Campbell CR1000X, Руководство по эксплуатации продукта

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measurement errors.
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4 common terminals
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Resistive Ground (RG) - used for non-isolated 0-20 mA and 4-20 mA current loop
measurements (see
Current-loop measurements (p. 61) for more information). Also used for
decoupling ground on RS-485 signals. Includes 100 Ω resistance to ground.
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Maximum voltage for RG terminals is ±16 V.
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2 common terminals
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Earth Ground Lug ( ) - connection point for heavy-ga
u
ge earth-ground wire. A good earth
connection is necessary to secure the ground potential of the datalogger and shunt
transients away from electronics. Campbell Scientific recommends 14 AWG wire, minimum.
NOTE:
Several ground wires can be connected to the same ground terminal.
A good earth (chassis) ground will minimize damage to the datalogger and sensors by providing
a low-resistance path around the system to a point of low potential. Campbell Scientific
recommends that all dataloggers be earth grounded. All components of the system (dataloggers,
sensors, external power supplies, mounts, housings) should be referenced to one common earth
ground.
In the field, at a minimum, a proper earth ground will consist of a 5-foot copper-sheathed
grounding rod driven into the earth and connected to the large brass ground lug on the wiring
panel with a 14 AWG wire. In low-conductive substrates, such as sand, very dry soil, ice, or rock, a
single ground rod will probably not provide an adequate earth ground. For these situations,
search for published literature on lightning protection or contact a qualified lightning-protection
consultant.
In laboratory applications, locating a stable earth ground is challenging, but still necessary. In
older buildings, new Vac receptacles on older Vac wiring may indicate that a safety ground exists
when, in fact, the socket is not grounded. If a safety ground does exist, good practice dictates to
verify that it carries no current. If the integrity of the Vac power ground is in doubt, also ground
the system through the building plumbing, or use another verified connection to earth ground.
See also:
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Minimizing ground loop errors (p. 121)
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Minimizing ground potential differences (p. 49)
2. Wiring panel and terminal functions 11