Hi,

I have some troubles with the *darn* prepositions again...

"A static force of 2.5 N shall be applied at the center of the key during the measurement."

Is it correct to use at here?
It sounds better with "applied to" in my ears...but since I´m not a native English speaker I don´t trust my instincts...

'at' is fine in this example.

Incidentally, if you're in the US, use 'center'. If you're in the UK, use 'centre'.