Boltek EFM-100 v.2 - Manual (Page 40)

C H A P T E R 4 - O P E R A T I O N
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Figure 32: Step Changes in Field Magnitude Indicate Lightning
Step changes in the magnitude of the electric field indicate lightning. Closer lightning produces larger
field changes than distant lightning. The EFM-100 can detect lightning out to about 24 miles.
Figure 33: Precipitation Noise
Rain, snow, and dust can carry an electric charge. If charged particles contact the field mill sense
plates the electric charge will transfer from the particle to the sense plate and will be detected as noise
on the field mill reading. During periods of heavy rain the precipitation noise can get quite severe.
Once the storm passes the noise will disappear. Precipitation noise can reduce the ability of the
software to detect distant lightning but nearby lightning can still be detected.