DAQ Card Readings fluctuate

[nknight]

I have two new DELL Desktop systems. Each has identical standard image of Windows 2000 that my company installs on all PC's. Then, I installed new PCI-MIO-16XE-50 cards and NiDaq software on each. Then, I installed our VB 6 application on each. One of the PC's digital (integer) readings fluctuate between 0 and 75 just sitting there with no cable attached to the DAQ card. The other PC's signal is steady at 0, which is what I would expect. Recommendations to resolve this fluctuation.

[JohnM 64]

nknight,

When I disconnect the cable to the E Series card in my computer, then my analog input signals are floating. This is the expected behavior, because the connection is open. The digital lines can also be configured to either be input or output and to logic low and high when using the Measurement and Automation Explorer that installs with NI-DAQ.

I would not worry about the fluctuation you are seeing without anything attached, because it is impossible to predict the behavior of the input channel when it is not connected to anything. If you would like to read in a steady zero, then connect your card to some type of breakout box and use a resistor to connect the input channel to ground. This will cause your signal to go to 0.

John M
National Instrume
nts