How to measure the second cut off point

[LimKH]

Hi, I new in labview therefore post such question(pls view my VI for more clarification). I managed to measure the first -3dB cut off freq from a array of data. The problem is how can i edit so that i can measure the 2nd -3db cut off point? I need it because i need to measure the 3dB bandwidth of filter response. Thanks

[Dave_Kaufman]

If your data will always look similar to this (notch filter), try this:

1) After converting to dB, find the index of the min value of the array using the min/max function.
2) Split the array at that index using the split array function.
3) For each of these two arrays, do what you already did: find the max value, threshold and interpolate.

Dave.

[LimKH]

thanks dave