West Control Solutions MRC 8000 - Manual (Page 10)

10
Preparations for Wiring 2.5
2.5.1 WIRING GUIDELINES
Electrical noise is a phenomenon typical of industrial environments. The following are guide-
lines that must be followed to minimize the effect of noise upon any instrumentation.
2.5.1.1 INSTALLATION CONSIDERATIONS
Listed below are some of the common sources of electrical noise in the industrial environ-
ment:
• Ignition Transformers
• Arc Welders
• Mechanical contact relay(s)
• Solenoids
Before using any instrument near the devices listed, the instructions below should be
followed:
1. If the instrument is to be mounted in the same panel as any of the listed devices,
separate them by the largest distance possible. For maximum electrical noise
reduction, the noise generating devices should be mounted in a separate
enclosure.
2. If possible, eliminate mechanical contact relay(s) and replace with solid state
relays. If a mechanical relay being powered by an instrument output device
cannot be replaced, a solid state relay can be interposed to isolate the instrument.
(Continued on next page)
3. A separate isolation transformer to feed only instrumentation should be
considered. The transformer can isolate the instrument from noise found on the
AC power input.
4. If the instrument is being installed on existing equipment, the wiring in the area
should be checked to insure that good wiring practices have been followed.
2.5.1.2 AC POWER WIRING
Earth Ground
The instrument includes noise suppression components that require an earth ground
connection to function. To verify that a good earth ground is being attached, make a resis-
tance check from the instrument chassis to the nearest metal water pipe or proven earth
ground. This reading should not exceed 100 ohms. Each instrument should have a dedicated
earth ground. Do not chain link multiple instrument ground wires.
Neutral (For 115VAC)
It is good practice to assure that the AC neutral is at or near ground potential. To verify this, a
voltmeter check between neutral and ground should be done. On the AC range, the reading
should not be more than 50 millivolts. If it is greater than this amount, the secondary of this
AC transformer supplying the instrument should be checked by an electrician. A proper
neutral will help ensure maximum performance from the instrument.
2.5.1.3 WIRE ISOLATION/SEGRATION
The instrument is designed to promote proper separation of the wiring groups that connect to
the instrument. The AC power wire terminals are located near the top of the instrument
boards. The analog signal terminals are located near the bottom of the instrument boards.
Maintain this separation of the wires to insure the best protection from electrical noise. If the
wires need to be run parallel with any other wiring type(s), maintain a minimum 6 inch space
between the wires. If wires must cross each other, do so at 90 degrees to minimize the