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8.1.5 Checking the Calibration
One-Point Calibration
The absorption coefficient entered under Result a1 must remain unchanged. Also, check
the data in the following code numbers:
Display Value
Coefficient a2 0
Coefficient a3 0
Factor 1
Offset 0
Square error 0
If one of these values differs, please check your calibration.
With negative absorption coefficient (Result a1):
The count rate calculated as zero rate I0 must be higher than the read-in count rate.
With positive absorption coefficient:
The count rate calculated as zero rate I0 must be lower than the read-in count rate.
Two-Point Calibration
After calibration the following values should be displayed:
Display Value
Coefficient a2 0
Coefficient a3 0
Factor 1
Offset 0
Square error 0
If other values should be displayed, check your calibration or the data you have entered.
Multi-Point Calibration
Absorption coefficients and thus the curve function are calculated from the value pairs
entered. At the same time, a factor (square error) will be calculated (only if more than
three value pairs were entered), indicating how well the calculated curve approximates
the entered values. The lower the displayed numerical values, the better the curve fit.
The square error is a criterion for the quality of the curve fit within one
curve shape. It
cannot be used as a criterion for selecting a certain curve shape. The decision for the
most appropriate curve shape for the data is made in auto calibration mode.
Square error value:
< 0.0005 very good calibration
< 0.0019 good
< 0.002 still useful
With larger values, check your calibration for incorrect entries.
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