acqusition with DAQmx 6281

[maurino]

 HI,

i have a several problem. i have a daq 6281, and programming whit labview 7.1.

my problem is : acquisition continuos of frequenzy up to limit value with a external clock.

i have try a frequency acquisition (ON DEMAND in a timed loop, but don't secure the sample time costant because don't is a real time software) but i can't enter the external clock, wherby i have try a counter continuos acqusition with external clock but i can't stop the acquisition in the limit value.

what i do???

HELP me

thanks in andvances 

[maurino]

 and this is a method for read the buffer during the acquisition?????????????

[AndreaN]

Hello maurino,

I think this is the right example for you to take a look at...

http://zone.ni.com/devzone/cda/epd/p/id/5013

I hope it helps, 

[maurino]

hi Andrea,

the example helped me, but in this moment i have an other question: during the continuos acquisition i want controls the single sample(for example if the frequecy of acquisition is >83 kHz, i want exit from acquisition also if the simple (whereby the number is before determinated) don't is finish.

you have understand my problem??

thanks you in advances 

[AndreaN]

Ciao maurino,

so basically you want to acquire the frequencies and stop the acquisition if the value is greater than a value you specify (for example 83 KHz).

Well in this case you cannot use a buffered acquisition becuause at every iteration you get an array with the number of samples you've set.

So you need to acquire one point at each iteration and then compare the value with the your threshold and if it's greater you exit from the while loop and from the application.

Ciao, 

[maurino]

Ciao Andrea,

ti scrivo in italiano che facciamo prima.

tu hai ragione, io ho provato a fare un'acquisizione alla volta, ma poi in tempo di campionamento nn è più lo stesso. In sostanza io devo acquisire la frequenza di un encoder situato su di un banco prova auto, dal quale ricavarmi la coppia e la potenza. dalla frequenza ricavo la velocità e da essa l'accelerazione con il rapporto incrementale( corretto cn la retta di regressione), perciò il Tempo di campionamento deve essere precisissimo, altrimenti la derivata mi viene un casino.

hai qualche idea su come posso fare la misurazione, la quale deve fermarsi dopo una cert vrequenza, poichè sennò la macchina si fonderebbe.

grazie mille per la messaggistica quasi istantanea 

[AndreaN]

Maurino since this is the "International" forum we need to write in english so everybody can interact.

If you prefer writing in Italian go to the Italian forum at this link:

http://forums.ni.com/ni/board?board.id=7170

Please create a new post with your question. 

Thank you, 

Message Edited by Ryan_82 on 07-16-2009 09:39 AM

[maurino]

excuse-me Andrea, i don't know, whereby i have write the post in italian forum (your link) and if you want, please reply.

 (i have write in italin because i have understand then you are italian.)