Immagini

DESCRIPTION

Exhibit 205 is a very sensitive Hoffmann electrometer composed of two similar halves in a "D" form internal to which a suspension wire supports a small wing with a single platinum vane which is free to rotate. It is surrounded by a heavy copper heat shield which contains the bobbins and operates in partial vacuum effected through a stopcock on the underside. The instrument rests on three columns formed of two metals with thermal dilation coefficients so as to avoid stressing the suspension wire. Near the wing there is small mirror which deflects a light beam by the angle of torsion which deflection is visible through the telescope. The top of the instrument is a ceramic cap which can be removed for adjusting the screw which hold the suspension wire. When a difference of potential is applied to the two halves, the electrostatic force causes a torsion of the suspension wire and a reorientation of the reflecting mirror. Figure 5 is a reproduction of a drawing from reference 1. The threshold sensitivity of the Hoffmann electrometer is about 10 millivolt. .

ISCRIZIONI

1. No. 932 E.Leybold's Nachfolger A.G. Koln

BIBLIOGRAPHY

• [1] URL [ http://vacuum.ramapo.edu/physics/physics-doc/amsci/AmSci01/tbLib/Electrometers.html ]

Dati Catalografici