Metrohm Vision – Diagnostics - Manual (Page 41)

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The display shown on the above is for NIR on a Static Sample module, and shows a Gain Factor of 2.
Other instrument configurations operate at other gain factors, all the way up to 4000 and beyond in
the visible area of the spectrum. The Gain Factor is a function of the specific sampling configuration,
and should remain relatively constant over time. A dramatic change may signal a block sample beam,
a missing reference, or other significant problems.
With XDS, this program reports gain information for the
NIR and visible regions.
When running the Gain Adjust on the XDS the screen on
the left appears.
The view above shows a fairly typical XDS Rapid Content
Analyzer. The gain program sets the internal reference
paddle over the sample opening, and takes gain readings
for both NIR and Visible regions.
Gain Factor is a measure of signal amplification. In the NIR region (1100-2500nm) it occurs in steps of
1, 2, 4, 10, 20, 40 and 80. In the Visible region (400-1100nm) the gains range from 1 to 80,000.
Gain Adjust can be helpful when troubleshooting an instrument. For example, a gain of 80 in NIR and
80,000 in Visible is a sign that the lamp is burned out, or some other sort of failure. Note that the
gain factors are reported in Performance Test, and can be called up from the Diagnostic Database.
This permits the user to see if the gain factor has changed significantly over time.
10.2 Manual Gain
Gain Adjust provides a method to adjust the gain potentiometers on manual gain instruments,
manufactured before 1995. When a manual gain system is detected, the screen switches to a
detailed diagram with adjustment arrows and feedback on gain status for the technician. A sample of
the manual adjustment screen is shown for reference:
Manual Gain Display and Instructions
Users with manual gain instruments will use this program to adjust their detectors for optimum
response. An upgrade to AutoGain is available from authorized service locations worldwide.