Manual

38
IM 12D06D05-01E
6-2. Cell constant manual
The intention of this calibration routine is to fine
tune a sensor for which only the nominal cell
constant is known, or recalibrate a sensor that
has been changed (or damaged) in the course
of operation. Choose 1st or 2nd compensation
to suit the calibration solution used. The solu-
tion should be prepared or purchased, meeting
the highest standards of precision available.
Allow the sensor to reach stable readings for
both temperature and conductivity before ad-
justing to correspond to the calibration solution
value. The setting of a cell constant for a new
(replacement) sensor is also possible in this
routine. This avoids the need for entry into the
commissioning mode, which may have another
authorization (password) level.
Press the keyandchoose“
Execute: Cali-
bration.
” Press “
Cell constant (manual)
” to
execute calibration.
6-3. Cell constant automatic
This routine is built around the test method
describedinOIML(OrganisationInternationale
de Metrologie Legale). International Recom-
mendation No. 56. It allows the direct use of
the solutions prescribed in the test method, au-
tomatically selecting the appropriate tempera-
ture compensation. The look up table is used
to find the appropriate conductivity reading for
themeasuredtemperature.Seeappendix3for
OIMLsolutions
Press the keyandchoose“
Execute: Cali-
bration.
”Press“
Cell constant (automatic)
”to
execute calibration.
6-4. Air (zero) calibration
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
for all installations during commissioning. After
some time in service a dirty sensor may well
show a high zero offset because of fouling.
Clean the sensor and try again.
•Waitforthesensortodry(becauseaircal
must be made with no current flow in the
sensor, that is, the sensor must be dried
while being exposed to air).
•Thesensormustbeinstalledinan
environment free of electromagnetic
interference and radio frequency
interference.
Press the keyandchoose“
Execute: Cali-
bration.
”Press“
Air calibration
”toexecuteit.
CAUTION
The temperature compensation should be set
to NaCl when confirming zero during air calibra-
tion.
6-5. Sample calibration
With the sensor in situ, a sample can be taken
for laboratory analysis. Sample calibration
records the time and reading, and holds these
in memory until the analysis has been com-
pleted. The laboratory data can then be entered
regardless of the current process value, without
the need for calculations.
Press the keyandchoose“
Execute: Cali-
bration.
” Press “
Sample
” to execute sample
calibration.
Press [
Take Sample
] to record a collected
samplevalueinmemory.Re-entertheSample
Cal. screen and press [
Start calibration
] to
perform a sample calibration. This updates the
recorded data.
6-6. Temperature coefficient calibration
Simply input the solution conductivity at the
reference temperature (T
R
) after allowing the
sensor to stabilize at elevated temperatures.
The ISC450G will calculate the temperature
coefficient for you. The ideal temperature for
this calibration is the normal process value (T
P
).
This calibration is enabled if the Temperature
Compensationissetto“TC.”
Press the keyandchoose“
Execute: Cali-
bration.
” Press “
Temperature coefficient
” to
execute this calibration