Immediate Sampling?

[Dominick_8.5]

Let's say that I want to get two samples at a rate of 1 second.

1. Will it grab the first sample (S_1) immediately and then grab the second sample (S_2) 1 second later.

2. Or wait 1 second before grabbing the first sample (S_1) and then wait another second before grabbing the second sample (S_2)?

1.

When a sample is taken ->   S_1                     S_2
                  Time ->   0.00  0.25  0.50  0.75  1.00  1.25  1.50  1.75  2.00  2.25

2.

When a sample is taken ->                           S_1                     S_2
                  Time ->   0.00  0.25  0.50  0.75  1.00  1.25  1.50  1.75  2.00  2.25

[Christian Mergl]

Hey,

What you are talking about is called "Round Robin Sampling". More about that here: http://digital.ni.com/public.nsf/allkb/4F9D107D8B26233B86256F250057C9B3

If you are using e.g. an NI M-Series DAQ card you can perform this with setting the AI Convert Clock via the DAQmx Timing Property Node.

Christian

[Dominick_8.5]

Ok, I'll say it this way.

Does the card, sample first then wait?

Meaning, if the sample rate is 0.5 sec, then the card will sample first, and then wait 0.5 sec before sampling again.

I called, and one of the NI app engineers said yes.

[Christian Mergl]

Well, if you have an standart multifunction DAQ device and would not configure it for Round Robin Sampling, it is using Inverall Sampling.

That means that it Samples both Channels as fast as possible (and immediately after start) then wait the second and sample both again.

Can you tell me whats the purpose of your question? Why do you wanna know that?

Christian