Metrohm 781 pH/Ion Meter - Manual (Page 101)

7 Various functions
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variance
If at least 4 standards have been measured then the calibration function
will be calculated iteratively according to the principle of the smallest
mean-square error. The resulting variance will be given here. However,
if the value calculated for c(blank) is sufficiently small then the variance
will be given after only three standards have been measured. A more
detailed explanation of these calculations is given in Section 9.2.2.
Each subsequent manual alteration of the calibration data slope, pH(0)
and c(blank) will be documented by the entry ' manual ' against these
parameters
no.of standards
The number of standards actually measured will be given here. This can
be lower than that given in the calibration parameters, as a calibration
can be terminated prematurely with <QUIT>; only the standards which
have already been measured will then be used for the calculation of the
calibration data.
cal.table: original, delete n, reset cal.
This entry can be used to delete individual buffers from the calibration
table (' delete n ') or to delete all the calibration data of an electrode Id
(' reset cal. ').
original
If you use <SELECT> to chose the option '
original ' then all the
standard data previously deleted with ' delete n ' will be reinsert-
ed in the calibration table and used for calculating the calibration
data.
delete n
From a calibration list containing at least 3 standard entries you
can remove individual standard data by selecting ' delete n ' and
entering the number of the standard to be deleted in the line:
delete n: 1..9
The deleted standard will then be indicated in the calibration table
by ' deleted '. The measuring points of deleted standards are also
indicated in the graphical display by an 'o' instead of a '+'.
You can reinsert all deleted standards in the calibration table with
the option ' original '.
reset cal
With this option you can reject all the calibration data of an elec-
trode Id. You are then in the same state as before the first calibra-
tion: slope = +59.2 mV or -59.2 mV per ion charge, E(0) = 0 mV,
c(blank) = 0.