Campbell CR300 Series Product Manual page 125

All critical inputs and outputs on the data logger are ESD protected. To be effective, the earth
ground lug must be properly connected to earth (chassis) ground.
Communications ports are another path for transients. You should provide communications
paths, such as telephone or short-haul modem lines, with spark-gap protection. Spark-gap
protection is usually an option with these products; so, request it when ordering. Spark gaps
must be connected to earth (chassis) ground.
For detailed information on grounding, see Grounds (p. 10).
16. CR300 series maintenance 112