Find rise time, fall time of a waveform from a Picoscope

[govindsankar]

I have a wafeform from a picoscope and I need to decode it to measure the rise time, fall time etc. Unfortunately there are no such options available in the driver I downloaded for controlling the picoscope, I can only obtain the waveform. So I would like to use normal LabVIEW VIs to obtain the rise time, fall time of the obtained waverform from the picoscope. How can i do that. Thank you. 

[Tom_Powers]

If you know when the excitation turns off (e.g. the start of the fall time) and you know that it is an exponential decay and you believe that it is a constant decay time* you can just go to the diagram tools pallet and select.

Mathematics -> Fitting -> Exponential fit

You will need to create an X array for time as that is one of the required inputs. 

Alternately you can take the natural log of the data and do a linear fit.

I work with systems where I have to calculate the decay time of a cavity and the loaded Q can be a function of the stored energy so we do two fits.  One to the 100% to 95% of the starting value and one is from 100% to 20% of the starting value.  we overlay three plots on semi-log plot (vertical log, horizontal linear) plot when the data and the two fits line up we know we had a constant Q.

[AnalogKid2DigitalMan]

Check out the Transition Measurements.vi under Signal Processing/Wfm Measure palette.

EDIT: Added link:

https://zone.ni.com/reference/en-XX/help/371361R-01/lvwave/transition_measurements/

-AK2DM

[govindsankar]

What is the signal in the transition measurements VI. What should I connect to that? I have also attached the small VI which is a for loop with a random number generator to generate the waveform. Thank you. 

[billko]

If you don't start figuring things out for yourself, you'll never learn how to do stuff.  Read the help files I pointed you to in your other topic.  Experiment.

I'm sorry if this sounds brutal, but sometimes there's no way else to put it.

[govindsankar]

I did read the help files, but I couldnt understand. Thats why I posted my doubt here. The help says it accepts the input signal of a waveform. But I dont know what that means. I thought its the input signal to the waveform, thats why I tried the thing above. I always read the help or google. When both these doesnt work and I have no idea, that is when I post in the forum. 

[Kyle97330]

A waveform is a specific data and wire type in LabVIEW.  If you are looking to create a simulated one to use for testing, use these VIs:

https://zone.ni.com/reference/en-XX/help/371361R-01/lvwave/waveform_generation_vis/

[govindsankar]

I am not trying to use a simulated one. I have a waveform from an oscilloscope. I need to use that. The program above was just for learning. 

[GerdW]

Hi govindsankar,

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@govindsankar wrote:

I am not trying to use a simulated one. I have a waveform from an oscilloscope. I need to use that. The program above was just for learning. 

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So you should have learned by now the difference between a scalar DBL (from your random function) and a waveform (datatype) in LabVIEW. Did you?

Why did you try to replace a waveform by that random function?

Which kind of datatype does your "oscilloscope" provide? Which color has the wire coming out of the scope device driver VIs?

Did you take all those Training resources as offered at the top of the LabVIEW board? It seems you (still) need to learn the LabVIEW basics…

[govindsankar]

I have figured out waveform data type. So I wrote a program where I get the data from the oscilloscope. I am using that data which is an array of voltages and I know the time difference deltaT is 2,384*10^-6. So I have given these both values to build a waveform and the output of that, I have given to transition measurements to measure rise time and fall time. I have attached a mini program with the values obtained from picoscope. Is this correct. Is what I understood is correct. Thank you.