Keep the staring time constant on x axis on waveform graph

[ankit]

Hello

I am having some trouble on how to keep the starting time constant on a wave form graph and display the data from the starting time to the the current time. I want to keep the starting value on the x axis as the starting time of my graph and then just keep filling the graph as more data comes in.

Also attached a VI for explaining my doubt.

Any suggestions / ideas?

Thanks

Ankit

[ankit]

Suprising still no comments.

Is this such a silly question ? I think I am missing something basic here about waveform graph. Again I am just trying to keep the start time constant and still update the x scale of the graph. If I use autoscale then it adjusts both the starting and ending values on the graph which is not the objective.

Any suggestions / ideas

Thanks

Ankit

[Norbert_B]

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@ankit wrote:
[...]

 I think I am missing something basic here about waveform graph.[...]

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That is true. The waveform graph just displays the data you are presenting him....
The graph either uses a 1D numeric array as input or a waveform. When using a numeric 1D array, the values are displayed in regard to the index, so x will start with 0 and end with (size of array).
When using a waveform type, the waveform defines t0 (start) and dt ("timeresolution") where the values have the same timedifferences between. In this case, t0 will be the first value, all other values will be displayed at t0+index*dt.
Now the problem is that timestamps cannot be displayed in an infinit small resolution. The next point is that you always write a new t0 into your waveform each iteration. Therefore, your graph is moving.....

hope this helps,
Norbert

[ankit]

Thanks Norbert

Now I understand why the starting time was changing on that graph beacause of new values written to t0. But here is my problem, I am getting some data from a probe (Temp, Rel Humidity). I know when a value comes from the probe but the probe doesn't give any time stamp so I have to add timestamp to each of those values. t0 is not constant in this case as sometimes probe timesout and doesn't return any value . So i only want to add a timeatmp when I get a value and store and display the timestamp and the corresponding data together.

How can I add time stamps to a set of values (data) coming in LabVIEW without having a constant t0?

Thanks once again

Ankit

[Norbert_B]

Ankit,

in this case you have to use a XY-Graph. In the standard waveform graph, it is mandatory that the values are equidistant (at least, the graph displays them in that way).
Using the XY-Graph, you can "print values against other values", in your case: measurements against timestamps.

hope this helps,
Norbert