The voltage limits on DAQ boards

[ksyz]

HI, I am using NI-6224 DAQ card with 16 differential input. The device input limit is +/- 10 V.

When the input voltage in a channel is above the limit (say 12V), i found that other channels' reading will be affected (the voltage acquired increased slightly) and the error in channel 1 and channel 9 are the most obvious. Is it normal?

Thanks!

[Tom_W_[DE]]

HI ksyz-

The M Series Help explains that the working voltage for your device is +-11V on any pin relative to AI GND.  This means that if you exceed this limit on any pin then operation will no longer be predictable which explains why you're seeing strange results.  I would suggest that you reduce the amplitude of your input if possible.  You may need to add some external signal conditioning (such as an SCXI-1125) to meet this requirement.

Hopefully this helps-

[ksyz]

Thanks Tom, I now know where the strange reading come from.

One more question, the NI-6224 provides four input ranges (+- 10, 5, 1, 0.2V). Does it mean no matter what I input to the expected maximum and minimum value in the DAQmx Read/ Create virtual channel in LabVIEW, the range will only be the one of them? or  the LabVIEW will automatically choose a suitable gain according to the maximum/ minimum input value?

i.e. Is it meaningful to input +- 0.1V range in the LabVIEW for the NI-6224?

Thanks again,

Ksyz

[Tom_W_[DE]]

Hi ksyz-

Yes, those are the only gain/range settings supported by your hardware.  If you choose a range that is not directly supported, NI-DAQmx will automatically coerce the range to the next highest supported range.

Thanks-