I've been looking at the example Sim Phone.vi that comes with labview and would like to generate similar tones out of our usb 6008 device. I can get a very faint sound out of our usb 6008 using the example Gen Multi Volt Updates-SW Timed.vi Does anyone know the best way to alter Sim Phone.vi to have the sound come out of the Analog output of our usb 6008 device. ( I have a small speaker connected to the Analog out on our USB 6008)
PS: we are using labview 7.1 Does anyone know the Analog output frequency range of the usb-6008? Is this possible?
According to the manual (http://www.ni.com/pdf/manuals/371303a.pdf), the 6008 can update up to 150Hz. That is a bit slow for audio work.
Another concern is that the output has a 50 Ohm series resistance, so connecting a low-impedance (4-16 Ohm) speaker may be too much of a load to get any real volume out of it. It may work if you use a higher impedance speaker (I think I have seen 32 Ohm somewhere..), but I'd use a simple op-amp as a buffer to get more drive capability.
We won't be going past 75Hz and we currently have it hooked up to a audio amplifier. We are just trying to get an example of how to create an audio/frequency signal out of the usb 6008 analog output channel.
As stated earlier you could most certainly use the USB device to generate sound, but that would be at a max update rate of 150 Hz. While according to Nyquist theorem you could get frequency information for signals below 75 Hz, you may notice that the quality of the data in that spectrum to be very low due to having so few samples.
While technically possible to produce you really should look for a device with a faster Analog Output update rate. I would look for a device that supports Analog Output at least 10x the maximum frequency that you want the user to hear. Some great, yet lower cost products, would be the M-Series line of products. They would give you the performance that is really needed in the type of application that you are talking about.
If you still want to use the USB Device, then you would need to use code similar to that found in the example Gen Mult Volt Updates-SW Timed (Found here: C:\Program Files\National Instruments\LabVIEW 7.1\examples\daqmxbase\Dynamic\ao).
Best of luck getting your system together,
Otis Training and Certification Product Support Engineer National Instruments