Sartorius DCU 3, Operator'S Handbook Manual

Page: 52 / 150

Operators Handbook DCU3 – System
6., Main function „Control Loops“
BAEDCU3 - Rev. 4.6 - 0504 6 - 18
6.12
p
O
2
-Gasmix Controller / O
2
– Enrichment
The DCU3 - system can control the pO
2
by mixing of two gases, e.g. N
2
and O
2
, via the pO
2
Gasmix
controller. This controller directly triggers the valves for N
2
/O
2
in splitrange mode via pwm outputs. The
control method is preferably used for gas supplies which are connected to a tubing gas supply system
for bubble free gas input into the culture medium.
When the O
2
-enrichment method is applied the controller increases the oxygen portion in the inlet air
by controlling a 3/2-valve of the air supply.
6.12.1 Operating Display
For a description of the tags, the physical units or entries, the displayed value or function
and of the required inputs see the table in section
6.3, Controller Operation in General.
6.12.2 Special Notes
Depending on the process requirements the control can be based on the following gases:
– alternate supply of N
2
and air at low O
2
consumption
– alternate supply of air and O
2
at high O
2
consumption
– alternate supply of N
2
and O
2
at considerably varying O
2
consumption
Which gases are supplied depend on the gas sources connected to the gas mixing unit.
For better control results we recommend to supply a carrier gas (such as air) at a constant
flow, which is then enriched by O
2
and N
2
. You can connect the carrier gas to the Auxiliary
inlet of the Gasmix unit.
You will have to adjust the max. gasflow rate for the current process via the rotameters in
the O
2
and N
2
line of the gasmix unit. For this the O
2
/N
2
valves must be fully open). The
max. flowrates depend on the Gas mixing unit applied and the intended process.
For the O
2
-enrichment method the controller parameter “MIN” must be set to “MIN: 0%” in-
stead of “MIN: -100%”.