Thermo Scientific Scientific AquaSensors DataStick User Manual page 34

The first buffer should generally be a 7 pH standard to set the measurement offset.
After selecting the 2-point pH buffer calibration method, the sensor should be placed in the first standard and when sensor
and temperature readings are stable, click the CALIBRATE button to initiate the calibration or click EXIT to return to the main
measure screen.
Once the calibration has been initiated it will take between 15 seconds and 2 minutes depending on sensor and temperature
measurement stability. During this period, the abort sequence can be initiated as shown with the active Abort button.
Once the 2-point buffer calibration has successfully completed storage of the first point, the status box will prompt the user to place
the sensor in the second solution before initiating calibration of the second point. Please note that the reading will not be adjusted
after the first calibration point. Calibration changes will only take effect after both calibration points have been accepted.
Thermo Scientific AquaSensors™ DataStick™ Measurement System User Guide 32