National Instruments NI 9478 - Manual (Page 15)

© National Instruments Corp. 15 NI 9478 Operating Instructions and Specifications
for that channel. Use the following equation to calculate the
percentage of the total power budget each output channel uses in
your application.
To verify that your application keeps the NI 9478 within safe
operating specifications, calculate the average percentage of
total allowable power each channel uses, then add together the
percentages for all the channels. For operation in ambient
temperatures from 55 to 70 °C, the total average power of all
channels must remain under 100%. For temperatures below 55 °C,
the total average power of all channels can run up to 150%.
where P is the percentage of total allowable power the channel uses
I
out
is the output current in amperes while the channel is on
length is the total cable length in meters, shown in Figure 4
freq is the frequency rate in kHz at which the output channel goes
through an on-off cycle
P 4% I
out
2
⎝ ⎠
⎛ ⎞
0.12% length 0.2 – ( ) I
out
2
⎝ ⎠
⎛ ⎞ 0.04% I
out
1 + ( ) + freq + =