Metrohm tiamo 2.4 Manual - Manual (Page 1131)

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5 Method
tiamo 2.4
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tiamo determines the calibration data for the concentration measurement
as for the pH calibration in accordance with the number of the standard
solutions used.
￭ 1-point calibration
– s: the existing value is retained, if available. If not, the theoretical
slope U
N
/ z is used.
–
– c
B
: is set equal to zero.
￭ Two-point calibration
–
–
– c
B
: is set equal to zero.
￭ Three- and multiple-point calibration
With at least three calibration solutions the calibration function is
determined according to the method of least squares. The sought cali-
bration parameters s, E(0) and c
B
are calculated iteratively. If the value
for c
B
is lower than approx. 0.2% of the lowest concentration, it is set
equal to zero. In such a case a linear relation between U
i
and log(c
i
)
results.
With four or more calibration standards, the variance Var is always cal-
culated and output. If c
B
= 0, the variance is even calculated for three
standards.
U
i
: measured potential
U
i,c
: potential calculated from the calibration curve
n: number of measuring points
F: degrees of freedom (2 for c
B
= 0, 3 for c
B
≠ 0)
Command variables
The following command variables are generated by the CAL LOOP Conc
command in the method run and can be used in formulas under the des-
ignation 'Command name.Variable identification':
Identifi-
cation Description
.BLV Blank value calculated from the calibration
.BSY Command status; 1 = BUSY, HOLD or ERROR; 0 =
READY; invalid (variable not available) = Command has
never been started