Ch. 2 (Electromagnetic Compatibility) Flashcards
Conducted coupling
Except solid state
Internal EMI sources
Power lines
Motors
Cell phones
Except “incandescent lighting” or “electrical power cables”
EMI sources (natural)
Atmospheric electricity
Cosmic radiation
Electrostatic discharge
Spark in the air
CRT
Cathode Ray Tube
What interferes with CRTs
RFI
Unwanted signals
CM - common mode
DM - differential mode
An example of common mode
Locking up a computer
Differential mode affects
Corrupting transmitted signals
Types of EMI
Except unbalanced DM fields
Coupling mutual capacitance/inductance
Except signal injector
Tunnel problems
Except unbalanced DM fields
Man-made EMI sources
Electrical power
Generator
Communications electronics
ESD =
Electrostatic Discharge
Types of ESD
Spark
Radiated
Contact
ESD immunity
Contact level 2 - 4 KV
Contact level 4 - 8 KV
Air level 2 - 4 KV
Less than 5KVA
No separation necessary
Separation requirements for fluorescent lamps
5.12”
Separation from power in grounded metal conduit
6”
Separation from unshielded power lines near grounded metal conduit
12”
Separation from unshielded power lines near open pathways
24”
Separation from electrical motors & transformers
47”
Mitigate unwanted signals w/ ___
Ferrite beads
Magnetic scheme
Filters unwanted signals
Two types of EMI
Man-made
Natural
How to measure EMC
There is no technique
EMC =
Electromagnetic Compatibility
Separation for arc welders
31.5”
Electromagnetic fields are ___ undesirable
Not always
___ are created when inductive and capacitive circuits are switched on and off
Electrical fast transient (EFT) disturbances
Inadequate gaskets/enclosures can be a source of ___
Radiated interference
RMS power
.707
Difference between two grounds should be no more than ___
1.00
Modern electronics are ___ susceptible to EMI
More
Instrumentation shield grounding
Grounding for longer shield runs
One end
Both ends
Minimum CM rejection ratio
40 dB
Visible light
10 to the 15th power
