NI-9237 Internal Power 150 mW

[ngthai]

NI-9237 Internal Power = 150 mW
I have a question, is this 150 mW per bridge? (i.e., per RJ50 port) (NI-9237 has 4 ports), so the module is 150 x 4 = 600 mW limit?

or is it already 150 mW per the whole module?

[ZYOng]

The NI-9237 Datasheet has another section for the chassis power, so I believe that 150mW is for each channel.

[ngthai]

Thank you for answering.
I just tested myself using 240 ohm resistors, plugging into EX+ EX- terminal of two RJ-50 ports:
When I powered (i.e., DAQmx Create Virtual Channel.VI) with 5V (or 10V), the 2 measurements (using DVM) dropped to 4.69V.
When removing 1 resistor (i.e., only 1 resistor is plugged into EX+ EX- of one port), DVM measured 6.56V.
In both examples, total power consumption = 180 mW. So total is only 150 mW for the whole module (with some redundancy to 180).

My new question is: If 9237 auto dropped excitation to not exceed power consumption (for example from 5V as intended to 4.69V, for a ratio of 1.0661), do I need to manually multiply my AI+/- output by that factor to get the true signal? Or Labview automatically does that for me? (knowing that I do supply in calibration factor in ue V/V as shown)

[ZYOng]

You're right!

The NI 9237 automatically reduces internal excitation voltages as needed to stay below 150 mW.

See When Should I Provide an External Voltage to NI 9237 Module?

As for your second question:

The ADC in the 9237 will use the actual excitation voltage as the reference NOT necessarily the value specified by the user in the task.

Reference: https://forums.ni.com/t5/LabVIEW/Ni-9237-Excitation-Voltage/td-p/2170040