I'm using M5 scales kit for a pet dispenser project.

When I print the weight on the screen of my M5 core basic; it is not stable.
I mean that the reported weight is displaying changing values over time.
I reset the scales kit (so it shows "0") and I don't touch or move it for several minutes and I can see the weight value is changing over time.

What did I miss ?
At the moment I didn't put a cover plate on top of the scales kit. Can it be the reason ?

Thank you for your help.

Best regards