offset doesn't work

[KevinLilian]

Hello guys,

Have a problem with signal express. I am just building a simple test.

As Figure 1 shows, target singal is normal sine wave with 1V offest.

                                                                                                                        Figure 1

Figure 2 shows that the offset effect quickly dishminished on the generated signal (detected).

                                                                                                                  Figure 2

I am very confused on this phenomenon. Anyone can help give an explanation?

If I want to a normal sine wave with steady offset, what should I do?

Thank you

Kevin 

[BauerPower · Accepted solution]

Hey Kevin!

The reason that's occuring is because you are using AC coupling on your input, so the DC component is being filtered out. The PXI-4498 is an AC coupling only device so unfortunately you won't be able to read that 1V offset on the input.

http://digital.ni.com/public.nsf/allkb/0F81C33977056A7D862566F1005CAA71

The following user guide is where it states the 4498 can only perform AC coupling:

http://www.ni.com/pdf/manuals/372125f.pdf

Hope this helps clear things up!

[KevinLilian]

Thanks Rob,

It helps.

Kevin.