Arnie Nielsen Consulting LLC - Southeastern Michigan IEEE EMC

Arnie Nielsen Consulting LLC - Southeastern Michigan IEEE EMC
IEEE EMC June 2010 Chapter
Meeting
Automotive EMC Component
Specs - A Contemporary
Perspective
Essential PCB Design Rules
IEEE_June 2010
© Arnie Nielsen Consulting LLC
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Arnie Nielsen Consulting LLC
[email protected]
248-305-8264 (M 248-982-0401)
Instrumentation Engineer - 5 years
Powertrain Hardware-Software Electronics Design
Engineer - 10 years
Tech Specialist - 22 years
•
•
•
•
Electronic Design
EMC
Reliability
Product Assurance
Electronics - EMC Consulting - 5 years
© Arnie Nielsen Consulting LLC
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Consulting Projects
Item Company
Product
1
Compact Power Inc (LG Chem)
Electric Vehicle Battery Electronics (Volt)
2
Holley Performance Products
Electronic Throttle Body
3
Android Industries
TPMS (wheel/tire assembly line)
4
Methode Electronics
Center Cluster Stack
5
Vectrix
Electric Motorcycle
6
RGIS
Handheld Data Terminal (inventory)
7
GHPS (KDS)
BLDC, DSP Amplifier
8
Kostal
Electric Vehicle Connectors
9
MRM
Vehicle Internet
10
BASF
Shielding
11
Cobasys
Electric Vehicle Battery Electronics
12
L3 Communications
Vehicle Communications
13
Haitec
Taiwan OEM Vehicle
14
LiteOn
Body ECU
15
Whetron
Keyless Entry, Auto Wiper
16
Calsonic
Entertainment
17
eCho
Immobilizer
18
Delta
Power Distribution
19
Advanced Microelectronics
Headlight Control
20
Elitech Technology Ltd
Inverter
21
Delphi
Power Sliding Door
22
Clarion
Car PC (Infotainment)
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Meets all specifications but what are we missing ?
But it met Specification ?
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Reference Sampling
Documents, Books
1. EMC Specification, EMC-CS-2009
(http://www.fordemc.com)
2. EMC Design Guide for Printed Circuit Boards
(http://www.fordemc.com)
3. Noise Reduction Techniques in Electronic
Systems, Henry Ott
4. High Speed Digital Design, Howard Johnson
5. Introduction to Electromagnetic Compatibility,
Clayton Paul
6. “In Compliance” Magazine
7. ITEM - Interference Technology
© Arnie Nielsen Consulting LLC
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Web Sites
1. www.fordemc.com
2. www.clev.clemson.edu/emc
3. http://www.compliance-club.com/
4. http://www.interferencetechnology.com/
5. emcesd.com, Doug Smith
Organizatons
1. SAE EMC committees (EMC, EMI, EMR). Meet
often, much faster publication turn around time
than international organizations
2. IEEE, ISO, CISPR, others
3. SAE Reliability Committee
© Arnie Nielsen Consulting LLC
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Summary - Punch Line
1. Specs are idealized simulations, not “real world”
2. Much of industry specs based on old issues.
3. Much time and cost spent on non value exercises
by contemporary practitioners due to limited
knowledge of specification history - don’t know
when to “hold or fold”.
4. Little time left for “sandboxing”
5. DV testing often late in design cycle - need more
simple development testing to identify issues early.
6. Meeting spec not sufficient to mitigate field issues
7. Main goal is to minimize field issues not just pass
specs.
8. More efficient EMC Process improvements:
• Up-front analysis, focus on contemporary
issues
• Design guidelines implementation.
• Simple development testing.
• Realistic data analysis and acceptance criteria.
© Arnie Nielsen Consulting LLC
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Summary of Automotive EMC History
1970’s
•
Minimal electronics – radio
•
Mostly concerned with ignition system interference
1980’s
•
Electronics increasing - starting with electronic ignition,
alternator voltage regulator, simple engine control
•
Quality of IC’s and manufacturing processes not mature
•
Automotive EMC design and test standards starting to be
developed to address above (e.g. OEM, ISO, SAE).
•
EMC evolving, many issues
1990’s
•
Explosion of electronics
•
Automotive electronics technology maturing - IC’s,
manufacturing processes, standards, testing
•
EMC specs and design practices becoming mature.
© Arnie Nielsen Consulting LLC
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Summary of Automotive EMC History
2000’s
•
Specs stabilizing, similar throughout industry.
•
Minimal EMC field issues (if design guidelines followed),
mostly Conducted Immunity.
•
Many specialized organizations in place:
OEM/Vendor EMC staff
Testing facilities/staff
Equipment vendors
Regulators and regulations
EMC committees
•
A lot of inertia, perspective limited.
•
Many OEM specs and International Standards exist
(Different but similar):
•
•
Ford, Mazda, GM, Hyundai, Toyota, Honda, BMW,
Nissan, etc.
•
ISO, CISPR, SAE, JASO, EU, FCC, Mil-Std, etc
EMC process has potential to be improved and simplified.
