Metrohm 781 pH/Ion Meter - Manual (Page 100)

7.1 Calibration and addition/subtraction data
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780/781 pH/Ion Meter, Manual
and from the calibration data report. The calibration date and time will
be updated and the temperature information and the calibration table
(see below) will be removed. In addition this action will be documented
by the entry ' manual ' under CAL.DATA/variance.
E(0)
This is the second characteristic quantity of the calibration function.
E(0) is the potential at log(c) = 0, i.e. the U-axis intercept of the calibra-
tion function in the U/log c plot. A more detailed explanation of the cal-
culation of the calibration data is given in Section 9.2.2.
E(0) can also be altered manually for test purposes. The other entries
under CAL.DATA will then be altered in the same way as for a manual
alteration of the slope (see above).
c(blank)
This is the third characteristic quantity of the concentration calibration
function. To a certain extent it reflects the curvature of the otherwise lin-
ear calibration function at the lowest concentrations. It is only calculated
when at least three standards have been measured (see also Sec-
tion 9.2.2). If the value for c(blank) is sufficiently small, i.e. if the influ-
ence of this quantity on the later result can no longer be measured,
then it will be set as zero. Instead the variance will then be calculated
even when only three standards have been measured (see below).
c(blank) can also be altered manually for test purposes. The other en-
tries under CAL.DATA will then be altered in the same way as for a
manual alteration of the slope (see above).
temperature
The calibration temperature is shown here.
temp.sensor
If the calibration temperature has been determined automatically by a
connected temperature sensor then its type will be shown here
(' Pt1000 ' or ' NTC '). A manually entered temperature for the calibration
will be indicated accordingly (' manual ').
c.dat.
The date and time of the calibration will be shown here.
cal.interval
If a calibration interval has been defined under
PARAMETER Conc/
Calibration parameters/cal.interval then it will be shown here.
It can be used together with the calibration time given under c.dat . to
estimate the time that the next calibration is due.