How to use Digital output to turn on sensor for Analog Input?

I am trying to use a digital output to turn on an array of sensors that I then wish to read on 16 analog input lines. I have a 6024E DAQ card. I am planning to take data at 10-20 hz, so not terribly fast, but I will be acquiring for long periods of time (days) so I will be streaming data to disk.
I have a fair bit of experience in Labview basics, but can quickly get out of my depth when I try something new (like this). I have V6.01.
It looks as though the best way might be to do the DO and then a single AI as individual events, then write to disk and continue through the loop. I am puzzled, however, how to keep this cycle on schedule given that I don't know how long it will take to sample 16 channels
, write the data to disk and get back to the starting point... perhaps this is so fast that I don't need to worry about it? The actual timing of the samples (be it 10 or 20 hz) isn't too critical, as long as I can record at what time they were taken... it would be frustrating to find that I was several seconds off after days of data.

Hello,
Thank you for contacting National Instruments.
If you are worried about the time of your acquisition being off, then you should associate each voltage measurement with a timestamp. This will allow you to know the exact time at which the sample was taken and you will never be off. You can use the Get Date/Time in Seconds.vi in our while loop with your AI code so that you can read a sample and read the time. You can than log the voltage value and the timestamp to your file.
Regards,
Bill B
Applications Engineer
National Instruments

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How to use counter output pulses to trigger analog input?

Hello all,
I hope the kind people using this forum can help me, a lowly beginner LV programmer! I have been attempting to create a VI that produces a user defined number of TTL pulses, separated by every n seconds. Each TTL would be outputted to a stimulator, which in turn generates its own TTL. Using the stimulator-generated TTL, I would like to trigger finite analog data acquisition (e.g. for every TTL, trigger the collection of a data sweep that contains 4000 samples (collected at 4000 Hz), with 1000 samples collected pre-trigger. I would like to also be able to see each data sweep as it is triggered on a chart. As I understand things (lots of online/book/forum reading), I should be using the counter output to generate my TTL pulses, and syncing each counter produced TTL with analog input, as well as using a reference trigger. Also, the AI part should be started first, so that I don' t miss any counter outputs. If it matters, I also need to use one of the AI channels to acquire the TTL, so I can see my stimulator-induced responses to the stimulator in time.
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Hello,
Due to the fact that analog tasks themselves are not retriggerable, a
pulse train produced by a counter is always used as the sample clock
for the analog input task in order to recreate a retriggerable effect
for analog input. This can be done by creating a finite pulse train set
to retriggerable using the DAQmx Trigger Property Node, or the pulse
train could be continuous and just be gated by another signal. Neither
of these methods can be properly applied in hardware to create a
retriggerable reference trigger. You can however implement something
similar in software by just stopping and restarting your reference
triggered analog input task within a loop. There will be some delay
between when the task is stopped and restarted, as these events require
software intervention, but if there is enough time between when each
trigger signal is generated, there should not be any noticeable delay
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I have attached an example of this!
Mark B
===If this fixes your problem, mark as solution!===
Attachments:
RC001 v_1mod.vi ‏25 KB

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led control.vi ‏7 KB

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How to combine Digital Output, a delay and Analog Input in a fast loop

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