Hanna Instruments HI 21 Series - Manual (Page 23)

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• Use a Checktemp or another calibrated thermometer with
a resolution of 0.1° as a reference thermometer.
• Immerse the temperature probe in
the beaker with ice and water as near
to the Checktemp as possible.
• Press and hold first CFM and then
CAL to enter the temperature cali-
bration mode.
• Execute the password procedure.
• With HI 21, the meter will ask for the calibration procedure
code number. Use or to select code 1 for the tem-
perature calibration and press CFM to enter.
• CAL will blink on the LCD until the
meter confirms a steady reading.
• When the reading has stabilized at
a point near the first calibration
point, CAL will stop blinking and an
intermittent CFM will prompt the user
to confirm the first calibration.
• If the reading stabilizes at a reading
significantly variant from the first
setpoint, an intermittent WRONG
will prompt the user to check the
beaker or baths.
• After pressing CFM the unit will switch to the second cali-
bration point.
• Select 25 or 50°C by pressing or .
0 °C
(32 °F)
°C
• When the reading has stabilized at
a point near the first calibration
point, CAL will stop blinking and an
intermittent CFM icon will prompt the
user to confirm the first calibration.
• If the display stabilizes at a value
significantly different from the first
setpoint, an intermittent WRONG
icon will prompt the user to check
and adjust the simulator and start
again.
• After pressing CFM the unit will switch to the second cali-
bration point at 350 mV.
• With HI 22 it is possible to select 1900 mV by pressing
or . After that, proceed as described above.
Note A measure is considered stable when it varies little within a
sequence of acquisitions. The number of acquisitions is fixed
so that the waiting time for blinking “CFM” is about 20 sec-
onds.
Calibration procedure may be interrupted by
pressing CAL. If the calibration procedure is in-
terrupted this way, or if the controller is switched
off before the last step, no calibration data is
stored to EEPROM.
TEMPERATURE CALIBRATION
The pH/mV controller is factory calibrated for the mV and
temperature inputs. However, the user may also perform a
temperature calibration.
• Prepare a beaker containing ice
and water at 0°C/32°F and an-
other one with hot water at 25°C/
77°F or 50°C/122°F.
0 °C
(32 °F)
°C
50 ºC
(122 ºF)
°C