Motorola MVME712B - Manual (Page 14)

Specifications
MVME712A/D3 1-3
1
Cooling Requirements
Motorola VMEmodules are specified, designed, and tested to operate reliably
with an incoming air temperature range from 0 degrees C to 55 degrees C (32
degrees F to 131 degrees F) with forced air cooling. Temperature qualification
is performed in a standard Motorola VMEsystem 1000 chassis. Twenty-five
watt load boards are inserted in the two card slots, one on each side, adjacent
to the board under test to simulate a high power density system configuration.
An assembly of three axial fans, rated at 71 CFM per fan, is placed directly
under the MVME card cage. The incoming air temperature is measured
between the fan assembly and the card cage where the incoming airstream first
encounters the module under test. Test software is executed as the module is
subjected to ambient temperature variations. Case temperatures of critical,
high power density integrated circuits are monitored to ensure component
vendors specifications are not exceeded.
While the exact amount of airflow required for cooling depends on the
ambient air temperature and the type, number, and location of boards and
other heat sources, adequate cooling can usually be achieved with 5 CFM
flowing over the module. Less air flow is required to cool the module in
environments having lower maximum ambients. Under more favorable
thermal conditions it may be possible to operate the module reliably at higher
than 55 degrees C with increased air flow. It is important to note that there are
several factors, in addition to the rated CFM of the air mover, which determine
the actual volume of air flowing over a module.
FCC Compliance
These MVME712 family VMEmodules were tested in an FCC-compliant
chassis, and meet the requirements for Class A equipment. FCC compliance
was achieved under the following conditions:
1. Shielded cables on all external I/O ports.
2. Cable shields connected to earth ground via metal shell connectors
bonded to a conductive module front panel.
3. Conductive chassis rails connected to earth ground. This provides the path
for connecting shields to earth ground.
4. Front panel screws properly tightened.
For minimum RF emissions, it is essential that the conditions above be
implemented; failure to do so could compromise the FCC compliance of the
equipment containing the modules.