i want to use a multivitamin shield on my face and want to use a spf mostirizer so which do i put on first?

this is the shield it looks likes it would be good for the skin since it has alot of vitamins

The chirp is a low battery warning. If new batteries did not keep them from chirping, replace the units. I like the photo electric ones better than the ion ones.

You need to know the effect of the springs and shock absorbers to calculate.