delay value

[IDILIO]

I want to compare the value of a variable with the value of the same variable 10 seconds before.

What is the best way to obtain the value of that variable 10 seconds before without any waiting time?

[RobCole]

Previous values are not stored in LabVIEW automatically. You have to tell it to store the value and recover it yourself when you need it.

Rob

[altenbach]

How often does the value change?

You need to keep track of 10s worth of data. This could be a single point if you record at 0.1Hz or millions of points if you record very fast. Can you tell us a little more about your application?

Typically you would maintain the history in a shift register.

I don't understand what you mean by waiting time? Please explain. 

[IDILIO]

The easy way to do this is get the value from the variable then put a Wait and then get the value from the variable again but in this case the comparation have a waiting time (from the Wait funtion) so is not done imediatly...

Note that the 10s. is also a variable and can be any value...

[Florian.Ludwig]

Hi,

can you post the vi? This would make it way easier to see what you are talking about.

Regards

Florian

[GerdW]

Hi IDILIO,

"so is not done imediatly"

When you get the variable's value the second time you can compare immediatly - as you compare with a already stored older value...

It seems you're using local variables to reach your goal. You should know LabVIEW uses wires to store values!

[NarayananK]

Hi,

Attached VI is an imagination of what is understood by me on comparison of delay value.

Hope it helps.

Regards.

[IDILIO]

See attached Example.vi

What I want is compare the value actually in the screen (on indicator "Value") with the value that was on that indicator 10s. (delay control) before.

With this vi I cannot show the result for every values in the Value (the comparation is done only for one value every 10s.) and the result is showed 10s. after I want.

[IDILIO]

NaruF1,

Can you please post this .vi compatible with version 8.20?

Thanks

[GerdW]

Hi IDILIO,

when you want to compare the current value with a value in the past and with a variable delay you have to create a history of your values.

As shown in your example I would create an array of values (like a ringbuffer). Now you would be able to compare the current value with each value in that buffer...