B. Principle design
A possible error in measurements of the DC electric field are
spurious effects caused by charges deposited on the surface. A
solution to this issue is to rotate the sensor during the
measurement [6, 7].
The probe has two electrodes mounted as halves on the
surface. When the probe rotates in an electric DC-field a
current is driven between these electrodes. The integral of this
current is proportional to the electric field. The current is
measured by a battery powered electrometer inside the probe
and the signal is sent to recording instruments via an optical
fiber. The probe is held in position, between two masts, by this
optical fiber at one end and a Kevlar thread at the other end.