Further patent issued for encoded photometric infrared spectroscopy

Paul Boughton

Aspectricsa leading supplier of encoded photometric infrared (EP-IR) spectroscopy analysers has received a fifth US patent for its EP-IR disc technology and associated optics.

“This patent further strengthens the Aspectric EP-IR encoded disc technology and will allow Aspectrics to develop and deliver new EP-IR products to the marketplace in a more timely manner” said ceo Paul Salsgiver Jr.

The company continues to file additional patent applications covering its fundamental technology to cover recent improvements and variations on the various systemsadditional markets where the company may most effectively leverage its technologyand those features most often requested by its customers.

The company has dozens of patent applications currently pending and will bolster its portfolio with further filingsfrom its intellectual property counsel Fenwick and West.

Aspectrics EP-IR technology enables real-timeparts-per-billion monitoring of dozens of chemical components under hostile environmental conditions commonly found in industrial processes.

Applications under development by Aspectrics OEM customers using its EP-IR technology include ambient air and stack gas monitoringengine emission analysisfoods and semiconductor processes.

At the heart of the Aspectrics EP-IR analyser is a rotating disc onto which up to 256 concentric encoding tracks are used to encode dispersed radiationwhich is then collected and imaged onto a single-channel detector.

EP-IR spectroscopy relies upon a photometrically simpleyet rugged and efficient designwhere the incoming infrared beam from the sample is imaged on to a diffraction grating based spectrograph. The dispersed radiation from the grating is imaged across an aperture above the surface of a rotating encoder disk. The encoder disk has a series of reflective trackswhich are spatially located within the dispersed grating image to correspond to the wavelengths and wavelength regions used for the analysis

Each track has a pattern that produces a reflected beam with a unique sinusoidal modulation for each individual wavelength. The reflected beams are brought to an image on a single detectorwhich generates a signal that forms a discrete interferogram. The intensity contribution for each wavelength component is obtained by applying a Fourier transform to the interferogram.

The EP-IR spectrometer is designed to encode the analytical information in the same way as an interferometerbut without the environmentally sensitive components of an interferometer. The compact design enables very precise intensity measurements under hostile environmental conditionswhich enables EP-IR to replace conventional analyser technologies such as non-dispersive infrared absorption (NDIR) and Fourier transform infrared (FTIR) currently used in many process monitoring and control applications.  

FTIR for mobile monitoring

Meanwhilethe Gasmet DX range of portable FTIR gas analysers supplied by Quantitech is becoming popular with stack testers for mobile emissions monitoringaccording to the company. With its multi-component analytical abilities and speed of responseperhaps the only serious limitation of FTIR for stack monitoring has been its inability to measure oxygen. Quantitech has now overcome this with the addition of a Zirconia cell to its Gasmet Portable sampling system that is normally used with the gas analyser.

This TÜV-approved sensor detects oxygen to 0.1volumepercent and is fully integrated with the FTIRso that results are processed and displayed by the same Calcmet software that handles the FTIR results.

The Gasmet system uses no dilution or dryingso that trace concentrations of water-soluble gases such as hydrogen fluoridehydrogen chloride and ammonia can be analysed in wetcorrosive gas streams. All active surfaces in the sampling system can be heated to up to 180°C to prevent condensation problems.

The sampling system is equipped with several safety features including automatic zero gas flushing in case of system error or power loss and temperature and gas flow alarms from the sampling system.