Why is the mode selection disabled in max for NIDAQ-USB-6009?

[Kevin2]

I try to use NI-USB-6009 AO to generate sine wave.

1) I want to use MAX, but the mode selection and Rate are all disabled in "Analog Output" section.

2) I find a VB example to generate the sine wave, but i got an error message.

I want to know if the NI-6009 has limited function support or not........???

The attachment include the screen shot.

thanks a lot!

Kevin

[johnsold]

Kevin,

I do not use MAX or VB but I suspect that the problem is that the USB-6009 only has software timed AO, so "Rate" is not applicable.

Lynn

[Kevin2]

Lynn,

Sorry, i do not quite understand the meaning of "Software timed AO". You mean i need to control the USB-6009 sample interval time by myself or ....?

Thanks!

Kevin

[johnsold · Accepted solution]

Kevin,

Yes. Software timed means that the device has no internal clock or buffer. You call the AO Write with one data point. Then you call AO Write later with another data point. Repeat until done. This means that the maximum AO update rate is about one hundred hertz or a little faster. It also means that there will be a lot of timing jitter due to OS latencies at speeds like that.

Think of AO on the USB-6009 as a way of setting occasionally varying DC voltages for your system.

Lynn