Hach Ultra ORBISPHERE 3625, Operator'S Manual

Page: 72 / 96

66 of 90 Calibrations - 3625 Package Analyzer
Operator Manual
ORBISPHERE
Procedure
• On the instrument, pressing
ESC
displays the main menu.
•
× Ø
select
CALIBRATE
;
ENTER
•
× Ø
select
O2 IN AIR
;
ENTER
• Wait 5 minutes until the values read on the instrument display are stable.
•
ENTER
to save value and terminate calibration.
The instrument will accept the calibration with
CALIBRATION COMPLETE
, then returns
to the calibration menu. A message is sent to the PC software.
7.6 Thermal Conductivity CO
2
and N
2
Sensor Calibration
The thermal conductivity sensor must be calibrated after servicing. After installing a new
membrane, wait 30 minutes minimum before performing a calibration. See sensor
maintenance manual for calibration gas specification.
Four calibration methods are available:
•
Fraction
: Using a known composition (preferably pure) of CO
2
(or N
2
) at
atmospheric pressure.
•
Partial pressure
: Using a known composition of CO
2
(or N
2
) at ~5 bar
(recommended).
•
Calibration kit
: Requires optional HUA calibration kit. Using a known
concentration of dissolved CO
2
.
•
Reference package
: Using a package with a known gas concentration content as
a reference.
Table 7-2:
Thermal Conductivity Sensor Calibration Methods
Calibration method Indicative
time*
Benefits Drawbacks
Fraction
(barometric pressure)
10 min Quick and easy
Less reliable than partial
pressure
Partial pressure
(at 2-3 bar)
10 min Quick and easy
Slight risk of accuracy loss
when installing the sensor
back into flow chamber
Dissolved
(using optional
equilibrium vessel) 2 hours
Most accurate method
when properly handled
Long operation,
Risk of manipulation mistakes
Dissolved 5 min Accurate and quick
Requires optional Orbisphere
Calibration kit