Count what is countable, measure what is measurable. What is not measurable, make measurable.Apparently, some geezer, name of Galileo Galilei, may have said this. Good on him.
Here are some things we measure (and count). You might call them process variables.
Mash temp (right after start). pH at 15 mins (if we remember)
First runnings from the mash tun - gravity (actually brix) and pH (cooled to around 40C) and subsequently as run-off proceeds.
Copper volume, gravity, pH.
FV volume and gravity
Progress of fermentation - temp and gravity
(yeast) Cell counts and gravity at racking
Post-conditioning gravity and pH
Plus we have to smell and taste stuff. Yep, there's a lot of beer that has to be tasted. Oh well.