Manual

Installation-Wiring
Installation - Wiring, Chapter 3
WATLOW Series 1500 User's Manual 29
Input Power Wiring
Microprocessors are in a way like trout…
They require a clean environment to be successful and to prosper. A clean environ-
ment means on one level an environment that is free of excessive dust, moisture and
other airborne pollutants. But primarily it means a "clean" source of input power from
which to base all its operations. What is "clean power?"
Clean power is simply a steady, noise-free line voltage source that meets the rating
specifications of the hardware using it. Without clean power to the integrated cir-
cuitry, any microprocessor chip is doomed to failure.
Just as the water you get from a tap nowadays may not be acceptable to drink in
some locales, so the line voltage coming into your facility may not be acceptable for
your microprocessor devices. You may have to filter or "clean" the water or the
power. In industrial environments, the potential for pollutants increases, especially
electrical noise due to high level power consumption occurring in one place.
The recommendations we are providing for you are ways to achieve a minimum level
of clean input power protection. In almost all cases these guidelines will remove the
potential for input power problems. If you've applied these measures and still do not
get results, please feel free to call us at the factory. We are here to see that our
control products work well and do the job they were designed to do.
Definitions
Ground Loop - A condition created when two or more paths for electricity are
created in a ground line, or when one or more paths are created in a shield.
Earth Ground - The starting point for safety and computer grounds. It is usually a
copper rod driven into the earth.
Safety Ground - A ground line run along with electrical power wiring to protect
personnel.
Computer Ground - A ground line for the ground connections to computers or
microprocessor-based systems. This line is isolated from safety ground.
Common Mode Line Filter - A device to filter noise signals present on both power
lines with respect to ground.
Differential Mode Line Filter - A device to filter noise signals present between the
two power lines themselves.
The Dos and Don'ts of Clean Input Power
Do keep line filters as close to the control as possible to minimize the area for
interference pick up.
Do use twisted pair wire and possibly shielded wire from line filters to the control