Orion Star A221 and Star A321 Portable pH Meters
4
pH Calibration
One to five pH buffers can be used for calibration. Always use fresh pH buffers and select buffers that bracket
the sample pH and are one to four pH units apart. Prepare the pH electrode according to the instructions in
the electrode use guide. Connect the pH electrode and any other electrodes to be used (ATC probe, reference
electrode) to the meter. Power on the meter and set the measurement mode to pH.
1. In the measurement mode, press
f1 (cal)
.
2. Rinse the pH electrode and any other electrodes in use with distilled water, blot dry with a lint-free tissue
and place into the pH buffer.
3. When the electrode and buffer are ready, press
f3 (start)
.
4. Wait for the pH value on the meter to stabilize and stop flashing and perform one of the following actions:
a. Press
f2 (accept)
to accept the displayed pH value.
b. Press
f3 (edit)
to access the numeric entry screen and edit the pH buffer value.
i. Press
,
,
or
to highlight a number, decimal point or negative sign; press
f3 (enter)
to select the highlighted item and repeat until the buffer value at the measured
temperature is shown above the numeric entry screen.
ii. Press
f2 (done)
to exit the numeric entry screen.
iii. Press
f2 (accept)
to accept the entered pH value.
5. Press
f2 (next)
to proceed to the next buffer and repeat steps 2 through 4 or press
f3 (cal done)
to save
and end the calibration. If five buffers are used, the calibration will save and end once the fifth buffer value
is accepted.
a. If a one point calibration is performed, press
f2 (accept)
to accept the displayed slope value or press
f3 (edit)
to access the numeric entry screen, enter the slope value and press
f2 (accept)
.
6. The meter will display the calibration summary including the average slope. Press
f1 (meas)
to export
the data to the calibration log or press
f2 (print)
to export the data to the calibration log and a printer or
computer. The meter will automatically proceed to the measurement mode.