© Arnie Nielsen Consulting LLC
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Automotive EMC Standards
SAE Document
Vehicle
J551-1
J551-2
J551-4
J551-5
J551-11
J551-12
J551-13
J551-14
J551-15
J551-16
J551-17
Component
J1113-1
J1113-2
J1113-3
J1113-4
J1113-11
J1113-12
J1113-13
J1113-21
J1113-22
J1113-23
J1113-24
J1113-25
J1113-26
J1113-27
J1113-28
----J1113-41
J1113-42
-----
Description
Vehicle, General & Definitions
Ignition Interference
Radiated Emissions
Electric Vehicle Emissions
Immunity, Off-Vehicle Source
Immunity, On-Board Transmitter
Immunity, Bulk Current Injection (BCI)
SAE
Status
International
Equiv
Cancelled
Cancelled
ISO 11451-1
CISPR 12
CISPR 25
Cancelled
Cancelled
Cancelled
ISO 11451-2
ISO 11451-3
ISO 11451-4
Immunity, ESD
Immunity, Reverberation Chamber
Immunity, Power Lines
ISO 10605
Component, General & Definitions
Conducted Immunity, Power Leads
Conducted Immunity, RF Power Injection.
Immunity, BCI
Immunity, Transients
Immunity, Coupling Clamp
ESD
Immunity, Absorber Lined Chamber.
Immunity, Power Lines, Magnetic
Immunity, Stripline
Immunity, TEM Cell
Immunity, Tri-Plate
Immunity, Power Lines, Electric
Immunity, Reverb Chamber, Mode Stiring.
Immunity, Reverb Chamber, Mode Tuning.
Immunity, Portable Transmitters
ISO 11452-1
ISO 11452-10
ISO 11452-7
ISO 11452-4
ISO 7637-2
ISO 7637-3
ISO 10605
ISO 11452-2
ISO 11452-8
ISO 11452-5
ISO 11452-3
Radiated Emissions, Narrowband
Conducted Emissions, Transients
Environmental Conditions and Testing for Electrical
and Electronic Equipment – Part 2: Electrical Loads
Cancelled
Cancelled
Cancelled
ISO 11452-11
ISO 11452-9
Cancelled
CISPR 25
ISO 7637-2
ISO 16750-2
© Arnie Nielsen Consulting LLC
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Automotive EMC Standards
SAE Document
Description
IC
J1752-1
J1752-2
J1752-3
Misc
J1812
J2556
J2628
Function Performance Status Class
Power Spectral Density (PSD), RE Data Analysis
Characterization, Conducted Immunity
OEM (sample)
EMC-CS-2009
MES PW 67600
GMW3097
DC-10614
TSC7001, et al
28401NDS02
ES96200
GS95002
Ford
Mazda
GM
Chrysler
Toyota
Nissan
Hyundai
BMW
Other Related
2004/104/EC
European EMC Directive
FCC Part 15J
Emissions
Mil-Std 461
Requirements for the Control of Electromagnetic
Interference Characteristics of Subsystems and
Equipment
Handbook for Robustness Validation of Automotive
Electrical/Electronic Modules (Old version
published in 1978).
SAE J1211
SAE
Status
IC, General & Definitions
IC Radiated Emissions, Loop Probe
IC Radiated Emissions, TEM Cell
International
Equiv
IEC
IEC
IEC
4/2009
The Present Status of the International Automotive EMC Standards
Poul Andersen, Poul Andersen Consulting
37249 Hebel Rd
Richmond, Michigan 48062 USA
[email protected]
http://www.cvel.clemson.edu/auto/auto_emc_standards.html
© Arnie Nielsen Consulting LLC
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Causes - Relative Contributions
100
80
60
40
20
0
A=Customer
Does Not Like
Product
(Requirements
not specified or
incorrect)
B=System Does
C=Can Not
Not Fit
Diagnose
(Interfaces)
Problem (Trouble
Not Indicated)
D=Component
Failure
E=Manufacturing
Fault
Examples of top 3 causes:
A: Most american cars until recently
B: Boeing 787
C: Most automotive electronics TNI > 50 %
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Test Methods/Limits Observations
•
Meeting EMC specs necessary but not sufficient to
mitigate field issues - Main goal is to minimize field
issues not just pass specs.
•
Originally, EMC for automotive electronics was poor
so a lot of tests were “invented”. There were
minimal design practices for automotive EMC.
•
Many EMC tests are idealized simulations of the real
world.
•
Major purpose is repeatability, not necessarily what
is required to find real world issues.
•
Most OEM specs and processes are very severe,
time consuming and expensive to implement.
•
Diverts from time to “sand box” where many issues
are found - focus on major contemporary concerns.
•
Contemporary electronics much improved. EMC is
minor issue compared to “Big Picture” - see figure
•
DV testing often late in design cycle - need more
simple development testing to identify issues early.
© Arnie Nielsen Consulting LLC
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Test Methods/Limits Observations
•
EMC testing is typically the first time the system
is “rung out” (system components
interconnected and functionally examined).
•
Testing methods have many limitations and
compromises not appreciated by contemporary
practitioners - don’t know when to “Hold or Fold”
•
Much testing addresses old issues with limited
value add especially for modules that follow
known basic EMC design rules and are mature.
•
Different people looking at the same data can
come up with quite different conclusions
depending on their background, insight and
flexibility.
