Metrohm Vision – Diagnostics - Manual (Page 40)

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10
Gain Adjust
Instrument amplifiers automatically adjust gain level based upon sample absorbance. The gain is
“turned up” for highly absorbing samples, and “turned down” for spectroscopically bright samples.
The “gain factor” range is between 1 and 80 for NIR and 1 and 8000 for visible detectors, with some
isolated exceptions. The gain factor is reported in the Performance Test for Autogain instruments; the
Gain Adjust test is not normally part of customer-run diagnostics.
Gain factor is a measure of gain multiplication for a given sample. The test is run with the instrument
reference (ceramic in reflectance, air in transmission). The gain factor reported in Vision should be
consistent over time, with a given module configuration.
The detector module electronics are set at the factory for optimum resolution and gain settings. Do
not attempt to adjust these settings unless operating a manual gain instrument (manufactured before
1995).
10.1 Autogain
The Gain Adjust feature can be a useful diagnostic tool, though it is not required for normal
operation. Gain is never user-adjusted on the AutoGain instruments. The name of the test comes
from a capability required with older systems.
To start Gain Adjust, click on Diagnostics,
then Gain Adjust.
The instrument must be connected and in
communication for this to function.
Click on Gain Adjust to see the Gain Factor
on Autogain instruments, and to verify that
the instrument is reading within the correct
range on the instrument reference.
The display gives the current reading, along with minimum and maximum allowable voltage.
Run Gain Adjust with the instrument
reference in the correct position.
Click between NIR and Visible with the
button provided.
Exit when finished. Gain Factor is reported
as part of the Performance Test and is
stored in the Diagnostic Database.
Autogain Display