In-Situ pH/ORP Sensor - Manual (Page 2)

Page 2
Calibration Procedure
The pH/ORP sensor requires separate calibrations for
pH and ORP. In-Situ recommends the following process
for calibrating both parameters.
ORP—Quick Cal
The Quick Cal procedure produces excellent results for
ORP as long as the solution is stored as recommended
and used before its expiration date.
1. Fill the Cal Cup with Quick Cal solution and place
the instrument in the solution.
2. Follow the instructions in the Calibration Wizard
until the calibration is complete.
pH—Traditional Calibration
The pH sensor is most accurate after a multi-point
traditional calibration. After using the Quick Cal
solution to calibrate ORP, empty the Cal Cup, rinse it
and the sensors in clean water then in the lowest pH
buffer you intend to use.
1. Fill the Cal Cup with the lowest pH buffer you
intend to use for calibration.
2. Follow the Calibration Wizard in the software or on
the Con TROLL® PRO.
3. In the pH Calibration Wizard, specify how many
calibration points you intend to use, and the
solution for each. Click Next and follow the wizard
to perform a 2- or 3-point calibration. Be sure to
rinse the Cal Cup and sensors between solutions.
4. At the end of the Wizard, click Finish to write the
newly calculated calibration coefficients to the
sensor. The pH/ORP sensor is now calibrated and
ready to use.
If the instrument will be used in a day or so, leave the
sensors installed. Remove the Cal Cup and rinse it and
the sensors. Add about 50-100 mL of tap water to the Cal
Cup. Return the probe to the Cal Cup for transport. For
longer storage, see Sensor Handling and Storage below.
Calibration Notes:
• Only one solution is required for ORP calibration.
Quick Cal or ZoBell’s solution are recommended and
available from In-Situ Inc. The reference millivolt
value is available in the software for a traditional
calibration with ZoBell’s. A custom solution may be
used in a traditional calibration if the mV value at
the calibration temperature is known.
• pH 4, pH 7, and pH 10 buffers are available from
In-Situ Inc. for pH calibration. Always begin with the
lowest buffer value when performing a multi-point
calibration.
• Ensure that every port is filled with a sensor or a
plug before calibrating.
• For best results, calibrate at the same temperature
as the expected sample temperature.
• Prior to calibrating, rinse the Cal Cup and the front
end of the instrument in clean water, and shake dry.
• The Cal Cup fill line indicates the approximate
amount of solution to use. The temperature sensor
should be submerged at least one half inch.
• Most sensors stabilize in 1 to 3 minutes if
properly hydrated before calibration. To minimize
stabilization time, do not handle the instrument
during calibration readings.
• To shorten the calibration time, you have the option
to accept the calibration when stability is “Nominal.”
If the early value is accepted, the calibration point
will be designated “USER SET” in the calibration
report. If the calibration was performed through to
stability then the sensor will operate according to
specifications.
• Cal solutions may be flushed down the drain with
running water, or saved in a separate container and
used to rinse the next time you calibrate with the
same solution.
• Calibrate the sensor after replacing the reference
junction and/or the filling solution, during routine,
scheduled maintenance, or every 2-6 weeks in the
absence of other indicators.
• Recalibrate the sensor after replacing the
reference junction or the filling solution; during
scheduled maintenance, or every 2-6 weeks if
sensor readings drift.
Software Indicators During
Calibration:
UNSTABLE indicates the sensor response does not
meet the criteria for a valid calibration point.
NOMINAL indicates the sensor deviation meets early
stabilization criteria. The Accept button becomes
available when stability is nominal. You may accept the
early value, or wait for complete stability.