•
Considering how EMC testing is done (test
setup and limits are much more severe than
real world) should have more flexibility,
especially when one considers that most EMC
issues are 3-6 sigma events.
© Arnie Nielsen Consulting LLC
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Test Methods/Limits Observations
• Simple pass-fail criteria (e.g. limit line) results in
too much non value work (not real world issues).
• Does not indicate degree of compliance
• Hard to compare different samples - need
variables data.
• Should use statistical approach to make better
business decisions
• Issues not presently addressed (e.g.):
•
•
•
Temperature
Combined stresses
Part degradation
• Power supply electrolytic cap
• Battery impedance increase.
• Cracked I/O caps
• Worn out transient suppressor
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Test Methods/Limits Observations
• Functional Safety concerns (e.g. Toyota
unintended acceleration) generating potential
new set of requirements.
• Non Compliance = Prosecution
• IET 2008 Guide on EMC for functional safety
(177pages)
• IEC 61508 - Functional safety of
electrical/electronics/programmable electronic
safety related systems (7 parts)
• ISO 26262 - Road vehicles, Functional Safety.
In development, adaptation of IEC 61508.
Estimated July 2011.
© Arnie Nielsen Consulting LLC
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Conflicting Goals
•
The responsibility for meeting EMC requirements is
the Product Design (PD) Engineer.
•
Although it is admirable for the EMC community to
try and do the best job possible, it has a tendency
to go to extremes regarding testing requirements
and limits.
•
Such EMC groups are typically a separate
community and have a narrow view. This may be in
conflict with some of the realities of the PD engineer
•
Limited time on each project
•
Must address many other design and
manufacturing aspects.
•
Keep to schedule.
•
Keep costs down (weigh cost/benefit).
•
Make a profit.
© Arnie Nielsen Consulting LLC
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EMC Process Improvements
• Process has potential to be improved and simplified
but its extremely hard to change and think “out of
the box” with so much inertia (OEM/Vendor EMC
staff, Testing facilities/staff, Equipment vendors,
Regulators and regulations, EMC committees).
• Fundamental test concepts not embraced by EMC
community but essential for field issue mitigation.
•
Failures are good (early in design process) information theory
•
Randomness is good.
• Litigation fears preventing any major change
•
May be perceived as making less severe.
•
Opinion - not really an issue
© Arnie Nielsen Consulting LLC
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EMC Process Improvements
•
Even so, certain practices can be implemented to
improve the process:
•
EMC group should be integrated with systems
engineering and not a separate organization (ideally
co-located).
•
Up-Front analysis, focus on contemporary issues.
•
Verify design guidelines implementation
•
Simple early development testing
•
Realistic data analysis and acceptance criteria.
•
If product has already passed one OEM spec, other
OEM’s should accept (minor alterations).
•
Limited focused testing for mature products.
© Arnie Nielsen Consulting LLC
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EMC Process Improvements - cont’d
•
One generic automotive EMC spec for the industry.
•
“A Generic Automotive (Tier1) EMC Test Standard”,
http://www.autoemc.net/Standards/StandardsMain.
htm
•
Many existing standards can make this relatively
easy. Most OEM specs already use.
•
Vendors can design to one spec - Lowers
staffing/time/cost and results in a better product for
all.
•
Examples in other industries
• Military = Mil-Std 461
• IC’s = JEDEC
• Consumer = UL standards.
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Simple EMC Development Tools
RE - Magnetic Field Probes
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Simple EMC Development Tools
RE - RF Detector placed on wiring
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Simple EMC Development Tools
RE - Digital Radio
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Simple EMC Development Tools
•
Noise Generator connected to Injection Clamp
•
Use for DUT Power Input Noise
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Simple EMC Development Tools
Adjustable Current Injection Clamp
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Simple EMC Development Tools
Magnetic Field - attach to Noise Generator
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Simple EMC Development Tools
•
ESD Gun - Modified Lighter
•
Apply in low light to see paths
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Radiated Immunity
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General Setup for Radiated Immunity and Emissions
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Radiated Immunity (RI) Observations
•
Test not like real world
•
Test = Alignment of antenna and DUT/Harness
maximizes susceptibility
•
Real = Random harness routing, inefficient
coupling, sheet metal.
•
Test = Exposes large area
•
Real = Exposure to only part of system.
•
OEM limits too severe (Ref Mil-Std 461 ground
= 50 v/m max).
•
High limit based on high power on-board
transmitters (rare these days).
•
Contemporary = Cell Phones (only for certain
DUT’s): “Cell Phone Interference in Automotive
Cabin”, Craig Fanning
© Arnie Nielsen Consulting LLC
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Radiated Immunity (RI) Observations
• Field strength varies widely in actual vehicle - can
be >100 v/m difference only a few inches apart.
• Real = Field falls off rapidly from point source.
• Field impedance (E/H) different for test vs vehicle.
• Proposal - Use more realistic data analysis based
on probability of concern and realization of how
limit was determined.
• Example = determine susceptibility field strength
average and standard deviation.
• Only resolution needed to make engineering
business decision is high, medium and low (e.g.
test at 100v/m but acceptable at 80 v/m)
© Arnie Nielsen Consulting LLC
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Example of RI Data
•
•
•
Does it meet intent of 100 v/m ?
