User Manual

<11. CALIBRATION OF ISC (Inductive Conductivity)>
11-3
IM 12A01A02-01E 5th Edition : Oct. 31, 2013-00
D
Non-conductive piping
Conductive piping
Distance D (mm)
0 10 20 30 40 50
0.90
Correction factor (x nominal C.C.)
0.95
1.30
1.25
1.20
1.00
1.05
1.10
1.15
Figure 11.3 Relationship between the distance from the sensor to side wall and the cell constant
11.1 Cell constant (manual)
Theintentionofthiscalibrationroutineistone-tuneasensorforwhichonlythenominalcell
constant is known, or to recalibrate a sensor that has been changed (or damaged) during
operation. Choose the 1st or 2nd temperature compensation to suit the calibration solution used.
The solution with an appropriate precision should be prepared or purchased. Allow the sensor to
reach stable readings for both temperature and conductivity before adjusting to the value of the
corresponding calibration solution.
The cell constant of the calibrated sensor should also be set up here.
11.2 Cell constant (automatic)
ThisroutineisbuiltaroundthetestmethoddescribedinInternationalRecommendationNo.
56 of OIML (Organisation Internationale de Metrologie Legale). It allows the direct use of the
solutions prescribed in the test method, automatically selecting the appropriate temperature
compensation.Thelook-uptableisusedtondanappropriateconductivityreadingforthe
measuredtemperature.SeeAppendix3forOIMLsolutions.
11.3 Air calibration
Executeaircalibrationrst,ifneeded.
With the clean dry cell in open air, the reading should be zero. The air cal compensates for
excesscablecapacitance,andgivesabetteraccuracyatlowreadings.Thisshouldbedone
when a sensor is installed or replaced. After some time in service, a dirty sensor may well show
a high zero offset because of fouling. Clean the sensor and try again. Moreover, air calibration
should be made in an environment free of electromagnetic interference.
Waitforthesensortodrybecauseaircalmustbemadewithnocurrentowinthesensor,thatis,
thesensormustbedriedwhilebeingexposedtoair.
ISC
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