HACH LANGE ORBISPHERE 3654, User Manual, Page: 38 / 58

36
Calibrations
6.2.3 Calibration in H
2
or N
2
at elevated pressure
The sensor can be calibrated in pure H
2
or N
2
gas at an elevated pressure. This method
requires an accurate pressure gauge connected to the exit of the flow chamber.
WARNING
Handle H
2
gas with great care. It is extremely flammable and explosive.
When calibrating in gas phase, the flow chamber and sensor head must be dry.To ensure that
the flow chamber and sensor components are dry, remove and dry them with a clean soft tissue.
1.
Set the gas measurement phase to
Gaseous
and set the calibration medium to
In a liquid
or a gaseous sample at known concentration
(as detailed in Calibration medium on
page 31 ).
2.
Connect a source of pure H
2
or N
2
gas to the inlet of the flow chamber, as illustrated in
Figure 10 on page 34 , and adjust the gas flow exiting from the flow chamber to be in the
range of 1 to 5 bar (it is best to use a pressure close to the application conditions).
3.
Press the
CAL
button. Remember, this button
may have been locked out to prevent an
accidental reset (see
Locking out the
instrument’s CAL button on page 32 for details).
4.
A brief clearing message
[---]
appears.
5.
Press
CAL
again within a 3 second period. The
instrument then displays the absolute pressure
of calibration gas (i.e. gauge pressure plus
atmospheric pressure).
6.
Modify this reading using the
Up/Down Arrow
keys until the displayed pressure agrees with
that of the gauge plus atmospheric pressure.
7.
Press
CAL
again.
If the instrument makes two consecutive
measurements with less than 1% difference, it
calibrates against this stabilized value. The LCD
then displays the message
[CAL]
to indicate
calibration has been successfully completed
If the calibration does not complete, the LCD
displays the message
[Err]
. The reason for
this calibration error is either that the measured
gas partial pressure is under 5 mbar, or that a
wrong instrument key was pressed during the
calibration steps.