Metrohm 781 pH/Ion Meter - Manual (Page 68)

6.2 pH measurement (pH mode)
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780/781 pH/Ion Meter, Manual
The prestir and poststir pauses represent waiting periods in which stir-
ring does not take place. The measurement itself only starts when the
complete stirring sequence has ended.
Please note that this parameter is binding for the report output and for
storing a measured value. Therefore when you start a measurement
with <MEAS /PRINT> the stirrer will be switched on and off according-
ly. This is why you should preferably carry out drift-controlled measure-
ments (see Section 5.2 and Section 5.3).
6.2.2 Calibration parameters
PARAMETER pH
:
├
calibration parameters
: ├
temperature*
├
drift
├
report
├
cal. interval
├
no.of buffers
├
buffer type
├
low lim.slope
├
up lim.slope
├
low lim.pH(0)
├
up lim.pH(0)
└
offset Uoff state
(*only appears if no temperature sensor is connected)
The calibration parameters describe the most important settings for the
calibration such as buffer types and tolerance values. The evaluation of
the pH calibration is described in Section 9.2.1.
temperature 0.0...25.0...99.9 °C
Just as for the measuring temperature, the calibration temperature
should also be entered when no temperature sensor is connected. If
the measuring and calibration temperatures are different then this is
absolutely necessary for the automatic temperature correction of the
electrode slope. The temperature is also stored with the suffix ' manu-
al ' and marked in this way in the calibration report.
The exact temperature recording is also important for the pH calibration
as the pH/Ion Meter works with automatic buffer recognition (see below:
buffer type ).
drift 0.1...0.5...9.9 mV/min
Just as in the pH measurement, the potential measurement for the pH
calibration is drift-controlled. However, this drift control cannot be
switched off. Please note that, in contrast to pH measurement, the drift
for the pH calibration is entered in mV/min. It is therefore inevitably dif-
ferent from the drift for pH measurement (see Section 6.2.1).