12
that the electrode offset is less +/- 1.5 pH. Replace the buffer and/or the
electrode. Press CLEAR key and repeat from 2.2. Er1 may appear if
the STAND/STAND I key is pressed before the electrode settles to
within
+/- 1.5 pH of the buffer value. Allow sufficient time for the electrode
to stabilize before taking any action.
2.5 Remove the pH electrode from buffer 7.00(model 6250/ model 6219)
or 6.86(model 6250C/ 6219C), rinse with distilled water and
immerse in buffer 4.01 or 10.01 (model 6250/ model 6219) or
4.00 or 9.18 (model 6250C/ model 6219C). Set the instrument to
display the temperature of the second buffer, as in 2.3. The
displayed temperature must be within 0 to 50.0 degree C range.
2.6 Allow sufficient time for the pH electrode to stabilize. Press
the SLOPE/STAND II key. The SLOPE indication will stop flashing
and stay on. The instrument will display the second buffer value
corresponding to the temperature of the second buffer as set in 2.5.
Refer to Table 1. If the reading still drifts, repeat 2.6 until a stable
reading is obtained. The micro computer inside the instrument will
calculate and compensate for the pH electrode slope deviation
corresponding to the values of the two calibration buffer. The
instrument is dual point calibrated and is ready for measurements.
If Er2 is displayed, check to make sure that the correct buffer is used
andthat the slope of the electrode is not off by more than +/- 30%
from the theoretical slope. Replace the buffer and/or the pH electrode.
Press CLEAR key and repeat from 2.2. Only buffer 4.01 and 10.01
(model 6250/ model 6219) or buffer 4.00 and 9.18 (model 6250C/
model 6219C) may be used to slope the instrument. Er2 may appear
if the SLOPE/STAND II key is pressed before the electrode settles to
/- 30% of the buffer value. Allow sufficient time for the
electrode to stabilize before taking any action.
pH MEASUREMENTS
The STAND and SLOPE indications must be on, indicating that the
instrument is dual point calibrated and ready for measurements.
