Endress+Hauser Liquistation CSF48 - Page 170

Inputs: ISE Liquistation CSF48
170
17.3.3 Compensation
Depending on the selectivity of the ion-selective electrode vis-à-vis other ions (interference
ions), and the concentration of these ions, such ions could also be interpreted as part of the
measuring signal and thus cause measuring errors.
When measuring in wastewater, the potassium ion - which is chemically similar to the
ammonium ion - can cause higher measured values.
The measured values for nitrate can be too high due to high concentrations of chloride.
To reduce measuring errors resulting from such cross-interference, the concentration of the
potassium or chloride interference ion can be measured and compensated for with a suitable
additional electrode.
For the pH, chloride and the potassium electrode, you can only configure an offset. The set-
tings for compensation of the effect of interference ions are available only for ammonium
and nitrate.
Path: Menu/Setup/Inputs/ISE/Electrode slot/Compensation
Function Options Info
Compensation Options
•Off
•On
Factory setting
Off
If you want to use the compensation function, you must
have installed a compensation electrode (potassium or
chloride) in another electrode slot and have configured
it in the software.
Offset -14.00 to 14.00 pH
-100 to 100 mg/l
Factory setting
0.00 pH
0.00 mg/l
The offset compensates for a difference between a
laboratory measurement and an online measurement
which is caused by interference ions. Enter this value
manually.
If you are using a compensation electrode, keep the
offset at zero.
Compensation type Options
•Chloride
•pH
•Potassium
• pH and potassium
Factory setting
Chloride
Potassium
The options depend on the parameter to be
compensated. You compensate for chloride when using a
nitrate electrode, and you can compensate for potassium
and pH when using the ammonium electrode. The
factory setting depends on the electrode used.
Comp. electrode Choice of slot If you have installed and configured several
compensation electrodes of the same type in the
CAS40D sensor, in this function you have to define
which electrode is used for compensation. Generally, you
have a potassium or chloride electrode and Liquiline
recognizes the right slot.
Selectivity coefficient -10.00 to 10.00
Factory setting
-2.00 (chloride)
-0.85 (potassium)
The coefficients are empirical values.