electrometer
noun
elec·trom·e·ter i-ˌlek-ˈträ-mə-tər 
: any of various instruments for detecting or measuring potential differences or ionizing radiations by means of the forces of attraction or repulsion between charged bodies
Example Sentences
Recent Examples on the Web Using an instrument called an electrometer, built by Pierre and his brother, Marie measured the mysterious rays emitted by thorium and uranium. 
Adam Hadhazy, Discover Magazine, 10 Oct. 2019
Adam Hadhazy, Discover Magazine, 10 Oct. 2019 Word History
First Known Use
1749, in the meaning defined above
Medical Definition
electrometer
noun
elec·trom·e·ter i-ˌlek-ˈträm-ət-ər
: any of various instruments for detecting or measuring electric-potential differences or ionizing radiations by means of the forces of attraction or repulsion between charged bodies