16
removed from the drying column and spread evenly, one
granule deep on a tray. The desiccant should then be heated
for approximately one (1) hour at about 400ºF (200º C). It
should be allowed to cool in an airtight container before
refilling the acrylic drying column. The felt filters should also
be pre-dried at 200º F (100º C) for about 30 minutes before
assembly.
3.2.2 System
Function
Figure 3.2-4 is a block diagram illustrating the Dehumidifier
Controller and Dehumidification System connected to the Model
5506 Chamber.
Figure 3.2-4 Controlled humidity chamber block diagram
The Humidity Sensor measures the relative humidity inside the
chamber. The Sensor output signal is then compared to the set
point. When the humidity measured in the chamber exceeds the set
point the Controller turns on the pump circulating the test chamber
air through the desiccator or injecting dry gas through a solenoid
valve. For the desiccator system the desiccant absorbs moisture,
thereby lowering the humidity level inside the chamber. For the dry
gas system the dry gas replaces the wet air that is ejected into the
atmosphere or through a vent. When the humidity level drops below
the set point, the Controller turns off the pump. The pump will then
cycle on and off automatically as required by the Controller to
maintain the desired humidity level.
Power to operate the Dehumidification System is controlled by a 3
amp solid-state relay. When the measured humidity deviates from
the R.H. set point the Controller turns on the relay which then
supplies the necessary 115/230 VAC power to the system.
