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how to improve time interval between two measurments

Hi All..
I have 3 Vi each of one measures from different devices. And i set the execution order by error cluster. I wonder what is duration between of each of execution? if you look at the VI that i attach, u see that 3 (one of which is seen as question mark)  are  connected serially, but the problem is that there is a delay between measurements that i can distinguish just looking data values acquisation(then should be really high). How can i improve time interval between measurements? I need to measure 3 output when the conditions are the same for all, but when there s delay the condition of device 1 and 3 could be different and effecting my project.
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Message 1 of 16
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Hello,

>> I wonder what is duration between of each of execution?

You can use the tick count function and a sequence structure (not usually recommended, but ok for debug purposes like this).


>>
How can i improve time interval between measurements?

It sounds like you want your 3 measurements to be relatively independent, but to all be triggered by the same event.  How about setting up a loop for each measurement -  using an event structure in those acquisition loops - and then monitoring your "trigger condition" in a 4th independent loop, which will trigger a user event to cause the other loops to execute accordingly.

If you are eventually going to scale things further, you may explore other architectures instead of simply creating more loops.


If you can clarify what you're trying to do here, we can probably help you further!

Best Regards,

JLS

Best,
JLS
Sixclear
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Message 2 of 16
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Without really looking into the code, my first response would be to run the 3 sub vi's in parallel if possible.  You can run the error cluster into all 3 (if the inputs of the sub vi's aren't dependant on the outputs of any of the other sub vi's), then you can build an error array from the error out on the 3 sub vi's and wire that array to the "merge errors" vi.  Make sense?

Nate

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Message 3 of 16
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Hello JLS..
First i would like explain what i want to do with this VI. I have one power supply and 2 multimeters. after initializing all those guy i would like to start measurement as following. I write specific current to power supply, and writing s completed i wait for a specific time ( thats the reason why i use the timer ), at the end of the waiting time, I want to measure outouts of the power supply and the of other 2 multimeters at the same time (i know that it s not possible, but would be the best solution i dunno),and keeping measurements till i stop. So according to ur suggestion my trigger would be a start command, but why would i use seperate loop for each one?
in the further step, the ratio between signals from meters gonna be my x values as outout of the supply is y. And i ll plot x-y graph.
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Message 4 of 16
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Hi Nate,

3 devices are independent. Most important to me is that i would like to measure outouts of those guys almost at the same time. If i run them parallely, what would be the advantage of that comparing the serial process?
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Message 5 of 16
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These vi's sort of show the difference.  Look closely at the millisecond timer values of each and you should see that the parallel vi is always in sync and the serial vi is not quite in sync.  Think of the sequence structures as sub vi's.

Nate

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Message 6 of 16
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hi npoling..
sorry , I should have indicated before that i m using LV7.0 so i can not open ur viäs. Could you please convert them them_
thanks
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Message 7 of 16
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Here are jpg's of the block diagrams I created to show the difference between the serial and parallel data flow.  I do not have 7.1 installed on my machine right now so I am missing the link to convert back to 7.0 from 8.0.  You can re-create the vi's from the jpg's in 7.0.

Nate

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Message 8 of 16
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Thanks npoling...
In the parallel structure means that all 3 sub VI will be executed at the same time?But in my application , in each loop there ll be a GPIB write and read function which means that thez can not be executed at the same time.. then what s gonna be execution order?

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Message 9 of 16
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While the images show differences between dataflow, it really doesn't address the concept of acquiring data from separate instruments at the same time. For that, you might want to look at the types of triggers available for the instruments. I don't know about the power supply, but the meters support both hardware and software triggers. If you have an external source, you would configure them all to use the hardware trigger. Otherwise, configure them for a software triggers and you would then issue a GET (Group Execute Trigger). The measurement for all three would occur at the same time. You would then read the data. Once the data is acquired, it doesn't matter whether your VIs are in parallel or not. No matter what, you can only read data from one instrument at a time anyway.
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Message 10 of 16
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