ɪn nˈaɪntiːnhˈʌndɹɪd sˈɛvənti sˈɛvən, ɹˈɑːbɚt fɹˈæŋklɪn dɪzˈaɪnd ɐn ᵻlɛktɹˈɑːnɪk stˈʌd fˈaɪndɚ ðæt ɹᵻlˈaɪd ˌɔn ɐn ɪntˈɜːnəl kəpˈæsɪɾɚ tə mˈɛʒɚ tʃˈeɪndʒᵻz ɪn dˈɛnsᵻɾi bᵻhˌaɪnd ðə wˈɔːlɪŋ.
In 1977, Robert Franklin designed an electronic stud finder that relied on an internal capacitor to measure changes in density behind the walling.