Teledyne 5000B - Near Infrared Photometer - Manual (Page 87)

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Operations/Analysis Unit 4
Teledyne Analytical Instruments
A Business Unit of Teledyne Electronic Technologies
Figure 4-1. Optical System
4.4.2 Sample cell
The sample cell, generally constructed of 316SS, is located in the path of
the NIR radiation, between the source and the detector modules. Each com-
pound in the sample path exhibits its own characteristic absorption spectrum.
Cell spacer thicknesses will vary depending upon the absorbance of the compo-
nent of interest at the measuring wavelength. Due to the possible variation of
absorption with temperature, it is either necessary to maintain the sample at a
constant temperature during analysis or to compensate for the minor frequency
shifts of the water bonding which can change due to sample temperature varia-
tions.. To achieve this, two separate methods of temperature control are em-
ployed for constant temperature control.
1. A preheater (heat exchanger coil) is used on the incoming sample
stream to raise or lower it to the desired temperature controlled
level.