Micromod MOD: Modcell 2050R Users Guide - Manual (Page 18)

IB-23C650
INSTALLATION
The combination device suppresses transients and effectively reduces
other noise forms such as electromagnetic (EMI) and radio frequency
(RFI) interferences. These devices can be connected to multiple units to
reduce overall cost.
Input signals
• Twisted wire pairs are essential. The wire type should be stranded, not
solid. The largest wire gauge allowed is best and the more twists per foot
the better. A 2-inch lay (6 twists per foot) should be the minimum used.
• In addition to the above, signal wires should be physically isolated from all
power conductors (separate conduit, cable race, etc.)
• Shielded wire is also essential. Shields should be terminated at the
instrument or in the field in accordance with local regulations.
CAUTION: 1. Never terminate a shield at both ends. One end should
always be left "floating" or ground currents may be
introduced.
2. Thermocouple shields should be terminated at the
process measurement end. Most thermocouples are
constructed where the sensor is electrically equivalent to
the process connection (grounded junction).
Equipment grounding:
• Grounding practices defined by the National Fire Protection Agency
(NFPA) in their National Electrical Code (NEC) handbook or State agency
amendments to this code should be strictly observed.
• Existing ground conductors and ground paths should be periodically
inspected and tested to insure continuity and compliance with current
code requirements.
• For best noise reduction performance, the microprocessor-based device's
ground terminal should be connected to a nearby grounded large metal
structure, using the shortest length wire possible. If a three-wire cordset is
used to power the microprocessor-based device through a receptacle, the
ground wire is generally too long and too noisy to be a good ground.
REMOTE SET-POINT CONNECTIONS
When a remote set-point is required, connections are made to the Input 2
terminals, Figure 2. This is an isolated universal input which accepts the same
signals as the process input. Make remote set point connections to the
terminals identified as I/O2 in Figures 3 through 10.
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