Timing the dataacquisition

[mara]

I need to measure data in a while loop every second. How can I in LV 7.1 make sure that my vi acquires the data exactly every second? As an idea I thought it may be useful to use a queue, due to further processing, but I'm not sure. I'm curious to see your suggestions.

Thank for help.

Mara

[DOC-doc]

Hi Mara

If you want to measure data every second EXACTLY, you need to use a trigger.
It can be generated by your card.

If you don't need the exact timing, you can use a timed while loop in parallel to your other processings.

Doc-Doc

[mara]

Hi Doc-Doc

It has to be exactly every second. I never used a trigger before. How do I generate a trigger and how have I to handle it?

Mara

[DOC-doc]

Hi Mara

Sorry, you don't need to generate a pulse.
You can use :"C:\Program Files\National Instruments\LabVIEW 6.1\examples\daq\anlogin\analogin.llb\Cont Acq&Chart (what you want of difficulty)".

There you will find that you can set your timing very acurately and read the data from time to time (or whenever you want).

Cheers.
Doc-Doc

[Stuart_G]

If it really needs to be exactly every second you should probably consider using LabVIEW RT. Even with the trigger method Doc-Doc mentions there could be significan latencies if you are using Windows.

Stuart G

[mara]

Hi Doc-Doc

Unfortunately I haven't a DAQ. I should trigger a oscilloscope. Since I use a TCP/IP connection it would be preferable if the trigger supports this.

Mara

[DOC-doc]

Hi Stuart

There is no need to use LabVIEW RT to take a measurement every second. A continuous bufferd acquisition has no latency (at least not more than 1 clock cycle on the card).

Doc-Doc

[DOC-doc]

Then I don't understand exactly your process. Do you want to trigger a scope every second EXACTLY, and want to get this data on your PC ?
I am correct ?

In this case, you should plug a function generator set to 1 Hz to your Scope trigger input.
And check by TCP/IP whenever data is ready for transfer.

Do not try to use soft trigger to trigger your scope by TCPIP : it will never be acurate since you don't know how much time it takes to send your order to your system. Even with a RT system

[Stuart_G]

Correct...I didn't see where she was doing a buffered acquisition.

[mara]

Well I'm not a LabView master (not yet). So how do I realise a continous buffered acquisition?

Mara