CW, 400-1000 MHz
Average = 83 v/m, Std Deviation = 13 v/m
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Radiated Emissions
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Radiated Emissions (RE) Observations
•
Test not like real world
•
Test = Alignment of antenna and DUT/Harness
maximizes emissions measurements
•
Real = Random harness routing, inefficient
coupling, sheet metal.
•
Many specs overcomplicate their RE limits by
having many bands and associated limits. The
limits are only applicable in a lab environment for
a particular setup. In the vehicle, there are many
variables which amplify or attenuate the signal..
•
Limits are good only for test setup, changes with
different harness lengths (up to 20 dB
differences).
•
“Automotive EMC Test Harnesses, Standard
Lengths and their Effect on Radiated Emissions”,
Martin O’Hara, James Colebrooke
•
Spectrum Analyzer/Receiver not like real radio
© Arnie Nielsen Consulting LLC
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RE Spec Limits
• The main factor that determines a spec. limit are the
sensitivities of on-board or nearby radio and
communication antennas and receivers.
• In the AM band, the antenna factor (ratio of antenna
output voltage to field strength) plus the attenuation
from the antenna to the radio due to antenna cable
capacitance is about 20 dB.
• In addition, there is some attenuation between noise
sources within the vehicle and the antenna due to
sheet metal and differences in polarization.
• Assuming a radio sensitivity of 1 uv (0 dbuv), the limit
= 30 dbuv/m (20 + 10)
© Arnie Nielsen Consulting LLC
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RE Limits, cont’d
• For FM entertainment radio and mobile
communications, the antennas and antenna cable is
much more efficient (antenna factor is 0 - 6 dB) and
attenuation due to the vehicle sheet metal (openings,
slots) is less due to small signal wavelength.
• Assuming a 1 uv sensitivity, the limit = 10 dbuv/m.
• The limit increases at 20 db/decade at higher
frequencies to account for the fact that radio receiver
antenna output voltage decreases at that rate
(aperture size of a tuned antenna decreases with
frequency). This can be seen by the following
equation which shows the (1/f) relation (20
db/decade):
e = (33 * E) / f (quarter wavelength antenna)
e = antenna output voltage,
E = field strength (v/m) impinging on antenna
f = frequency (MHz)
© Arnie Nielsen Consulting LLC
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RE Spec Limits, cont’d
• The following equation provides useful conversions
for testing:
dBuv/meter = dBm (reading of spectrum analyzer)
+ 107 (converts power across 50 ohms of spectrum
analyzer to volt) - preamp gain in db (if used)
+ AF in dB (antenna factor, changes with
antenna/frequency)
• For example, a reading of - 60 dBm on the spectrum
analyzer at 100 MHz (assuming 26 dB amplifier in
series with spectrum analyzer) would be:
dbuv/meter = -60 + 107 - 26 + 14 = 35 dBuv/meter =
56 uv/meter
© Arnie Nielsen Consulting LLC
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© Arnie Nielsen Consulting LLC
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•
Typical OEM limits are much more stringent than
the FCC's, especially when one considers that
FCC limits are measured 3 meters away from the
radiating device and the OEM limits are at 1
meter. The typical OEM limits are more
restrictive:
•
Radiating devices on the vehicle are closer
to radio transceivers on board the vehicle.
•
A vehicle contains many radiating devices.
•
Customer satisfaction
OEM RE limits (1 meter) typical
Frequency
(MHz)
uV/m
dBuV/m
0.10 - 25
31.6
30
25 - 200
3.2
10
200 - 1000
3.2 - 15.8 10 dBV/m - 24 dBV/m
FCC Class B RE limits (3 meters)
30 - 88
100
40
88 - 216
150
43.5
216 - 1000
200
46
© Arnie Nielsen Consulting LLC
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Example of RE Data
• Which One is Acceptable ?
• Top = Few spikes over Limit, technically fails
• Bottom = All spikes under Limit, technically passes
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Example of Using the Wrong Part
Early detection would prevent multiple layouts
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RE Data Analysis
Reference SAE J2556
• The present method of using only a limit line for
determining module radiated emissions acceptance
is too simplistic and is not the most effective way to
make competitive business decisions. The limit line
approach does not address many real issues.
• It is very difficult if not unpractical to get the same
results at each frequency from different test labs for
radiated emissions due to the many variables
involved.
• However, it is possible to establish correlation
between different labs on a statistical basis. For
example, if only the highest emission levels are
compared independent of the emission frequencies
a higher degree of correlation is possible.
• Such an approach may be justified under the
assumption that the test facility design does not
significantly affect the total emissions power but
mainly leads to the radiated power spectrum
redistribution.
© Arnie Nielsen Consulting LLC
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• The simplistic approach of being below a limit line
may still result in instances of a customer concern.
• For example, even if the RE is all below a limit line,
it is more probable that a concern would exist if
there are many spectral lines close to the limit (i.e.
the spectral density is high).
• Another situation that may result in overdesign
would be to fail a module that only had a few data
points slightly over the limit but otherwise showed
little emissions.
• There are many differences between the module
test setup and the vehicle configuration (e.g.
harness configuration) and it is unlikely that there is
a one to one correlation between the lab and the
vehicle (at each frequency).
