Campbell Scientific CS110 Electric Field Meter - Manual (Page 28)

CS110 Electric Field Meter
August 2, 2005 Thunderstorm at Logan, Utah
-5000
-4000
-3000
-2000
-1000
0
1000
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3000
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5000
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7000
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9000
5:34:00 5:40:00 5:46:00 5:52:00 5:58:00 6:04:00 6:10:00 6:16:00 6:22:00 6:28:00 6:34:00 6:40:00 6:46:00
Mountain Standard Time (1 sample per second)
Electr
ic Field (volt/meter
)
FIGURE 12. Electric field measured with CS110 during local
thunderstorm
Figure 12 illustrates the atmospheric electric field monitored by a CS110
during a local thunderstorm. As illustrated in Figure 12, the atmospheric
electric field changes dramatically from fair weather conditions (
≈ -100 V/m)
during the course of this thunderstorm. The abrupt electric field change
observed at approximately 6:12 am was due to a hazardous cloud-to-ground
lightning discharge. A lightning hazard warning algorithm would ideally issue
an alarm, or perhaps various caution/alarm levels, during the critical front-end
portion of the storm illustrated in Figure 12, as the electric field is seen to
deviate from a typical fair weather field and approach levels capable of
producing hazardous lightning discharges. There is no universal hazard alarm
level based on atmospheric electric field, although two levels that have been
used are
≥ ⏐1000 V/m⏐ [LPLWS] and ≥ ⏐2000⏐ V/m [NAVSEA]. Obviously
the lower the level used the more risk reduction available, at the expense of
increased down time for operations suspended for lightning hazard warning.
Campbell Scientific, Inc. is not liable for the reliability and performance of
the warning algorithms implemented by users of our equipment. While
lightning warning systems can greatly reduce the probability of death or
injury from lightning discharges, they cannot reduce this probability to
zero.
As previously mentioned, both lightning detection and electric field
monitoring are used for lightning warning systems in high-risk
applications. Lightning detectors with serial digital outputs can be
interfaced to the CS110 resulting in both lightning detection and electric
field monitoring for a given site. The CS I/O port, along with the three
general purpose 0 to 5 V digital I/O ports (C1 - blue, C2 - yellow and C3 -
green) available on the CS110 Power cable (CS110CBL3-L) can be used
for a serial digital interface. Control ports C1, C2 and C3 can also be used
to conditionally control warning and alarm indicators.
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