10
D . O . C A L I B R A T I O N
Calibrate the instrument frequently, especially if high accuracy is required.
The instrument can be calibrated in maximum 2 points: 0.0% (
zero calibra-
tion
) and 100.0% (
slope calibration
).
The zero calibration of the
HI 2400
is very stable, therefore this procedure
needs to be performed only whenever the probe or the membrane is replaced.
However, because the slope calibration is more critical, it is recommended to
perform this procedure every week.
INITIAL PREPARATION
• Pour small quantities of HI 7040 Zero Oxygen
solution into a beaker. If possible, use a plastic
beaker to minimize any EMC interferences.
• Make sure the probe is ready for measurements (see probe preparation on
page 7), i.e. the membrane is filled with electrolyte and the probe is
connected to the meter.
• Switch the meter on by pressing the
ON/OFF
switch.
• For an accurate calibration, it is recommended to wait
for at least 15 minutes to ensure precise conditioning of
the probe.
• Remove the protective cap from the D.O. probe.
• Set the appropriate altitude factor (see page 14). Make
sure the salinity factor is set to zero (see page 13).
ZERO CALIBRATION
• Submerge the probe into HI 7040
zero oxygen solution
and stir gently for 2-3 minutes.
• Press
CAL
. The “~” tag will blink on the LCD until the
reading is stable.
• When the reading is stable, “CFM” starts blinking. Press
CFM
to confirm the “0.0%” D.O. calibration.
• If the reading is within the limits (±15% f.s.), the
meter stores the value (and adjusts the slope point).
HI 7040
HI 7040
CFM
BUF
CAL
CFM
BUF
CAL
%
