18
8.
Rinse the pH and Temperature sensors in distilled water and blot them dry.
9.
Place both sensors into a small sample of secondary buffer (pH4.00, 9.23 or 10.01), so that the
bulb and reference junction are both covered, as per the diagram in step 6, above.
DO NOT
place the electrodes directly into the buffer bottle.
NOTE: pH9.23 and pH10.01 buffers are highly unstable. Avoid using these buffers if
possible. Discard immediately after use
.
10.
Select pH Calibration for the same Channel as selected in step 7, above.
(e.g.
→
→
F1:Calibrate
F1:Calibrate
→
→
F1:Channel 1
F1:Channel 1
→
→
F1:pH
F1:pH
).
The display should now look similar to the example shown in step 7. Note that the
900-I3
has
automatically recognised the second buffer.
Wait for the displayed reading to stabilise before attempting to calibrate the
900-I3
.
Press
to calibrate to the displayed buffer.
Otherwise, enter an alternative buffer using the Numeric Keypad, and then press
.
11.
The
900-I3
is now ready for pH measurements for the Channel that was calibrated. Discard the
used samples of buffer.
Rinse the pH and Temperature sensors in distilled water and blot them dry before placing them
into unknown samples.
4.4 pH Calibration Notes
1.
A 1-point calibration should be performed at least weekly. In applications where the electrode
junction can become blocked, such as dairy products, mining slurries etc, a 1-point calibration
may have to be done daily.
2.
A full 2-point calibration should be performed at least monthly. Of course, more frequent
calibration will result in greater confidence in results.
3.
Calibration information for each Channel is retained in memory when the
900-I3
is switched
off, even when the power supply is removed. This information can be recalled or printed later
using the GLP function (see section 8).