Grounding between function generator and ADC

[jrenfree]

Hi all,

I'm having some issues with a generated signal from an HP function
generator, and I believe the problem may be a grounding problem.
Basically, I'm emitting a signal with an HP function generator and
receiving that signal with a Nation Instruments 6070E DAQPad. The
signal I'm sending out is a simple sine wave, , but for some reason,
when the chirp is complete, the function generator does not output 0
volts, but instead there is some DC Offset. I called HP and they said
that it might be a grounding problem.

Anyways, what is the correct and best way to ground my equipment
together? The HP generator (HP33120A) includes a chassis ground BNC
connector on the back of the unit, but I don't believe I need to use
this. The DAQPad includes switches for each analog input to choose
between a floating signal source or a ground-referenced signal
source. I believe that the HP is a floating source generator, so
these switches should be set to a floating signal source. Besides
that, the DAQPad doesn't appear to have any connections for a chassis
ground.

I believe that I'm connecting it the correct way, as there aren't very
many options, but I just want to make sure that I'm not missing
anything obvious here.

Thanks!

 

[David L. Jones]

"jrenfree" <jrenfree@gmail.com> wrote in message
news:823e987d-4e96-46ea-a81d-0e0a825d4e3e@w24g2000prd.googlegroups.com...

Hi all,

I'm having some issues with a generated signal from an HP function
generator, and I believe the problem may be a grounding problem.
Basically, I'm emitting a signal with an HP function generator and
receiving that signal with a Nation Instruments 6070E DAQPad. The
signal I'm sending out is a simple sine wave, , but for some reason,
when the chirp is complete, the function generator does not output 0
volts, but instead there is some DC Offset. I called HP and they said
that it might be a grounding problem.

Have you verified this on an oscilloscope?
It might very well be normal, with the sine wave ending at some non-zero
point.

Anyways, what is the correct and best way to ground my equipment
together? The HP generator (HP33120A) includes a chassis ground BNC
connector on the back of the unit, but I don't believe I need to use
this. The DAQPad includes switches for each analog input to choose
between a floating signal source or a ground-referenced signal
source. I believe that the HP is a floating source generator, so
these switches should be set to a floating signal source. Besides
that, the DAQPad doesn't appear to have any connections for a chassis
ground.

I believe that I'm connecting it the correct way, as there aren't very
many options, but I just want to make sure that I'm not missing
anything obvious here.

NI DAQ cards have many different input configurations.
You'll need Non-Referenced Single Ended mode.

Dave.