Knick Stratos Pro A2 CC Série Guide Rapide page 11

pH Value Calculation
Calculating the pH Value by Means of Dual Conductivity
Measurement
When monitoring boiler feedwater in power plants, dual conductivity
measurement can be used to calculate the pH value. For that purpose,
the boiler feedwater conductance is measured before and after the
cation exchanger. This commonly used method of indirect pH value
measurement does not require much maintenance and has the fol-
lowing 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
Two sensors are used to measure the conductivity before and after
the cation exchanger. The pH value is inferred from these two conduc-
tivity values.
Cond measur-
ing point A
Cation
exchanger
Cond measur-
ing point B
H O
2
You can enter more parameters for calculating the consumption of
the ion exchanger (size, capacity, effi ciency). The remaining capacity
is displayed in the Diagnostics / Monitor menu. After replacement of
the ion exchanger an entry must be made in the SERVICE menu.
Sensor A
TC: NH / NaOH
3
Sensor B
TC: HCl
pH
11