A/D conversion by PC sound card?

There are several limits. The most important one is that sound cards do not go down to DC; they are AC coupled with cutoffs at a few Hz. So if you want to make general measurements like DC voltage, temperature, pressure, or many other real-world quantities you need to provide external modulators to convert them to AC, and some sort of software demodulation to recover the original values. In theory you might be able to modify the card to go to DC, but the problem is that these cards are usually operated from a single supply voltage and if you remove the input capacitor then your input signal must be biased up to half the card's supply voltage somehow... not trivial, if you expect to maintain any sort of DC accuracy.

Another problem is timing. Under Windoze, you have to be very careful when you are trying to correlate measurements with timing events in your program. Windows and the sound card don't start conversions exactly when you give a command... there is a variable and unknown delay that can't simply be calibrated away. Same thing for outputs. So if you need to know what your data looks like at the time of some event, you should record that event on the second channel of the stereo card... even if you created the event yourself in software and sent it to the D/A.

Finally, there is the fact that most sound cards have only 2 A/D channels, and those that have more must use non-standard drivers that you would have a hard time finding how to program for.

If you will discuss exactly what you are trying to observe, perhaps we can come up with a good recommendation.

Best regards,

i Bob Masta dqatechATdaqartaDOTcom D A Q A R T A Data AcQuisition And Real-Time Analysis

You will probably be better served by a device made for the purpose.

This a 4 channel, 10 bits/channel D/A converter with software for $25US

Dear Bob, I can say nothing. :D thank you so much. if any new, I will post it.

Best regards, Boki.

: )

Thank you very much for information.

Best regards, Boki.