Butch,
I'm wondering why you need to use a PFI. AI start lets you select an
analog input channel as a trigger, if you are scanning the signal from
which you wish to trigger. I believe that PFI0 is used when you wish to
trigger from a signal which is not being scanned.
I'll admit, while I'm not sure why when you make this connection, you're
getting the offset, but in looking at the E-series connections, I've
noticed that in NRSE mode, the PGIA which is reading your input is
floating and not referenced to the board ground. PFI0, however, is
referenced to a digital ground, and thus your offset, because the NRSE
(-) (AISENSE) and digital ground are NOT referenced to one another.
I would try using your input channel as the trigger channel instead of
PFI0.
Give that a shot.
Mark
In article <397f50dc@newsgroups.ni.com>,
"Butch Husky" wrote:
>
> I'm using an E-series to gather some signals, and because I need
pretrigger
> scanning, I have to trigger off a Programmable Function Input. Fine
and
> dandy,
> EXCEPT that whenever I hook up the PFI, it offsets my voltage signal
By like,
> 5 volts! Specifically, this occurs when I hook in AISENSE from the
low end
> of my
> signal up to the AISENSE pin (The acquisition must be NRSE because of
the
> signal conditioner I have). What could possibly cause this?
> I've checked my grounding a million times, there's nothing floating at
all.
> Is there some kind of configuration (beyond hooking up a signal and
typing
> in "PFI 0" to the
> Analog Start.vi) that I need to do before I can use PFI0 as a trigger
input?
>
>
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