Can I send Analog out with different sampling rate of 2 channel ?

[Nok]

Hi...
I have 2 questionss... Help me pls.

1. I don't know if it is possible to send analog out (DAC0 and DAC1) at the same time with different sampling rate.

2. I try send DAC0 and DAC1 by define the channel of AO config with value (0,1) and set the same sampling rate. it works but why the frequency is twice in both channel? (I set 40 Hz but at the oscilloscope is 80 Hz)

Thanks for any kind help. 🙂

[Anonymous]

Hey Nok,

The analog outputs on our devices use the same updating clock and
triggers so you can not change the update rate separately for DAC0 and
DAC1.

However, the update rate is just the rate that the device outputs your
waveform not the frequency of your signal. For example if you set the
update rate to 1000 S/s, had a buffer size of 25 that contained one
period, then you waveform would have a frequency of 40 Hz. Using this
mythology you can change the number of periods loaded into the buffer
for each channel to achieve different output frequencies on each
channel.

Here are some links that might help.

http://sine.ni.com/apps/we/niepd_web_display.display_epd4?p_guid=B45EACE3E6B356A4E034080020E74861&p_node=DZ52313&p_source=External

http://sine.ni.com/app
s/we/niepd_web_display.display_epd4?p_guid=B123AE0CBC9E111EE034080020E74861&p_node=DZ52313&p_source=External

I hope this helps out.

Joshua P.
Application Engineering
National Instruments

[Anonymous]

Hi.. JoshuaP

Thanks for ur help. I try to do my program by ur way that set
different buffer between 2 channels in order to make different
frequency.

but it doesn't work well when I use defferent buffer.

Could u pls help me check my program. The aim of this program is I try
to make the function generator in which can send 2 channel with
different frequency and shape at the same time.


Thanks a lot for your kind help!!!

[Anonymous]

Hey Nok,

Give this a try. It uses the Basic Function Generator.vi instead of
the VI you made. If you want you can look at the internals of the
function generator to see what is going on.

I hope this helps out.

Joshua P.
Application Engineering
National Instruments

[Nok]

Thaks again, Joshua P.

That's working very well.