< 7. Calibration >
7-7
IM 12F5A1-01E
the mg/l (or ppm) indication to blink during calibration operation. When the span calibration is
completed normally, “CAL.END” appears.
Note: If an error occurs during calibration operation, “END.E5” or “END.E7” is displayed in the message. When this message is
displayed, take countermeasures, referring to Sec. 7.4.
(5) Press the
YES
key to end the calibration and switch the FC400G to the MEAS mode.
Press the
YES
keytoswitchtheFC400Gtothe<MEASURE>or<HOLD>mode(“HOLD.
ON”inthemessagedisplay).When“HOLD.ON”isdisplayed,pressthe
NO
key to select the
<MEASURE> mode.
7.3.2 SpanCalibrationUsingtheStandardSolutionMethod
Note: Topreparestandardsolution,thefollowingmaterialsarerequired:approx.2to3litersofpurewater,approx.20to30millilitersof
pH7buersolution,approx.100to150mgofNaCl,andcommerciallyavailablesodiumhypochlorite,orNaClO(thequantityof
whichissomuchthatafreechlorineconcentrationofapprox.80%oftheoutputrangecanbeobtainedbydilution).
Span calibration using the standard solution method is performed as follows.
Note: Beforeperformingspancalibration,conrmthattheelectrodedoesnotremainopentotheairasafterzerocalibration,andthe
electrode rotates smoothly in the measuring tank.
Start span calibration at the point when zero calibration using the method described in Sec. 7.2.1 or
7.2.2isnishedand“SPAN”isdisplayedinthemessagedisplay.
Note: WhencalibrationisperformedusingthemethodinSec.7.2.1,theFC400GisintheMEASmode(or<HOLD>mode)and“SPAN”
is not displayed. Refer to (2) of Sec. 5.4.1 and display “SPAN” in the <CAL> mode.
(1) Press the
key to enter the span calibration mode.
Free chlorine concentration is displayed in the data display.
(2) Prepare standard solution.
First prepare a solution to dilute commercially available sodium hypochlorite solution. Prepare
asolutionfordilutionsothatitconsistsof10millilitersofpH7standardsolutionand50milliliters
of NaCl per one liter of pure water. Calibration requires 2 to 3 liters of dilution solution. Prepare a
standard solution by diluting the sodium hypochlorite solution using the dilution solution so that
thefreechlorineconcentrationisapprox.80%oftheoutputrange.
Notes: • To prepare a standard solution, sample water may be used instead of dilution solution.
•Toprepareaspancalibrationsolutionaccordingtotheocialmethod,dilutethesodiumhypochloriteusingtapwatersothatthe
freechlorineconcentrationisapprox.80%oftheoutputrange
(3) Supply the standard solution to the detector.
When the zero point has been calibrated using the open input circuit method, close the needle
valveatthesamplewaterinletofthedetectorandremovethesamplewaterpipingfromthejoint
of the measuring tank. Set the tubing and hardware so that sample water can be supplied at a
owrateofatleast100ml/minusingaheaddierenceorapumpandconnectittothedetector
at the sample water inlet.
When zero point has been calibrated using the chlorine-free-water-based measurement method,
supply standard solution using the hardware used for the zero calibration.
(4) Measure the free chlorine concentration of the standard solution correctly using manual analysis
(e.g.anamperometrictitrationmethod).Theexactfreechlorineconcentrationofthestandard
solution changes over time. Perform the operation in item (5) immediately after the manual
analysisisnished.
(5) Enter the obtained value in the data display and perform span calibration.
Conrmthattheobtainedvaluehasbeenenteredcorrectlyandpressthe
ENT
key. This causes
the mg/L (or ppm) indication to blink during calibration operation. When the span calibration is
completed normally, “CAL.END” appears.
Note: If an error occurs during calibration operation, “END.E5” or “END.E7” is displayed in the message display. When this message is
displayed, take countermeasures, referring to Sec. 7.4.
(6) Reattachthetubingtothedetector.Opentheneedlevalvetoallowthesamplewatertoow.
Adjusttheapertureoftheneedlevalvesothatthesamplewaterowsatthespeciedowrate.
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