39
38
Note
For a correct conductivity calibration, the probe shield or the calibration
beaker must be used.
The conductivity calibration menu includes
3 different types of calibration: Conductivity,
Absolute conductivity and Salinity.
The “Conductivity” option allows a single point
calibration with a standard solution selectable by
the user. This calibration is temperature
compensated.
The “Absolute conductivity” option allows a single point calibration with a
conductivity solution of known non-temperature compensated value at the current
temperature.
The “Salinity” option allows calibration with a standard salinity solution.
The 3 calibrations are related, so that each one will calibrate all 3 measurements.
Note
To improve accuracy, choose a calibration standard near the sample
conductivity.
Choose “Conductivity calibration” from the “Calibration” menu, select the
calibration type using the arrow keys and press
Select
to confirm.
Conductivity
• Select the “Conductivity” option and press
Select
to confirm.
• Fill the calibration beaker with a conductivity standard (see APPENDIX D -
“Accessories” for choosing the proper HANNA standard solution).
• Pour additional standard into a second beaker to be used to rinse the sensor.
• Immerse the sensor into the rinse standard by raising and lowering the beaker
a few times to ensure that the EC sensor channels are filled with fresh standard.
• Place the calibration beaker over the EC sensor and dislodge any trapped
bubbles. Screw the beaker into place. Wait for the reading to stabilize.
• The main display shows the actual reading, while the secondary level displays
the current temperature and the standard value.
• To change the standard value, press
Cal. point
and the list of available standard
values is displayed: 0 µS/cm, 84 µS/cm, 1413 µS/cm, 5.00 mS/cm, 12.88
mS/cm, 80.0 mS/cm and 111.8 mS/cm.
Single point Custom % saturation calibration
• For a calibration at another known value place sensor and temperature probe
into the known solution and change the calibration value, press the
Cal. point
softkey and select the desired point.
• To insert a different calibration value, press
Cal. point
and then
Custom
.
Insert the desired value using the keypad, then press
Accept
.
• When the reading is stable, the “Ready” message is displayed. Press
Confirm
to store the calibration point.
• The following messages will appear: “Storing” and “Calibration completed”.
• Press
OK
to return to the “Calibration” menu.
• Press
ESC
twice to return to the main menu.
• Press
Measure
to return to the measurement screen.
D.O. concentration (only
HI 98194
)
Verify the barometric pressure, conductivity and
temperature reading are correct. Calibrate them
if necessary. To calibrate the D.O. concentration
range, a solution with known Dissolved Oxygen
concentration value is needed. The solutions used
to calibrate with should be determined
independently (for instance by Winkler titration). Place the D.O. sensor with
temperature sensor into the known solution.
• From the “DO calibration” menu, select the “DO concentration” option, insert
the known concentration. Allow the sensors to reach thermal equilibrium with
the solution. Stir or agitate if possible to keep fresh solution in front of the
membrane and press
OK
.
• When the reading is stable, the stability timer will count down and <Confirm>
will appear. Press
Confirm
to accept the value.
• When the messages “Storing” and “Calibration completed” appear, the
calibration is completed. To return to the “Calibration” menu, press
OK
.
• To return to the main menu, press
ESC
twice.
7.5 CONDUCTIVITY CALIBRATION (HI 98194, HI 98195 only)
A conductivity calibration is used to adjust for variations in cell factors by using
a standard solution of known conductivity. Oily coating and biological
contaminants are the primary cause of calibration drift in conductivity sensors.
This type of fouling changes the apparent cell geometry, resulting in a shift in cell
constant. Before performing a conductivity calibration inspect the EC sensor for
debris or blockages. The EC electrodes are situated inside the two small channels
found in the bottom of the conductivity sensor. Clean using the small brush from
the probe maintenance kit. Flush with water. A mild detergent may be used to
remove oily coatings. Always flush with clean water after cleaning.
