08-16-2018 09:10 AM
I found this topic from back in 2007.
Has any way been developed to take a single ended and multiple differential measurements within a short period of time?? I don't want to say simultaneously because I know that is a different DAQ Card. I'm using a PXI6229. I'm measuring four differential voltages ( "x" vac@400hz) and want to compare the phases of each to my single ended ref voltage of 5 vac@400hz. I think I want to acquire them (all 5 voltages) as "simultaneously" as I can. I have no problem reading the 4 diff voltages..and no problem reading the SE ref voltage separately, its just getting them at the same time that's the trouble.
Not using Signal Express..
Thanks..
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08-16-2018 09:30 AM
It may depend on the device you are using but I would try just tying the ground of the SE to the negative input of a channel configured for differential... possibly through a 1 M-ohm resistor if isolation is a concern.
Ben
08-16-2018 11:24 AM
I tried that and it gives really bazar waveforms. Could you provide an example where I "configure","start" and "read" the channels as soon as possible in my created vi?? I think if I "read" the differential channels then the single channels as close as possible in a single vi that may work. Right now I read differential channels in one subvi then read the single ended channels in another subvi. I think this delay from one sub vi to another is long enough my phase calculations is wrong.
08-16-2018 11:30 AM
I was suggesting you ONLY have a single task reading all channels as differential including the SE channel.
You can try it out in MAX by creating a task that has all differential channles and work with your wiring for the SE channel and tie the "-" side of the Diff. channel to ground or AI return.
Ben
08-17-2018 05:28 AM
That worked!! Thanks..