| 摘要 |
The apparatus which predicts the onset of thunderstorm and the occurrence of close thunderbolts, includes a composite sensor with several metal pipes radially installed with equal separation on a hemispherical electrode, a plurality of corona needles are provided on a insulator at the end of each metal pipes, and the needles are electrically connected together within the composite sensor. The hemispherical electrode is connected to a circuit that counts the number of electric field-changes for certain time intervals. In case the receiving frequency exceeds a pre-determined level, it issues the first alarm. The groups of corona needles are connected to the circuit that measures the corona current, and issues a second alarm, in case the current exceeds a pre-determined level. In addition, the circuit includes circuitry that picks up the large amplitude corona current changes that accompany the polarity change and issues the thunderbolt warning. The apparatus thus has the ability to issue three different types of alarms to indicate , first that thunderclouds are approaching from a distance, second that thunderclouds are coming closer or are developing overhead, and finally that thunderbolts are approaching very close.
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