Easy aquireing

[ebalci]

Hi chemph,

I'm sorry if I couldn't understand or solve your problem.

We have been discussing about some methods of finding out what your card's capabilities are.

Did you try them? Have you checked your card's documentation?

If I knew the answer to your question I would tell you directly in my first post. I'm just trying to help you to find the answer.

From what I see from the NI web site, it is not possible to achieve 1,000,000 Hz. But 100,000 seems OK.

The card's rating is 200,000 Hz. But still I do not know if this is also valid for multiple channels sampling simultaneously.

NI website does not mention this.

You also did not tell anything about your application. What do you want to do with your card?

The card may have less than what you think but it may still be suitable for your current application.

There are many possibilities for "red marked" parameters, depending on your application.

The NI cards and DAQmx library are designed to have those options so that you choose the best for your needs.

So, you need to specify your hardware and define your application so we can get further.

Why don't you e-mail or call NI directly to find out the specifications of your card? 

Message Edited by ebalci on 11-24-2008 08:13 AM

[chemph]

Hi ebalci,

thanks for your answers. I really forgot to describe what I want to do with my card.

There is a Mashine with some sensors like force, pressure, temperature and distance. These signals comes to the card as 0-10V voltage signals. These signals I want to aquire during the mashine is running (circa 30 seconds).

 I saw, that the function DAQmxReadAnalogF64 returns with the number of samples which I defined for the buffer size when I make a little Delay after reading. What I want to say is: BufferSize: 5000; read ==> returns with 5000 samples and not only one time. Maybe there are many buffers with the same size and each buffer will fill and I read a hole buffer and then the next hole buffer.

I will contact the ni support, but thank you very much for your answers.

chemph 

[chemph]

Hi,

now, I came a bit nearer to locating the problem. With ni Max, alls measurements are ok, also the resr with the frequence generator and 200 kHz is ok. The Problem must be in Saving the data to a file. I used ArrayToFile and fprintf, both methods seem to be much too slow. When aquireing data with a very low rate (e.g. 5 Hz), everything is ok because the Buffersize will never be needed. In this case, I defnetly reed faster than I write to the buffer. But When reaching a point, the data will come too fast, that the buffer load will become higher and higher; because of reading the buffer load will also decrease, but the increasing is higher. This problem also exists when running the ni example 'ContAcq_To_File'. Running it with 200,000 Hz will cause an error after running a bit. I also made a test with a Delay after the Read-Function. At first (a fer ms) nothing happened, but later (delay = some seconds) the buffer hav probbobly an overflow. So the problem is not in getting the data; it is in handle the data (or saving the data to an file) after reading with an acceptable speed.