Everyone should have and learn how to use a multimeter. Even the cheap ones work well. You can check the resistance of your atomizers, check pv
batteries, and even go through a drawer full of regular
batteries and throw the bad ones away, check outlets, etc. I have like 7 meters, cause I use them for my work, but I keep an inexpensive one in the house for simple stuff like checking
batteries. I couldn't live without it.