How can I update the x-axis to match a time reading in a waveform chart?

[MicTomReiSr]

I am recording data in real time and displaying it in a waveform chart. However, I have yet figured out how scale the x-axis to match the actual time scale of my data. I've played with the accompanying property node but that has not produced the desired result. My guess is that there is a combination of xscale.range.maximum and xscale.multiplier values that need to get updataed in a certain way, but how is still unknown to me. If you could assist I'd appreciate it.

[Dennis_Knutson]

look at the shipping example called Real-Time Chart.

[MicTomReiSr]

This example suffers from the same dilema. By modulating the time delay (multiplying by a random number for example) the x-axis maximum value fluctuates about the actual time. The maximum value on subsequent time stamps sometimes is less than the previous value. See the attached modified version of the Real-Time Chart vi. Watch the x-max value fluctuate up AND down.

[Philip_Courtois]

Hi Mike,

I created a small example that does what you want. It works by using an XY-Graph instead of a Waveform Graph. This is necessary because you don�t want a fixed �dt� between each data point. Only the XY Graph can accomplish this.

Have fun!


Best regards,
Philip C.
Applications Engineer
National Instruments

[MicTomReiSr]

Philip,

Thanks for the response. I'm unfortunately operating with 7.0, not 7.1. Can you send along that VI in an older format?

Thanks,
Mike

[Dennis_Knutson]

I can't open the 7.1 example either but there is a shipping example of using an XY Graph that might help. It's called Variable-Time Chart XY. It uses a buffer so that the graph will operate like a chart. If I had known that your dt was changing, I would have mentioned this example in my previous answer. Sorry for the confusion.

[Philip_Courtois]

Hi Mike,

I now attached my VI in version 7.0.

Basically my VI has the same functionality as the shipping example � tell me which one you prefer�

Have fun!


Best regards,
Philip C.
Applications Engineer
National Instruments
www.ni.com/ask

[Ben]

Nobody has recomended using a Waveform Chart!

A waveform chart will plot the points based on the "t0" of the waveform.

The waveform chart will maintain the buffer so all you have to do is apply the new data.

The "t0"'s of updates from more than one plot do not have to match-up.

See the attached LV7.0 example and jpg.

Ben

Note:
"t0" values for an individual plot must be increasing values.

[Monireh]

Hello

I have the same problem(i want to display the actual time in the x-axis of the waveform chart) but i don't know how to modify my program. i was wondering if you can please help me in this manner

<i have attached my program& i'm using labview 8.2>

Looking forward to recieving from you

[Dennis_Knutson]

You copied that program from somewhere and you don't really understand anything about it, do you? There are some strange functions there. At least one of the VIs seems to do what a standard function does.The VI you asked for help in another thread, is clearly not necessary.

The answer for displaying the actual time on the x axis has already been given. Just look at the Real Time chart example. You just have to use your wait time the same as the example does.

Message Edited by Dennis Knutson on 03-27-2010 04:10 PM