Quadrant electrometer built by Pierre Curie, 1880s.

Pierre Curie (1859-1906) married Marie Curie (1867-1934) in 1895, when he was already an internationally recognised physicist. With his brother Jacques, in the 1880s, he discovered piezo-electricity (the fact that crystals under presure produce electric currents) which they used to build a new type of electrometer and measure small electrical charges. An electrometer is an instrument for measuring electrical potential without drawing any current from the circuit under test.