Electric Field Mill
An Electric Field Mill is an electro-mechanical device which measures the strength of a static electric field.  One or more electrodes are alternately exposed to and then shielded from the field to be measured.  The electric current which flows to and from the electrodes is proportional to the strength of the electric field. Typical Electric Field Mill

Most modern electric field mills use a rotating slotted disk to alternately expose and shield the electrodes.  This generally results in a beam like coverage above the electrodes. A less used design employs electrodes mounted on opposite sides of a rotating shaft.  This arrangement provides an arc-like (circular) coverage which is perpendicular to the length of the shaft.

Some Electric Field Mill links -

  • Section 6.4 has a "text book" style description of Electric Field Mills:

Chapter 6, Instrumentation and Measurements  (pdf)

  • Section 3.2.2 of Introduction to Electrostatics describes measurement of electric fields with Field Mills:

Workshop in Electrostatics   (pdf)

  • Section 47.1 of the Measurement, Instrumentation, and Sensors Handbook deals with Field Mills:

Chapter 47, Electric Field Strength  (pdf)

  • Principle of Operation for an Electric Field Mill used in atmospheric research at New Mexico Tech:

Electric Field Meter -- E100

  • Description of a Field Mill used at University of Alabama, Huntsville:

CAMEX-4 MIPS Field Mill  (description)
Electric Field Mill Fabrication  (construction)

  • Description of a homemade Electric Field Mill construction project:

My Fieldmill Voltmeter Project  - construction & calibration
Measuring Hi Voltages  - theory

  • Scientific American "Amateur Scientist" Electric Field Mill construction article:

Detecting the Earth's Electricity

  • One page article describing field mills used to measure atmospheric electric fields at Kennedy Space Center:

Electric Field Mills

  • Some commercial Electric Field Mills:

Ambient Weather -  BOLTEK EFM-100 Electric Field Monitor
Campbell Scientific, Inc. -   CS110 Electric Field Meter
John Chubb Instrumentation -  JCI 131 Electrostatic Fieldmeter  (pdf)
Mission Instruments -  EFS 1001 Electric Field Mill
20060306, Lynn Ashley

Email:  la  at    a-tech.net