Thermo Electron Nicolet 380, Руководство пользователя, Страница: 63 / 135

Using energy screens
Depending on the types of detectors you use, the system may include
a set of four energy screens. These metal screens help prevent
detector saturation and signal distortion by blocking out a portion of
the energy at all frequencies of the infrared beam. If your experiments
deal with information from a broad range of frequencies, these
screens may be the most effective means of reducing the light level.
The energy screens are labeled A, B, C and D. The following table
shows the percentage of the infrared energy that each screen passes.
It also lists the detectors typically used with each screen, as a starting
point for correcting linearity problems.
Screen % Transmitted
*
Detectors Typically
Used With Screen
None 100 DTGS
A 30 MCT-A
B 10
C 3
D 1
*
These are nominal values that may vary due to diffraction and
detector variations.
To correct for photometric accuracy, you may need to add a
“heavier” screen (one that transmits less infrared energy). With
corrections for photometric accuracy you will notice some reduction
in the signal-to-noise ratio but will obtain more reliable quantitative
data. Generally, the signal-to-noise ratio is reduced less than is the
signal intensity.
Nicolet 380 User’s Guide
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