USB-6009 Analog Waveform Output

[RMCvisor]

I'm trying to create an analog waveform from a USB-6009 device through one of the analog output channels. However, through the DAQ Assistant, I can only select the 1 Sample (On Demand) setting. When I test the device, I can only push a constant voltage out. If anyone has any advice on how to create an analog voltage waveform using this device, I would like to know.

[WM_John_Weeks]

The USB-6009 has no waveform-generation capability. Using NI-DAQmx 7.5 you can get support for software-timed waveform generation. Note that the spec for analog output on the USB 6008/9 is just 150 samples/second.

[RMCvisor]

Thank you so much for your reply. It has been very helpful. You said, "Using NI-DAQmx 7.5 you can get support for software-timed waveform generation." I am only a novice at LabVIEW and data acquisition in general. What did you mean by software-timed waveform generation? I have NI-DAQmx 7.5 downloaded and installed already. Also, you said, "Note that the spec for analog output on the USB 6008/9 is just 150 samples/second." Does this mean that I cannot generate a waveform that is more than 150 Hz?

[WM_John_Weeks]

>I am only a novice at LabVIEW and data acquisition in general.

I don't use Labview (I write in C++) so I can't help you with that. I try to answer questions about C/C++ and general hardware questions.

>What did you mean by software-timed waveform generation?

That's where the software driving the device sends a sample to the DAQ device, waits for the prescribed time interval, then sends the next sample. So the timing of the waveform is driven by the software, using the computer's clock, instead of by the DAQ hardware. Software-timed is less reliable and has (often) lots more jitter because of competition for CPU resources.

>Does this mean that I cannot generate a waveform that is more than 150 Hz?

It's worse than that. It means you can't generate a waveform faster than 150/N Hz, where N is the number of samples (data points) that define the waveform.

[RMCvisor]

Thank you for explaining those things to me. My ultimate goal is to create a sine waveform around 15-40 Hz that is able to be fed into an amplifier that will make another component oscillate. I only have the USB-6009 device to do it with. Since you don't use LabVIEW, I'll have to find out the limitations on that end. However, do you think it will be possible to use the USB device as a signal generator in that way or will 150 samples/sec inhibit it from being implemented? If this can't be done, do you have another solution for the problem?

[WM_John_Weeks]

Well, at 40 Hz you would have fewer than 4 points/cycle of your sine wave. That's not much of a sine wave!

At 15 Hz you would get 10 points/cycle, which isn't real good, but would be recognizable.

Also, if you check out the analog output specs, it has a range of 0 to 5V, so you can't make any waveform with negative-going voltages.

Lots of folks have siezed on these low-cost devices because they're cheap. In fact, I think they're a good value. But you do get what you pay for!