Campbell Scientific CS110 Electric Field Meter - Manual (Page 19)

CS110 Electric Field Meter
CS110 CS I/O cable (CS110CBL2-L). Examples of CS I/O peripherals include
the CR1000 Keyboard Display and the COM220 phone modem.
The CS110 also offers SDI-12 communication or SDM (Synchronous Device
for Measurement) control capability utilizing the CR1000 control ports
available through the CS110 POWER CABLE (CS110CBL3-L).
4.4 Site Recommendations
Many factors can distort and/or change the electric field at a given sight. For
example, vegetation growth can reduce the effective height of an elevated
instrument above the ground and can created unwanted space-charge due to
corona discharge. Gravel rings or concrete pads around a given site are
recommended to prevent changes in effective instrument height due to
vegetation growth. Electric field meters used for lightning warning at Kennedy
Space Center use a 25-foot radius gravel ring around each electric field meter
[LPLWS].
Animals and people within the vicinity of an electric field meter can
significantly alter the measurements. Fencing off a given site may be best for
some applications. However, installing a small metal fence around an electric
field meter site may result in corruption of measurements at large electric fields
because of corona discharge from sharp metal points on the fence.
Aerosols, dust, and automobile exhaust should be considered when selecting an
electric field meter site, as they can affect the local electric field.
In theory, the effects of tall nearby objects can be accounted for in site
correction. Yet, because of possible corona current along with general field
distortion, it is recommended that electric field meter sites should not be
located near tall objects. Kennedy Space Center site requirements stipulate
having no objects protruding higher than 18
° above the horizon, as seen from
the ground at the electric field meter location [LPLWS]. Roof mounted
electric field measurements are practical if a site correction can be done to
account for field distortions.
Also a good Earth ground connection to the CS110 and associated mounting
hardware is necessary to make a given site appear as a vertical extension of the
Earth ground. It is recommended that the integrity of this Earth Ground
connection be checked periodically by verifying that the resistance of the stator
to Earth Ground rod is <1
Ω.
Although the list of factors that can impair electric field measurements is long,
experience has shown that useful electric field measurements can be made by
paying careful attention to the above mentioned details.
5. Factory Calibration and Site Correction
5.1 Factory Calibration
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 in Figure 5 is used for factory calibration of
the CS110 Electric Field Meter. The large physical size was incorporated to
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