Thunderstorm Electric Field Mill EFM550 Advance warning of overhead lightning threat Vaisala Thunderstorm Electric Field Mill EFM550 integrates with Vaisala local area, real-time lightning systems to monitor the development and dissipation of overhead lightning threats by measuring the local atmospheric electric field. It also identifies when the threat has passed, providing valuable information to operations especially vulnerable to lightning.EFM550 data can be displayed using optional Vaisala ALARM Automated Lightning Alert Risk Management Software to show current electric field measurements numerically and graphically.Advance warning of overhead lightning threatExceptional reliability and low maintenanceFlexible siting and easy installation Resources Datasheet Thunderstorm Electric Field Mill EFM550 Vaisala Thunderstorm Electric Field Mill EFM550 integrates with Vaisala local-area, real-time lightning systems to monitor the development and dissipation of overhead lightning threats by measuring the local atmospheric electric field. Download PDF