14
3.2.1 Ion Calibration Procedure
The pHPLUS Direct 2 can measure a variety of ions. Ion measurement
requires an ISE (Ion Selective Electrode)—(sold separately) which
measures the speci
fi
c ion of interest—such as ammonia or
fl
uoride.
The available ion calibration values 0.1, 1.0, 10.0, and 100.0 ppm.
Chose any 2 or 3 consecutive values and prepare the corresponding
ion calibration standards. Turn on the meter and select the ion mode by
pressing the
MODE
key. For the best results, always calibrate
fi
rst with
the lowest standard value, followed by the next lowest standard.
1. Dip the electrode into the standard solution. Add ISA (Ion
Selective Adjustment solution) if required. Stir the solution
gently with the electrode. Press the
CAL
key to begin the
calibration mode.
2. The display will show “
CA
” (to indicate the calibration
mode) momentarily followed by “0.1”
fl
ashing. To select the
appropriate standard, use the
or
keys.
3. Press
ENTER
to con
fi
rm that the ppm value is the desired
standard. The displayed value will then show the corresponding
mV reading for the selected ppm value. Allow the reading to
stabilize.
4. When the mV reading is stable, press
ENTER
to complete the
calibration for the
fi
rst standard. The display will show the next
highest calibration standard value. Rinse the electrode with clean
water.
5. Dip the electrode into the next highest standard solution. Add
ISA if required. Stir the solution gently with the electrode. Press
the
CAL
key to begin the calibration mode.
