The quadrants, the mobile element and a part of the suspending string are protected and insulated by an extractable cylindrical metal case (diameter 9 cm, height 12.5 cm) the lid of which is attached to and supported by two rods on the sides. In the centre of the lid a small hollow column (height 8 cm) protects the upper part of the top of the string on which the needle is suspended.
The suspending screw, which also adjusts the height of the needle, terminates with a very small wire clamp for connections to the needle.
When not in use, the needle is brought to rest on the quadrants.
On the top of the case there is a wire clamp that also acts as the knob of a small metal rod that penetrates into the case and has at the bottom a very thin metal strip; on rotating the knob appropriately, this strip can be brought into contact with the metal rod of the mobile element to allow its earthing and, if necessary, to eliminate any residual charge.
With this kind of electrometer it is possible to reach very high levels of sensitivity, but it is slow, scantily dampened and rather unstable.