Operators Handbook DCU3 – System
5., Main Function „Calibration“
BAEDCU3 - Rev. 4.6 - 0504 5 - 2
5.2 pH - Calibration
The pH electrode is calibrated by a two-point calibration using liquid buffers. The calibration is done
before the electrode is installed in the culture vessel. For details about preparing of the pH-electrode
and handling during calibration see the operating information delivered by the manufacturer. For de-
tails about mounting the electrode into the culture vessel, see the fermentor´s operating manual.
The calibration determines the „zero drift“ and „slope“ of the electrode. The measured pH-value is cal-
culated from the electrode voltage using the Nernst equation, considering the „zero drift“, „slope“ and
„temperature“. During calibration the temperature is entered manually. For pH-measurement during
the process temperature effects are compensated via the measured temperature in the fermentor.
The impact of heat during the sterilization can cause a zero drift of the electrode. To compensate for
such effects the DCU3 - system allows to recalibrate the pH-electrode during the process. You can
measure the pH-value in a sample taken from the fermentor and enter this value into a corresponding
menu. The software recalculates the zero drift and displays the corrected „in-situ“ pH-value afterwards.
The operating display for the pH - electrode shows the pH value, the electrode voltage and the elec-
trode parameters „zero drift“ and „slope“. Thus the functioning of the electrode can be easily checked.
5.2.1 Operating Display
Tag Entry Displayed value or function, required input
pH pH Display of measured pH value,
input of pH-value measured in sample for recalibration
ELEC mV Display of measured electrode voltage (raw signal)
TCOMP Display “temperature compensation”
TEMP Display of temperature for temperature compensation
ZERO mV Display of zero drift
SLOPE mV/pH Display of slope
Start Calibration Enabling the calibration function
Start Recalibration Enabling the recalibration function (during the process)
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