Kelvin quadrant electrometer
1890
1890
1912
1886
1902
1960-1979
1867
1924
1891
1900
1895
1895
1890
1900
1876
1801-1825
1902
1891
1913
1946
1924
1886
1929
1945-1954
1857
1960
1876
1861
1875
1867
1901
1867-1896
1880-1890
1900-1926
1857
1888
1855
1901
1870-1889