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17. Selecting pH6.88 or pH7.00 as the Primary Buffer
The
WP-91
is factory set to automatically recognise pH4.00, pH6.88 and
pH9.23 buffers. However, some users may prefer to use pH7.00 instead
of pH6.88 and pH10.00 instead of pH9.23. The following procedure
describes how to set which of these buffers are automatically recognised
at calibration.
1. Switch the meter
OFF
.
2. Press and HOLD the
key while switching the meter back on.
3. The buffer selection menu is now displayed.
Select >F1:6.88pH
Buffer F2:7.00pH
The arrow indicates the current selection.
4. Press
to select pH6.88 as the primary buffer.
Press
to select pH7.00 as the primary buffer.
Press
to quit buffer selection and retain the current setting.
5. The display will now show the currently selected high pH buffer.
Select >F1:9.23pH
Buffer F2:10.0pH
The arrow indicates the current selection.
6. Press
to select pH9.23 as the high pH buffer.
Press
to select pH10.00 as the high pH buffer (the display shows
10.0 for the latter, but this buffer is stored as pH10.00).
Press
to quit buffer selection and retain the current setting.
7. The setting is kept in memory when the meter is switched off, even if
the battery is removed. The buffers are re-set to pH6.88 and pH9.23
during initialisation.
Note:
pH6.88 buffer is a DIN 19266 and NBS Primary-standard pH
solution. Its use is highly recommended for the most accurate
possible results. If pH7.00 buffer is used, ensure that it is
manufactured to 0.01pH accuracy. pH7.00 buffer has a buffer
capacity less than half that of pH6.88 buffer and is therefore
much less stable.