Hanna Instruments HI 221 - Manual (Page 9)

9
• The instrument automatically defaults to the ORP
measurement mode if HANNA P type ORP electrode
is detected.
• Submerge the ORP electrode tip (4 cm/1½”) into the
sample. Allow a few minutes for the reading to sta-
bilize.
• The instrument displays the mV reading on the primary LCD.
• If the reading is out of range, the closest full-scale value will be displayed
blinking on the primary LCD.
TAKING TEMPERATURE MEASUREMENTS
Connect the HI 7669/2Wtemperature probe and turn the
instrument on. Dip the temperatureprobeinto the sample and
allow the reading on the secondary LCD to stabilize.
Calibrate the instrument frequently, especially if high accuracy is required. For
best results and constant display of electrode condition and electrode response
on the bar graph gauges we suggest at least a daily calibration.
The instrument should be re-calibrated:
• Whenever the pH electrode is replaced.
• At least once a day.
• After testing aggressive chemicals.
• If high accuracy is required.
• If CAL DUE message is displayed during measurement.
Every time you calibrate the instrument use fresh buffers and perform an
electrode cleaning procedure (see page 32).
PREPARATION
Pour small quantities of the buffer solutions into clean beakers. If possible, use
plastic or glass beakers to minimize any EMC interferences.
For accurate calibration and to minimize cross-contamination, use two beakers
for each buffer solution. One for rinsing the electrode and one for calibration.
pH CALIBRATION