Metrohm NIRS XDS Transmission OptiProbe Analyzer - Manual (Page 64)

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7.2.4 Gain Test
The Gain Adjust feature can be a useful diagnostic tool, though it is not required for normal
operation. Technically, gain is never adjusted on the XDS OptiProbe Analyzer. The name of the test
comes from a capability required with older systems. With XDS, this program reports gain
information for the NIR and visible regions.
To start Gain Adjust, click on Diagnostics,
then Gain Adjust.
The instrument is connected and in
communication for this to function.
The view above shows gain as measured on a fairly typical OptiProbe Transmission Analyzer. Actual
gains may vary based upon position of probes, distance between them, and alignment. Gain Adjust
requires that the transmission probes be aligned facing each other, either in the calibration fixture,
Vial Heater Module, or the sample cell. Vision 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.