User Manual

<17. CALIBRATION OF SENCOM pH/ORP>
17-3
IM 12A01A02-01E 5th Edition : Oct. 31, 2013-00
pH
3cal
= ITP -
(273.15 + t
2
)(ITP - pH
2
) + (1 - ) x (273.15 + t
1
)(ITP - pH
1
)
(273.15 + t
3
)
t
3
- t
1
t
2
- t
1
( )
t
3
- t
1
t
2
- t
1
pH
n
: pH value of n-th buffer solution
T
n
: Temperature of n-th buffer solution (ºC)
ITP: ITP value displayed in calibration settings (see section 16.2.4)
  Assign7.00astheITPvaluewhenaspecicvalueisnotavailableorfortherst
calibration of a sensor.
Donotusethe3rdsolutionwhosepHvalueiswithinpH
3cal
±1.
l zero/slope1,2(3point)
This calibration type is the line-segment type three-point calibration.
If the relation between electromotive force and pH is not in proportion for a wide range, divide the
relevant range into two sections and obtain the zero (asymmetry) and slope (sensitivity) in each
section to perform calibration.
Limitations
• ThreedifferentbuffersolutionswhosedifferenceinpHvaluebetweenbuffersolutionsis1
pH or more should be used.
 (1stbuffer<2ndbuffer<3rdbufferor1stbuffer>2ndbuffer>3rdbuffer)
• Thetemperaturedifferencebetweenthe1stand2ndbuffersolutionsshouldbe20ºCor
less.
• Thetemperaturedifferencebetweenthe2ndand3rdbuffersolutionsshouldbe20ºCor
less.
17.1.2 Automatic calibration
Calibration can easily be performed by following the calibration menus.
Pre-selectthebuffersolutiontobeusedfromamongNIST/DIN19266,DIN19267,US,andUser
denedbufferinCommissioning→Measurementsetup→Calibrationsettings→pHsettings→
Buffers(selectset).SeealsoAppendixtable1.
IfyouselectUserdenedbuffer,calibrationisperformedbasedontheconditionsregistered
inbuffertables1to3.Useoftheproperbuffertableallowsthesystemtoperformreliable
calibration.
In the same way as manual pH calibration, select the calibration type from among [zero/slope],
[zero/slope/ITP(3point)],and[zero/slope1,2(3point)].
Calibrationisperformedstepwise;followthepromptsdisplayedonthescreen.
Astabilitycheckisconductedateachmeasurementpoint.Proceedtothenextsteponlyafterthe
reading has stabilized.
NOTE
Whenasensororanelectrodeisexchangedorreplaced,sensorwellnessdatashouldbereset.
When a sensor is replaced, the replacement can be recorded manually into a logbook. (Refer to
thegure15.11.)
17
SENCOM