User Manual

<17. CALIBRATION OF SENCOM pH/ORP>
17-1
IM 12A01A02-01E 5th Edition : Oct. 31, 2013-00
17. CALIBRATION OF SENCOM pH/ORP
The FLXA21 checks the status of sensors including the connection.
While an error is issued, calibration cannot be performed.
NOTE
Donotdisconnectthesensorduringcalibration.
BeforepHmeasurement,calibratethepHsensorwiththestandardsolution.
BeforeORPmeasurement,checktheelectrodeasapartofregularmaintenance.
NOTE
A default is “10 min” for “Auto Return”. When maintenance like a calibration that may take much
timeisperformed,“60min”or“Disable”isrecommendedtobeselected. (Refer to the section
16.7.3.)
Calibration
Execute:
Calibration
HOLD
Setup:
Commissioning
Change language
Start Quick Setup
Execute & Setup Calibration pH
pH
ORP
Temperature
Manual
Automatic
Sample
Temperature calibration
or
Only when “pH + ORP” is selected
on the Sensor setup screen
Figure 17.1 Calibration
The calibration items include pH, ORP, rH, and Temperature.
The item to be calibrated is determined according to the settings made in the Sensor setup and
Measurement setup in Commissioning.
Press
toselectExecute:Calibration,choosetheitemtobecalibrated,congurethe
calibration settings, then perform calibration.
NOTE
Notethefollowingwhenperformingcalibrationwithbuffersolutions.
1. Beforestartingacalibration,makesuretheelectrodesystemisproperlycleanedand
the electrodes are fully functional. They must then be rinsed with clean water to avoid
contamination of the calibration solution(s).
2. Always use fresh buffer solution to avoid the risk of introducing errors from contaminated or
oldsolutions.Bufferssuppliedasliquidshavealimitedshelflife,especiallyalkalinebuffers,
which absorb CO
2
from the air.
3. YokogawastronglyrecommendsNIST/DIN19266bufferstandardsforthebestaccuracy
and buffer capacity. Commercially adjusted buffers (e.g., pH 7.00, 9.00 or 10.00) are a
compromise as a standard, and are often supplied without a temperature dependency
curve.TheirstabilitywillneverbeasgoodasNIST(JISequivalent)solutions.
Alwaysensurethatthesensorsareproperlyconditioned,cleanandlledwiththecorrect
electrolyte solution (if appropriate) before starting a calibration. Refer to the sensor instructions
for details.
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SENCOM