USB 6211 AO 2.2 VDC maximum

[just start]

The output from AO0 (relative to AO GND) can be only up to 2.2 VDC (measured by a multi-meter) when using NI MAX to test it.

The device is connected to computer with a USB cable.

What could be wrong?

Thanks,

Hui

[Now_With_Underscores]

Hey Hui,

I just want to make sure I understand your question.  When you open up the test panel in Measurement and Automation and set the analog output voltage to 10 volts, your DMM is only showing 2.2 volts.  Is this correct?  

If this is the case, are you trying to drive anything during this measurement?  If you try to pull too much current from the AO, the voltage will sag.  For the 6211, this current limit is 2mA/channel, 4mA/Device.  If you haven't already, try disconnecting the load and just measuring the output.  Do both analog outputs exhibit this behavior?  Does setting the voltage to -10 volts cause a similar issue?  Also, is the device plugged directly into the machine (not through a USB hub)?  If none of these suggestions get you up and running, can you please describe your setup in more detail.  Thanks!

[just start]

John,

it seems that the channel is overloaded. when i get rid of the load, the output voltage is just fine from -10V to +10V.

One more question, when I use one of the AI to measure the voltage output, it is not as stable as I expect. Again, the measurement is done in test pannel of Measurement and Automation, continuous sampling mode. Why there are so much noise? How can I get rid of them if I use DAQmx assisstant in labview 7.1

Thanks,

-Hui

[Now_With_Underscores]

Hey Hui, 

I would recommend getting a voltage follower and installing it between your output and the load.  This will allow you to increase the sourcing current maximum, but will introduce a slight time delay into the output (depending on the opamp used, this will be between a few nanoseconds and a few microseconds).  Voltage followers are available at most electronic stores.

For your AI issue, I'd look at this developer zone article for help on what could be causing the instability.  Hopefully this gets you on your way.