Isolation for the analog outputs of a USB 6211

[LionelB]

Hi,

I want to use the analog outputs of a USB 6211 DAQ to drive two small DC motors through an amplifier. The issue is that the AO of the USB 6211 are not isolated and that my COM ("common") wire of the amplifier is also connected to the ground. As I want to avoid to establish a ground loop, I would like to know if National Instruments recommends a certain type of analog isolator or a particular manufacturer?

My problem is very similar to another thread entitled " How to properly ground analog output signal". The solution found in the latter case was to connect the AO lines to ground with a pull down resistor. However, this solution seems to me difficult to reproduce has it probably depends on the difference between the ground potentials. I would prefer to use a magnetic/galvanic isolator but if digital isolators are very easy to find (from Analog Devices, Texas Instruments, etc.), I did not found any isolator dedicated to analog signals .

Are there such components suggested by NI? Can I use a small 1:1 transformer? If yes, do you have any reference?

Thanks in advance,

Lionel

[mallorim]

Hi Lionel,

The best solution would really be for you to connect a bias resistor between AO+ and the amplifier’s ground and between AO- and the amplifiers ground as can be seen in the Developer Zone Article Field Wiring and Noise Considerations for Analog Signals. This would prevent any ground loops.

With regards to third party isolators, we do not have any suggestions that I know of. It seems reasonable that you could use a transformer, but once again, we don’t have any preferred manufacturers.

Hope this helps. Regards, Mallori M.