iQntrol DOS-MODBUS
Original manual in German Version 1.0.2 2022.10.06
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8.2.5
Main menu
Calibration
pH (2-point)
for calibration of the pH electrode
pH (phenol red)
For adjusting the pH display value according to a phenol red
measurement
mV - Redox
for calibration of the redox electrode
Not available for the time control O
2
disinfection process
The calibrations are text-guided; the most important steps are explained in brief texts. Completed steps are acknowledged with
the
OK
A button. Values are adopted automatically once the measured electrode voltage remains stable for approx. 15 seconds.
8.2.5.1
Main menu
Calibration
pH 2-point (pH electrode)
pH7 = Offset voltage
The optimal offset voltage is at 0 mV ± 30 mV.
pH4 = second buffer solution for determining the conductance voltage
Inclination mV/pH = conductance voltage
The optimal conductance voltage at 25°C is approx. 59 mV/pH.
Example: (pH7 – pH4 = 3 pH x 59 mV = 177 mV)
The values of the most recent successful calibration are displayed below.
At the end of the pH calibration, the measuring results of the offset voltage and the conductance voltage are displayed and an
electrode evaluation is carried out. In case of minor deviations, the calibration is adopted immediately. In case of "medium"
deviations, a cleaning notice is displayed. In case of major deviations, the exchange of the pH electrode is suggested. If the
exchange of the electrode does not remedy the problem, the fault may be with the electrode cable or the measuring amplifier.
Notice - Evaluation of the electrodes:
Cleaning notice
At an offset voltage > ± 61 mV, the voltage value is shown in yellow and the calibration ends with a cleaning notice.
At a calibration voltage < 52 mV or > 63 mV/pH, the voltage value is shown in yellow and the calibration ends with a
cleaning notice.
Error notice
At an offset voltage > ± 91 mV, the voltage value is shown in red and the calibration is rejected with an error notice!
At a calibration voltage < 50 mV or > 65 mV/pH, the voltage value is shown in red and the calibration is rejected
with an error notice!
If the calibration is rejected with an error notice, the device continues the regulation using the values from the
most recent successful calibration.
It is necessary to investigate the cause of the failed calibration!
8.2.5.2
Main Menu
Calibration
pH - phenol red (tablet measurement)
Carry out phenol red measurements according to the manufacturer’s
specifications and enter the determined value.
Please note the limited measuring range and other characteristics of the phenol
red measurement.
Calibrations above ± 0,6 pH (offset 40 mV) end with a notice.
Calibrations above ± 1,0 pH (offset 60 mV) are rejected.