Micromod MOD: Modcell 2050R Users Guide - Manual (Page 17)

IB-23C650
INSTALLATION
GROUND CONNECTIONS
The primary power ground system consists of the plant electrical ground
(equipment grounding conductors). AC ground and chassis ground are
connected when the termination housing is connected to the control module.
If this path is insufficient to dampen out noise spikes on the ac line, the
chassis ground may be connected directly to panel ground. The circuit
common for all signals is negative.
Electrical Noise
Electrical disturbances can be caused by lightning, motors and motor driven
devices, relays, solenoids, and communication equipment. These
disturbances often introduce electrical noise in power lines, transmission lines,
and site grounds. The successful operation of any microprocessor-based
device depends, in part, on the precautions taken to minimize the effect of
these disturbances. Often called "transients" or "voltage spikes", this form of
noise is infinitely variable in terms of amplitude, frequency, and duration.
Common sources of this type of noise are:
• loose or poor quality connections (especially power connections)
• arc welding equipment
• switches operating inductive loads
• relays, solenoids and other coil operated devices
• high current conductors – electric heater circuits
• fluorescent or neon lamps
• motors and motor driven devices
• switch mode devices – SCRs, thyristors
• lightning
• electrostatic discharges
Suggested Preventative Measures
Primary power circuit distribution system:
•
Ideally, each microprocessor-based device should be provided with an
independent dedicated power source. Where this approach is not feasible
due to space availability or cost per device, an acceptable alternative is to
install constant voltage, isolation transformers in the branch circuit where
the microprocessor-based device is installed.
• In addition to the above, install a combination transient surge suppressor
and noise filter in the instrument side of the power distribution system.
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