1. Place the sensor in pH buffer 7 or 6.86 and allow the temperature and pH readings to stabilize. 2. Press and hold Cal for three seconds. 3. Highlight pH and press enter. If pH is not listed as an option, check the System Setup menu to ensure pH is enabled in the ISE Sensor Type menu.4. Highlight 1 point and press enter.5. If necessary, use the up and down arrow keys to adjust the pH buffer value. Note the pH mV reading which ideally should be between -50 and +50 in buffer 7.6. Press enter to complete the calibration or press Cal to cancel. 7. ‘Calibration Successful’ will display for a few seconds to indicate a successful calibration and then the instrument will return to the Run screen.8. If the calibration is unsuccessful, an error message will display on the screen. Press the Cal key to exit the calibration error message and return to the Run screen. See the Troubleshooting guide for possible solutions.