CM4 Four-Point Continuous Monitor
CM4 Technical Manual
iii
EMC Considerations
Overview
Your Honeywell Analytics instrument has been designed to comply
with applicable Electromagnetic Compatibility (EMC) standards at
the time of manufacture. The design includes filtering, shielding and
bypassing techniques. At the time of certification, simulated customer
Input/Output (I/O) schemes were tested.
All methods used in your equipment for emission supression and
reduction of susceptibility are interactive. Modifications to the
instrument will most likely result in increased emissions and higher
vulnerability to other radiated fields.
Following the guidelines in this EMC Considerations section will ensure
your instrument maintains the highest degree of EMC integrity. The
guidelines listed apply only to I/O emissions and do not apply to A.C.
and D.C. instrument power connections.
Cabling
At a very minimum, all cables should include a braided shield. Ideal
results have been obtained with twisted pair cabling which has a foil
shield surrounding each pair plus foil and 90% braid shielding around
the bundle. While this yields the best results, it can be very expensive.
In addition, ensure local electrical code requirements are met.
Cabling Type
The following cable parameters must be considered:
Braid
Must have minimum 90% coverage.
Foil
When used with braid, provides 100% coverage.
NOTE:
Do not use foil alone, it has a tendency to break.
Twisted Pair
Provides for cancelling of magnetic fields.
Stranded Pair Provides the greatest surface area MDA Scientific product testing uses
>90% braid with foil (around the bundle); twisted pair; stranded 24 AWG
(minimum wiring for all qualification and certification testing).
Examples:
Belden 83652 2-conductor
Belden 83653 3-conductor
Belden 83654 4-conductor
Belden 83656 6-conductor
All examples are 18 AWG stranded, with 100% shield coverage.
Shield
Termination
Continuation of the shield to the cabinet earth ground is most important.
For discrete wire terminations, pigtails to the cabinet (connector)
ground should be extremely short (absolutely no greater than three
inches).
For multiconductor connector terminations, only 360° shielded shells
should be used.
Connectors
All qualification and certification of MDA Scientific products were
achieved with high quality connectors, providing 360° shield coverage.
These connectors generally had metal shells.
Failure to properly secure the connector to the equipment will result in
high emission levels. Also, poorly constructed or improperly assembled
connectors can be a high source of radiated noise and provide a path
for external signals into the instrument.
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