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PH220-en-US_v3.5 3/21
Calibration (pH)
The sensitivity of a pH electrode degrades over time, it is 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]).
Buffers are solutions of a known pH that have the useful property of resisting changes in pH.
These can be purchased pre-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 pH7.
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 inaccurate by more than 1 pH 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).
3.
During calibration, the pH reading flashes on the main display.
4.
When calibration is complete, the instrument displays ‘SA’ followed by ‘End’ and then
returns to the normal operation mode.
5.
For a 2- or 3-point calibration, repeat steps 1 ~ 4. When performing 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 a only a reminder and
will turn off when the electrode is calibrated (the reminder does not affect operation).
