Yokogawa 2-Wire Dual Channel Transmitter/Analyzer FLXA21 - Manual (Page 238)

<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 fluid. 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 coil Receive 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 field 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 field 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.