LaMotte pH PLUS Direct Meter - Manual (Page 10)

3. CALIBRATION
3.1 pH Calibration
The meter is capable of calibrating up to 3 points using USA or NIST (nSt)
pH buffer standards or 2 points with Low Ionic (Pb) pH buffer standards. All
new calibration values will automatically override existing data.
USA pH 4.01,7.00 and 10.01
NIST pH 4.01, 6.86 and 9.18
Pb pH 4.10 and 6.97
It is recommended that you perform at least a 2-point calibration at room
temperature (25 °C) using standard buffers, starting with the first buffer at pH
7.00 (USA), pH 6.86 (NIST) or pH 6.97 (Pb) followed by other buffer values.
For a 1-point calibration, the calibration should be performed with a pH buffer
value closest to the expected sample value being measured. Otherwise
calibrating at pH 7.00, pH 6.86 or pH 6.97 is advisable.
The meter has automatic buffer recognition that identifies the correct pH
buffer values during calibration. If non-standard pH buffers other than the
above standards are used, or the electrode has worn out, the LCD will flash
“
Er1”. Press the CAL key to abort calibration and resume measurement. In
general all pH buffer values have the window of up to +/- 1 pH tolerance
during calibration.
Ensure that you use new pH buffer solutions during calibration. Do not reuse
buffer solutions as they may be contaminated and affect the calibration and
accuracy of measurements. Always store buffer solutions in a dry, cool
environment if possible.
Before use, remove the plastic protective cap on the pH electrode and
condition the glass bulb by soaking it in tap water for 1-2 hours. This hydrates
the glass bulb if the electrode is too dry or has not been used for a long period
of time. Always rinse the probes with tap water or rinse solution before and
after each calibration/sample measurement to avoid cross-contamination. For
details refer to section 5 on Electrode care and maintenance.
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