count revolution per minute with NI 9237 and strain gauges

Hello community,

i am a labview beginner and i need some help.

I work on a alternating bending machine which is bending a specimen. An AC motor produces the alternating bending. The AC motor in question has a revolution of 1380 per minute. My aim is to count the load cycle. For this i will use a NI 9237 Modul. I installed four strain gauges on the machine, wired them with a wheatstone full-bridge and connect this with the NI 9237. I want to count load cycle out of the determined continuous signal with the zero crossing function. I tried to do this but i always get a different and wrong value. I also tried to adjust the sample values as advised in other posts.

Thank you all in advace for your help.

Engin