• For example, even if a module was below a limit
line using the bench test configuration, in the
vehicle there may be an entirely different
configuration so that those frequencies that were
below the limit line are now connected to a system
which more effectively radiates and results in a
customer concern (and conversely).
© Arnie Nielsen Consulting LLC
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PSD Calculation
If there are narrowband (discrete peaks) emissions
above a Preferred Limit and any peak does not exceed
a defined level (e.g. 6 dB) over this Preferred Limit.
There is a high density of spectral lines near the limit
(e.g. within 3 dB).
1. Consider the data points in terms of (x/L) 2 where x is
the value of the data point in linear terms (uv/m) and L
is the preferred limit at the frequency of the data point.
For example, if a data point is 20dB uv/m (10 uv/m) and
the preferred limit at that frequency is 10dB uv/m (3.2
uv/m), the (x/L) 2 value would be (10/3.2) 2 = 9.8.
The squaring gives exponentially more weight to data
points that are high relative to a preferred limit. It also
gives an indication of spectral power hence the PSD
designation (receivers are sensitive to power impinging
on their antenna).
2. Compute Power Spectral Density (PSD) for a given
frequency span:
PSD = ∑ (x / L) 2 / (Frequency Span / Resolution)
© Arnie Nielsen Consulting LLC
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PSD Example
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Conducted Immunity
© Arnie Nielsen Consulting LLC
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Sampling of OEM Specs - CI
OEM
Test Name
Type
Parameters
Ford,
ES-XW7T-1A278-AC
CI 210
Sine
50-10KHz, stepped
CI 220 A1
CI 220 A2
CI 220 B1
CI 220 B2
CI 220 C
CI220 D-G
CI 230 A-D, Pwr Cyc
CI 260 A-C, Dropout
Transient
Transient
Transient
Transient
Transient
Transient
Complex
Sq Wave
CI 260 D, Dip
Sq Wave
CI 260 E, Bat Recov
CI 260 F, Random
Complex
Complex
Ramp
BMW, GS 95002
Ripple
Sine
50-20k, 1min sweep
BMW, GS 95003-2
Ramp
Engine Start
Dip, Very Brief
Dip, Brief
Complex
Complex
Complex
ISO 7637-2
Ramps, sine
0-Ubmax, 1v/min
ISO Pulse 4
0.5v steps
Hyundai, ES-X82010
Voltage Fluctuaton
Dip
Ramp
Engine Start
Engine Start
Chattering
Ign Key Intermittent
Instantaneous
Interrupt
Triangle
Complex
Triangle
Complex
Complex
Sq Wave
Sq Wave
Sq Wave
8-16v, 1v/sec
Single 100ms dip (ramp)
0-12v, 0.1v/s-1v/min
5-12v
ISO Pulse 4
5 pulses, 10-50ms
5 pulses, 0.5-3s
Single pulses, 1ms-20ms
GMW3172
Voltage Drop
Voltage Dropout
Superimposed Volt
ISO Pulses 1-5
Dips
Complex
Sine
Transients
5% steps from V-min, PW=5 sec
Ramps
Sweep, 2 superimposed, 1-12KHz, 12-72KHz
ISO 7637-2
ISO Pulses 1-5
Transients
ISO 7637-2
Slow volt Inc/Dec
Re-initialization
Micro-interruptions
Triangle
Dips
Dropouts
Starting
Ripple
Complex
Sine
V-nom to 0, 0.5v/min
5% steps from V-nom, PW=5 sec
V-nom to 0v,
PW=10us to 300ms
Ramps, sine
Sweep 50Hz-20KHz
Ripple
Drop Out
Voltage Dip
Low Voltage Mem
Ramp up
Ramp down
Transients
Sine
Dips
Dips
Complex
Complex
Complex
ISO 7637-2
15Hz-250KHz
11 to 0v, 10us-1sec
11 to 5.5-3v, 100us-.5s
Ramp, 12.6v-6.5
Ramp (50mv max step), 0v-Vmax, .1-60sec
Ramp (50mv max step), Vmin-0v
GMW3097,
GMW3100
Nissan,
28401NDS02
DCX, DC 10614
DCX, DC-10615DR2
© Arnie Nielsen Consulting LLC
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Conducted Immunity Observations
•
Majority of contemporary EMC field issues are in
this category.
•
Randomness is good for detecting issues - foreign
to test community.
•
Hot plugging (or missing/late ground) has been
identified as major reason for Electrical Overstress
•
Often misidentified as ESD
•
Bosch SAE paper 2009 (2009-01-0294)
•
USB and OBD (Europe) connectors use
extended ground pins.
© Arnie Nielsen Consulting LLC
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Load Dump
• Most every spec has wrong test simulator.
• Many modules over-designed using typical simulators.
© Arnie Nielsen Consulting LLC
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Load Dump Analysis
© Arnie Nielsen Consulting LLC
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•
Load Dump is a big concern since it exposes
electronic components to very high energy levels
that may cause damage.
•
Due to the sudden disconnection of electrical
load from the alternator while operating without a
battery or a discharged battery.
•
These conditions can exist, for example, with a
loose battery terminal, damaged battery or
during a jump start.
