03-23-2009 04:36 AM
Hi,
The application I am workng on requires me to drive a number of differential analog outputs. Is there a way to do this?
Thanks,
Alex
03-23-2009 12:41 PM
Hi Alex, there are lots of possible configurations for sourcing multiple differential analog outputs. What is your application and what are your requirements?
How many channels?
DC performance?
AC performance?
What bandwidth?
What form factor?
How much power?
Do the channels need to be synchronized?
The more information you can provide about the application the better.
Regards,
Daniel
Conditioned Measurements03-24-2009 03:24 AM
Hi,
We are driving an piece of avionic equipment. It has the following numberof channels:
15 x Analog in, differential, Rin > 200kOhms
15 x Analog in, differential, Rin > 100kOhms
The above are DC signals, most of the +-10V one channel needs to be +-50V (can I series up a couple of channels?)
Ideally the form factor would be cPCI/PXI. The outputs would need to be synchronised I think.
Thanks
03-24-2009 11:40 AM
For many applications a differntial input can be driven by a single-ended output. It may not be as ideal as a differential to differential configuration because there may be less noise rejection and possibly more distortion. However, since you are dealing with DC signals, that might not be as important for you.
How much resolution do you need on your channels? What resolution in Volts do you need?
Here are a couple of options for the +/10V channels
PXI-6733
http://sine.ni.com/nips/cds/view/p/lang/en/nid/11311
Or the PXI-6723
http://sine.ni.com/nips/cds/view/p/lang/en/nid/13765
On either of those pages you can click on the datasheet to get a family overview of the Multifunction DAQ AO boards
http://www.ni.com/pdf/products/us/4daqsc362-365_372-373_368.pdf
The +/-50V channel is more distinct. There are multiple options, and probably several more beyond what I can think of.
1) You are right to ask if you can place several channels in series. You can place multiple outputs in series if the channels are isolated from each other. At the moment National Instruments has a channel to channel isolated analog output offering on the SCXI platform. You could place 5 channels from a single SCXI-1124 http://sine.ni.com/nips/cds/view/p/lang/en/nid/1870 in series to get the +/-50V output range you need. This would require both PXI and SCXI in your final solution. You could get what you need from a PXI/SCXI combination chassis like the PXI-1050. Make sure to consider this article http://digital.ni.com/public.nsf/allkb/B5974E16550E16178625715A006C7DDC when selecting a board to control SCXI.
2) You could use GPIB from your PXI chassis to control a GPIB instrument that can source +/-50V directly. Since GPIB is a parallel bus, you could use several isolated devices together to get up to the +/-50V that you need.
I'm sure there are a dozen other ways to achieve the +/-50V, but those are a couple for starters that hopefully simplyify system design to a tolerable level.
By the way, the Online Product Advisor might be helpful to you in piecing together the entire system: http://www.ni.com/advisor/