03-06-2003 04:23 PM
03-07-2003 04:22 PM
01-11-2008 10:30 AM
Hi Mike,
***Yes, I am aware I am replying to a very old post***
I have encountered this exact same issue with every version of older NI-DAQ and even newer NI-DAQmx I have ever used. It occurred with the version that shipped with Labview 6.x all the way up to the latest version, whatever ships with Labview 8.x. Not to mention the recently recalled NI-DAQmx 8.6.0f12 which I have not tried... and will not! I have 3 new drink coasters!
Basically here is a crude work around. First, you can only put the SCC CO-20 module in 2 specific slots on any of the SCC chasis boards. They are the only 2 slots that can handle A/O device modules (either voltage or current output).
All the CO-20 does, is provide a shunt resistor to convert voltage supplied by the board into current. I=V/R. My work around is to just configure it in MAX as an FT-01 or a voltage device. That way, the board just gives it voltage, and magically, by way of the shunt resistor, you get current out of the module. Then, just convert your values mathmatically in your code.
You can also build your own MUCH CHEAPER "home-made" CO-20 using an FT-01 and a shunt resistor of your choice (usually 250 or 500 ohm. This is pretty basic current loop stuff, but it works well. FT-01 modules are only about $30 and a resistor is $0.15. An SCC-CO20 costs way more than that. > $200???
NI has in the past just told me I had the SCC-CO20 in the wrong slot (not the case) or some other hoopla. Sadly, I have not gotten much support on this issue. Once I figured it out on my own, I stopped asking them. Mainly, because I really dont think anyone understands the problem, or because I have not explained it properly, or because SCC equipment is old and they don't want to spend alot of time on it anymore (which is understandable). Someday, if ever given the chance, I would like to show this little gremlin to an NI rep first hand.
Anyway, I still say it is a BUG in NI-DAQ but just wanted to let you know, I feel your pain, Brother! You are not crazy or alone.
Braincramp.