West Control Solutions MRC 9000 - Manual (Page 22)

Section 2 2-3 Edition 3
Rev G
2.2 PREPARATION FOR WIRING
This product is in conformity with the protection requirements of EU Council Directive 89/336EEC on the approxi-
mation of the laws of the Member States relating to electromagnetic compatibility. The factory cannot accept
responsibility for any failure to satisfy the protection requirements resulting from a non-recommended modification
of this product.
Electrical noise is a phenomenon typical of industrial environments. The following are guidelines that must be
followed to minimize the effect of noise upon any instrumentation.
Installation Considerations
Listed below are some of the common sources of electrical noise in the industrial environment:
• 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 used to isolate
the instrument.
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 practices have been followed.
AC Power Wiring
Earth Ground
The instrument includes noise suppressing components that require an earth ground connection to function. To
verify that a good earth ground is being attached, make a resistance 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 115 VAC)
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 performed. On the AC range, the reading should not be more than 50
millivolts. If it is greater than this amount, the secondary of the AC transformer supplying the instrument should
be checked by an electrician. A proper neutral will help ensure maximum performance from the instrument.
Wire Isolation/Segregation
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 bottom of the power supply board. The analog signal terminals are
located near the bottom of the instrument boards. Maintain this separation of the wires to insure the best protec-
tion 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 contact with
each other and reduce cross talk. Cross talk is due to the electro magnetic field induced by a wire as current
passes through it.