NuAire NU-5510, Руководство по эксплуатации и обслуживанию, Страница: 4 / 64

OM0135 4
1.4 Incubator CO
2
Control
The NuAire direct heat Incubator incorporates a microprocessor-based, non-dispersive infrared CO
2
induction sensor. The amount of energy received at the detector is an approximate logarithmic function of
the CO
2
concentration in the gas between source and detector. The wavelengths used are absorbed only by
CO
2
making the measurement insensitive to other components, such as water vapor. Detector linearization
is performed with 32 bit digital accuracy. Advanced design provides a very stable output minimizing drift
and requiring less frequent calibration. The output is digital, alleviating tolerances brought about by
analog signals. The sensor is within the chamber air plenum so very accurate CO
2
control is achieved.
The CO
2
sensor consists of a control board and a detector assembly connected by a cable. Calibration of
this control is accomplished through the front of the unit where there is a CO
2
test port.
1.5 Incubator Construction
The outer shell of the air-jacketed Incubator is cold-rolled steel with a powder coat paint finish. The front
frame surface of the outer shell is heated with a foil type heater directly attached behind the front perimeter
opening.
The front frame perimeter heater, as well as the outer front door heater is duty cycle controlled (manually
adjusted for specific ambient conditions) to balance the heat that reaches the chamber and thus reduces the
possibility of condensation forming on the inner glass door and the inner chamber walls.
The inner chamber is 16 gauge, type 304, polished stainless steel using crevice-free construction, which
provides an easily cleanable inert surface that does not in itself promote biological growth. In addition, all
shelves, shelf supports, guide rails and the air plenum are easily removable and can be autoclaved to
remove contamination.
Remember: The chamber is not selective. The growth environment is applied equally to all
microorganisms within the chamber.
1.6 Incubator
Humidity
A relative humidity level of up to 95% is achieved in the Incubator by the use of a stainless steel pan filled
with distilled water no purer than 1 mega ohm, and placed on the bottom of the chamber. It is necessary to
set the duty cycle (0-100%) of the door and front perimeter heater in proper proportions to reduce the
possibility of condensation forming on the glass inner door and the chamber walls. It is also important to
thoroughly wipe the walls and the glass door clean before adding the humidity water pan. Condensation
will occur more readily at contamination points. There is no electronic sensing and thus no automatic
control of the humidity level in the air jacketed Incubator. An air pump injects fresh air into the chamber
at a preset duty cycle to reduce condensation forming on the chamber walls and front glass door. The air
injections are settable by the user to help control condensation. (See section 8.8 for this option.)
1.7
Cabinet Ventilator Fan
An axial fan is mounted to the bottom cover panel of the Incubator and runs continuously when the unit is
switched on. This fan pulls air into the cabinet shell thru the top panel louver openings and discharges it
out of the bottom of the unit. The operation of this fan is necessary to assure accurate chamber
temperature control over the 60

F to 85

F ambient temperature range that the equipment may see.