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Verfügbare Sprachen
Verfügbare Sprachen
Free chlorine control
Free chlorine is determined by applying a constant potential between two plati-
num electrodes placed in the water stream. The measured current is proportional
to the free chlorine.
The ratio between free chlorine and the measured current depend from three
important factors:
• the temperature of the water (between 10...40°C).
• the pH of the water (between 5...9 pH).
• the rate of flow through the electrodes (should be at least 20 cm/s).
The first two points are automatically compensated by the R335. The third point
cannot be compensated for. The rate of flow should be kept as constant as pos-
sible by placing the electrodes in suitable bypass such as model S404C.
There is no need for a zero calibration nor for a salinity compensation.
Since there are no stable calibration solutions available for free chlorine, it is
only possible to adapt the readings on the R335 by measuring the free chlorine in
the system with a photometer and then calibrate to the measured value. Also the
water flow should never be interrupted while calibrating, because the electrodes
whould require some time to stabilise again. Therefore, the system should only be
calibrated after it has been running normally for several hours.
In order to guarantee a stable and reliable control of free chlorine, the following
points should be carefully considered:
• connect a pH electrode for pH compensation.
• connect a Pt1000 for automatic temperature compensation.
• use a bypass to keep a constant rate of flow through the electrodes.
• calibrate only after the whole system is running properly for a longer period.
No special maintenance is necessary except for a regular control and calibration
of the electrodes (at least weekly for highest accuracy).
Model R335 also permits to connect a combination platinum electrode and meas-
ure the ORP (mV). This provides an additional check of the free chlorine. The
potential will vary between ca. 300 mV (no free chlorine) to ca. 900 mV (a lot of
free chlorine).
pH °C
Cl
S404C
pool
pump
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