Calibration (pH)
The sensitivity of a pH electrode degrades over time, it is very important to frequently calibrate the
meter to the electrode. pH electrodes can be thought of as batteries in that they run down with time
and use.
Calibration is performed using standard buffer solutions at room temperature (78°F, 25°C). Buffer
solutions are solutions of a known pH that have the useful property of resisting changes in pH.
These can be purchased already mixed or in capsule form and are usually available in three pH
values, pH 4.00, pH 7.00 and pH 10.00.
Calibration is always performed using the pH 7.00 buffer first, followed by a second calibration.
Select pH 4 buffer for the second calibration if typical measurements will be less than pH7 or use a
pH 10 buffer if typical measurements will be greater than ph 7.
In order to obtain the most accurate results possible, a pH meter should be calibrated at
least once each day.
pH Calibration Procedure
1. Place the electrode into a 7.00 pH buffer solution. Press and hold the CAL button until “CAL”
appears in the display.
2. The instrument automatically recognizes the solution and calibrates to that value. Note that if
the solution is off by more than 1 pH unit from the 4, 7, or 10 pH buffer, or if the electrode slope
is low, the instrument will assume an error and abort the calibration (End will be displayed, and
the unit will return to the normal measurement mode.)
3. During calibration, the pH reading flashes on the main display.
4. When calibration is complete, the instrument automatically displays ‘SA’ followed by ‘End’ and
then returns to the normal operation mode.
5. For a two or three point calibration, repeat steps 1-4. When doing a 2 or 3 point calibration,
calibrate with pH 7 buffer first, then follow with pH 4 and/or pH 10.
CAL Reminder Display
When in pH measurement mode, the CAL icon will appear if a calibration has not been performed
after 15 on/off cycles of the instrument. The CAL display is simply a reminder and will turn off when
the pH electrode is recalibrated. The reminder does not affect function in any way.
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