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Roundness calculations

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Me again 🙂


I tried to implement MZC calculations

MZC is Minimum Zone Circle, two concentric circles that just enclose the profile on both outside and inside.


Now I have 4 elements in array X: circles centre X, circles centre Y, radius outer circle, radius inner circle. Because of this 4 elements Xminimum and X maximum in cluster Bounds also need 4 elements.


In this case I have two constraints, so I put them in the array “Inequality constraint…”

It’s strange that I don’t need to add an element in the array “Inequality constraint min” and “Inequality constraint max” in the “Bounds” cluster, just like the “X” case above. Even strange is the fact that I get different results depending in the number of elements in those “Inequality” arrays?


What is the “Objective function value” for and what should I wire there?

Now I used the difference between outer radius and inner radius since this is the MZC, but is this correct?

Why do you square and sum this array?


I’m sure this is close but not correct since when I run it on some profiles I have, those MZC circles are close to the profile but never touch it.


So can you please advice a little more?

Thanks a lot



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Message 21 of 24

MZC is also working fine now Smiley Very Happy

Updated version attached 


Thanks DSPGuy (aka Jim, yes I read a lot this week-end Smiley Tongue ) you learned me a lot!




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Message 22 of 24

Hi, I'm also trying to write this roundness program, and this thread has been extremely helpful. 


A question I have is...why did you use the X&Y graph instead of a polar plot? and how would you write this using a polar plot? I'm having a difficult time implementing a polar plot


Thanks for your help

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Message 23 of 24



Is there a specific reason why it needs to be a polar graph?


Can you post the code you already have?

Kind Regards,
Thierry C - CLA, CTA - Staff R&D Engineer, RF Semiconductor Test - National Instruments
If someone helped you, let them know. Mark as solved and/or give a kudo. 😉
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Message 24 of 24