Any training class is a considerable investment in terms of cost and your time. You can’t afford to waste any of your precious time and you need to attend something that is useful and improves your productivity. After five years of presentation throughout the world, this workshop is well polished, practical and relevant.
The aim of this workshop is to help you identify, design, prevent and fix common EMI/EMC problems with a focus on earthing and shielding techniques. Learning how to fix earthing and shielding problems on the job can be very expensive and frustrating. Although it must be noted that most of the principles involved are simple, this workshop will give you the tools to approach earthing and shielding issues in a logical and systematic way.
This workshop focuses on the issues of interest to you if you are working in design, operation or maintenance of analog or digital systems involving sensors, data acquisition, process control, cables, signal processing, programmable logic controllers, power distribution, high speed logic etc.
The circuit board layout section concentrates on design and layout of circuits and components on a printed circuit board. The overall focus is on useful design and systems issues; not about regulations and standards. The idea is that you will take this material back with you to your work and apply the key principles immediately to your design and troubleshooting challenges.
WHO SHOULD ATTEND?
Building service designers
CAD managers
Consulting engineers
Data systems planners and managers
Design engineers
Electrical and instrumentation technicians
Electrical contractors
Electrical engineers
Electrical inspectors
Electricians
EMC specialists
Electronics and systems engineers and technicians
Instrumentation and control engineers
Logic designers
Maintenance engineers
Mechanical engineers
Power system protection and control engineers
Printed circuit board designers
Project engineers
Safety professionals
Signal integrity specialists
Technical managers
Test engineers
MORE INFORMATION: http://www.idc-online.com/content/practical-shielding-emcemi-noise-reduction-earthing-and-circuit-board-layout-66
Electromagnetic Interference and Electromagnetic Compatibility (EMI/EMCAishwary Singh
• Characterizing the threat
• Setting standards for emission and susceptibility levels
• Testing of Equipment on heavy Vibrations
• Testing for standards compliance
For queries,
Aishwarya
palsinghaishwarya@gmail.com
Electromagnetic Interference and Electromagnetic Compatibility (EMI/EMCAishwary Singh
• Characterizing the threat
• Setting standards for emission and susceptibility levels
• Testing of Equipment on heavy Vibrations
• Testing for standards compliance
For queries,
Aishwarya
palsinghaishwarya@gmail.com
Presentation on emc testing and measurementRajat Soni
discuss the options for EMC testing for compliance with the EMC Directive from the point of view of a manufacturer who wishes to achieve as much progress as possible, in-house, on a limited budget. It is not addressed to test houses nor to those manufacturers who have the resources to emulate most or all of the facilities of an accredited test house in their own premises. There are many small-to-medium sized enterprises who are able to dedicate a modest budget of several thousands or tens of thousands of pounds to an in-house EMC test set-up and who wish to gain the maximum benefit from so doing.
A rhombic antenna is a broadband directional wire antenna co-invented by Edmond Bruce and Harald Friis, in 1931, mostly commonly used in the high frequency (HF) or shortwave band.
Satellite Link Design:
EIRP, Transmission Losses, Free-space transmission, System noise temperature and G/T ratio, Noise figure, Design of downlinks, Design of uplink, Design of specified C/N: combining C/N and C/I values in satellite links, Overall C/No, Link design procedure.
By completing this presentation will be have a clear idea about Antenna's working principles, Antenna's Types & Antenna's Parameters. At the end to this document you'll have a brief idea about Antenna's Tilt vs Distance Calculation & Cluster wise optimum Antenna Selection procedure. Impact of antenna PIM & VSWR have been described elaborately in this document as well.
OTDR(OPTICAL TIME DOMAIN REFLECTOMETER)Shail Mishra
OTDR, OPTICAL TIME DOMAIN REFLECTOMETER, How to calculate link budget, Basic of Wavelength, FTTH Network, Working Principle of OTDR, OTDR BASIC PARAMETER.
Maui EMC Presents: An Electical Engineers Guide to EMC/EMI. This show helps with some basic concepts of Electromagnetic Compliance and Interference. This is a great starting point for engineers looking for some basic definitions about EMC/EMI.
