Lightning detector

Details Lightning detector Lightning detector

2000-10-13

2003-07-01

Karlsen, Ernest (Department: 2829)

Electricity: measuring and testing

Testing potential in specific environment

C324S076190

Reexamination Certificate

active

06586920

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The Present invention relates to a lightning detector and, more specifically, to a lightning detector by utilizing the characteristics of a coherer equipped with a decoherer
2. Description of the Related Art
There have heretofore been put into practice or proposed a variety of lightning detectors which can roughly be classified into (1) those without using a coherer and (2) those using a coherer.
Some devices pertaining to (1) uses {circle around (1)} a lightning wire of, for example, a high-tension transmission line. In this case, however, the detector line (lightning wire) inevitably becomes lengthy for maintaining a precision for detecting the potential relative to ground, and the detector line itself is subject to be destroyed by a thunder-bolt.
There has further been proposed a method or a device {circle around (2)} which confirms the presence of a thundercloud based upon the data from a so-called meteorological radar (cloud radar) to estimate the degree of danger accompanied thereby. However, the device becomes expensive though the reliability is not so high. Concerning the method or the device {circle around (2)}, it has been attempted to render an overall judgement by taking into consideration the data obtained from artificial satellites and telemeter-measured values of precipitation without, however, satisfactory results.
Further, {circle around (3)} a device, SKYSCAN (™), taught in U.S. Pat. No. 5,541,501 has been placed in the market in the U.S.A. and in other countries. This is a lightning detector which displays the distance from the lightning position by comparing and analyzing the frequency and intensity of electromagnetic waves due to lightning.
As the manual of the product states “BE AWARE THAT STORMS CAN FORM DIRECTLY OVER YOUR LOCATION, OFFERING LITTLE OR NO ADVANCE WARNING EVEN WHEN USING A SKYSCAN”, however, this device is not capable of detecting lightning just overhead, and it Lust be said that its reliability is very low.
The method or the device (2) was developed based on the re-discovery that the coherer sharply reacts to a change in the intensity of the electromagnetic field inclusive of the static electric field, and there have been proposed many variations as taught in, for example, {circle around (4)} Japanese Unexamined Patent Publication (Kokai) No. 50154/1996, {circle around (4)} Japanese Unexamined Patent Publication (Kokai) No. 180911/1997 and {circle around (5)} U.S. Pat. No. 5,399,962. However, the device of the publication {circle around (4)} is often affected by alternating electric field noise from, for example, a high-tension transmission line, by the modulated carrier waves of broadcast or communication and, particularly, by PWM (pulse width modulated) intermittent wave noises, and, hence, malfunctions, accounting for a major cause of inhibiting the widespread use as the lightning detector with coherer.
The device of the publication {circle around (5)} is a highly sensitive coherer having a low self-operation voltage (threshold voltage), which is very effective in detecting a very weak spark discharge. This device, however, is rather cumbersome to use for the spontaneous aerial discharge of large electric power such as of thunder discharge (lightning). This device has not been proposed for detecting lightning and, besides, involves a problem in practice.
The device of the publication {circle around (6)} is a surge protector for a high-tension transmission line and uses a coherer. This device detects damped wave disturbances but is not designed for detecting lightning. The damped wave disturbances are caused by spark discharge due to a thunder-bolt or a short-circuit (abnormal discharge inclusive of arc discharge or corona discharge caused by salt damage). The device of the publication {circle around (6)} has been designed for detecting abnormal conditions on the high-tension lines.
That is, the coherer has wide frequency characteristics and exhibits a considerable degree of sensitivity even for artificial spark discharge noise. The frequency spectrum of artificial spark discharge noise exists chiefly in a high-frequency region of about 1 Mhz or higher. On the other hand, the electromagnetic waves of lightning discharge have low frequencies in the regions of from VLF to MF. According to the prior art, the frequencies could not be distinguished. Since high-frequency noises were easily picked up, the sensitivity to the electromagnetic waves of lightning became relatively low.
With the conventional techniques {circle around (1)} to {circle around (3)} and {circle around (4)} to {circle around (6)}, it is difficult to reliably detect the intensity of the electromagnetic waves of not smaller than a predetermined value caused by thunder-bolt.
There has not yet been known a lightning detector equipped with a lightning circuit for protecting itself and with a coherer, capable of detecting thunder that is approaching or is separating way.
SUMMARY OF THE INVENTION
The present inventors, therefore, have accomplished a lightning detector capable of more correctly detecting lightning by incorporating a lightning circuit having a low-pass filter (hereinafter often abbreviated as LPF or is often called “filter transformer”) and/or an aerial discharge gap between the antenna and the coherer, to offer the function of detecting thunder that is approaching or is separating away.
It is therefore an object of the present invention to provide a lightning detector which is capable of reliably predicting lightning free from the danger of being struck by lightning by using a relatively simply constructed coherer with a decoherer.
Another object of the present invention is to alert the degree of danger of lightning by using an indicator by detecting and storing lightning data and thunder data of a plurality of thunder-bolts at a distance, and by comparing at least two pairs of these data.
A further object of the present invention is to produce an indication/alarm by statically detecting the fact that the lightning detector is approaching the lightning range and/or by dynamically detecting whether the thunder-bolt is approaching/moving away.
The invention provides a lightning detector comprising an antenna, a coherer with a decoherer, a low-pass filter installed between the antenna and the coherer, an indicator and a power source, the lightning detector detecting the intensity of impulse electromagnetic waves of not smaller than a predetermined value produced by a thunder-bolt outside the lightning range, and producing an indication and/or an alarm on an indicator to tell that the detector is approaching the lightning range.
The invention provides a lightning detector as met forth above
1
, wherein the coherer comprises one filled with metal particles or metal particles coated with an oxide film between a pair of electrodes in an insulating tube that is sealed, and the decoherer comprises one that gives mechanical vibration to the coherer from the external side.
The invention provides a lightning detector as set forth above, wherein the coherer is equipped with a lightning circuit capable of adjusting the aerial discharge gap.
The invention provides a lightning detector as set forth above, wherein the lightning circuit is equipped with an exclusive coherer (coherer No.
2
) for the lightning circuit, separate from the coherer (coherer No.
1
) for the alarm.
The invention further provides a lightning detector as set forth above, wherein a plurality of thunderbolts stronger than a predetermined level are measured and recorded as electromagnetic wave intensity difference &Dgr;En and sound pressure difference &Dgr;Pn, the moments of inputs of these signals are stored in a storage medium in time series, a red lamp is turned on when a gradient of time difference &Dgr;Tn of &Dgr;En and &Dgr;Pn of when a pair of electric signal and sound signal are input, is (−) over a time of at least m pairs (m is a positive integer), a yellow lamp is turned on when the gradient of time difference &Dgr;Tn is close to (0) an

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