Data Acquisition Through The PCI-6071E

[Phillip Heyrman]

I am attempting to do a 3 channel, single rate scan of signals coming
from sensors through the PCI-6071E using LabWindows. I have used both
a program I wrote myself and the LabWindows sample multi-channel
scanning program and received the same results. When I run a test
program, one signal comes through fine, but the other two do not. The
other signals usually sit around 0 V with a little fluctuation, but
when I begin my SCAN they drop to around -2 & -4 V. At the end of the
SCAN process, the signals return to there normal state, but that data
that has been read in is the incorrect data. I can see this happening
on an oscilloscope I have attached to the line as well, so I know the
readings from the card are correct. Is there somet
hing I am doing
with my programs that is causing this, or does this show some kind of
hardware setup issue?

Any help would be appreciated.

[JustinBritten]

Phillip,

I suspect that the problem you are seeing is due to hardware connections. Especially since you have tried using one of the LabWindows/CVI shipping examples and received the same results.

I would recommend that you first test your acquisition using the Measurement & Automation Explorer (MAX) Configuration and Diagnostic Utility. You can open a Test Panel on your DAQ card and perform an acquisition on your input channels to verify the signals are as you expect. If you verify that you are receiving correct signals in MAX then you can pin-point that the problem exists with your software program.

Also, take a look at the following Application Note which explains how to correctly measure your transducer.

Field Wiring and Noise Considerations for
Analog Signals
http://zone.ni.com/devzone/conceptd.nsf/2d17d611efb58b22862567a9006ffe76/01f147e156a1be15862568650057df15?OpenDocument

Regards,
Justin Britten

Applications Engineer
National Instruments