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Model FCL-1056 SECTION 1.0
DESCRIPTION AND SPECIFICATIONS
SECTION 1.0.
DESCRIPTION AND SPECIFICATIONS
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1.1 APPLICATIONS
The FCL free chlorine system is intended for the deter-
mination of free chlorine in fresh water. Unlike free
chlorine analyzers from other manufacturers, the FCL
does not use expensive sample conditioning systems
or messy reagents to control pH. Instead, the analyzer
automatically compensates for changes in the pH of
the sample. The FCL is not intended for the determi-
nation of total chlorine or combined chlorine (like
monochloramine). Nor, can the FCL be used for the
determination of chlorine in seawater.
1.2 FEATURES
The FCL uses a membrane-covered amperometric sen-
sor. A polarizing voltage applied to a platinum cathode
behind the membrane reduces the chlorine diffusing
through the membrane and keeps the concentration of
chlorine in the sensor equal to zero. The current gen-
erated by the cathode reaction is proportional to the
rate of diffusion of chlorine through the membrane.
Because the concentration of chlorine in the sensor is
zero, the diffusion rate and the current are proportion-
al to the concentration of chlorine in
the sample.
All amperometric free chlorine sensors respond to
changes in pH. Although free chlorine is a mixture of
hypochlorous acid and hypochlorite ion, hypochlorous
acid alone is responsible for the sensor current.
Because the relative amounts of hypochlorous acid
and hypochlorite ion depend on pH, a pH change will
cause the current and the apparent free chlorine con-
centration to change, even though the true concentra-
tion remained constant. Most manufacturers solve the
pH-dependence problem by treating the sample with
acid, which lowers the pH and converts hypochlorite
ion into hypochlorous acid. The Model FCL avoids the
expense and inconvenience of sample conditioning by
measuring the pH and applying a correction to the
raw chlorine sensor signal. The correction is valid
between pH 6.0 and 9.5. For samples having pH
between 9.5 and 10.0, consult the factory.
The Model FCL is available in two options: Model
FCL-01 with manual pH correction and Model FCL-02
with continuous pH correction. Choose the FCL-01
if the pH varies less than 0.2 or if pH changes are
predictable or seasonal. Choose the FCL-02 if the
pH varies more than 0.2. To provide the continuous pH
correction, the Model FCL-02 requires a separate
pH sensor.
Maintenance is fast and easy. Replacing a membrane
requires no special tools or fixtures. A screw cap holds
the pre-tensioned membrane in place. Replacing the
electrolyte solution takes only minutes.
The FCL includes the easy-to-use Model 1056 analyz-
er. The analyzer features two fully programmable 4-20
mA outputs and four fully programmable relays. The
back-lit, four line display allows the user to read sam-
ple pH and chlorine concentration at a glance.
Valves, rotameters, and pressure regulators to control
sample flow are things of the past with the Model FCL.
A constant head overflow sampler ensures the correct
sample flow to each sensor. To eliminate wiring
hassles, quick-disconnect Variopol cable is standard.
Stable free chlorine standards do not exist. The chlorine
sensor must be calibrated using the results of a labo-
ratory test run on a grab sample.
• COMPLETE SYSTEM INCLUDES sensor, connecting cable, analyzer, and flow controller
• CONTINUOUS pH CORRECTION eliminates expensive and messy reagents and trouble-
some sample conditioning systems
• MEASURES FREE CHLORINE IN SAMPLES having pH as high as 9.5
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• VARIOPOL QUICK-DISCONNECT FITTINGS make replacing sensors easy
• FEATURE-PACKED ANALYZER: dual outputs, four fully-programmable alarm relays, and
large four line display
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In some cases, the sensor can be used in samples having pH as great as 10.0. Consult the factory.