•
A simplified model of the alternator is a voltage
source (Vs) in series with a resistance (function
of Alternator RPM).
•
Vs = Constant * Field current * alternator RPM
•
If there is a sudden disconnection of load
current, the alternator terminal voltage suddenly
increases (voltage drop across alternator
resistance decreases).
•
Duration of this transient is dependent on how
long it takes the field circuit to bring the
alternator into normal voltage regulation (the
time constant of the alternator field coil).
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•
A realistic simulator was determined by building
actual alternator driven by electric motor and
comparing results on actual DUT’s.
•
Historical simulator circuits only looked at energy
equivalency but this model also looked at the Action
Integral.
∫ I 2 dt
•
Historical simulators damaged MOV but actual
alternator did not (although same energy delivered
to MOV)
•
Difference was Action Integral. Simulator built to
give approximate same Action Integral as actual
alternator.
Schaffner simulator = 38 A 2 sec
Actual Alternator = 8
New simulator = 10
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Load Dump Test Procedure
Calibration:
•
Set transient generator to specified voltage with
the DUT disconnected and SW1 open (open
circuit).
•
Verify voltage waveform across R4 - with DUT
disconnected and SW1 closed.
Test:
•
If Central Load Dump is being evaluated, add
alternator zener diode (nominal 33V peak) across
DUT after calibration.
•
All circuits under test shall be exposed
simultaneously (at test fixture). Note that in some
cases this will also subject certain DUT outputs if
they are connected through a load to power.
•
Connect DUT, close SW1 and subject to
specified transients.
•
Functionally test ESC at nominal voltage after
this test.
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ISO 7637
•
Many specs use ISO 7637 for transients
•
ISO 7637 transients too idealized
•
Simulation not real or effective - charge up cap then
discharge through resistor network.
•
Developed in days of ignition breaker points.
•
Out of date, developed over 30 years ago
•
Ford EMC spec only realistic version (in appendix
of latest 7637). Recreates actual mechanism
•
IEEE, 2005, “Comparison of ISO 7637 Transient
Waveforms to Real World Automotive Transient
Phenomena” Keith Frazier, Sheran Alles
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Mechanical Contact Characteristics
1.
2.
3.
4.
5.
6.
7.
8.
9.
Contacts start to move apart.
Switch current suddenly goes to zero.
L current continues dV/dt = I / C
Distance increases and Vf increases.
Rise of Vf slower than rise of V (Mechanical inertia).
Repetitive flashovers occur.
Air breakdown means Switch voltage = 0.
C discharges into network.
Continues until energy dissipated and can’t
flashover.
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Transients - ISO Example
Conclusion = Not realistic simulation
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Inductor Suppression Diode Placement
Near inductor - provides protection for intermittent
wiring harness opens. Worse for Radiated Emissions
(RE). Larger loop area for fast rise/fall times.
Near driver - reduces RE
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SAE J2628 Details
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SAE J2628 (2007) - Characterization,
Conducted Immunity
1. Addresses Major Issues
• Design Margins
• Voltage Interruptions and Transients
• Power Dropouts and Dips
• Current Draw
• Switch Input Noise
2. Existing ISO Type Transients (e.g. ISO 7637) not
realistic or effective.
3. Collaborated with Ford EMC group (Keith Frazier)
to develop realistic simulations.
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SAE J2628, Design Margins
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Design Margins Example
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Chattering Relay Configuration
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Power Cycle, Power Interruptions During
Start-Up (Waveform F)
The purpose of this test is to verify proper DUT startup during ignition key-on (ignition switch or relay
bounce) which can be severe over the full vehicle
temperature range. This is especially important for
verifying proper software initialization.
Relay 2 provides the power on-off cycle and relay 1 is
connected in a chattering configuration to provide the
random noise representing contact bounce at power
up and after.
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Inductive Transients - Pulse A1, A2, C
Pulse A1 and A2 simulates the transients produced by
switching off power to the DUT and an inductive load
(L) that is in parallel with the DUT.
Pulse C is produced by switching off an inductive load
that shares a common power feed with the DUT.
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Inductive Transients - Pulse A1, A2, C
Test
Mode
SW2
Closed = 220 Ω
SW3
Closed = 10nF
SW4
Closed = 6 Ω (Hi Current)
Open = 39 Ω (Lo Current)
1, 2
SW1
Closed = Non
Chattering
Open =
Chattering
Closed
A1
Closed
Closed
Closed
A1-a (1)
1
Open
Open
Open
Closed
A2-1
1
Closed
Open
Open
Open
A2-1, C-1
2
Closed
Open
Open
Open
A2-1, C-1
3
Open
Open
Open
Open
A2-2, C-2
2
Closed
Open
Closed
Open
A2-2, C-2
3
Open
Open
Closed
Open
(1) Special for Development
Mode 1 = 0.2 Hz, 10% Duty Cycle
Mode 2 = Pseudo Random Sequence
Mode 3 = Same as mode 2 but with chattering relay
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A1
A1a - Chattering
A2
C
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Inductive Transients - Pulse B1, B2.
