Format of DAQmxGetDevAIVoltageRngs

[CVilla]

When calling DAQmxGetDevAIVoltageRngs, how do you know how many voltage ranges are available?  You pass in the size of the array, but the function does not return anything but success/failure.

[Bueller]

Hi CVilla,

Please check the following discussion forum.

Regards,

Faris A

[CVilla]

Thanks for the reply, but that is not quite what I was asking.  I know the function returns pairs of floats to describe the range, but that doesn't help to determine just how many pairs there are.  Anyway, I think I will fill my array with a clearly invalid value and use that as a sentinal value.

[Bueller]

Here's a link that will hopefully answer your question.

If not please include your device model number.

Regards,

Faris A

[CVilla]

I'm sorry, but none of that says how to tell how many pairs of values were returned by DAQmxGetDevAIVoltageRngs.

I would like to query this in software because I am writing a software module for our customers who want to include Analog input with out software.  They will use a variety of DAQ boards - there is no single model number to give you.  Hence the desire to query the device in software.  If using a sentinal value is what I need to do, that's fine.  I just wanted to check if there is a better way to do it.

Thanks,
Chuck

[nickb]

Hello Chuck,

I am unaware of any DAQmx call you could make to get how many ranges were returned, so I think that you are left processing the array yourself to decide how many ranges were returned.  Here is some code that I wrote that tells you how many ranges were returned.  I think that in the end it is going to come down to you performing a similar operation.  Let us know if you have any further questions.

#include <NIDAQmx.h>
#include <stdio.h>

int main ()
{
    double myDoubleArray[512] = {0};
    int i;
    double max;
    double min;
   
    DAQmxGetDevAIVoltageRngs ("Dev1", myDoubleArray, 512);
   
    for (i=0; i<512; i=i+2)
    {
        min = myDoubleArray[i];
        max = myDoubleArray[i+1];
       
        if (min == max)
            break;
       
        printf("min is %.2f and max is %.2f\r\n", min, max);
    }
   
    printf("There are %d viable ranges", i/2);
    getchar();
   
    return 0;

}

[CVilla]

Thank you for your reply.

That is similar to what I planned.  I just wanted to be sure that there was not a better way.  Thanks for giving me the details!

Chuck