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Introduction
EP-IR is a new
technology that provides opportunities for uncharted territories.
One of these territories
is moisture analysis.
What limit of detection
for moisture can be achieved?
EP-IRGAS Encoded Photometric- Integrated Real-Time Gas
Analysis Solution
–Incorporates an
Aspectrics
128 channel EP-IR spectrometer and
an integrated CIC Photonics 6m 4Runner long path gas cell
Equipment
EP-IR Spectrometer
- Encoding disk
- 128 wavelength channels
- Vibration insensitivity
- Compact (short path)
spectrograph
- Mid IR range
- TE- cooled detector
4Runner Long Path Gas
Cell
- 6m pathlength
- Integrated IR source
- Stainless steel
construction
- Laminar gas flow
- High energy throughput
~40%
EP-IR Spectrometry
Diagram provided by Aspectrics
Principles of Operation
- Step 1
- Infrared source
projects the beam through the sample compartment onto the diffraction grating
- Step 2
- The grating dispersed
the beam on the 128 channel encoded disk
- Step 3
- The spatially located
reflective tracks on the encoded disk read the corresponding wavelengths
- Step 4
- Unique sinusoidal waves
are created for the individual tracks on the encoded disk
- Step 5
- Infrared beams are
brought back together to a single detector, which generates an interferogram
- Step 6
- Fourier Transform is applied
to the interferogram, determining the intensity of the wavelengths
EP- IR vs NDIR/FTIR
- EP-IR
- High sensitivity
- Highly rugged
- Partial MIR spectrum analyzer
- Scan speed (100 scans/second)
- No hydroscopic material
- Industrial FTIR
- High sensitivity
- Mildly rugged
- Full MIR spectrum
analyzer
- 1- 4 scans/second scan
speed
- Sometimes hydroscopic
material
- NDIR
- Medium sensitivity
- Rugged
- Not a full spectrum
analyzer
Moisture at Varying
Resolutions
Typical Gases on EP-IR
Multicomponent 5000 with
256 channels
Diagram provided by Aspectrics
Calibration (14.27ppm) -
Water2.abin
Calibration (7.14ppm) -
Water6.abin
Calibration (0.84 ppm) -
Water5.abin
Chemobuilder
- Aspectrics software
designed to generate and validate calibration
files.
- Chemometric quantification
algorithm is based on PCR.
- Can automatically
calculate PCR parameters based on
calibrated spectra
Calculated Reference
Spectra
Calibration Fitting
Calibration Linearity
Conclusions
- For this particular
system configuration, the system has an LOD for moisture of about 1ppm.
- We used an incorrect
configuration parameter of the EP- IR unit.
- Some of the results seem
to be affected by permeation of atmospheric moisture
- There is room for
improvement in the LOD
Future Work
- Update EP- IR units firmware to incorporate
latest signal processing algorithms.
- Re- run moisture
calibrations inside a secondary purging enclosure
- Testing different gas
cell pathlengths
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