Can I use a NI-9244 to measure 2-wire 480V single phase AC?

[MStewart]

Since the 9244 module is rated for a maximum of 400V L-N and 800V L-L, to measure 480V, I would need to connect to AI0 and AI1 and leave the Neutral input floating. The manual shows all single phase measurements referenced to the Neutral input and has some instruction about converting L-N measurements to L-L, but it is worded poorly so I am not sure if it is telling me that I can directly measure the voltage across AI0 and AI1, or not.

Can anyone confirm that I can make measurements with the 9244 wired in this configuration, before I drop the $$$ to purchase it?

[GerdW]

Hi MStewart,

the manual says:

- input range typically ~1000V

- withstands 800Vrms continuously and 1000Vrms for 1s

I see no problem in using this module to measure 480V L-N. If you don't believe you should just call NI sales department before purchasing…

[ChristophersonJ · Accepted solution]

Hello MStewart,

A distinction needs to be made between Vpk and Vrms.  

@GerdW is correct that the device input range is ~1000Vpk (997.5Vpk). However, this translates to ~352.6 Vrms

The 800 Vrms rating for Line-Line (L-L) measurements is for multi-phase applications.

Since you are taking a single-phase measurement, you would use a AIx-Neutral (L-N) connection.

The diagram for this is detailed in figure 12, page 25 of the Manual:

< http://www.ni.com/pdf/manuals/376131b.pdf > 

So in order to measure above 400Vrms on this device you will need to use an external power transformer to step down the voltage, as mentioned in the following White Paper (specifically in the Measuring Voltage section):

< http://www.ni.com/white-paper/8198/en/ >

In summary the 9244 cannot measure 480Vrms directly.  You would need to pre-adjust the signal down to less than or equal to 400Vrms

I hope this helps clarify your question!

Cheers,

-ChristophersonJ