Operation - Grundfos AQC-D13 Instrucciones De Instalación Y Funcionamiento

11.1.3 Influence of temperature
The current generated on the electrodes depends on the
temperature of the sample water.
• The measured value increases by approx. 4 % per 1 °C
increase.
• Temperature variations can be compensated by the measuring
amplifier, if the temperature compensation function is
activated.
– The temperature can be measured with a Pt100 temperature
sensor optionally integrated into the measuring electrode.
– The temperature measuring signals are transferred to the
measuring amplifier and calculated using the electrode
signals.
11.1.4 Influence of the pH value on the chlorine measurement
Free, active chlorine is considered as the total of molecular
chlorine gas (Cl ), hypochlorous acid (HOCl) and hypochlorite
2
-
anions (OCl ). Dissolved chlorine gas in molecular form
practically does not exist at the application-dependent pH values
(pH 4.5 to 8.2), but is subject to hydrolysis in the presence of
water according to the equation
Cl + H O HOCl + HCl
2 2
The resulting hypochlorous acid is the actually effective
compound for disinfection of the water. The dissociation of acid to
anions is primarily according to an equilibrium dependent on the
pH value according to the equation
+ -
HOCl + H O H O + OCl
2 3
% HOCl
100
80
60
40
HOCl
20
0
4 5 6 7 8 9
pH
Fig. 20 HOCl-OCl diagram
The measuring cell for chlorine primarily only determines the
portion of hypochlorous acid that is relevant for disinfection.
Since the dependence on the pH value is particularly large in the
actually relevant range between pH 7 and pH 8.2, this
dependence must be compensated for in the measuring amplifier
if the pH value varies considerably. The pH value must therefore
also be measured, and the pH compensation function must be
activated on the measuring amplifier.
18
-
% OCl
0
20
40
- 60
OCl
0 °C
80
10 °C
30 °C
100
10 11

11.2 Operation

11.2.1 Switching on
See section 10.7 Switching on.
11.2.2 Operating state
Observe the installation and operating instructions of
Caution
the measuring amplifier and the device controlled!
For information on operation of the measuring cell in
the operating state, please see the installation and
Note
operating instructions of the relevant measuring
amplifier.
11.2.3 Adjusting / setting the quantity of sample water
• Set the quantity of sample water with the regulation (G) so that
a small amount of water runs through the ascending pipe in
the cylinder.
G
Fig. 21 Optimum quantity of sample water
1. Slowly adjust the regulation (G):
– Counterclockwise: increase
– Clockwise: decrease
Caution
Do not unscrew the regulation completely!
The delay time of the measuring cell can be reduced
Note
by increasing the sample water flow rate.