9171 power requirements

[PatMcHargue]

Folks;

I note from the specifications for the NI cDAQ-9171, <http://www.ni.com/pdf/manuals/374037a.pdf> the maximum power drawn is 500mA (2.5W) - the total allowed through a USB2.0 port. <http://www.instructables.com/answers/How-can-i-tell-how-much-power-a-usb-port-supplies/>

Given that I want to use the  cDAQ-9171 (2.5W) with an NI9234 (900mW) in this carrier,how can I guarantee that this won't draw more from the USB 2.0 port than is allowed? The total is 3.4W required for the 9171/9234 combination, compared to the 2.5W rated USB 2.0 maximum.  I know already that this works, but I'd like to be able to provide assurance as to why, given that the specs say that there could be an issue.

TIA;

Patrick

[M.J]

Hi Patrick,

The 9171 is specified to draw a maximum of 2.5W which is the total available from USB 2.0 port. However in your setup it will only draw the necessary power to run the 9234 which is a per your calculation 900mW. Therefore the maximum power specification of the 9171 is not added to the power requirement of the 9234 when calculating the power draw of your system.

Does this information help you move forward?