Electromagnetic Interference (EMI) can cause
system malfunction, communications interruptions, loss of data and
erroneous measurements. With the increased quantity and mobility of RF
threats, EMI management has become a critical issue in facilities
design. Protection in an urban environment, where
systems and users are in close proximity to potential threats, requires
an understanding of the coupling and physics to find the most effective
Washington Laboratories has over 25 years of
experience in the management and control of interference phenomena with
particular expertise in Radio Frequency noise abatement, Lightning
Protection, EMF Measurements, RF Shielding and Systems Design.
Examples of interference sources in the
Military and Government
TV/Radio and communications
Banks and Financial
WiFi and Wireless
Rail and subway systems
Research and Medical Facilities
Motors, lighting and electrical
Managing these threats
takes an understanding of the interaction between the sources and the
Protection for Systems
Data, communications, voice, video and broadband
services require protection against Electromagnetic Interference (EMI).
Shielding systems are often employed in building facilities to protect
sensitive systems from radio frequency sources in the urban environment.
Communications security must be robust and free from eavesdropping or
Protection in the Laboratory
Research hospitals, biotechnology and life sciences
organizations deal with extremely sensitive sensors and systems during
research and development. The small signals that are detected in
animal-cell activities are measured in billionths of amperes, which can
be overwhelmed by intruding signals from mobile networks, WiFi access
points, TV/AM/FM broadcast and other sources of man-made noise.
Protection in the Workplace
Electromagnetic Fields (EMF) are a
concern for worker safety and health, as well as potentially interfering
with sensitive electrical equipment. High-amplitude AC power currents
can generate low frequency magnetic fields that are difficult to control
and to reduce. Shielding is one of the options to reduce these fields.
Washington Laboratories takes a
systems-level approach to the problems of radiated interference. Our
objective is to find the most cost-effective methods of controlling
interference. A complete design methodology must take into account the
Quantifying the threat
System sensitivity and
probability of interference
Reduction and control
of potential sources
configuration to minimize interference coupling
materials and construction methods
Design Considerations and Methodology
potential for interference depends on the level of interference and
the level of susceptibility. To solve an interference problem, one may
suppress the source or harden the victim. Our approach is to specify a
degree of both, as appropriate for the situation.
For many installations, it is not
possible to predict the possibility of interference; however, based on
judicious selection of equipment and an appropriate level of appropriate
shielding, a high degree of confidence can be achieved.
Interference and Mitigation
There are two primary considerations when
considering "low-noise" design for facilities. The two concerns are
based on frequency and nature of potential threats to equipment
operations and accurate measurements.
It is important to separate the two concerns
because the nature of the design and mitigation techniques are
fields are primarily generated by 60Hz AC power currents. The major
sources are from long conductors, particularly distribution cabling.
From experience, the major source of magnetic fields are from legacy
wiring that has may have multiple ground conductors and are not in
compliance with current codes that require single-point-grounding.
In addition, older equipment may
have significant "leakage current" that causes ground currents to flow
along presently uncontrolled return paths.
To mitigate this type of situation
often requires expensive and extensive shielding. For new installations,
compliance with NEC requirements often preempts this source of
interference. In addition, newer equipment is more likely to have low
leakage current because safety standards are more strict than in the
past. Higher leakage currents constitute a safety risk as well.
Other methods of construction can be implemented to reduce the
potential for magnetic fields, including separation and placement of
equipment with respect to potential interference sources.
Avoid the use of bus duct risers. Use conductors in conduit risers
in electrical distribution. The close bundling of phase conductors
results in a net cancellation
of the fields that radiate from
Locating high-current conductors as far as possible from sensitive
Locate power distribution transformers as far away as possible from
With the above technique in place,
it is possible that magnetic field threats may be entirely mitigated
without special measures. However, the exact arrangement equipment and
systems needs to observe critical noise-reduction measures, such as
proper shielding of cables, equipment grounding and minimization of
Radio Frequency Fields
High frequency interference is
of concern in urban environments. The potential for applying shielding
around the space is a consideration. The exact determination will be
made after measurements of the existing fields are performed.
A shield system that would be adequate
to protect the equipment may involve a foil-based shield material up to
frame and panel designed installations. There are several possible
options for achieving the necessary attenuation. The ultimate level is
dependent on an assessment of the existing field levels and the
sensitivity of the equipment.
Shielding Effectiveness is used
to describe the amount of reduction offered by a shield to an impinging
source. The levels are normally specified in terms of decibels (dB) over
some frequency range. Proper shield design must take into account the
following electrical and mechanical penetrations:
Electrical outlets, lights and switches
handling units, HVAC
Fire Alarm Systems
Doors, window and
A complete and comprehensive study and
review of a facility is recommended for cost-effective and practical
design to protect electrical and electronic systems from Electromagnet
This award demonstrates our commitment to the
quality of data and services provided to our customers.
WL provides EMC Training
on Nuclear Environment and MIL-STD 461 requirements
Washington Labs teams up with HCT in Seoul Korea to provide training on EMC technical requirements for Nuclear Power plants and MIL-STD-461 requirments. The training was held in April 2012 and hosted by Korea's pre-eminient EMC Laboratory, HCT. read more...
Washington Labs, Inventec Partnering in China
Washington Laboratories has entered a joint agreement to work with Inventec Lab in Shanghai, providing Expert Reviews of Chinese Evaluations.
As you know, EMC conformity is essential in designing and operating nuclear facilities - and we can help you manage the many issues involved from the commissioning process right through to daily operation. You can read more about our services right over here...
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