Data Conversion; Gain And Offset; Optimization - ASD TerraSpec User Manual

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B.2

Data Conversion

B.3

Gain and Offset

B.4

Optimization

ASD Document 600541 Rev. G
The serial number is also accessible in the RS
the splash screen or the Help->About menu item.
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When using the RS application, ViewSpec can convert spectral data to
ASCII text files.
Conversion can be done one file at a time. Or, several files can be merged into
a single text file, which is a useful feature when inputting data into other
analysis programs.
Gains and offsets are determined during optimization by an optimization
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algorithm in the RS application. You can observe this process in the RS
application by depressing the OP button on the top right-hand toolbar. The
gains, offsets, and integration time will then appear in the lower left hand
corner. These parameters are set by the optimization routine and cannot be set
manually.
The Gain Value is the inverse of actual gain. A decrease in Gain Value will
produce a higher gain. The maximum Gain Value is 16. Under the low light
levels that create such a gain, small changes in Offset will translate into large
changes in dynamic range.
Offset causes a downward shift (from Y=32,768 DN) in a SWIR spectrum
such that the max value of the spectrum and the minimum value of the
spectrum (Dark Current - off screen) are equidistant from the line y=32,768.
Under ideal conditions, where there's enough light, there will be about 32,768
DN of signal immediately after optimization, +/- 1,000. This means that
optimization "creates" about 16,000 DN of dark current and about 16,000 DN
of dynamic range. But this dynamic range will disappear with either a slight
increase in signal (if the signal started out low to begin with) or a slight
increase in dark current (increases with ambient temperature).
The TerraSpec spectrometer must be re-optimized for:
• Every 30 minutes when used with ASD's Hi-Bright MugLite or contact
probe.
• Changes in temperature.
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Appendix B Reference Information
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and Indico applications from
TerraSpec® User Manual
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