User Manual

<Appendix 3 For ISC (Inductive Conductivity)>
App.3-10
IM 12A01A02-01E 5th Edition : Oct. 31, 2013-00
FLXA21 is programmed with the following table of conductivity of Potassium Chloride (KCl)
solutions at 25°C. This is used in the Automatic Cell Constant setting calibration feature.
(See section 11.2) The table is derived from the Standards laid down in “International
RecommendationNo.56oftheOrganisationInternationaledeMétrologieLegale”.
Table 4 KCl values at 25 °C
mol/l mg KCl/kg of solution Conductivity
0.001 74.66 0.1469 mS/cm
0.002 149.32 0.2916 mS/cm
0.005 373.29 0.7182 mS/cm
0.01 745.263 1.4083 mS/cm
0.1 7419.13 12.852 mS/cm
1.0 71135.2 111.31 mS/cm
Ifitismoreconvenient,theusermaymakesolutionsfromSodiumChloride(NaClorcommon
table salt) with the help of the following relationship table. This table is derived from the IEC norm
60746-3.
Table 5 NaCl values at 25 °C
Weight % mg/kg Conductivity
0.001 10 21.4 µS/cm
0.003 30 64.0 µS/cm
0.005 50 106 µS/cm
0.01 100 210 µS/cm
0.03 300 617 µS/cm
0.05 500 1.03 mS/cm
0.1 1000 1.99 mS/cm
0.3 3000 5.69 mS/cm
0.5 5000 9.48 mS/cm
1 10000 17.6 mS/cm
3 30000 48.6 mS/cm
5 50000 81.0 mS/cm
10 100000 140 mS/cm
n Measurement principle
Contrary to contact electrode conductivity, the EXA ISC Series analyses the conductivity with
outanycontactbetweenelectrodesandprocessuid.Themeasurementisbasedoninductive
couplingof2ringtransformers(Toroids)bytheliquid.
V
3
V
1
N
3
N
1
drive coilReceive coil
I=V
2
×G
Theconvertersuppliesareferencevoltageatahighfrequencytothe“drivecoil”.Thecoreofthis
coilisofahighpermeabilitymagneticmaterial,andastrongmagneticeldisgeneratedinthe
toroid.
Theliquidpassesthroughtheholeinthetoroidandcanbeconsideredasa“oneturn”secondary
winding.
Themagneticeldwillinduceavoltageinthissecondarywinding.Theinducedcurrentinthe
liquidwindingisproportionaltothisvoltageandtheconductanceoftheliquid“oneturnwinding”
isaccordingtoOhm’slaw.