Yokogawa 2-Wire Dual Channel Transmitter/Analyzer FLXA21 Manual de usuario descargar pdf (Pagina 203)

<17. CALIBRATION OF SENCOM pH/ORP>

17-2

IM 12A01A02-01E 5th Edition : Oct. 31, 2013-00

17.1 pH calibration

There are the Manual, Automatic, and Sample modes of pH calibration.

17.1.1 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15.11.)

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.

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Yokogawa 2-Wire Dual Channel Transmitter/Analyzer FLXA21 Manual de usuario Pagina 203