< 7. Calibration >
7-1
IM 12F5A1-01E
7. CALIBRATION
Calibration is required to correctly measure free chlorine concentrations using the FC400G.
Calibration is performed for the zero point and span. There are two methods to calibrate the zero
point: open input circuit and chlorine-free-water-based measurement methods. Also, there are two
span calibration methods: sampling and standard solution methods. Calibration is performed at start-
up or when operation is restarted after being stopped for a long period of time.
Also, calibration is performed periodically (recommended every month or so) during operation. This
chapter describes the calibration procedure.
7.1 Running-in
In general, calibration requires running-in. Always run in the FC400G at start-up or when it restarts
after being temporarily stopped.
Running-inrequires,rst,polishingoftheindicatorelectrode.ComplywithSec.6.1.4onhowtopolish
the indicator electrode.
After polishing, install the polished indicator electrode and select “CELL. ON” in the <CELL> mode.
Then press the
YES
key to rotate the electrode. Operate the free available chlorine analyzer for
approx.onehour.
Calibrationcanbeconductedafterthisapprox.1hrrunning-in.
Note: It is recommended that electrode polishing be performed even when calibration is performed periodically during operation.
However,electrodepolishingcanbeomittedifthecalibrationintervalisshortanditcanbedeterminedthattheelectrodeisnot
contaminated.
The characteristic readings of the indicator electrode are temporarily not stable immediately after polishing the electrode.
Therefore,afterelectrodepolishingisperformed,leavetheFC400Grunningforawhile(approx.1hour)underthemeasurement
conditions until the characteristic readings of the indicator electrode stabilize. Calibration is performed following this running-in.
7.2 ZeroCalibration
The method of calibrating the zero point of the free available chlorine analyzer includes two
approaches; open input circuit and chlorine-free-water-based measurement methods.
Intheformertheelectrodeisexposedintheairsothatnocurrentowsbetweentheindicator
electrode (rotating electrode) and counter electrode. The latter uses chlorine-free water (e.g., water
lteredthroughactivatedcharcoal).
Duringautozerocalibrationwiththeactivatedcharcoallter,chlorine-free(chlorinenotincluded)
water must be used.
If the FC400G generally measures free chlorine concentrations as low as 0.1 mg/l, conduct zero
calibration using the chlorine-free-water-based measuring method.
However,theopeninputcircuitmethod,easytoconduct,isgenerallyused.
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