EP-IR analysers challenge

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 simple,
yet rugged and efficient design, where 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 tracks, which 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 detector, which 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 encoder, which 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 interferometer, but 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 applications, as a single
EP-IR system can replace multiple NDIR modules and provide better performance.