bluelab OnePen User Manual page 7

pH 4.0 or pH 10.0 calibration
1. Rinse probe in fresh tap water, shake off excess water.
Place the clean probe in either pH 4.0 or pH 10.0
calibration solution.
2. To calibrate pH4 hold the 'CAL' button until "CAL"
displays, then release.
3. Wait until •'s stop flashing from left to right, "4" stops
flashing and "PASS PH4" displays.
On a successful two-point calibration the following icons will be displayed.
Successfully Calibrated
pH7 Calibrated
After pH calibration, the OnePen™ returns to pH/Temperature measurement
mode.
Calibration Status
pH4 Calibrated