how to convert waveform on waveform chart to waveform on waveform graph

[Gurminder]

Plzzzzzzzzzzzzz reply sooon...

[smercurio_fc · Accepted solution]

Your other post indicates this is for a thesis, which I consider homework. What have you done? What do you understand? What do you get from a waveform chart? Do you have one plot, or 10 plots? If you have one plot, what do you get as the datatype for the chart's data? If you have more than one plot, what do you get? What is the datatype that a waveform graph accepts? Have you looked to see how that's defined?

As an example, let's say you have one plot on your chart. When you get the data you get ...  a 1D array of values. That kind of makes sense, right? Well, what's the waveform datatype? It's composed of a starting time, delta time between points, and an array of values. Hmmmm... So how about using the Build Waveform function? Just a thought...

[Gurminder]

Actually i aquired data from accelerometer on waveform chart of Lab VIEW, i.e voltage in time domian(apmlitude versus time). I have to find some parameters of my signal in frequency domain for my thesis work...problem is various frequency domain express VIs or functions can only wired to waveform graph . Some of the Frequency domain VIs get wired to waveform chart but getting blank plot there....i m totally confused......plz help as only few days left for my thesis submission.....thanks.

[Gurminder]

Main problem is i m unable to convert time domain signal in frquency domain, according to me the reason for this is the acquisition of signal on waveform chart......i think if it displays on waveform graph, i can get frequency domain signal.

[altenbach]

Charts and graphs are fundamentally different and there is no 1:1 relationship that allows easy conversion:

A chart is like a FIFO buffer, accepting one (or several) points at a time, appending it to the existing data. There is a finite size history buffer, and once it is filled, the oldest data is irreversibly lost as new data arrives. X is typically time.

A graph takes a finite collection of points and graphs them at once. If a new set of points arrives, the new data is shown and the old data is irreversibly lost. X can be anything you want (time, frequency, distance, etc.).

You can get all current data from a chart by reading the history buffer via a property node. Remember that very old data might have fallen off the far end of the buffer by the time you try to read it.

Charts and graphs are polymorphic and accept simple data (scalars for charts, arrays for graphs) or more complicated datatypes (waveforms, dynamic data, etc.). Charts and graphs assume that the x-values are linear and thus spaced equally, and can be fully described by a single pair of values: x0 (the x-value of the lefmost point) and dx (the x increment between points). For simple data, these value pairs descibe the linear relationship between the index of the array elements and the actual associated x-value and vice versa.

(If the x-values are not linear, you need an xy graph)

If you transform between simple time domain data and frequency domain data, you can calculate [f0, df] from [t0, dt] using well known relations that you can figure out using a google search.

Once you have a (semi-) working program, feel free to show it to us so we can give advice on improvements and verify that you are doing things right.

[altenbach]

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@Gurminder wrote:

Main problem is i m unable to convert time domain signal in frquency domain, according to me the reason for this is the acquisition of signal on waveform chart......i think if it displays on waveform graph, i can get frequency domain signal.

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BIngo! Except that you are confusing cause and effect. What matters is the underlying data, not how it is displayed.

[Gurminder]

Thanx a lot sir for ur valuable answer, but still i m in trouble, it may be because i m unable to implement ur solution in my VI, i.e i didn't get ur solution, . Sir, actually the thing is "I Want to Convert the time domain signal i got on "waveform chart" into frequency domain ." I used spectral measurement express VI  but instead of getting amplitude v/s frequency proper graph, i got a single vertical line from which i can't analyze the frequency components and without that i can't proceed further in my VI.  

[altenbach]

Well, there are at least a million possible scenarios with that outcome. How are we supposed to guess what you are doing wrong?

We can only help if you show us your code.

[Gurminder]

Thanks sir , ur solution in ur very 1st reply makes my problem solved. Build waveform function actually works for me toconvert/transfer the signal from waveform chart to waveform graph. Actually in first attempt i used this function outside the loop, thats why i didn't get the desired results, but yesterday when i kept them inside loop , i got the waveform on waveform graph.......

[Gurminder]

I want to find out the power in the peak frquency of my acquired acceleration signal(which i already converted into

frquency domain), also i want to find out approximate entropy of time series signal.  plzzzzzz help me, as i m not getting any reply for it from few days....