"voltage changes" refers to when the electrical force or pressure in a circuit varies or shifts. It means the amount of electrical energy flowing through a circuit is either increasing or decreasing. Full definition
Such tiny engines could be designed to gauge voltage changes in neurons and could deployed directly into the brain to perform the job. (kavlifoundation.org)
The fuel level sensor output voltage changes depending on the movement of the fuel mechanical float. (mechanics.stackexchange.com)
At the same time, she measured electrical signals in neighboring neurons using microelectrodes that can record small voltage changes across a neuron's membrane. (sciencedaily.com)