how to measure the Low duration of the waveform ??

[ateproject2007]

I have a waveform (see the attached picture ), which has no fixed frequency. But  the Low duration in the waveform is fixed and keep the same all the time, the High duration is not fixed. My question is that how to measure the waveform to get the Low duration  automatically by Labview programming ? Thanks so help and if can give me a example vi to demo the way ? thank.

[K_Bull]

Hi,

Could you clarify your problem please. Are you after getting the low duration (Which you have mentioned that it is fixed)? Or are you after getting the number of times the low voltage (assuming it is voltage) appears? Or are you after getting the total time of the wave that it stays low? Does the measurement happen after the sample waveform is acquired or while the acquisition is in process?

Regards,

[ateproject2007]

Hi:

    i just want to know the duration time for one time Low voltage last. I can get the waveform sample use fixed sample numbers or continuesly acquision. thanks for help .

[K_Bull]

Hi,

Are you acquiring data from an analogue module? Is the waveform a double data type? To find the time it is low, you need delta T.

Regards,

[ateproject2007]

the waveform is analog input of voltage ,i get it by DAQmx DAQ acquire. Could you give a example vi ?Thanks.

[K_Bull]

Hi,

Did this need to be online processing or offline processing?

Regards,

[ateproject2007]

on line processing needed.thanks. 

[Dennis_Knutson]

Have you tried using the Pulse Measurements function on the Signal Processing>Waveform Measurements palette? Wire in your waveform and select 'low pulse' for the polarity input.

[wired]

I've never used it, but there is a Zero Crossing Pt-by-Pt Vi that you could use as well.  Since your data appears to be fixed-amplitude, you could offset it if it is unipolar, and then use the VI to find the plus-to-minus Zero crossing, then the minus-to-plus zero crossing.  Just count the # of samples acquired between the two.

I guess it all depends on your implementation and application.

[ateproject2007]

can i use Analog trigger---Falling edge to triger it to get measurement ?