DAQmx Create Channel Minimum and Maximum Value default to largest possible for the wired physical channel

[SteveP]

Proposal : If left unwired, the DAQmx Create Channel Minimum and Maximum Value inputs would default to the maximum value for whatever physical channel was wired.  Currently for example, AO Voltage defaults to +/- 10 V.  Some devices such as the USB 6008 are limited to 0 to +5 V.  For programs that allow for different daq devices to be used and changed at run time, one does not know ahead of time what the allowable input limits will be and cannot be assigned.  Is it possible to use the DAQmx Device property I/O Type:Analog Output:Voltage:Ranges to obtain the limits and then wire that result however this involves extra coding to make use of them.  If the DAQmx Create Channel is used at many places in a vi it becomes cumbersome to have to extract the property for every instance of use.  i.e. even if DAQmx Create Channel is done once, another call to it does not retain the values previously set.  A solution would be for DAQmx Create Channel to simply obtain the minimum and maximum values based on whatever physical channel was wired to it and use them.

[RavensFan]

That sounds good in theory, but the problem is that when you place the DAQmx Create Channel on the block diagram, LabVIEW probably won't know what device you are connecting to.

1.  You will not have yet connected a purple wire that tells what device you are connecting to.

2.   The data that is on that wire can be determined programmatically either through a front panel control or perhaps through other processes such as loading the information from a configuration file.  At edit time, there is nothing on the wire that tells what the device is.  Only during runtime does the information make it onto the wire to tell the Create Channel VI anything about which device it is supposed to create a channel on.

3.  The physical device may not even be defined yet.  Only until a DAQ card appears in MAX do you get any kind of connection between a channel (Dev1/ao1) and the true physical device (USB-6008).

Message Edited by Ravens Fan on 01-21-2010 07:44 PM

[SteveP]

I'm not concerned about seeing the correct values at edit time.  They could still show +/- 10 V for example.  If they were obtained at run time and thus avoided an error by not having wired the correct limits, that would be fine enough for me.