Presentation on emc testing and measurementRajat Soni
discuss the options for EMC testing for compliance with the EMC Directive from the point of view of a manufacturer who wishes to achieve as much progress as possible, in-house, on a limited budget. It is not addressed to test houses nor to those manufacturers who have the resources to emulate most or all of the facilities of an accredited test house in their own premises. There are many small-to-medium sized enterprises who are able to dedicate a modest budget of several thousands or tens of thousands of pounds to an in-house EMC test set-up and who wish to gain the maximum benefit from so doing.
A rhombic antenna is a broadband directional wire antenna co-invented by Edmond Bruce and Harald Friis, in 1931, mostly commonly used in the high frequency (HF) or shortwave band.
Satellite Link Design:
EIRP, Transmission Losses, Free-space transmission, System noise temperature and G/T ratio, Noise figure, Design of downlinks, Design of uplink, Design of specified C/N: combining C/N and C/I values in satellite links, Overall C/No, Link design procedure.
By completing this presentation will be have a clear idea about Antenna's working principles, Antenna's Types & Antenna's Parameters. At the end to this document you'll have a brief idea about Antenna's Tilt vs Distance Calculation & Cluster wise optimum Antenna Selection procedure. Impact of antenna PIM & VSWR have been described elaborately in this document as well.
OTDR(OPTICAL TIME DOMAIN REFLECTOMETER)Shail Mishra
OTDR, OPTICAL TIME DOMAIN REFLECTOMETER, How to calculate link budget, Basic of Wavelength, FTTH Network, Working Principle of OTDR, OTDR BASIC PARAMETER.
Maui EMC Presents: An Electical Engineers Guide to EMC/EMI. This show helps with some basic concepts of Electromagnetic Compliance and Interference. This is a great starting point for engineers looking for some basic definitions about EMC/EMI.
Nowadays, mobile consumer electronics devices integrate various wireless interfaces like WIFI, Bluetooth, GPRS and GPS. Various approaches exist to protect the wireless interfaces against ESD stress. In recent years, researchers have focused on so‐called 'co‐design' techniques to solve both functional and protection constraints together which requires both RF and ESD design skills. However many IC designers still prefer to work with 'plug‐n‐play' protection concepts where the ESD clamps exhibit low parasitic capacitance, low series resistance and low leakage. This paper presents measurement results of 3 different SCR based protection approaches that exhibit high Q‐factor and low and stable parasitic capacitance over a broad voltage and frequency range. The clamps are used for protection of LNA circuits in 90nm and 40nm Low Power (LP) CMOS technologies.
Lightning, Surge Protection and Earthing of Electrical and Electronic Systems...Living Online
Few topics generate as much controversy and argument as that of lightning and surge protection of electrical and electronic systems. Poor practices in earthing, and incorrect application and selection of lightning and surge protection devices can be the cause of continual and intermittent problems in a facility, often resulting in lost production and equipment failure.
This workshop looks at these issues from a fresh yet practical perspective and enables you to reduce expensive down time on your plant and equipment by the correct application of these principles. Essentially the workshop is broken down into the methods used to prevent lightning entering a facility such as dissipation arrays and those that divert surge energy away from sensitive equipment.
Dissipation systems are discussed with associated earthing systems. The unique properties of various surge protection devices are reviewed, enabling you to select the correct device suited to the application required. Earthing and surge protection for telecommunications and IT systems are examined in detail as well as the impact of lightning and simple techniques for minimising its impact.
MORE INFORMATION - http://www.idc-online.com/content/lightning-surge-protection-earthing-electrical-electronic-systems-industrial-networks-13?id=6987
Practical HV and LV Switching Operations and Safety RulesLiving Online
In this workshop, we will take a look at the theoretical aspects of safety as well as the practical and statutory issues. One of the main causes of electrical accidents is said to be incorrect isolation of the circuits where work is to be done. To ensure safety of operators and maintenance personnel, proper switching procedures are necessary and more so when the circuits have multiple feeds and are complex. The possibility of voltage being fed back from secondary circuits needs to be considered as well. This workshop emphasises on the isolation procedures to ensure proper and safe isolation of HV, LV and secondary circuits.
Electrical safety is not just a technical issue. Accidents can only be prevented if appropriate safety procedures are evolved and enforced. This includes appropriate knowledge of equipment and systems imparted through systematic training to each and every person who operates or maintains the equipment. We will cover all these aspects in detail.
