LabVIEW
Old and new value of value change event are same
Hi Jasraj,
using "value (signalling)" fires a value change event even when the data stays the same.
Simple solution:
Compare old and new data in the value change event and us e a case structure with the result.
Or only fire events when the data really change…
Hi Jasraj,
how can I compare??
Use a comparison function:
It may be because of value signalling is placed in timeout event.
Well, even then you don't need to fire an event with each timeout!
I guess your VI works exactly in the way you have programmed…
When you need specific help you should attach your VI!
Hi Jasraj,
When old value and new value both are same then comparison doesn't make any sense.
When you want to avoid unneccessary code execution a comparison with a case structure makes a lot of sense!
Where should I place value signalling ?
Whereever you need it.
Did you read my comment above?
Without any VI you will only get generic answers on your generic questions…
@jasrajrajpurohit wrote:
even then you don't need to fire an event with each timeout!
Where should I place value signalling ?
Events are primarily for user interactions. If you think you need to fire an event whenever a timeout occurs, it would seem more reasonable to place all that code inside the timeout event and it will execute at that time. If you also need to sometimes manually fire a value changed event, you can assign "timeout" and "value changed" to the same event case.
You really should explain what you are trying to achieve. Most likely there is a better solution overall.
@jasrajrajpurohit
The compare was suggested as a solution to something else, that fits the symptoms you describe. I think it was assumed that you want to do some action when the value changes. As the event is fired even when it doesn't change (e.g. by sending value (signaling) with the same value), you can prevent the execution of the task by comparing. If the values are the same, no need to execute the task.
I think your problem happens before that. You don't understand why the values are the same. The compare is not your problem.
It is hard to tell without looking at some code why you'd get the same value... I'd have a good look at the place(s) where the value is changed. maybe even make a dummy place where it is changed. See if a definitely absolutely sure change of value still produces the same values in the event structure.
Or post some code...
Search LabVIEW like a graph! Hi Jasraj,
Please suggest the solution
I want .......... "Whenever I change the ROI of Image the value change event of ROI descriptor should be executed"
Simple: delete that "value (sgl)" property node in the timeout event!
Now your VI will only react on user interaction…
