TestEquity FOV Series, Installation & Operation Manual

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OPERATION
T
HEORY OF
O
PERATION
Heating
When powered, the FOV oven chamber heats to and then maintains the currently programmed
temperature set point. The oven comes from the factory with a temperature set point of “OFF”. The
set point may be adjusted by the end-user using the Set Temperature controls.
Heating is controlled by a microprocessor controller board that stores the temperature set point.
The microprocessor senses the chamber air temperature via a solid-state probe located in the
airstream on the right wall of the oven chamber. When the processor detects that the chamber
temperature has dropped below the temperature set point, it pulses power to a heating element in a
recirculation air duct space located above the oven chamber.
The processor employs proportional-integral-derivative analytical feedback-loop functions when
measuring and controlling the chamber air temperature levels. 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 is derived from the rate of change in
the difference. The integral function slows the rate of pulses when the temperature nears the set
point to avoid overshooting.
FOV ovens rely on natural heat radiation for cooling.
When the oven is powered, the chamber air temperature cannot go below the ambient room
temperature plus the internal waste heat of the oven. Waste heat is generated primarily by the
operation of the blower fan motor and the resulting air compression in the duct spaces. In practice,
the temperature floor is
a20°C
.
The oven depends on the operation of the blower fan to maintain temperature uniformity and
stability in the chamber.
Air Circulation
The oven continually circulates air internally while powered. Air is forced through the small vent
holes on the right side of the chamber, blows across the shelf space to the large holes on the left
side, and is then pulled up into a heating and recirculation air duct by the action of the blower fan.
The oven is provided with a dampener vent that may be opened or closed using a dampener slide
located on the oven top. FOV forced air ovens must be run with the dampener closed in order
to achieve the stated temperature performance specifications.
The dampener is intended to speed drying or evaporation rates
after
the heated portion of an
application is complete. Opening the dampener vent while the oven is running may speed the rate
of material drying, depending on the nature of your application. However, it also introduces cool air
into the chamber while allowing heated air to exit. This will likely impact the temperature
performance of the oven.