Chapter 1
Using the Mainframe
© National Instruments Corporation
1-3
Caution
When installing the mainframe in your system, ensure that the air inlets and
outlets are not obstructed. This prevents damage to the mainframe and installed modules
due to overheating. Clean the air filter regularly.
Variable Speed Fan
Normally, the speed of the four internal circulation fans is determined by
the ambient temperature of the air drawn into the mainframe. One fan cools
the power supply module and three fans cool the VXI modules inserted into
the mainframe. You can override the temperature-controlled speed of the
fans by changing the position of the Fan Speed Control Switch on the rear
of the mainframe to High. This forces all four fans to remain at full speed
all of the time. The two fan modes are:
•
Variable Speed Mode (factory default): Quiet operation (~ 75%
airflow) at <30 °C ambient temperature; high speed operation at
>40 °C ambient temperature.
•
High Speed Mode (switch selectable): Full airflow at all times.
Figure 1-2. Forcing the Fan to High Speed