EP-IR analysers challenge NDIR technology at five companies

Paul Boughton

Five major global chemical companies are among the first customers for new encoded photometric infrared (EP-IR) spectroscopy analysers that have just been launched in the USA.

Such analysers rely 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 rugged encoder spectrograph employs a highly-efficient modular optical system and a multi-channel precision rotary encoderwhich is capable of acquiring spectra at rates up to 100Hz

An 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.

Manufacturer Aspectrics believes that an opportunity exists for EP-IR to replace the nondispersive infrared (NDIR)Fourier transform infrared (FTIR) and gas chromatographic technologies currently used for process monitoring and environmental applicationsas a single EP-IR system can replace multiple NDIR modules and provide better performance.

“We are pleased that we are now shipping the first orders for our EP-IR technology to our customers” said company ceo Paul H Salsgiver Jr. “While the details of individual clients and their particular agreements remain confidentialthe shipments represent the first of what could potentially be substantial future orders for dozens of EP-IR units.

One chemical company for exampleis evaluating the unit as an on-line process monitor to eventually replace 80FT-IR process monitors” he added.

Applications under development by Aspectrics’ first customers include ambient air and stack gas monitoringand also engine emission analysis.