Orion Benchtop pH/ISE Meter Instruction Manual
Calibration and Measurement of pH
19
C. Orion 420Aplus pH Calibration and Measurement
Autocalibration
Autocalibration is the feature of the Orion 420Aplus Meter that
automatically recognizes three buffers, 4.01, 7.00, and 10.01, within a
range of ± 0.5 pH units. Results greater than ± 0.5 pH units from the
correct value will trigger an operator assistance code. At this point, a
manual calibration can be performed or the calibration can be ended and
repeated with fresh buffers. During calibration the user waits for a stable
pH reading. Once the electrode is stable, the meter automatically
recognizes and displays the temperature-corrected value for that buffer.
Pressing yes enters the value into memory.
NOTE: Do not scroll when using autocalibration. If you
want to exit the menu at any time, press measure.
Manual Calibration
To calibrate with buffers other than 4.01, 7.00, or 10.01, use the manual
calibration technique. The chosen buffers must be greater than one (1) pH
unit but less than four (4) pH units from the next closest buffer. The
calibration sequence is the same as autocalibration except that the buffer
values are scrolled in and then entered.
NOTE: For manual calibration you must use or .
Even if the value displayed is the correct value for your
buffer, you must press a scroll key to start the editing
process. Press yes to accept each digit. Otherwise
the meter assumes autocalibration is being performed.
Three Point pH Calibration
Up to a three (3) point calibration can be performed on the Orion 420Aplus
Meter. Both autocalibration and manual calibrations may be used within the
same calibration curve. For example, autocalibration may be used with the
7.00 and 10.01 buffers while manual calibration would be used with a
3.78 buffer.
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