Swann AMI Powercon Operator's Manual page 12

AMI Powercon
Product Description
Measuring
principle
Specific
Conductivity:
Cation Con-
ductivity (Acid
Conductivity):
Temperature
compensation
Standard
Temperature
10
When a voltage is set between two electrodes in an electrolyte so-
lution, the result is an electric field which exerts force on the
charged ions: the positively charged cations move towards the neg-
ative electrode (cathode) and the negatively charged anions to-
wards the positive electrode (anode). The ions, by way of capture
or release of electrons at the electrodes, are discharged and so a
current I flows through this cycle and the Ohms law V = I×R ap-
plies. From the total resistance R of the current loop, only the resis-
tance of the electrolyte solution, respectively its conductivity
of interest.
The cell constant of the sensor is determined by the manufacturer
and is printed on the sensor label. If the cell constant has been pro-
grammed in the transmitter, the instrument measures correctly. No
calibration is must be done, the sensor is factory calibrated. Mea-
suring unit is S/cm or S/m.
Conductivity from all ions in the sample, mainly the alkalization
agent. The contribution of impurities is masked by the alkalization
agent.
Only with AMI Powercon acid.
The alkalization agent is removed in the cation column. All cationic
ions are exchanged with H+, all anionic impurities (ions with nega-
tive charge) pass through the column unchanged.
The mobility of ions in water increase with higher temperature
which enlarges the conductivity. Therefore, the temperature is mea-
sured simultaneous by an integrated Pt1000 temperature sensor
and the conductivity is compensated to 25 °C. Several temperature
compensation curves, designed for different water compositions,
can be chosen.
After cation exchanger (cation conductivity), the temperature com-
pensation curve strong acids has to be set.
For more information see: Influence of Temperature on Electrical
Conductivity, PPChem (2012)
The displayed conductivity value is compensated to 25°C standard
temperature
1
/ , is
R
A-96.250.341 / 061015