configuration DAQmx 6281 with labview 7.1

[maurino]

Hi,

i have a problem of configuration the acquisition card NI 6281, because i don't understand what are the  measurement method and if i select the "2 counters (large range or high frequency)", what I have to schedule in labview???

i hope to is clear i this short exposition, and i hope in the response.

thanks you, in anticipation 

[AdnanZ]

Are you interested in measuring frequency? If so, what is the range of the frequency that you are measuring? If you are interested in doing this with DAQmx, you will be using counters. Now, if you measure small frequencies, you just need one counter but when measuring higher ranging frequencies, you will be using two counters to get a much better measurement. If you need help with programming, have a look at the shipped examples of DAQmx in LabVIEW.

[maurino]

Hi,

thanks you for the response.

yes, i must measurement the frequency of a incremental encoder and

the range of frequency than i use is (0Hz-83Khz). i want understand what method of measurement i must utilize.

i have carried out tests but i have ever problems of sample.

my applicatoin is a calculus of velocity of rotation of a wheel of car, whereby the frequency value is incremental.

could you suggest a method of measurement than i must adapter, and in this case any example.

i see the example of labview, but the problem of the measurement method not is resolved.

thanks in advance

[maurino]

and i make configure both the counters for the mesurement a large range (than requires a 2 counters)??

can i change the timebase?? what is he timebase of default?? 

[lucius]

Hi Maurino,

unfortunately there is no definite bandwidth for which you should select either the one or the two-counter method, as you can read here.

As suggested in that document, select Start»All Programs»National Instruments»NI-DAQ»NI-DAQmx Help, and search for 'quantization error': you'll then be able to make a correct choice.

More in general, I suggest you to read the How-to Guide to Frequency Meausurements in DAQmx.

Regards,

Lucius

[maurino]

hi lucuis,

i have see the document in the link.

the method is clear, but in the example tags, my frequency (generate with a function generation) while keeping costant, in my measurement application is variant.

and i don't understand the because 

[lucius]

Hi Maurino,

what do you mean with "variant"? which is the difference between an acquisition and the other? how's your signal made?

I am asking that because the examples are correct and if you have followed the instruction written in the document I suggested you, you should have no problem.

Regards,

Lucius

[maurino]

hi lucius,

my signal have original from acceleration of a car. i have modificated the exemple clearing the TIMING ICON, and this action is succesfull.

whereby seems to work for now. 

i have an other problem: in the timed loop the period is the time between 1 iteration and other???

thanks you very much for your help

[lucius]

Hi Maurino,

you're right.

Regards,

Lucius