"Setting NI USB-6211 Resolution in DAQmx?"

[A Sutherland]

Hi,

I have an application written in C# using DAQmx drivers. When I aquire voltage signals, I notice they have a very poor resolution on each of the voltage input ranges for the card (viz. [-10V, 10V]; [-5V, 5V]; [-1V, 1V] and [-0.2V, 0.2V]. It would seem that the card is reading with a resolution of < 8 bits as opposed to the 16 bits it should be acquiring data with. I initially thought that the card may be damaged, but I get the same problem with a 6024E card. If I aquire the same data with Signal Express, the card seems to be working properly at the 16 bit resolution. This leads me to believe that something must have crept into my software that is reducing its resolution, if that is even possible? My question then is: "Is there a way to explicitly set the resolution on a NI card using DAQmx in C#?"

Regards

A.N Sutherland 

[Chris G in AE]

Mr. A.N Sutherland,

There is no way to set the resolution on the two NI cards that you are using with DAQmx.  These cards have a 16bit ADC that either works or does not work.  Since you've verified with Signal Express (great test by the way), we know that the cards are functioning properly.  

I'm curious how you're implementing your DAQmx tasks in C#.  Take a look at the ANSI C examples located in the Start » All Programs » National Instruments » NI-DAQ » Text-based Code » ANSI C examples to get a good idea of how to implement your analog input task.  These examples are out of the box code, so you should be able to easily test the functionality of the card with them.  

Please post back if you have more questions or are still seeing a problem even with the examples.  Thanks, and have a great day!

Regards,

Chris Garyet

Applications Engineer

National Instruments

www.ni.com/support