The IOD1 ion detector consists of a small control box with a telescoping probe. The probe can be grounded or the hand that is holding it can be used as ground through a metal strip on the outside of the control box. The probe is capable of making relative measurements only, not absolute.
I haven't had a whole lot of use for it over the years. The one documented place I did use it was for simply detecting charge on an aluminium cone in a non-conventional propulsion experiment called the Hamel 45GD experiment as shown in these photos.