NOTE:
No method of lightning warning completely eliminates the risks associated with lightning.
Lightning detectors give no warning until a detectable discharge has occurred. Atmospheric
electric field meters give warning prior to the first strike for storms developing overhead,
along with some indication of the end of a thunderstorm. However, there are occurrences of
cloud-to-ground lightning discharges striking the ground several miles from the electrified
cloud where the discharge originated [NOAA]. Electric field monitors may give no practical
warning in these instances because the electric field in the vicinity of the strike point may not
indicate hazardous levels until milliseconds before the strike. Consequently, while lightning
warning systems can greatly reduce the probability of death or injury from lightning
discharges, they cannot reduce this probability to zero.
7.5 Factory calibration of the CS110
Electric field meters are typically factory calibrated using a parallel plate method, where a uniform
electric field is developed by applying a known voltage between parallel conductive plates. The
large hexagonal parallel plate electric field calibrator illustrated below is used in the factory
calibration of the CS110 Electric Field Meter.
The large physical size was incorporated to minimize non-ideal fringing effects. Sharp corners
were avoided in order to prevent corona discharge. All metal parts of the calibrator are
manufactured from stainless steel. The inside surfaces are polished to reduce the surface charges
in order to provide a stable zero electric field. All outer surfaces are electronically connected and
tied to earth ground, while the insulated inner plate is driven by a high-voltage amplifier. The
high-voltage amplifier is calibrated annually against a reference that is traceable to the National
Institute of Standards and Technology (NIST).
CS110 Electric Field Meter 20
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