HACH LANGE ORBISPHERE 3654, User Manual, Page: 39 / 58

37
Calibrations
6.2.4 Calibrating in a liquid H
2
or N
2
solution
The sensor can be calibrated in a standard liquid solution that has a known concentration of H
2
or N
2
.
You can create a solution with a known concentration by dissolving H
2
or N
2
in water at a
measured temperature and pressure. Alternatively, analyze a carbonated beverage
independently by some acceptable means.
Note:
A flow rate lower that 150 ml/min can be used for the calibration, but you must ensure that all
measurements made after the calibration are made at exactly the same flow rate as is used for the
calibration. To ensure accurate results it is recommended to use a model 32311 Flow Meter as described in
Model 32311 flow meter on page 39 .
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.
1.
Set the gas measurement phase to
Dissolved
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.
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).
3.
A brief clearing
[---]
message appears.
4.
Press
CAL
again within a 3 second period. The
instrument then displays the concentration of H
2
or N
2
, based on the last value of the calibration
coefficient.
5.
Modify this reading using the
Up/Down Arrow
keys until the displayed concentration agrees
with that of the calibration solution.
6.
Press
CAL
again.
7.
Start the flow of the standard (calibration)
solution through the flow chamber. Adjust the
flow until the liquid is foam-free. The flow rate
should be a minimum of 150 ml/min and be
stable.