Making a app that records data of the iphone's movment at 120Hz but locked at 100?

I am building a data logging app that logs the iphone's movement data at 120 hertz and 200 but for some reason its always capped at 100. does anyone know if there a hardware issue or is there a code problem that could be linked to this. made in Xcode.

Making a app that records data of the iphone's movment at 120Hz but locked at 100?
 
 
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