User`s manual

Cooling Requirements
The VXIbus System Specification requires module manufacturers to
establish a cooling specification for each of their modules. The
specification is to consist of:
1. the airflow required (in liters/second) for adequate cooling, and
2. the pressure drop that occurs across the module when the specified
airflow is applied.
Note Module cooling requirements are described in the VXIbus System Specification
(Rev 1.4) in Section B.7.2.4. Mainframe cooling requirements are discussed
in Section B.7.3.5.
For ease of integration, you should label the airflow requirements for your
finished application circuitry on an outside shield of the module. For
example, the label might read: 0.3 liters/sec @ 0.2 mm/H
2
O.
Due to the nature of a breadboard module, it is not possible to specify
cooling requirements without knowing the application and the amount of
power to be dissipated. Given the application, however, cooling
requirements may be estimated as follows:
1. Determine the airflow required as a function of power dissipation.
To maintain a 10°C rise, approximately 0.08 liters/second are
required for every watt dissipated. For example, if a module
dissipates 20 watts, 1.6 liter/second of airflow is required for cooling.
2. Establish the relationship between airflow and pressure drop. For a
breadboard loaded with typical components (such as ICs, relays, and
a few heat sinks), the curve shown in Figure 2-11 may be used to
determine the pressure drop across the module. Determine the
pressure drop as the intersection of the curve and the required
airflow. For example, if the airflow required is 1.6 liter/second, the
pressure drop is approximately 0.04 mm H
2
0.
Figure 2-11. Pressure Drop vs. Air Flow
22 Configuring the Agilent E1490C Chapter 2