Shel lab BACTRON300, Инструкция по установке и эксплуатации, Страница: 34 / 86

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OPERATION (CONTINUED)
Accessing the Workspace Chamber
Items such as media containers and laboratory equipment can be introduced to or removed from
the sealed workspace chamber through the pass box. The pass box functions as an airlock,
creating a near anaerobic environment through three partial atmosphere evacuations to reduce air
volume, followed by gas replenishment injections. The evacuations take the pass box pressure
down to -18 inches of mercury pressure, which will not boil sample media. Remaining oxygen is
captured by the O
2
scrubber catalyst, located in close proximity to the pass box and chamber
circulation fan.
Normally the pass box is cycled by users initiating an auto cycle. The BACTRON comes with a
control to manually cycle the airlock in the event of an auto cycle malfunction.
Users can access and work glove-free in the anaerobic workspace chamber by donning the sleeve
assemblies attached to the front panel arm ports. The sleeve assemblies are compatible with exam
gloves for handling pathogenic samples. After being donned
– but prior to opening the arm port
doors
– the sleeve assemblies and ports are cycled by using the foot pedal controls to apply
reduced pressure to the sleeves with the vacuum pump, then to charge the sleeves with AMG.
Three evacuation and gas backfill iterations are required.
Cycling and effective use of the sleeve assemblies requires bare skin contact between the widest
p
art of the user’s forearms and the cuff ring of the sleeve assembly. Smooth, small items held in
hand may be introduced into the workspace chamber through the sleeve assemblies.
Incubators
BACTRON300 and BACTRON900 are each provided with a cabinet style incubator in the
workspace chamber. The BACTRON600 and BACTRON900 come with two rotating shelves (Lazy
Susans) in a side storage incubator.
Each incubator is controlled by a microprocessor board with a solid state temperature sensor probe
attached to the incubator body, along with two heating elements. The processor employs
proportional-integral-derivative analytical feedback-loop functions when measuring and controlling
the chamber air temperature. PID-controlled heating pulse intensities and lengths are proportional
to the difference between the measured chamber temperature and the current set point. The
frequency of pulses are derived from the rate of change in that difference. The integral function
slows the rate of pulses when the temperature nears the set point to avoid overshooting.
The temperature set point is set by the end-user.
Each incubator relies on natural heat radiation for cooling. An incubator can achieve a low-end
temperature of the ambient room tempe5°C.
The PID functions are also used to optimize incubator warming rates for hotter or cooler
environments. If the BACTRON is moved to a new location with a significant temperature
difference, it may require 24 hours of incubator run time for the processor to fully adapt to the new
thermal environment. This is why the incubator should run at its application set point for 24 hours
prior to loading samples or verifying the temperature display accuracy. Additionally, the heat loss
from leaving the incubator doors open for long periods of time (an hour or more) can trick the
controller into thinking it is operating in a cool environment. This can result in a period of
temperature overshoots.