Search point in waveform

[leocavadas]

I have 2 signals (square and sine) in same time range, I need get a trigger point in sine wave (i did it with Basic Trigger Level VI) and I need now search the last falling point in square wave before of sinewave trigger point.

Logic Steps:

1- Search trigger point index in sine wave;(i did it)

2- Go back in index until find the first (or last if look since start index - index 0)fall edge in square wave. How i do it?

Figure in attach

[smercurio_fc]

I would suggest using the Transition Measurements VI (Signal Processing -> Wfm Measure) to get your fall times. Then it's a simple matter of finding which array element is the first that's less than your trigger point.

[leocavadas]

How I get all fall times? the Transition Measurements return only to 1 cycle (1rs, 2rs, 3rs...), dont return index, dont return fall times array....I dont understand.

Thx for help.

[smercurio_fc · Accepted solution]

Just use a loop. When the start time and end times are the same (i.e., zero) you've reached the end.

 

Message Edited by smercurio_fc on 09-09-2008 01:27 PM

[leocavadas]

Your Help is great, but i have a problem yet...my START and END TIMES in measurement info always show me 3,3E9....don't interest if i put first, second or other EDGE number or other sample wave...always give me result like START TIME = 3,3E9 and END TIME = 3,3E9. What did I wrong?

I have a square wave with aproximated -18 and 5 (low and high lvl) and 48 transitions in 3 seconds sample.

The example Pulse and Transtitions Measurements.VI work fine, i ran it.

Thx for help again...

[smercurio_fc]

There is a wiring error in the example I posted. The "reference levels" cluster is wired to the wrong input terminal on the VI. It just so happens, though that in this case it doesn't affect the results. I tried it using a square wave between -18 and 5 with about 46 pulses in 3 seconds and it seemed to work just fine. Can you upload your data?

[leocavadas]

Data in attached....thx

[smercurio_fc]

Unfortunately, you did not save the waveform control with the actual data. Rerun the parent VI so the control is populated. Note: make sure this subVI's front panel is open. Then right-click on the waveform control and select Data Operations -> Make Current Value Default. Then save the VI and upload it again.

Message Edited by smercurio_fc on 09-10-2008 03:06 PM

[leocavadas]

I'm sorry....Data saved in attach

[smercurio_fc]

Hmmm... That's quite peculiar. Off-hand I don't see anything particularly odd about your waveform, so I don't see why that function would not work. I'll need to look at this in more detail...