EFM-100C RS485 Electric Field Monitor

A short-range lightning detector helpful in monitoring nearby thunderstorms. The EFM-100 also detects the high electric-field conditions which precede the first lightning strike. The EFM-100 is a great companion to the LD-250 providing the best of both long range and local lightning detection. For close lightning strikes the EFM-100’s accuracy is unsurpassed.

SKU: EFM-100 Categories: , Brand:



Measuring the static electric field generated by thunderclouds the Boltek EFM-100 not only detects nearby lightning but can detect the atmospheric conditions which precede lightning. Electric field data is displayed and graphed on your desktop computer using the included software.

For complete electrical isolation from the field mill outside, the EFM-100 connects to your computer using a fiber optic cable. The EFM-100 features aluminum and stainless steel construction for corrosion resistance, gold plated connectors throughout, and the highest quality ball-bearing brushless dc motor for excellent reliability.

The electric charge contained in a thundercloud also generates an electric field. This field can be measured on the ground.

Electric fields develop wherever there is a difference in electric potential. If the electric field gets high enough you can feel your hair stand on end (if this happens outdoors during a thunderstorm crouch down with your feet together as you are about to be struck by lightning.) An electric field is what attracts your hair to a charged comb or a charged balloon.

Electric field is measured in Volts per meter (3.3 feet) The electric fields which accompany thunderstorms normally measure in the thousands of Volts per meter, usually abbreviated to kV/m.

Lightning is detected as a sudden change in the static electric field.


• High accuracy lightning detection (0 to 24 miles / 0 to 38km)
• Monitors and alerts for weather conditions that precede lightning
• Standard RS485 data output with optional fiber optic package
• Electrical isolation from the field mill to PC or Laptop
• Customizable alarm distances and electric field levels
• SMS text messaging and E-mail alarm notifications
• Monitor up to four separate locations per computer
• Aluminum and stainless steel parts throughout for corrosion resistance
• Free software updates
• One year parts & labor manufacturers warranty

Parts Included

EFM-100 Electric Field Mill
100 feet (30m) of Power/Data Cat5 Cable
120V/220V AC Power Supply
EFA-21 Power / RS485 to USB Module
USB Cable
DIN rail clip for EFA-21 Module
6 Attenuator Plugs
1 mast (10” x 3/4” NPT)*
1 mounting flange (4” diameter)
Windows Software & Manual

Optional fiber optic package includes fiber optic cable, EFA-20 with USB cable, and EFA-10 with DB9 serial cable

*Custom mounting masts available


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