Ph Value Calculation - Burkert 8285 El. COND Mode D'emploi

pH value calculation

Note: 2 conductivity modules required
pH value calculation by means of dual conductivity
measurement
When monitoring boiler feed water in power plants, the pH value can be
calculated by means of a dual conductivity measurement. For that purpose,
the boiler feed water conductance is measured before and after the ion
exchanger. This commonly used method of indirect pH value measurement
does not require much maintenance and has the following advantage:
Normal pH measurement in ultrapure water is very critical. Boiler feed water
does not contain many ions. This requires the use of a special electrode,
which must be calibrated constantly and the service life of which is generally
rather short.
Function
The conductivity before and after the ion exchanger is measured using two
8285 El. COND modules. From the two calculated conductivity values, a
"Calculation Block" determines the concentration of sodium hydroxide solu-
tion and the pH value according to the calculation formulas shown below:
COND measuring
point 1
Cation
exchanger
COND measuring
point 2
H O
2
Calculating the concentration of sodium hydroxide solution /
pH value: pH value:
COND1- 1/3 COND2
c(NaOH) =
48
COND1 module
8285 El. COND
COND2 module
8285 El. COND
243
Calculation Block
pH = 11+log[c(NaOH)]
pH
c (NaOH) [mmol/l]
Secondary display
only
8285