soundcard for data acquisition

[blueguard]

I am in my last year in mechanical departement ,and my project is about machine vibration diagnostics and analysis , but i can not pay for an NI DAQ card ,so that i am planning to use the PC soundcard as a data acquisition card , and i do not no to what extend the soundcard is valid for this purpose, especially for multichannel measurements , and how i can interface the sound card to Labview? :question:

[thomas2609]

first find a data sheet of your sound card;

there you should find all important parameters; (cannesl, sampling rate, inputvoltages......)

input bandwith is about 20 Hz to 20 kHz (mind Nyquist–Shannon sampling theorem)

so you can measure 2 channels if you have a stereo(input) soundcard.

to use the soundcard in labview, just use the sound vi's

a wave file is nothing more than measured values and the sampling information ( dt = 1/sampling frequency)

thomas

ZITAT(blueguard @ Feb 4 2008, 04:26 PM)

I am in my last year in mechanical departement ,and my project is about machine vibration diagnostics and analysis , but i can not pay for an NI DAQ card ,so that i am planning to use the PC soundcard as a data acquisition card , and i do not no to what extend the soundcard is valid for this purpose, especially for multichannel measurements , and how i can interface the sound card to Labview? :question:

[Rolf Kalbermatter]

QUOTE(blueguard @ Feb 4 2008, 10:26 AM)

I am in my last year in mechanical departement ,and my project is about machine vibration diagnostics and analysis , but i can not pay for an NI DAQ card ,so that i am planning to use the PC soundcard as a data acquisition card , and i do not no to what extend the soundcard is valid for this purpose, especially for multichannel measurements , and how i can interface the sound card to Labview? :question:

Since you are doing vibration diagnostics one problem of sound cards is probably not that much of a problem for you. Sound card inputs are bascially always DC decoupled meaning they can't measure DC voltages and have a lower bandwith frequency of around 20 HZ.

Multi channel is often not possible unless you get some more high end type card that sometimes happens to have two IO channels. But still you should be aware of that sound cards are using chips that are selected to produce fair results for audio applications. The human ear is all but an exact measurement device and therefore you can get away with rather bad hardware components without most people noticing to much of a quality degradation. In the PC component industry where every dollar not spent for a product is both a marketing advantage as well as a possibility to make a few cent more profit, this results normally in the cheapest components selected that will just about do for the task at hand (and for some products the quality degradation is definitely noticable even for the human ear).

So using that hardware for measurements is not likely to produce accurate results. It will be more like guessing than actual measurement. If that is acceptable for your purpose will be something you have to decide for yourself.

Rolf Kalbermatter