Obtain card's available input ranges at run time ?

[Steve Parus]

Is it possible to obtain a daq card's available input ranges when a vi
is run ? My app will be run on different computers with different
cards and I'd like to be able to set the input limits based on what
card is in each computer.

Get DAQ Device Information.vi returns the device type code which can
be used with a lookup table but that requires prior knowledge of
existing card's ranges.

Steve

[mikeporter]

Just a thought, but shouldn't you be setting the input limits based on the signal you're measuring?

Mike...

[Steve Parus]

Signal level is often not known.

For each acquired data point, I'm configuring multiple samplings of
the signal with each sample taken at one of the card's gain settings.
These samplings are taken close in time to each other by setting the
interchannel delay to 10 or 100 usec. Overall repetition period
between these multiple samplings is slow (10 Hz max). I then look at
each set of data acquired at all the gain settings to find the one
with highest gain that did not saturate. That data is the one that is
kept. So when the signal is small, high gain is used. When it's
large, low gain is used. I could just use input ranges of some
arbitrary values in the channel-scan list (say 0.1, 0.5, 1.0, 2.0,
5.0, 10.0 V) and check the acquired data to see if
it exceeds those
limits, but it'd be better to use the actual input ranges the card has
available.

On Wed, 24 Sep 2003 22:48:05 -0500 (CDT), mikeporter
wrote:

>Just a thought, but shouldn't you be setting the input limits based on
>the signal you're measuring?

[JoshuaP]

Hey Steve,

I am sorry to inform you that there is not a direct way to read the available ranges for a specific device programmatically. What is available in DAQmx is the channel property Node. It allows you to read the configured voltage range (not virtual channel range). You could develop a simple VI that set several ranges and read back the voltage range setting to determine what gain values are possible. For example if you set the range to +-4V for most devices it would return the AI.Range set to +-5V. The gain setting in the screen shot only returns the gain setting for SCXI channels and does not return the gain of the DAQ device (Lots of people get confused on this).

Here is a KB that talks about how to gather the same information in traditional
DAQ.
http://digital.ni.com/public.nsf/3efedde4322fef19862567740067f3cc/c93d3954ec02393c86256afe00057bb0?OpenDocument


I hope you find this information useful.

Joshua