User Manual

<5. CALIBRATION OF pH/ORP>
5-2
IM 12A01A02-01E 5th Edition : Oct. 31, 2013-00
5.1 pH calibration
There are the Manual, Automatic, and Sample modes of pH calibration.
5.1.1 Manual calibration
The unit is adjusted to match the value of the buffer standards or a process solution with a known
pH value (buffer solution).
TheuserdeterminesthepHvalue,temperatureinuence,andstability.
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.
Atcalibration,weadviseleavingthesensorsforthreetoveminutesinthebuffersolutionbefore
proceedingtothenextstepevenwhenthereadinghasstabilized.Thiswillgivereliableand
accurate calibration results.
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3.9.)
l zero/slope
This calibration type is one-point or two-point calibration.
One-point calibration performs the zero adjustment only. Two-point calibration performs the zero
and slope adjustments.
l zero/slope/ITP(3point)
This calibration type is ITP-type three-point calibration.
If ITP does not have pH 7, three-point calibration is performed to obtain the zero (asymmetry),
slope (sensitivity), and ITP (isothermal point) for 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2ndbuffersolutionshouldbepH7±2.
• Thetemperaturedifferencebetweenthe2ndand3rdbuffersolutionsshouldbe5ºCorless.
The temperatures of the 2nd and 3rd buffer solutions should be at least 20ºC higher or lower
than the temperature of the 1st buffer solution.
• TocalculatethepHvalueofthe3rdbuffersolution(pH
3cal
), insert the pH and temperature
values of the 1st and 2nd buffer solutions and the temperature value of the 3rd buffer
solutionintothefollowingequation.