrogen to minimize errors introduced by background moisture. In contrast, MIDAC has designed the V-Series with a sealed and evacuable spectrometer compartment. Operating the instrument in a vacuum of 10-5 torr actually eliminates background moisture and the potential problems it creates. In addition, rapid evacuation rates enable V-Series analyzers to be set-up within 24 hours, compared to the two weeks usually required to attain a high quality purge.

Whether the evacuated or purged approach is used, detection limits in this realm would not be possible without an extremely high performance FTIR spectrometer. MIDAC has taken advantage of insights gained from years of DOE and SEMATECH funded research to optimize the sensitiviy of FTIR for measuring moisture in corrosive gases. Electronics enhancements such as a dual ADC providing 20 bits of dynamic range and a sensitive LN2 cooled InSb detector, (MCT and thermo-electrically cooled InAs detectors are also available), allow MIDAC systems to achieve signal-to-noise levels that are simply unattainable with off-the-shelf FTIR systems. In addition, all internal circuitry is designed for low energy dissipation for maximum durability under extended vacuum operation.

Complementing their superior sensitivity, V-Series systems also exhibit very rapid response to changing sample conditions. Tests show the analyzer capable of coming to equilibrium from a 50 ppb moisture challenge in less than 2 minutes and drying back down to below detectable limits in less than 2 minutes. V-series instruments achieve these response rates by using custom MIDAC 3 meter pathlength gas cells optimized for moisture analysis. Among the unique features of these “moisture stingy” cells are electropolished interior surfaces and full penetration welds to virtually eliminate sample moisture retention, and evacuated end caps to prevent moisture permeation through seals.

Of course, any instrument designed and built to measure impurities in corrosive gas matrices must also be resistant to the corrosive effect of these compounds. The V-Series accomplishes this through the use of nickel-coated or solid nickel gas cells, gold mirror surfaces, KalrezTM O-rings, and material compatible windows. (Kalrez is a registered trademark of E. I. DuPont)

The V-Series features a rugged optical design housed in a hermetically sealed chassis for maximum reliability in a variety of operating environments. In fact, the patented interferometer used in the V-Series is the same interferometer originally built for battlefield use aboard remotely-piloted vehicles and Blackhawk helicopters.

For some applications, operating the gas cell at temperatures up to 230oC can be advantageous. For these cases, a package including heater element, controller, insulating blanket and extended neck which thermally isolates the sample cell from electronics and internal optics is available. High performance turbo pumps, roughing pumps and vacuum gauges complete the hardware package.

The V-Series features a rugged optical design housed in a hermetically sealed chassis for maximum reliability in a variety of operating environments. In fact, the patented interferometer used in the V-Series is the same interferometer originally built for battlefield use aboard remotely-piloted vehicles and Blackhawk helicopters.

For some applications, operating the gas cell at temperatures up to 230oC can be advantageous. For these cases, a package including heater element, controller, insulating blanket and extended neck which thermally isolates the sample cell from electronics and internal optics is available. High performance turbo pumps, roughing pumps and vacuum gauges complete the hardware package.

Every aspect of V-Series development is motivated by the singular application of measuring moisture in corrosive gases — including software design. AutoQuant Pro and its Synthetic Process Control Module (AQ-SP) were specifically designed to automate and optimize moisture analysis using a MIDAC V-Series spectrometer. Spectral processing, quantification and trend analysis are provided in real-time, with consideration given to the non-linearities of water and its infrared spectrum. Absorbance spectra may be generated by means of a traditional background or by the use of a synthetic background spectrum. This synthetic background approach gives absolute quantification results, provides for "perfectly stable" spectra, and can improve sensitivity by a factor of 1.4. Spectra and quantitative results may be archived; and time of collection, concentration, and error analysis data may be later exported to any spreadsheet program (Excel, Lotus, etc.). Spectral files collected with AutoQuant Pro are compatible with Galactic Industries` Grams/32-AI software.

The V-Series also provides an important benefit of conventional FTIR technology: the abilitly to simultaneously analyze multiple components in the sample stream. This can be particularly beneficial in identifying and quantifying methane, carbon dioxide and other contaminants along with your moisture measurements.