Bomem-GRAMS User's Guide

Appendix D
Glossary
instrument (the source, all the optical components, the ambient air, as well
as any contamination there may be in the optical path).
spectral range
The range of frequencies (or wavelengths) over which the amplitude of
a spectrum is above the acceptable noise level. It is application dependent.
spectrometer
An instrument for producing a spectrum and measuring the wavelengths,
energies, etc. involved.
An FT-IR spectrometer has a photoelectric detector and produces
a spectrum that shows how the transmittance, absorbance, or reflectance of
the sample varies with wavelength. Such instruments are also called
spectrophotometers.
spectrum
1. A range of electromagnetic energies arrayed in order of increasing or
decreasing wavelength.
2. A distribution of transmission or absorbance levels over a range of
wavelengths, arrayed in order of increasing or decreasing wavelength.
stray light
1. Apparent optical energy, caused by nonlinearity, in a spectral region where
no energy is expected (Fourier stray light).
2. Modulated light reaching the detector without having passed through the
sample.
stream
A current or flow of material in a process. A stream is analyzed using a
sample accessory, typically a flow-through sample cell, connected to the
analyzer. One sample cell is used for each analyzed stream unless the
sampling system is set up for stream switching.
training set (see calibration set)
transmittance
A measure of the amount of light that passes through the sample, often
expressed as a percentage.
56 Bomem-GRAMS User's Guide