User Manual

<16. COMMISSIONING OF SENCOM pH/ORP>
16-16
IM 12A01A02-01E 5th Edition : Oct. 31, 2013-00
Wash time/measure time: Set the wash time in minutes. In a continuous wash, wash time is
replaced by measure time.
Recovery time: Set the recovery time in minutes.
Manualwash: Select“Disabled”or“Enabled.”
When this item is enabled, a wash cycle can be activated manually. On the
Calibration/Wash screen, press the “Start manual wash cycle” to perform a
manual wash.
Imp2wash: Select“Disabled”or“Enabled.”
When this item is enabled, a wash cycle can be started if the “Impedance 2
too high” error occurs with respect to the reference electrode.
Continuouswash:Select“Disabled”or“Enabled.”
A continuous wash cycle is started at the instant when this item is enabled.
In a continuous wash, the “Measure time” and “Interval time” are reversed
(see Figure 16.4).
Tw
Tr
Tint
Tw
Tr
Tint
Tw
Tr
Tint Tint
Tw’ Tw
Tr
Tw’
F050605_2.ai
Tint: Interval time
Tw: Wash time
Tr: Recovery time
Tint: Interval time
Tw: Measure time
Tw’: Wash time
Tr: Recovery time
When a continuous wash is disabled
When a continuous wash is enabled
Figure 16.4
The instrument has a function for checking whether measurements are normally made after
wash, allowing you to check a sensor response.
The wash recovery check is performed by making use of the time to recover half the wash-cycle
pHchange.Thehalfthewash-cyclepHchangerecoverytimereplacestherelaxationtimebythe
recovery time.
Whether to conduct the wash recovery check can be set on the Error settings 2/3 screen. Half
thewash-cyclepHchangereferstohalfthevalue(1/2∆pH)ofthedifference(∆pH)betweenthe
pHvalueduringnormalmeasurementofanexampleinFigure16.5andthepHvaluedetected
duringwash.IfthepHvalueduringwashisgreaterthan1/2∆pHwhen1/3tRhaselapsed,the
electrodeisassumedtobegood.Ifitissmallerthan1/2∆pH,thentheelectrodeisassumedtobe
bad.
However, for applications where the pH during wash shows almost the same value as the normal
pH,thedifferencewillbeapproximatelyzero.Insuchacase,disablethewashrecoverycheck.
AnexampleofsuchapplicationsisthemonitoringofwastewaterpH.Ifyouselectwaterjet
cleaninginsuchacase,thenormalpHaswellasthewashingtimepHwillbearoundpH7;the
differencewillbeapproximatelyzero,sotherecoverytimecheckwillnotworknormally.
This function is available either for ORP measurement only.