Can I measure AC milivolts with a 2.5VDC offset with a FP-AI-112 module?

[mattliterski]

I am trying to measure from 0 to .985 VAC with the FP-AI-112 input module, but can only see the 2.5 VDC that the AC signal is riding on.  Is there a way to filter out the DC and only read the RMS AC.

[Matt_S.]

Hi matt,

You should certainly be seeing that 1V ptp signal on that 2.5VDC carrier without filtering. There are all kinds of external circuits you could use to filter out the DC component, but it concerns me that you're not seeing your AC signal at all currently. Could you possibly post a screenshot of what you're seeing?

Regarding setting an offset in the FieldPoint AI module, currently there's no way to go about that. In LabVIEW or any other language you could simply subtract 2.5V from the value you're getting from your FieldPoint Read to have it plot with a 0 V offset, but this isn't going to change the resolution for your signal. Try posting a screenshot of the output of your FieldPoint reads (I'm assuming you're going to a chart or a graph). That may help us see what's going on.

Regards,
Matt S.