BERTHOLD TECHNOLOGIES LB 444 - Correction of Analysis Values

04/03 347 LB 444
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The following additional functions will be initiated for multi-point calibration after selec-
tion of the calibration mode with <enter> and <more>:
Calculation of curve function:
The curve function is calculated in accordance with the selected calibration mode from
the value pairs entered and corrected as described below (see 8.1.4 Correction of Analy-
sis Values).
Calculation of square error of curve fit:
The quality of the calibration curve is calculated from the differences between the calcu-
lated calibration curve and the value pairs entered.
Ideally, all points exactly match the calculated curve. The square error becomes “0”.
Check of calibration curve for turning points:
Within the limits of the current output values (Product Data menu), the system checks
the curve for a clearly rising or falling trend. If this is not the case, the error message
“Curve not clear” will be displayed.
8.1.4 Correction of Analysis Values
The count rates read into the Data input menu are dependent upon the density of the
product during reading-in. In the laboratory the density is usually determined at constant
temperatures. With constant concentrations but different temperatures during reading in
of the pulses one may get:
• the same lab values
• different density values and therefore
• different count rates.
To avoid calibration errors, the product temperature is stored as well. When calculating
the calibration curve, the entered laboratory value is corrected by means of the tempera-
ture coefficient. This correction is carried out only when:
• temperature compensation has been enabled in Config. Instrument
• a temperature coefficient has been entered.
The corrected lab values from which the calibration curve is calculated are displayed after
the coefficients and the square error.
The following two points are relevant only for density measurements. For concentration
measurements the temperature compensation is always enabled prior to performing cali-
bration.
No correction is required if the density has been determined at exactly the same tem-
perature at which the count rate was read in (e.g. densimeters on site). The density
value determined can be read in directly.
In this case, the temperature compensation is turned on only after calibration has been
performed.
Manual correction of sample values is required only if the measurement was run in g/cm
3
and the density of the samples has been determined at different temperatures.