MORE INFORMATION: http://www.idc-online.com/content/practical-hv-and-lv-switching-operations-and-safety-rules-25
Practical EMC and EMI Control for Engineers and TechniciansLiving Online
This workshop focuses on the issues of interest to you if you are working in design, operation or maintenance of analog or digital systems involving sensors, data acquisition, process control, cables, signal processing, programmable logic controllers, power distribution, high speed logic etc. The circuit board layout section concentrates on design and layout of circuits and components on a printed circuit board. The overall focus is on useful design and systems issues; not about regulations and standards. The idea is that you will take this material back with you to your work and apply the key principles immediately to your design and troubleshooting challenges.
WHO SHOULD ATTEND?
Electrical and electronic engineers and technicians
Engineers and technicians involved in the design and manufacture of electrical and electronic equipment which produce electromagnetic disturbances and may be susceptible to electromagnetic interference
Engineers and technicians involved with the maintenance and service of electrical and electronic equipment
Instrumentation and control engineers and technicians
Those that need to ensure that goods conform to the required standards
Those involved in the marketing and sale of goods that need to comply with the required standards
MORE INFORMATION: http://www.idc-online.com/content/practical-emc-and-emi-control-engineers-and-technicians-2
I would like to share some knowledge of surge protection devices.
This presentation highlights some concepts of surge and surge protectors.
Presentation Index is as follows:
> Types of Surge
> Sources of Surge
> Surge Current & Voltage waveform
> Importance of Surge Protectors
> Types of Surge protectors
> Location of Surge Protectors
Practical fibre optics for engineers & techniciansLiving Online
This comprehensive workshop will provide you with the necessary background to understand the fundamentals of fibre optic systems and their individual components including fibres, cable construction, connectors, splices and optical sources and detectors. Various pitfalls associated with the implementation of fibre optic systems are discussed and workable solutions to these problems are provided. It will provide you with the knowledge to develop the required techniques for design, installation and maintenance of fibre optic systems.
The workshop places significant emphasis on the practical techniques of component installation and system design. You will have the opportunity to get hands-on experience with mechanical and fusion splicing and with fitting the popular industrial fibre connectors. A fibre optic link design software package is provided to allow you to practice actual link design practicals using various parameters.
Finally, you will have the opportunity to practice using various fibre optic test equipment such as optical sources and power meters.
MORE INFORMATION: http://www.idc-online.com/content/practical-fibre-optics-engineers-and-technicians-27
Lightning and surge transfer to systems presentation by jmv lpsMahesh Chandra Manav
Lightning and Surge Strike and Protection Information from JMV LPS Architect/Electrical Consultants/MEP Consultants/EPC Companies/CEA/REC/PGCIL/Wapcos/Electrical Contractor
The term high voltage characterizes electrical circuits in which the voltage used is the cause of particular safety concerns & insulation requirements. High voltage is used in electrical power distribution, in cathode ray tubes, to generate x-rays & particle beams, to demonstrate arcing, for ignition, in photomultiplier tubes & high power amplifier vacuum tubes & other industrial & scientific applications .
Surge Protect, a critical issue you could not fail to know while implementing...Victor Lee
How high should we aim? Sparkovers (flashovers) which occur almost naturally in building wiring systems protect most equipment locations for surges above 6kV. So 6kV is the upper limit we should be concerned about. Note that poor or mediocre wiring insulation materials ironically help protect equipment better than excellent and expensive insulator materials.
There is increasing talk about “6kV surge protection”. We now realize why 6kV is being picked. However, we should keep in mind that so far such requirements are voluntary. But even if they do become mandatory, note that there are already designated “levels” of surge withstand capability: 2.5kV, 4kV, and 6kV, similar to CISPR 24. So it is probable that much like with CISPR 24/EN55024 we may only need to comply with a level lesser than max.
UNDERWATER ACOUSTIC MODEM FOR SHORT –RANGE SENSOR NETWORKS ijiert bestjournal
There is a growing interest in using underwater netwo rked systems for oceanographic applications. These networks often rely on acoustic communication,which poses a number of challenges for reliable data transmission. Commercial underwater modem that do exist were design for sparse,long range application ra ther than for small dense,sensor nets. This paper gives the design consideration,implementation details and challenges in design consideration.
