4:2
Service Manual 1001 5015 / Rev. 4
4.1.1
Poor Results
The points listed below can be considered as a check list for trouble shooting “poor”
results. The reasons for “poor” results can be divided into:
•
User problems
•
Poor calibrations
•
Outliers
•
Poor reference data
•
Instrument problems (Time for cleaning? see User Manual)
4.1.2
User Problems
•
Are they using the right calibration?
•
Has there been an adjustment to the slope or intercept in the calibration?
•
Are they sure that the moisture basis of the Infratec results is the same as that of
the reference results?
•
Do they use adjustment to dry content or constant moisture content?
•
How many sub-samples are used?
4.1.3
Poor Calibrations
•
Was the calibration developed for this type of sample?
•
Was there sufficient data to develop the calibration?
•
Was the calibration stabilised for instrument and temperature differences?
4.1.4
Outliers
Results with outliers should always be confirmed by a second analysis.
A sample may be classified as an outlier for a number of reasons:
•
The constituent concentration is outside of the calibration range.
•
The sample is of a variety for which the NIT spectrum differs greatly from the
samples in the calibration set.
•
The product is analysed with wrong AM.
•
There is too much foreign material in the sample.
•
Movements of the sample during the scan.
•
Too high absorbance.
•
Packing of sample not good
For each constituent, an outlier will be displayed as a letter (A-E) and a number
(1-5). The letter indicates what kind of outlier it is, as described below, and the
number describes the severity (the higher the number, the stronger the outlier).
A-outlier (residual) and B-outlier (leverage)
An outlier denoted by the letters A and B indicate how closely the NIT spectra of the
sample correlate with the spectra in the calibration set.
C-outlier (sub sample deviation)
An outlier denoted by the letter C indicates that the standard deviation between the
sub predicted values from the individual sub samples is above the set limit.
D-outlier (out of range)
An outlier denoted by the letter D indicates that the low or high limit for the constit-
uent has been exceeded by the predicted value of at least one of the sub samples. This
means that it is possible to get a D-outlier even if the average result on the display is
within the calibration range.
Summary of Contents for Infratec 1241
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