YOKOGAWA FC400G User Manual

< 7. Calibration >
7-6
IM 12F5A1-01E
7.3 SpanCalibration
NOTE
Beforeperformingspancalibration,conrmthattheelectrodedoesnotremainexposedtotheairas
after zero calibration, and the electrode rotates normally in the measuring tank.
Whenboththezeropointandspanarecalibrated,calibraterstthezeropointandthenthespan.
There are two span calibration methods. One is a sampling method in which the reading of the
FC400Gisadjustedtothevalueobtainedbymanualanalysis.Theotherisastandardsolution
methodinwhichthereadingisadjustedtotheconcentrationvalueofcalibrationstandardsolution
(freechlorineconcentrationofapprox.80%oftheoutputrange).
UseofthesamplingmethodissuitabletocalibratetheFC400Gmorecorrectly,forexample,when
always measuring near-zero low concentrations of free chlorine. In general, there is no practical
problem with span calibration using the sampling method.
Thesamplingmethodtakeslesse󰀨ortthanthestandardsolutionmethod.Notethattheelectrode
sensitivity is required to be initialized at start-up or when performing calibration immediately after
the indicator electrode is replaced. The electrode sensitivity can be initialized by setting the service
code08to“1”for“initializeelectrodesensitivity.”However,calibrationafterinitializingtheelectrode
sensitivityisperformedunconditionally.Beforeperformingspancalibration,besuretoconrmthat
the electrode mechanism block has been placed back into the measuring tank and is ready for
measurement.
Note: To initialize the electrode sensitivity, press the
YES
keywhen“CHANGE”isdisplayedinthemessagedisplaywhenentering
the<CAL>mode.(When“NO.CHGN”isdisplayed,pressthe
NO
keytodisplay“CHANGE”andthenpressthe
YES
key.)
7.3.1 SpanCalibrationUsingSamplingMethod
Span calibration using the sampling method can be performed as follows.
Note: Beforeperformingspancalibration,conrmthattheelectrodedoesnotremainexposedtotheairasafterzerocalibration,and
the electrode rotates normally in the measuring tank.
Start span calibration at the point when zero calibration using the method in Sec. 7.2.1 or 7.2.2 is
nishedand“SPAN”isdisplayedinthemessagedisplay.
Note: WhencalibrationdescribedinSec.7.2.1isperformed,theFC400GisintheMEASmode(orinthe<HOLD>mode)and“SPAN”
is not displayed. Refer to (b) in Sec. 5.4.1 and display “SPAN” in the <CAL> mode.
(1) Press the
YES
key to enter the span calibration mode.
Free chlorine concentration is displayed in the data display.
(2) Collect sample water for performing manual analysis.
Conrmthatthefreechlorineconcentrationofthesamplewaterremainsstablebeforespan
calibrationisnished.Collectsamplewaterforperformingmanualanalysisbyopeningthedrain
cock on the measuring tank.
Collect sample water while observing the liquid surface in the measuring tank to make sure the
tipofthecounterelectrode(silverchlorideelectrode)isnotexposedtotheair.
Note: Ifthecounterelectrodeisexposedtotheair,thereadingwilldroptozero,andwhenthecounterelectrodeisre-immersedintothe
samplewater,itwilltakesometime(usuallyseveralminutes)beforethereadingstabilizes.Ifitisaccidentallyexposedtotheair,
conrmthatthereadinghasreturnedtotheoriginalvalueandisstableandperformtheoperationinitem(4).
(3) Measure the free chlorine concentration of the sample water using manual analysis (e.g., an
amperometric titration method).
The free chlorine concentration of the sample water changes over time. Perform manual
analysis immediately after collecting sample water.
(4) Enter the obtained value in the data display and perform span calibration.
Conrmthattheobtainedvaluehasbeenenteredcorrectlyandpressthe
ENT
key. This causes

YOKOGAWA FC400G Specifications

General

Brand	YOKOGAWA
Model	FC400G
Category	Measuring Instruments
Language	English