Calibrating Ph - Xylem EXO Series User Manual

Calibration
5.5
pH
2-point
Most environmental water has a pH between 7 and 10. Therefore, unless you anticipate a pH of less than 7
for your deployment application, we recommend a 2-point calibration using pH 7 and pH 10 buffers.
Review the basic calibration description on pg 65.
Pour the correct amount of pH 7 buffer/standard in a clean and dry or pre-rinsed calibration cup. Carefully
immerse the probe end of the sonde into the solution, making sure the sensor's glass bulb is in solution by at
least 1 cm. Allow at least 1 minute for temperature equilibration before proceeding.
In the Calibrate menu, select pH or pH/ORP, then select pH.
Click 2 Point for the Calibration Points. Enter 7 as the value of the first standard and 10 as the value of the
second standard.
- Observe the temperature reading above the standard value. The actual pH value of all buffers varies
with temperature. Enter the correct value from the bottle label for your calibration temperature for
maximum accuracy. For example, the pH of one manufacturer's pH 7 Buffer is 7.00 at 25˚C, but 7.02
at 20˚C.
- If no temperature sensor is installed, user can manually update temperature by entering a value.
Click Start Calibration. Observe the readings under Current and Pending data points and when they
are Stable (or data shows no significant change for approximately 40 seconds), click Apply to accept this
calibration point.
Rinse the sonde in water and dry the sonde. Pour the correct amount of an additional pH buffer standard
into a clean, dry or pre-rinsed calibration cup, and carefully immerse the probe end of the sonde into the
solution. Allow at least 1 minute for temperature equilibration before proceeding.
Click Proceed in the pop-up window. Observe the readings under Current and Pending data points and
when they are Stable (or data shows no significant change for approximately 40 seconds), click Apply to
accept this calibration point. (It is best not to touch the sonde while stabilizing).
Click Complete. View the Calibration Summary screen and QC score. Click Exit to return to the sensor
calibration menu, and then the back arrows to return to main Calibrate menu.
Rinse the sonde in tap or purified water and dry the sonde.
3-point
Select the 3-point option to calibrate the pH probe using three calibration solutions. In this procedure, the
pH sensor is calibrated with a pH 7 buffer and two additional buffers. The 3-point calibration method assures
maximum accuracy when the pH of the media to be monitored cannot be anticipated. The procedure for
this calibration is the same as for a 2-point calibration, but the software will prompt you to proceed to a third
pH buffer to complete the 3-point procedure.
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