topic Re: record and display data in LabVIEW

record and display data

Roddy — Wed, 16 Dec 2009 22:43:48 GMT

What I would like to do is: display a data point every 1 sec but record the a data point every 10 sec.

I have been playing with the event case and loops to achive these but no mather what I get one or the other; I either record and display every sec or every 10 sec.

Thanks...

Re: record and display data

Darin.K — Wed, 16 Dec 2009 22:48:07 GMT

I assume you have a loop cycling every sec to display the points. Wire the iteration number to the integer and quotient function and divide by 10. Wire the remainder to a case structure. In the zero case, log your data, in the default case do nothing.

Re: record and display data

Harold_Timmis — Wed, 16 Dec 2009 22:48:23 GMT

you can use the Elapsed time.vi

Re: record and display data

Harold_Timmis — Wed, 16 Dec 2009 23:28:34 GMT

an example of Darin's:

Re: record and display data

Roddy — Thu, 17 Dec 2009 18:58:45 GMT

It works pretty good, but what about doing it with and event structure?

I try a couple things like creating and event for when the reminder is zero but that didn't work.

Re: record and display data

CAC10268 — Thu, 17 Dec 2009 20:32:35 GMT

Assuming you have a timeout case in your event structure, you can check the status of the remainder every iteration. Make a value change event case for a boolean, and whenever your remainder equals 0, just set the boolean's value using value signaling to generate the value change event.

Re: record and display data

Roddy — Fri, 18 Dec 2009 01:06:05 GMT

I actually did that but I can not get the data to record...

Re: record and display data

Roddy — Fri, 18 Dec 2009 05:34:41 GMT

Let me rephrace that... for some reason the event (for boolean value change) doesn't execute.

Re: record and display data

Guruthilak — Fri, 18 Dec 2009 08:41:40 GMT

hey roddy..

Just a question .. Does the VI actually stops when the stop butoon is hit....

I DONT THINK SO....

Guru

Re: record and display data

Balze — Fri, 18 Dec 2009 09:43:57 GMT

Guru,

why doesn't it stop?

The timeout is connected with 1000ms so it will stop after 1 sec, doesn't it?

roddy,

it's right that the event-structure does not execute if you connect the control directly (as you did).

Try to connect the control using a property node and its property value (changed).

This will trigger the event-structure.

(Maybe you should use the LabVIEW help. I'm pretty much sure there is an example in it how to programatically trigger event structures)

IMHO it's not a smart solution anyways. The idea of a event structure is to capture user events (i.e. the frontpanel activities).

In your case it'maybe better to use a timed loop with 1000ms loop time, replace the event-structure with a case-structure, take the Rest from your modulo division and connect "Sine2" inside the case "0" of the case-structure.

When the Rest of your modulo division is != 0 then nothing happens.

Best regards,

Rainer

Message Edited by Balze on 12-18-2009 03:43 AM

Re: record and display data

Guruthilak — Mon, 21 Dec 2009 05:38:13 GMT

Hello Rainer,

The stop "button" is directly connected to the the conditional terminal of the while loop and ,when executed, since there are no user events for this stop button, the loop will not stop (since the event structure will keep on waiting for an user event to occur).

Actaully i am not sure whether the event structure has been configured for the "stop button value change event" or not becasue i can see only one frame of the event structure

Guru

Re: record and display data

Dennis_Knutson — Mon, 21 Dec 2009 05:44:50 GMT

The loop will stop as long as there is a timeout event and there is obviously a timeout event since a timeout value is wired to it. It's not very elegant to do it this way, of course, but a value change event for the stop button is not absolutely required.