The basis for intelligent automation is communication. The increasing use of communication makes industry increasingly vulnerable for interference. This EMC lecture gives an insight on the disturbance mechanism based on real industrial cases and provides you solutions.
Similar to Practical Shielding, EMC/EMI, Noise Reduction, Earthing and Circuit Board Layout (20)
THE WORKSHOP:
This practical workshop covers all the essentials of process control and tools to optimise the operation of your plant and process, including the ability to perform effective loop tuning.
Practical process control is aimed at engineers and technicians who wish to have a clear, practical understanding of the essentials of process control and loop tuning, as well as how to optimise the operation of their particular plant or process. These persons would typically be primarily involved in the design, implementation and upgrading of industrial control systems. Mathematical theory has been kept to a minimum with the emphasis throughout on practical applications and useful information.
Inspection, Testing and Commissioning of Electrical Switchboards, Circuit Bre...Living Online
THE WORKSHOP:
Whether you are designing, specifying, installing, testing or commissioning electrical equipment from small to large commercial and industrial installations, you need to have a thorough understanding of switchboards, switchgear, circuit breakers and associated protective relays.
The overall focus of this workshop is on electrical inspection, testing and commissioning and will commence with a detailed examination of switchgear (and circuit breakers). Circuit breakers are critical components in electrical distribution systems and their operation significantly affects the overall operation of the system. Protection relays are then discussed. These are used in power systems to maximise continuity of supply and are found in both small and large power systems from generation, through transmission, distribution and utilisation of power in plant, industrial and commercial equipment.
We cover commissioning and periodic inspection of cables and their various failure modes and how to detect these faults. The often neglected topic of switchboards will be detailed next, followed by the interesting topic of interfacing to the control system (either PLC’s or other control devices).
Case studies and practical sessions are used throughout to illustrate key practical principles.
This workshop covers key elements in a practical and project focused way. Many people assume (wrongly) that inspecting, testing and commissioning is a fairly straightforward process and is simply a rubber stamp confirmation of a so-called outstanding design. Our experience in the field demonstrates quite the opposite; where the litany of problems ranges from design and installation errors to equipment manufacturing defects. It is best that these problems are identified and corrected before the inevitable downtime comes in an operational installation where many thousands of dollars are lost in correcting the faults. The situation today is made more challenging by the heightened safety requirements and interfacing to low powered electronic control and monitoring devices (such as PLC’s) using software that has to also be verified.
Hands on Data Communications, Networking & TCP/IP TroubleshootingLiving Online
THE WORKSHOP:
Data communication is given high priority in today’s industrial environment. This workshop is designed to be hands-on, providing the participants with essential knowledge and helping them to understand and troubleshoot systems.
This is a comprehensive two-day hands-on workshop that covers practical aspects of data communication such as serial communications, Ethernet networking, TCP/IP, Modbus, wireless communications and security.
This workshop is for enthusiastic engineers and technicians who wish to develop and enhance their practical knowledge in the field of data communications and networking. It will help them to understand the concepts behind data transmission, the various protocols involved, and the topologies that govern data exchange among various systems in industry. It will also equip them with the skills and tools to design and/or maintain these systems on an ongoing basis.
Fundamentals of Instrumentation, Process Control, PLCs and SCADA for Plant Op...Living Online
THE WORKSHOP:
This course represents a tremendous opportunity to gain expertise in all the key areas of the fast growing area of industrial automation in two days. Presented by an expert in the area but who is passionate with getting the key chunks of know-how and expertise across to you in a simple understandable manner which you can immediately apply to your job. This is most definitely not a boring lecture style presentation but an intensive learning experience where you will walk away with real skills as a result of the hands-on practical exercises, calculations, case studies and group sessions to ensure an understanding of the concepts and ideas discussed. You will undertake practical sessions at approximately 20 to 30 minute intervals to maximise the absorption rate.
Cosmetic shop management system project report.pdfKamal Acharya
Buying new cosmetic products is difficult. It can even be scary for those who have sensitive skin and are prone to skin trouble. The information needed to alleviate this problem is on the back of each product, but it's thought to interpret those ingredient lists unless you have a background in chemistry.
