BTD-300 Thunderstorm Detector

The BTD-300

The Biral Thunderstorm Detector BTD-300 is a standalone sensor providing real-time detection and ranging of thunderstorm activity within 45 nautical miles (83km). The sensor bases thunderstorm warnings on the detection and range of lightning flashes throughout the detection area, as well as the presence of strong electric fields and electrically charged precipitation occurring at the installation site. The strong electric fields and charged precipitation provide the ability to warn of the potential for nearby lightning activity before the occurrence of the first flash, with the subsequent flashes used for thunderstorm intensity and proximity monitoring.

Lightning flashes of all types (cloud-to-ground, cloud-to-cloud and intra-cloud) and polarities are detected, ranged and logged within 2 seconds of their initiation. Electric field disturbances associated with potential overhead thunderstorm development produce an alert after 5 seconds of monitoring. Such sensitivity and rapid alerts allow the greatest warning time of local thunderstorm development for the user, with the unique monitoring techniques providing an extremely low false alarm rate.

The operating principle of the BTD-300 is based upon sensing changes in the atmospheric electric field in the frequency band of 1-47 Hz. Such low frequency means that the sensor is most sensitive to slow-varying electrostatic fields associated with charge transfer from lightning flashes, nearby corona (point) discharge and the turbulent movement of strongly-charged aerosol associated with thunderstorm activity. In addition, charge transferred to the antennas by precipitation is analysed and used to determine whether the overhead cloud has the potential for thunderstorm activity. Radio emissions (both natural and man-made) are associated with considerably higher frequencies so do not produce interference on the sensor. Noise associated with mains power distribution (typically 50 or 60 Hz and harmonics) are removed by both analogue and digital filtering.

The range information supplied by the basic sensor can be supplemented with a bearing or direction if the optional Direction Finder module is used. The direction Finder module detects electromagnetic waves produced by lightning discharges in a band from approximately 3kHZ to 1MHz. The direction from sensor to discharge is reported to the nearest degree in the BTD-300 data output.

The BTD-300 can be configured for either Ethernet or RS422 serial communication. The data is output as an ASCII coded data string for easy integration with other data processing systems. For standalone use a comprehensive PC compatible software application is supplied which provides data visualisation, sensor control and data logging.

A relay output module is available to allow the direct switching of warning devices such as sounders and beacons. Three relays are provided to cover the warning and alert status of the sensor.