Metrohm Vision – Diagnostics - Manual (Page 16)

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A note on Wavelength Linearization:
Sometimes when initiating Performance Test, Vision will report “Instrument Error: Run Wavelength
Linearization”. The error report is posted near the end of the first set of 32 co-averaged scans, as
Vision processes the data. This error occurs when an instrument configuration has been changed, the
lamp is not on, the reference is not in the correct position, or due to a beam blockage. A
troubleshooting table is provided at the end of Diagnostics to assist you in solving this issue.
2.2 Noise Test
The tabular output of the instrument Noise portion of Performance Test provides a wealth of
information about the instrument. Instrument noise should appear as random spectral variability.
Structure in the noise spectrum or high noise is often caused by changes in environment but also may
be indicative of instrument problems. The Noise Test is the most sensitive diagnostic test used to
determine instrument performance. The display provides information about noise and amplifier gain.
Instrument Noise (Displayed at lower right quadarant during Performance Test)
Vision breaks each instrument test up into segments (wavelength regions), based upon the
instrument configuration. Acceptance specifications are applied to each segment. Segments can be
adjusted by the user under Tests Params (under Data Collection Method) prior to acquisition of any
spectra. Unless there is a reason to change segments, the user is encouraged to use the defaults.
Laboratory instruments generally use a ceramic reference in reflectance, or air in transmission.
Process instruments offer the option of reference vs. reference, sample vs. sample, or sample vs.
reference. Each result column in the noise test is explained:
SCAN#
Identifies which of the 10 sets of sample scans is being reported. A sample scan is defined as 32 sets
of co-averaged reference vs. reference scans for a laboratory instrument.