Calculating cutoff-frequency, bandwidth, impedance from given x/y-array

[OnlyOne]

Hello,

i have two arrays representing the measured frequency and voltage data.

Is there in labview something already included to calculate these values:

1. cutoff-frequency

2. bandwidth

3. impedance

Thanks for help

[NiAchilles]

I don't think Labview has anything that does that, you'll have to make your own code.  The bandwidth and cutoff frequencies shouldn't be too bad.  Just scan the array and remove any values that are 3dB (0.707) below the max, or whatever your cutoff is, and then you can use the statistic VI and get the first value, last value, and range. 

The impedance will be a whole different matter, not sure the best way to go about that. 

Hope that helps

[OnlyOne]

I have now two x/y-values for each frequency.

x: 100 / y: 0.702

x: ??? / y: 0.707

x: 120 / y: 0.712

How can i calculate the needed x-value for y=0.707 which is between these two values?

[Henrik_Volkers]

you need to do some interpolation 🙂

just hit Ctrl-Space to call Quick drop , enter interpol...   and you get a selection of possible ready made vis

Choose some of them, read the help  and use the one that fit your needs

Another way is the :

Threshold 1D Array Function

Owning Palette: Array Functions

Requires: Base Package

Interpolates points in a 1D array that represents a 2D non-descending graph. This function compares threshold y to the values in array of numbers or points starting at start index until it finds a pair of consecutive elements such that threshold y is greater than the value of the first element and less than or equal to the value of the second element.

If you cut an approriate portion of your data, this would work.

[OnlyOne · Accepted solution]

All of the vis only interpolate the y-value. But i neeeded the x-value for a given y.

Meanwhile i found the correct formula

X = ( (Y - Y1) * (X2 - X1) )  / (Y2 - Y1) ) + X1

[Henrik_Volkers]

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@OnlyOne wrote:

All of the vis only interpolate the y-value. But i neeeded the x-value for a given y.

Meanwhile i found the correct formula

X = ( (Y - Y1) * (X2 - X1) )  / (Y2 - Y1) ) + X1

---

Where is the problem to swap X and Y ???