My anxiety about my anxiety

I'm discouraged by the way we measure EDA as a single point response to a stimuli. So many factors can play into our current anxiety and to assume people are in "baseline" is very strange for me. What does it mean to be at baseline on a continuous spectrum. This would be like measuring our happiness but waiting for us to be "neutral", neither happy or sad. Is that possible? How does one detect that state?

I would like to measure the arousal of children who are taking an EDA test. Starting in the morning all the way to them taking the test and then afterwards. I'd expect to see the children get quite excited just by the novel environment and the requirements placed on them by scientists. This is especially true for children with SPD and Autism.