Hi lcaggio,
You're BNC-2210 is designed to work in differential mode with your DAQ board. It sounds like this is how you have things configured though. Here are my main suggestions for resolving this.
1) Make sure that the channel switch is set to "FS".
2) Make sure that your DAQ board has the BNC-2110 configured as an accessory. (accessed through board Properties in Measurement & Automation Explorer)
3) Make sure that your DAQ board is configured for the correct voltage range and that your inputs are configured for Differential.
Now, by default, the NI-DAQ driver will sample channels as quickly as it can between channels. Since your channels are floating, it is possible that there is channel cross-talk between your two channels and that is why it l
ooks good when you sample the channel individually but looks bad when you sample both channels together. This is corrected by increasing the period of time between sampling each channel. This is called the "Interchannel Delay".
4) The following Knowledge Base describes and links to documents that mention the importance of the interchannel delay.
What Are the Minimum and Maximum Values for the Interchannel Delay Setting on my DAQ Board?
http://digital.ni.com/public.nsf/websearch/9AE87416C8792FC286256D190058C7D3?OpenDocument
5) Connect an analog channel, both CH+ and CH-, to AIGND. This will ground the channel. Then sammple your first analog channel, followed by the grounded channel and then your second analog channel. The ground channel helps with channel cross-talk (channel ghosting).
Anyway, hope these suggestions help your project. Have a good day.
Ron
Applications Engineering
National Instruments
