Analog Input, Very High Noise Level 6034E

[DB-123]

I'm trying to sample from two analog input channels simultaneously. Both channels use the differential reference method. Channel 4 monitors a function generator outputing a wave at 40kHz between 10 and -10 volts. Channel 7 monitors a transducer outputing at 40kHz between 50 and -50 mV. For some reason, even if the transducer is not connected, I get +/- 1.25 V on channel 7 when the FG is running. Is this just a ridiculous amount of noise or did I not hook something up right? Also, when I graph these waveforms in LV, they looked squished (like a big solid block instead of a wave) even though I sample them at 200kHz. Any help with that would be appreciated also. Thanks guys.

Darren

[AnujD]

Darren,

It looks like you are dealing with a phenomena called ghosting. Channel 4 is inputting a relatively high volatage at 10 volts, and it is likely this voltage is still present residually in the capacitors. I would suggest grounding channels 5 and 6. You can find more information on this at http://digital.ni.com/public.nsf/websearch/5B86A63ECC0D48828625629800571743?OpenDocument.

Additionally, to see a cleaner wave signal in LabVIEW, I suggest just zooming in. Just look at a smaller time resolution on the x-axis of your graph.