Note: Deleted in Ford EMC-CS-2009
Pulse B1 and B2 simulates low side switching of an
inductive load and applies to DUT signal inputs that
are connected across the switch (e.g. A/C clutch
monitor). The pulse is produced at the start of period
T1 when relay 3 contact opens. R3 provides
adjustment of current through L2 to give different
waveform characteristics (B1 = high current, B2 = low
current).
B1
B2
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SAE J2628 - Power Dropouts, Dips
• Voltage Dropouts - high impedance (open circuit)
typically due to poor connections (e.g. hitting pothole).
• Voltage Dips
• Low impedance most commonly experienced
during engine starting.
• These dips can also occur as a result of a poor
battery connection when a high current load is
activated.
• Voltage dips can also be used to evaluate DUT
voltage regulator input step response by
monitoring the regulator output and looking for
stability (limited overshoot, limited ringing).
•
These waveforms apply to all power supply and
control circuits.
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SAE J2628 – Power Dropout, Dips
Test
Up, U1
3 cycles separated
by 20 s
High
13.5
100us, 300us, 500us,
1ms, 3ms, 5ms, 10ms,
30ms, 50ms
Same as Test A
Acceptance
Criteria
II
Same as Test A
High
II
C
13.5
100us, 200us, 400us
Same as Test A
High
I
D
13.5, 5.0 Same as Test A
Same as Test A
Low
II
A
13.5
B
T (1)
Duration
Impedance
1. Waveform transition time approximately 10us.
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Pulses A, B, C, D
UP
10T
9T
7T
8T
T
2T
0V
UP
10T
0V
T
9T
T
8T
7T
T
T
2T
T
T
T
T
UP
0V
T
UP
10T
U1
T
9T
T
8T
T
7T
T
T
2T
T
T
T T
0V
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SAE J2628 - Current Draw
• Measure True RMS current under various voltages
and temperatures
• Good indicator of:
•
Normal DUT Operation
•
DUT degradation
•
Inadvertent design-manufacturing changes
(conformity)
•
Sneak paths
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System Degradation Example
Switch Input
• Validation typically done with “pristine switches.
Open = infinity, closed = 0 ohms, minimal
switch bounce.
• More realistic test configuration shown below.
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SAE J2628 – Switch Input Noise
• Creates random bounce at switch transitions.
• Includes non ideal switch impedances.
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Electrostatic Discharge
(ESD)
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•
Handling - too many test strikes, cumulative
damage, will only see a few (at most) in the field.
•
ESD is highly variable event - many variables (e.g.
humidity, approach speed, module positioning
above ground plane)
•
Plastic parts hold charge - use air ionizer to
neutralize. Important when testing - subsequent
discharges not like first one due to charge buildup.
•
ESD can cause “walking wounded” - looks OK
after test but fails when exposed to other stress.
•
The order of applying ESD discharges (in total test
sequence) is important.
•
Most methods used for RF Radiated Immunity also
apply to ESD protection.
•
Some mechanical ESD events not tested - e.g.
underhood ESD from belts/pulleys, tire/bearings,
low carbon tires, fuel filter, etc.
•
Hot Plugging shown to be issue - often
misdiagnosed as ESD.
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Spark Gap PCB - Test Configuration
SMD resistor value shift used to determine
effectiveness of gap configurations
Placed on Ground Plane
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Spark Gap Test Results
A. Nielsen, 7Oct2004
10 KV
14 KV
Co nfigu ratio n
To tal # Hits Avg %
S td Dev %
Total # Hits
Avg %
Std Dev %
1
No Spark Gap or Cap
13
10.7
3.7
2
0.005 Air Gap
33
3
2.1
33
4.6
1.9
3
Add MDB
69
0.7
0.5
66
1.1
0.6
4
0.010 Air Gap
33
5.6
2
30
6.7
1.7
5
Add MDB
72
1.1
0.9
72
1.8
1.0
6
0.015 Air Gap
33
6.7
2.4
30
7.8
2.6
7
Add MDB
72
1.3
0.9
72
2.0
0.9
PCB: 4.5 x 6 inch, Ground plane, Multiple gaps ( unused gaps covered with Hum-Seal).
Compound = MDB-06-073, Thermoset encapsulant with adhesion additive.
Resistors = 2010 SMD, 10 K
Measurement = % shift in resistor value.
Test Setups: 1. PCB raised 3/8 inch above bench ground plane. 2. PCB ground connected directly to bench ground plane.
Procedure (Generally, some deviations): 6 hits, replace resistors before going to next set of hits.
Conclusions:
• Spark gaps do provide some protection, especially at
small gaps.
• Protection at practical gap sizes is very limited.
Product may function, but is weakened (walking
wounded).
• Coating spark gap with special compound improves
(also protects for dendritic growth).
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General Test Requirements
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Monitoring
•
Too much monitoring creates its own set of
problems
•
Spend too much time debugging specialized test
software or hardware.
•
Diverts from finding real concerns.
Acceptance Criteria
•
Often too severe or arbitrarily chosen.
•
Majority should be what the customer would
notice not necessarily what the component spec
limits are.
Development Testing
•
Development testing should be done by design
engineer - interactive process, failures are good.
•
Often done without regard to the cost/time/value.
•
Appreciate the need to get to root cause but
sometimes it’s for the sake of satisfying an
engineer’s curiosity and is not a good business
decision.
