Hanna Instruments HI 9931 - Manual (Page 16)

16
Make sure that the probe has been properly connected and
wired to the controller (see preceding pages) and that the
meter is plugged to the mains.
Calibration should be ideally performed at a temperature
similar to that of the liquid to be monitored.
Ensure that the controller is in the “READ” position.
ZERO ADJUSTMENT:
• Leave the probe in the air and
make sure that it is dry.
• The LCD should show 0. If neces-
sary adjust the "ZERO CAL" trimmer
to display zero.
SLOPE ADJUSTMENT:
• Pour sufficient amount of a known conductivity or TDS solution in
a beaker. The solution should be close to the sample stream to be
monitored. For example, when using the HI 9931, choose
HI 7031L with a 1.41 mS/cm value at 25 °C if the measure-
ments are in the 1.2 to 2.5 EC range. Similarly, utilize
HI 70442L with a value of 1500 ppm at 25 °C if controlling your
procress with HI 9934.
• Immerse the probe in the beaker esuring
that the holes on the sleeve of the
probe are completely covered.
• Stir the probe and gently tap it on the
bottom of the beaker to ensure that
any air bubbles trapped inside the
sleeve escape. Best results are obtained
when the probe is not too close to the walls of the beaker nor
lying on the bottom.
• Wait for the reading to stabilize.
Adjust the "SLOPE CAL" trimmer to
display the same value as the cali-
bration solution at 25 °C. For
example, with HI 7031L, you should adjust the dispaly to 1.41
mS/cm and with HI 70442 to 1500 ppm.
CALIBRATION CALIBRATION CALIBRATION CALIBRATION CALIBRATION
SET
READ
FINE COARSE
SET POINT
SLOPE
CAL
ZERO
CAL
0
Min 7 cm
(2.8“)
FINE COARSE
SET POINT
mS
EC
SLOPE CAL ZERO CAL
1.41