Astronics 407661-001, Руководство пользователя

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Publication No. 980824-114 Rev. A 1260-114 User Manual
Astronics Test Systems Specifications 1-9
Power
Dissipation –
Standard Open-
Collector
The cooling of the Adapt-a-Switch carrier is dependent upon the
chassis into which it is installed. The carrier can nominally
dissipate approximately 100 W. Even with all channels driven to
maximum outputs, up to six 1260-114OC plug-ins may be used
together in a 1260-100 without exceeding the maximum allowable
power dissipation of the carrier.
If the 1260-114OC will be used in conjunction with other cards, the
1260-114OC dissipation should be computed and summed with
the total worst-case dissipation of the remaining modules.
For example, a 1260-114OC module would dissipate the following
energy:
Quiescent power dissipation = 0.75W maximum
Channel dissipation =
[(Vol) * current * 96(# channels energized)] +
[(current)
2
* (path resistance) * 96(# channels energized)]
Total Power Dissipation = Qui Channel
Assuming all 96 channels are sinking a maximum current
of 200 mA and a path resistance of 0.5
Ω
:
Total power dissipation =
[(1.5) * 0.200 A * 96] + [(0.200 A)
2
* (0.5
Ω
) * 96]
+ ( 0.75 W) = 31.5 W at 55
°
C
This exceeds the acceptable power dissipation for an individual
plug-in module. If five additional modules are likewise loaded, then
the overall carrier dissipation is approximately 188 W, which is
above the typical cooling capabilities of the carrier and most
chassises in a two slot configuration. Therefore using a fully
loaded Adapt-a-Switch carrier with these cards operating at the
maximum extreme is not permissible. In practice, however, rarely
are more than 25% of the module’s channels energized
simultaneously, and rarely is full rated current run through every
path. In addition, temperatures are typically not run at the rated
maximum. Using the 25% rule, the power dissipated by each plug-
in should be no more than 8 W. If all six slots are used
simultaneously, this would amount to a total dissipation of
48Watts.
Additionally, if fewer plug-in modules are used, more power may
be dissipated by the remaining cards. By using a chassis with high
cooling capacity, such as the 1261B, almost any configuration may
be realized.