Dickey-John Instalab 700 NIR, Operator'S Manual

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OPERATOR’S MANUAL
Instalab 700 NIR Product Analyzer
11001-1574-201107
APPENDIX C 101
APPENDIX C
SYSTEM GAIN
The System Gain in the IL700 is automatically set using a software
algorithm. This system gain is an overall signal gain that is set at the factory
and most often never changes unless field technician activity is performed
that might require adjustment. This gain is essentially in series with the
mode gains and sets the overall signal level into the analog-to-digital
converter for the most transmissive optical filter with the mode gain set to
X1.
MODE GAINS
Mode gains can be adjusted by advanced users when necessary. Mode
gains are under software control and offer three selection (X1, X2, and X4).
At the factory, and occasionally in the field on an as needed basis (such as
optical filter replacement), a Diagnostics screen allows scanning of the
reference signal level for all optical filters installed in the unit. This
Diagnostics screen shows the recommended gains for each filter. Typically,
a couple of the optical filters may be X2 gain while most show X1. These
recommended gains can be manually stored and used thereafter for all
reference measurements.
With the reference gains established per above, the gains used for sample
measurements will be addressed. Every calibration file is based on either a
“Standard” gain selection or an “Enhanced” gain selection. The choice
between these two gain selections are made at calibration development.
• Most granular agriculture products use “Standard” gain
• Low reflectance products use “Enhanced” gain
During calibration development, the designer of the calibration will decide if
the “Enhanced” gain is warranted. For example, if all the difference log
values for all filters of interest are greater than 400, the “Enhanced” gain
selection most often is selected. In all cases, the gain selection is
embedded in the calibration file and is invisible to the end user.
The “Standard” gain selection uses the same gain as the reference (stored
value) for all sample measurements.
– Example: If filter F0 calls for X2 gain in measuring the reference, X2
will also be used when F0 measures the sample. All raw log values
for reference and sample are adjusted for a unity gain.
The “Enhanced” gain selection uses the stored reference gain similar to the
“Standard” gain except the gain is increased by a factor of two for the
sample measurement.
In the above example where X2 gain was used for both reference and
sample for F0, the “Enhanced” gain selection would use X2 for the
reference but X4 for the sample.