Bifilar electrometer

From Glossary of Meteorology

bifilar electrometer

An electrometer of the electrostatic type in which the potential to be measured is applied to two metal-coated quartz fibers, and the deflection due to their mutual repulsion is observed through a low-power microscope.

The bifilar electrometer is used for potential measurements in atmospheric electricity studies.
Compare unifilar electrometer.