Basic XY Graph Questions

[Dominj]

I'm trying to do some basic stuff with XY graphs but I can't seem to get it to work. I have two graphs. One uses a freqency that I get from a Labjack DAQ on the Y axis, and the other is a graph of a user controled variable. Both should be graphed against time. I can get time on the X axis, but I don't know how to make it start at zero. I see the relative time properties, but it starts it at a random number. Also, do I just connect the output from the variable and the frequency out directly to the graphy Y in, or do I have to put it onto a shift register or something? I use Labview 7.0, btw. Thanks for any help!

[ElSmitho]

---

@Dominj wrote:
I'm trying to do some basic stuff with XY graphs but I can't seem to get it to work. I have two graphs. One uses a freqency that I get from a Labjack DAQ on the Y axis, and the other is a graph of a user controled variable. Both should be graphed against time. I can get time on the X axis, but I don't know how to make it start at zero. I see the relative time properties, but it starts it at a random number. Also, do I just connect the output from the variable and the frequency out directly to the graphy Y in, or do I have to put it onto a shift register or something? I use Labview 7.0, btw. Thanks for any help!

---

To determine if you need a shift register, it'd be best to see some code. If you're not using a shift register or building an array etc... you're probably losing any data involved in for or while loops.

You can always tell the graphs not to auto-scale, and hence keep it at zero. Another option could be using a property node (super simple attached VI, play with the numbers, you'll get the idea - turn on context help too, it'll show you how it's arranged).

Not too terribly informative I know, but I'd rather see the code if it's not too complexe and troublesome to work through.

Hope those give you a starting theory.

Sincerely,
ElSmitho

[Dominj]

Thanks for the reply. I can't open your example b/c I only have LV 7.0. I cut out the small portion of my VI that I have graph stuff in, so maybe you can get a better idea of what I'm doing wrong. I have a labjack driver in this VI, so it might not work, but here goes.

[ElSmitho]

Sorry about the mixup.

However, it seems like you might only be passing along one data point into your RPM plot. This could be due to a shift register or building array failure inside of your Ecount.vi. I do not have a copy of this subvi, so I can't get inside and check out the guts. But looking at the wire, it seems fishy. Make sure you check this over and ensure you're getting the abount of data desired out of it by probing.

You're also using a tick counter. That little clock really isn't time, it's tick count. So, make sure you look over the context help on it. That explains why you're plots are starting where they start and not at zero.

Sincerely,
ElSmitho

I've also taken a screenshot of how i controled the graph range with the context help on the property node there.