can't plot a point at zero

[GregFreeman]

I have a code where I am plotting y versus x. I have elapsed time set up to 60 seconds. When this hits zero, it enters a case structure which has a VI in it that records the current x value for time(I have a timer set up) and y value and plots them. The only problem is that it leaves me with a data point at 1min but no data point for time = 0 when the code started. The only work around I can find is to put a second case in where if the total time < (very small number) it plots a point on the same graph. This is fairly inefficient im sure to have my code running through an extra case, even though its a simple one and I was wondering if there is any way to eliminate this problem?

[altenbach]

I am not good at reading long and complicated descriptions.

Could you instead just attach a small VI that demonstrates the problem?

(Maybe you could e.g. do a boolean ["i==0" OR "time elapsed"] as a case selector)

[GregFreeman]

Sorry, wasn't on a computer with labview earlier. I have version 8.2 Here is a snippet of my code that I am having the issues with. Also, since I am new to labview and have just been teaching myself at work, any advice would be much appreciated on making any of what i posted more efficient or cleaner etc. I know a state machine may be best because the code is a little too horizontal for my liking but it works so I'm not going to complain too much 🙂 Thanks in advance. 

[GregFreeman]

Typical sin, forgot attachment 😕

[altenbach]

Are you running this with the "continuous run" button??? 😮 Don't!

(Have you tried my boolean solution mentioned above?)

[GregFreeman]

Nope, im not using the continuous run button and no i haven't gotten around to trying the boolean. I will try that this afternoon. Thanks for the advice.

[Root_Canal]

You don't have to use seperate logic for the case where time is zero.

Instead, you can sneakily assign your start time to be exactly equal to the present time minus one data recording interval. This way, the clock starts at the elapsed time and intstantly records a point.

See the attached VI. There is a version saved for labview 8.0, and one saved for labview 8.6.

 

Cheers

-root

Message Edited by Root Canal on 10-21-2008 02:06 PM

[Karunya_R]

Hi,

Like you admitted, using a State Machine would be ideal in your case (and would also make it easier to understand  )

In you case you can just use a select case and check if the time is less than a minute or more than a minute. Use the time less than a minute as one of the states and time more than a minute as the next state. This way your code gets more concise, don't have too many cases structures and you dont have local variables.

Let me know if you have more questions about this!