USB-6008 analog output incorrect value. Cannot output more than 3V

[iln]

I'm using USB-6008's analog I/O but the analog output (AO0 or AO1) can only go up to 3 - 3.5V. The output can accurately follow the set value from 0 to 2.5V, but then it exponentially start lagging behind the set values and cannot go pass 3.5V.

The only weird thing about the circuit is that I have connected all the grounds (I/O analog and 5V source) together, but I don't see this affect the output.

Regards,

iliian

[Ana P]

Hi iln,

I suggest testing the Analog Outputs alone in your device. That is, just try to output a voltage in Analog Output 0 and then in Analog Output 1. For this case I suggest disconnecting the rest of your circuitry and just testing if the Analog Output terminals work. You can do this through the Test Panels in Measurement and Automation Explorer, if the Analog Output doesn’t work maybe the problem is in the device, if they work as expected, please give us more details on what you mean by connecting together all the grounds, I/O analog and 5V source. Do you have connected the grounds with the 5V terminal? Or what pins exactly you have connected all together? I hope this is helpful,

[iln · Accepted solution]

Thanks for the quick reply Ana.

It wasn't the NI board, nor the motor drive board. Apparently the interface to the motor drive (Motor Mind C: solutions-cubed.com), loads the analog output. A voltage following op-amp effectively isolated the USB-6008 output and solved the problem.

Regards, iliian