CEMP-E
TI 811-12
18 August 1998
underground well casings and building structural steel members in accordance with the National Fire
Protection Association No. 70 are other acceptable means of grounding. To meet grounding resistance
requirements, it may be necessary to combine several grounding techniques. Instrumentation systems
typically require a single point signal ground in addition to a power ground. The signal ground will be
connected to the power ground only at the building entrance. Signal grounding conductors which run
parallel to primary power or lightning conductors must be avoided. Floating signal grounding systems are
not acceptable because of lack of operating stability and shock hazard. All enclosures will be tied to an
equipment ground, which will be separate from communications and instrumentation grounds. Grounding
will be in accordance with IEEE Standard 142 and IEEE Standard 1100. Additional grounding and power
requirements exist for use in computer equipment areas such as the central station or island station.
These additional requirements, defined in FIPS-94, "Guidelines for Electrical Power for ADP Installations",
will be incorporated in the central station and island station design in addition to other stated
requirements.
16. SHIELDING. Electronic circuits sensitive to EMI will be protected by electrical shielding. Shielding
is used in telephone lines, twisted pairs, and other circuits to reduce the strength of interfering electric or
magnetic fields. Shielding will be grounded only at one end to preclude ground loops.
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