Instead of buying and hoping for the best, we can use data science to help us predict which products may be good fits for us. It includes various function programs to do the above mentioned tasks.
Data file handling has been effectively used in the program.
The automated cosmetic shop management system should deal with the automation of general workflow and administration process of the shop. The main processes of the system focus on customer's request where the system is able to search the most appropriate products and deliver it to the customers. It should help the employees to quickly identify the list of cosmetic product that have reached the minimum quantity and also keep a track of expired date for each cosmetic product. It should help the employees to find the rack number in which the product is placed.It is also Faster and more efficient way.
Explore the innovative world of trenchless pipe repair with our comprehensive guide, "The Benefits and Techniques of Trenchless Pipe Repair." This document delves into the modern methods of repairing underground pipes without the need for extensive excavation, highlighting the numerous advantages and the latest techniques used in the industry.
Learn about the cost savings, reduced environmental impact, and minimal disruption associated with trenchless technology. Discover detailed explanations of popular techniques such as pipe bursting, cured-in-place pipe (CIPP) lining, and directional drilling. Understand how these methods can be applied to various types of infrastructure, from residential plumbing to large-scale municipal systems.
Ideal for homeowners, contractors, engineers, and anyone interested in modern plumbing solutions, this guide provides valuable insights into why trenchless pipe repair is becoming the preferred choice for pipe rehabilitation. Stay informed about the latest advancements and best practices in the field.
Saudi Arabia stands as a titan in the global energy landscape, renowned for its abundant oil and gas resources. It's the largest exporter of petroleum and holds some of the world's most significant reserves. Let's delve into the top 10 oil and gas projects shaping Saudi Arabia's energy future in 2024.
Student information management system project report ii.pdfKamal Acharya
Our project explains about the student management. This project mainly explains the various actions related to student details. This project shows some ease in adding, editing and deleting the student details. It also provides a less time consuming process for viewing, adding, editing and deleting the marks of the students.
Sachpazis:Terzaghi Bearing Capacity Estimation in simple terms with Calculati...Dr.Costas Sachpazis
Terzaghi's soil bearing capacity theory, developed by Karl Terzaghi, is a fundamental principle in geotechnical engineering used to determine the bearing capacity of shallow foundations. This theory provides a method to calculate the ultimate bearing capacity of soil, which is the maximum load per unit area that the soil can support without undergoing shear failure. The Calculation HTML Code included.
2. Coupling Paths: Sources & Victims
Source Equipment
Radiated, cable to cable
case to case
Conducted through
common earth
impedance
Victim Equipment
Peripheral
Radiated,
Input
Radiated, case
to mains cable
Conducted via
common mains
impedance
External mains interference
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7. Receptors
RF, Communication, Radar, Telemetry Receivers etc.
(Anything intended for RF reception or using tuned circuits)
Digital Electronics, Software
(Anything that can be upset by shifting logic levels, timing or clock
disturbances, memory or data line toggling etc.)
Analog Electronics
(Any sensitive circuit that can amplify, rectify, saturate, shift levels etc.)
