Campbell Scientific CR1000KD CR800 and CR850 Measurement and Control Systems - Page 87

Section 7. Installation products, so it should always be requested when ordering. Spark gaps for these devices must be connected to either the earth ground lug, the enclosure ground, or to the earth (chassis) ground. 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 (chassis) grounded. All components of the system (dataloggers, sensors, external power supplies, mounts, housings, etc.) should be referenced to one common earth (chassis) ground. In the field, at a minimum, a proper earth ground will consist of a 6- to 8-foot copper-sheathed grounding rod driven into the earth and connected to the CR800 Ground Lug with a 12-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 vehicle applications, the earth ground lug should be firmly attached to the vehicle chassis with 12-AWG wire or larger. In laboratory applications, locating a stable earth ground is challenging, but still necessary. In older buildings, new ac receptacles on older ac 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 the verification that it carries no current. If the integrity of the ac power ground is in doubt, also ground the system through the building plumbing, or use another verified connection to earth ground. 87