The Lutz-Edelmann electrometer is a wire electrometer with an auxiliary field, built for the first time in 1905 by C. W. Lutz and Max Edelmann, who later modified and improved it several times.
The exemplar built by Vasco Ronchi is a faithful reproduction of the version presented by Lutz in 1923, which was built in the precision instrument company styled "Max Edelmann & Son - Münich", which was run by the son following the death of the father in 1913.
The instrument has an overall height of 19.5 cm; the base is round, diameter 15.5 cm, and is made of an aluminium alloy.
The cylindrical case (diameter 9.5 cm, height 12.5 cm) that protects and isolates the blades and the wire is extractable; the lid is fixed and held in place by four steel rods.
The blades (a pair of steel electrodes with a triangular cross section, arranged vertically and well insulated, with two edges, lengthened by a slight curvature of the lateral faces, side by side) are attached to the centre of insulating quartz disks placed at the top of two steel rods; these are assembled on a slide equipped with return springs and micrometric screws which make it possible to regulate the distance of the blades from the wire. Two small screws on the supporting rods allow regulation of the orientation of the two blades so that they are perfectly parallel to each other and to the wire.
The device for suspending the platinum wire is placed at the centre of the lip and attached to a round, insulating quartz window; the elastic quartz ring that holds the wire taut at the bottom is attached to the end of a rod in the shape of an "L" which, in turn, is fixed to the lid by means of a micrometric screw with which it is possible to regulate the elastic tension of the suspending wire.
The instrument is provided with four spare wires and the special tool for replacing them (Edelmann pliers).
Drigo-Alocco (1945), p. 855
C.W. Lutz, Physik. Zeitschr. 24 (1923), p. 166, p. 460