Sensitive Materials - Ammunition, Fuel
(Anything at risk of burning, exploding)
Human Beings - biological hazard
(Anything living)
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9. Conductive Connection
(Common Impedance Coupling)
System B
Load Input
Vin
V Connection has inductance, L
System B input = (Vin+V)
where V~ -L.d IL /dt
System A
IL
Input
Vin
Load
System A System B
IL
Problem
Solution
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10. Magnetic Induction
Load
System A
IL
System B
Vin
Rs
Zin
Vn
Mutual Inductance, M
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11. Electrostatic Coupling
Vin
System B
Load
System A
IL
Rs
Zin
Vn
Stray or parasitic
capacitance
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12. Real World Coupling
Noise Source
Magnetic
Induction
Victim
Electrostatic
(Capacitive)
Coupling
Posible Ground Loop or
Common Impedance Coupling
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13. Mutual C & L vs Lead Spacing
0,25 1,25
0,20
0,15
0,10
0,05
1,00
0,75
0,5
0,25
D D
1 mm
1,6 mm
C
Mutual
Capacitance
(pF/cm) M
(nH/cm)
Mutual Inductance
1 2 4 8 10 20 40 80 100
D (mm)
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14. Coupling via the supply network
50
ohms 50 μH
SOURCE VICTIM
Attenuation30
dB/km
20
10
Distribution system
Cable only
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15. Electromagnetic fields
V
D (m)
E-field I
R (m)
H-field
Propagation
V
E-field
H-field
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16. Rayleigh/Maxwell near/far fields
E a1/r3, H a1/r2
Electric field
predominates
Near field impedance
anywhere in this region
H a1/r3, E a1/r2
Magnetic field
predominates
Plane wave
Z = 377 ohms
Far field
Transition area
0,1 1 10
10 k
1 k
Zwave
100
10
Distance from source, normalised to l/ 2p
Frequency Max dimension
D (m)
Rayleigh
d = 2D2/l (m)
Maxwell
d = l/2p (m)
10 MHz
30 MHz
2
2
2
0,5
0,5
2
0,5
100 MHz
300 MHz
1 GHz
0,267 4,77
0,8
0,167
2,67
0,5
8,0
1,67
1,59
0,477
0,477
0,159
0,159
0,0477
Rayleigh & Maxwell
distances for
transition to
far field
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18. Radiated Emissions from PCB
(Differential Mode)
Signal current
Loop of area ‘A’
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20. Coupling Paths - Conducted Emissions
SMPS L
N
E
Signal cable
CIRCUIT
ICME
0 V
CC
VNsupply
CS CS
IDM
Measurement
Measurement
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21. Susceptibility to Radiated Field Coupling
E
Victim
Field coupling to cable
induces common mode
current at input
Possible standing wave in enclosure:
creates susceptibility/emission peaks
Field coupling to
PCB induces
differential mode
currents in circuit
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24. Transient Frequency
Type of
area
Transients/
hour
Industrial
Commercial
Domestic
Laboratory
17,5
2,8
0,6
2,3
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25. Electrostatic Discharge
Coupling paths likely to be:
• Stray capacitance
• Case bonding
• Track or wiring inductance due to magnetic fields
generated in the discharge
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26. Automotive Transients
Alternator load dump
100 ms 200 ms 300 ms
Inductive switching
10 μs 20 μs 30 μs
5 ms 10 ms 15 ms
Alternator field decay
80 V
14 V
VP
-0,2.VP
14 V
-80 V
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27. Supply Voltage Phenomena
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28. Supply voltage phenomena - important?
1 ms 3 ms 20 ms 500 ms 10 s
500%
400%
300%
200%
140%
120%
70%
40%
0,2 ms
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29. DO YOU WANT TO KNOW MORE?
If you are interested in further training or information,
please visit:
http://idc-online.com/slideshare
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Editor's Notes
Electromagnetic Interference requires two parties: a source, and a victim. Any electronic device has the potential to radiate or conduct emissions, and at the same time be susceptible to them itself. Some problems may exist where the victim is also the source.
Understanding of the mechanisms by which this takes place is essential to solving EMC problems.
To ensure compatibility between one item of equipment and any other in a given electromagnetic environment requires a comprehensive understanding of the ways in which this source to victim coupling is possible. The slide above outlines the ways in which this can happen.
Keep in mind that some of the paths only exist because of the parameters which are not taken into account - the inductance and capacitance of cables, for example.
EMI works like this. Always a noise source, a coupling path and a receptor.
The solution for reducing interference can be at the source, path or receptor.
Noise sources are everywhere.
Above is a list of considerations when changing the coupling between source and victim.
Receptors everywhere!
Any EMI problem will involve any or a combination of the above coupling mechanisms.
A minor re-routing can often eliminate a problem by removing a common conductor, which we are inclined to forget has resistance, inductance and capacitance whether we like it or not.
AC current in a conductor creates a magnetic field. This can couple with a nearby conductor and induce a current in that conductor. This usually happens where there are large and/or fast variations in current (i.e. high di/dt).
Note that there is no need for a common ground for this to take place - it can happen between isolated circuits.
One conductor can be affected by a changing voltage on another. The extent of this depends on the ratio of impedances between the load and the source.
The source impedance will be determined by the distance between conductors, their effective areas and the composition of whatever is between them (dielectric).
Electrostatic (capacitive) coupling usually happens where there are large and/or fast variations in voltage (i.e. high dv/dt).
