Operation; Theory Of Operation - Shel lab SCO6AD-2 Installation & Operation Manual

OPERATION

T O
HEORY OF PERATION
The SCO6AD-2 CO incubator provides a constant-temperature CO -enriched environment suitable
2 2
for mammalian cell sample cultivation and other incubation applications. The unit features an
automated high-heat, chamber decontamination cycle that does not require the removal of the CO
2
sensor or other electronic components. The incubator also comes with a glass viewing door allowing
visual inspection of samples without compromising the chamber CO or humidity environment.
2
Heating
When powered, the incubator heats to and maintains a user-selected target setpoint in the incubation
chamber. The incubator senses the chamber air temperature using a solid-state probe mounted on the
chamber interior wall. When the incubator detects that the chamber temperature has dropped below the
target setpoint, it pulses power to the heating elements inside the chamber walls and in the outer
chamber door.
The incubator uses Proportional – Integral – Derivative (PID) control to avoid significantly overshooting the
setpoint. This means the rate of heating slows as the chamber temperature approaches the target
temperature. If the chamber temperature is above the setpoint, the incubator uses minimum heating to
control the rate of cooling and avoid dipping below the setpoint.
Additionally, the PID loops optimize heating rates for the temperature environment around the incubator.
If the incubator is operating in a cool room, it will increase the length of heating pulses to compensate.
Likewise, when operating in a warm room the incubator uses shorter pulses. If the ambient temperature
conditions change significantly, there may be minor over or undershoots as the incubator adapts.
SCO incubators rely on natural heat radiation for cooling. These units can achieve a low-end temperature
just above the ambient room temperature plus the internal waste heat of the unit.
The exterior chamber door is self-heating to bolster the thermal uniformity and stability of the
chamber and to minimize condensation on the glass viewing door. Leaving the exterior door open
for long durations may adversely impact the temperature performance of the incubation chamber. It
may also create condensate on the viewing door. Door openings should be restricted to the
minimum necessary to view or access samples in the chamber.
CO Atmosphere
2
The controller controls the gas concentration of CO in the chamber atmosphere by operating an
2
internal injection solenoid valve connected to a gas intake port. The controller monitors the CO level
2
in the chamber using an infrared sensor located in the recirculation duct. The sensor operates on the
principle that a specific frequency set of infrared light is absorbed by CO
. The more CO present in
2 2
the chamber, the more of that band of infrared is absorbed. The sensor is only sensitive to CO , so
2
measurement accuracy is consistent, regardless of the presence of other gasses in the incubator.
27 | P a g e