Ph Calibration Procedure - LaMotte pHPLUS DIRECT 2 Manual

Before use, remove the plastic protective cap on the pH probe and
condition the glass bulb by soaking it in tap water or pH buff er
(preferably pH 4) for 1-2 hours. This will hydrate the glass bulb if the
probe is too dry or if it has not been used recently. Always rinse the
probe with clean water before and after each calibration or sample
measurement to avoid cross-contamination. For details refer to Section 5
on Probe Care and Maintenance.

3.1.1 pH Calibration Procedure

1. Turn on the meter and select pH by pressing MODE if necessary.
2. Press CAL to begin pH calibration mode. "CA" (calibrate) will
display briefl y. Notice that the pH reading and "pH" annunciator
will both blink.
3. Pour a known pH buff er calibration standard solution, e.g. pH 7.00,
into a clean, dry container. Dip the pH probe and temperature
probe into the solution. Stir gently and wait for the reading to
stabilize (approximately 30 seconds depending on the probe
condition).
4. When the pH reading has stabilized, the pH annunciator will
stop blinking. Press HOLD/ENTER to confi rm the value. "CO"
(confi rm) will display briefl y. The pH value is automatically
adjusted to the buff er value shown from your selected buff er group.
The example below shows a successful pH 7.00 calibration
at 25 °C.
5. For a one-point calibration with pH 7.00 or 6.86 only, press
CAL to return to measurement mode. However for the greatest
accuracy, perform a multiple-point calibration. Repeat steps 3
& 4 with additional pH buff er calibration standards. When you
have completed the preset number of calibration points, the
meter will automatically save the calibration, cease blinking,
and begin pH measurement.
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