Good evening,
When I install ODK Central on my server, will the data collected from the field be transferred to my machine or to the ODK servers?
Thank you
Dear Tarek, your ODK central server will receive the data. Obviously the field workers’s ODKCollect app needs to be configured using QR codes generated on your server
Thank you dear Dr_Vivek_Gupta for your response. My question concerns data security.
Understandable. It's very simple, if you are hosting your own server, you need to ensure its security but you also have data on your own infrastructure.
Welcome to the ODK forum, @Tarektrabelsi! We're glad you're here. When you get a chance, please Introduce yourself here! I'd also encourage you to add a picture as your avatar because it helps build community 
Central never shares collected survey data. Also, by default, Central does not send any usage information to the ODK team. You can choose to share anonymized usage analytics with the team, and helps them make Central better for you! See Usage Reporting in Central for more details.
You may also be interested in reviewing the documentation page on ODK Security.