Bomem-GRAMS User's Guide

Appendix D
Glossary
The transmittance T is the ratio of the intensity I of the light which passes
through the sample to the intensity I 0 of the light striking the sample.
transmittance spectrum
I
T = % T = 100T
I
0
The percent transmittance of a sample as a function of the frequency or
wavelength over a given spectral range.
The transmittance spectrum is calculated point-by-point from the sample
and reference spectra as follows:
sample
%Transmitt ance = ×100
reference
validation
Tests used to establish that an analyzer is operating correctly (instrument
validation) and is providing results within the expected degree of agreement
(calibration validation). Validation can include diagnostics on the reference
and sample spectra and predictions with known samples.
validation set
In spectrometer calibration, a set of standard samples similar to a training
set but used to validate a calibration model.
wavelength
The distance (λ) between successive points of equal phase in a wave.
In FT-IR spectrometry, wavelength is usually expressed in micrometers
(µm) or nanometers (nm).
wavenumber
The number (σ) of cycles of a wave in unit length. The wavenumber is
the reciprocal of the wavelength:
σ = 1 λ
The unit of the wavenumber is 1
cm or cm-1 .
Bomem-GRAMS User's Guide 57