Hanna Instruments HI 23 - Manual (Page 17)

33 32
To obtain accurate readings, use the calibration solution in
the selected range and closer to the values to be mea-
sured.
Offset Calibration
• To perform the EC or TDS calibration en-
ter the calibration mode, by pressing CAL
and entering the password.
• After the correct password is entered,
the control actions stop and the pri-
mary LCD will display the first EC or
TDS calibration value, with the "CAL"
indicator blinking. The secondary LCD
displays the temperature.
Note If the wrong password is entered the system reverts back to
normal operation, displaying EC or TDS values.
• 0 is the default value for the 1 st calibra-
tion point. Dry the conductivity probe
and leave it in air.
• Only when the reading is stable the "CAL"
indicator will stop flashing (after about
30 seconds) and the "CFM" indicator
will start blinking.
• Press CFM to confirm the calibration point;
the primary LCD will display the second
expected buffer value.
If the zero calibration cannot be performed,
"ERROR" will blink.
Cell constant calibration
• Select the solution value on
the primary display by press-
ing or if the selected
range has two possibilities
(e.g. 5.000 and 12.880
mS).
• Immerse the EC/TDS probe with the temperature sensor in
the selected solution. The level of solution must be higher
than the holes of the EC/TDS probe sleeve. Tap the EC/
TDS probe repeatedly on the bottom of the beaker and stir
to ensure that no air bubbles are trapped inside the sleeve.
CALIBRATION
The controller is factory calibrated for temperature as well as
for the analog input and outputs.
The user should periodically calibrate the instrument for EC
or TDS. For greatest accuracy, it is recommended that the
instrument is calibrated frequently.
Before beginning normal operation, it is recommended to
standardize the probe with the Hanna calibration solution
close to the expected sample value and inside the selected
range.
EC AND TDS CALIBRATION
The calibration points for EC and TDS are as follows:
Range Calibration point(s)
0.0÷199.9 µS/cm 84.0 µS/cm
0÷1999 µS/cm 1413 µS/cm
0.00÷19.99 mS/cm 5.00 - 12.88 mS/cm
0.0÷199.9 mS/cm 80.0 - 111.8 mS/cm
0.0÷100.0 ppm 42.0 ppm
0÷1000 ppm 800 ppm
0.00÷10.00 ppt 6.44 ppt
0.0÷100.0 ppt 55.9 ppt
The user should select the appropriate range to calibrate (setup
code 03). Calibration must be performed for each range used.
The temperature probe should also be connected to the pro-
cess meter (when using a different temperature probe). The
meters are equipped with a stability indicator. The user is also
guided with indications on the display during the calibration
procedure.
Initial Preparation
Pour a small quantity of the calibration solution (e.g. 1413 µS/
cm) into a beaker. If possible, use a plastic beaker to mini-
mize any EMC interference.
For accurate calibration use two beakers containing the same
solution, the first one for rinsing the probe, the second one
for calibration. By doing this, contamination between the so-
lutions is minimized.