A combination of coupling mechanisms exist in the real world. One type of coupling can dominate, but sometimes a combination is present.
This graph shows the effects of the spacing between conductors on their ability to couple from one circuit to another.
Although the picture above of the supply system impedance, this is in an ideal world. In reality, the impedance is determined very largely by whatever is connected to the supply. This is shown by the graph above, and makes predictions of coupling difficult.
Any conductor with an applied voltage and current will generate an electric and a magnetic field as shown.
The way in which these fields develop will be determined by the physical layout. Whether the electric or magnetic field will dominate depends on whether the current or voltage is predominant.
Radiated emissions can be divided into ‘near field’ and ‘far field’. In the near field, separate electric and magnetic fields exist. Which one will predominate depends on the source impedance as shown above. It is important to understand this, because they are measured differently and different measures are used to counteract a magnetic or electric field.
In the far field, the two merge into a composite electromagnetic plane wave. This is often considered to take place at about one sixth of a wavelength (/2), mainly because of Maxwell. This is true of point sources, but is substantially affected by the source dimensions as shown by Rayleigh, and illustrated in the chart above.
In most cases, the wanted signal is produced in differential mode. It is also possible to have interfering signals which are induced into a conductor in differential mode, and can in turn be radiated in differential mode. Ground plays no part in this case.
The cable can also carry signals in common mode, usually interfering signals they could also be internally generated). These are referenced to ground, very often by stray capacitances and inductances and can of course be radiated as common mode signals. Common mode signals become a problem when they are converted into differential mode, and get confused with the wanted signal.
In antenna mode, currents are equally induced in the signal conductors, and in the reference plane (often happens in aircraft travelling through magnetic fields). Becomes a problem if converted to differential mode.
Although depicted as happening between two separate modules, it is very possible for this to take place on a PCB.
The circuit drawn above shows a ‘small loop antenna’ smaller than /4 at the frequency of interest. (All PCB tracks are ‘small loop antennae’ up to a few hundred MHz).
The field varies with the square of the frequency, and is directly proportional to the signal current and the loop area, and can be substantial. Keep the area small.
Cable radiation is generally common mode, which is generally far worse than differential mode.
These common mode voltages can easily arise due to poor termination, as we will see in the module on cables and connectors.
The loop area is uncontrolled, hence unpredictable. Common mode current generally needs to be under 5 µA to meet cable emission standards!
As in the drawing above, where there are high switch-mode frequencies, capacitance to ground plays a major part. This allows large common-mode voltages to develop relative to ground.
In addition, differential mode signals can appear on the supply line or the signal cable as a result of SMPS noise being getting through to the signal cable from the supply lines, or directly onto the Live and Neutral from the switching oscillator.
Coupling can take place either directly to the circuitry, or via I/O or mains lines. Common mode interference eventually translates into differential mode, and resonance within an enclosure must be regarded as a possibility.
Transients and spikes are different from continuously generated EMI. Above is a list of likely sources.
Virtually all transient wave-forms are classified in this way. There is some variation in where the second time period, T2, starts from. In this slide it is shown as being from almost the start of the rise of the wave. However, as both of these times are specified as being + or - 30% in most cases, it is difficult to see why anyone bothers!
The graph above shows the results of a study carried out on mains supply and telecom lines to record the number and amplitude of transient voltages.
These figures obviously depend on the lightning strike density in various parts of the world, and the degree of heavy load switching in the vicinity of a particular site. Particularly with lightning (but also with switching surges) the mains connection density plays a part.
This slide shows different transients that can exist in a 12V automotive system. If not designed for, 12V components will fail at these high voltages.
The supply voltage can exhibit a variety of disturbances.
The ITIC (Information Technology Industries Council) curve shown above, demonstrates the fluctuation levels and time periods which are likely to upset a PC. From this it is obvious that short-duration voltage variations can definitely affect electronic equipment.
It is just as necessary to ensure that mains-powered equipment doesn’t introduce any of these phenomena which are
voltage dips (short-duration reductions in voltage)
interruptions (complete absence of power for longer than ~ 3 s)
harmonics
unbalance (voltage differences between phases)
flicker (rapid voltage variations which are annoying as they affect incandescent lighting)
transients