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Component Test Plan
The quality of event is highly dependent on
preparation. Poor test preparation has historically
resulted in retests and a lot of non-value work.
1.0 Introduction
1.1 Product Family Description
1.2 Theory of Operation
1.3 Physical Construction
1.4 EMC Specification Release
1.5 Approved Test Facility
1.6 Component Part Number(s)
1.7 Component Manufacturer(s)
1.8 Component Usage
2.0 EMC Requirements Analysis
2.1 Critical Interface Signals
2.2 Potential Sources of Emissions
2.3 Component Surrogate selection
3.0 Test Design and Requirements
3.1 Component Operating Modes/Functional
Classifications
3.2 Test Requirements
3.3 Input Requirements
3.4 Output Requirements
3.5 Load Box/Test Support Requirements
4.0 Test Setups
5.0 Test Report Requirements
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Designing PCB for EMC,
Essential Design Rules
(Ref Word Document)
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PCB Layout Examples - Filter Connectors (1980)
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PCB Layout Examples - Radio
Old (many grounds) vs New (one good ground)
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PCB Layout Examples - EEC
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PCB Layout Examples - Cluster
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Supplemental Product Assurance
Information
Product Assurance Robustness
(PAR)
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Key Elements
• Product Assurance Robustness (PAR) Plan
• Specifically designed to address contemporary
Issues. Based on case histories comparing
detection capability of Traditional vs. PAR.
• Similar philosophy to best OEM’s - Focus on
potential weaknesses early.
• Emphasis on Analysis and Development testing Most “Real World’ issues not found in DV.
• Best if multi-discipline analysis by expert(s) who
know what to focus on.
• Use surrogate data to reduce non-value testing.
• Reduce sample size - Allows increased monitoring
and less facilities (allows more focusing on product
and not on test complexity "red herring" issues).
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•
Focused testing and measuring degradation (not just
failures).
•
Addresses system interaction and degradation.
•
Combines EMC and Non EMC environments.
•
If fully implemented, less overall time-cost ( >50 %
possible) and more effective.
•
Viewed as risk since different - actually more rigorous
•
Successfully used on complex programs where no
OEM specs exist (aftermarket) - TacNet (Police),
Dockable Family Entertainment System, etc.
•
Degree of implementation depends on maturity level
(experience) of OEM and Vendor.
•
SAE J1211 revision (2008) and SAE J2628 (2007)
reflects this philosophy.
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Three PAR Stages - Summary
1. Analysis - Requirements, Thermal, Mechanical,
Electrical, Reliability, Referential Data - Use of
experts emphasized (electrical, mechanical, etc) to
focus testing.
2. Development - Formalized testing based on
analysis.
• Besides analysis, this is where real issues are
identified.
• Allows max flexibility to experiment and sufficient
reaction time.
• Stage where failures are good (maximize
information).
• Simple and low cost techniques that requires
minimal lab facilities.
• Uses Product Assurance Robustness (PAR) tester,
Ref SAE J2628
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Development Tests
Type
ID
Name
Description
General
G-10
Internal Inspection
Solder Joints, Connectors, etc
G-20
Functionality
Emphasis on Transition States.
C-10
Design Margins
Ramp Voltage, Upper-Lower Operating
Limits (UOL, LOL) Multiple Temps,
Two Methods (Rigorous, Abbreviated),
Includes C-20.
C-20
Interruptions,
Transients
Power Interruptions, Transients
C-30
Power Dips
Various Pulse Widths and Voltages
C-50
Current Draw
True RMS Current During Power On-Off,
Multiple Temps.
C-60
Overvoltage
True RMS Current at 19v, 24 v, Multiple
Temps.
C-70
Reverse Battery
Current
True RMS Current at -14 v
C-80
Oscillator Function
Momentary Short Oscillator, Verify
Recovery
Characterization
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Development Tests, Cont’d
Type
ID
Name
Description
Failure Modes
FM-10
Shorts to
Power-Ground
0.3 ohms, Monitor Current During Shorts
FM-20
Load Faults
Opens, Partial Shorts in Certain Loads
FM-30
Leakage Resistance All pins = 50K to Power or Ground
FM-40
Sneak Paths, Opens Open Power-Ground to DUT (at DUT)
EMC-10
RF Immunity
Bulk Current Injection (BCI)
EMC-20
Emissions
Current Probe on Harness or AM/FM
Radio
EMC-30
ESD
Pins = +/- 10kv, Controls = +/- 15kv
EMC-40
Crosstalk
Noise From Chattering Relay Coupled by
Parallel Wire
Env-10
Moisture Immunity
Apply Windex Directly to PCB, Verify No
Combustion.
Env-20
Mechanical
Disturbance
Plastic Hammer, Drop (15cm), Flexing of
PCB
Env-30
Resonant Search
Identify Potential Vibration Issues
Env-40
High Temp Exposure Monitor Suspect Hot Points.
Hot Box if Applicable
Env-50
Combined Envir
Exposure
EMC-RF
Environmental
High Temp-Humidity-Shock
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3. Validation - (Qualification, Endurance)
• This is often “Test for Success” oriented - “Feel
Good” testing that can give false sense of
acceptability.
• Specified by customer - Plan depends on OEM
flexibility. Simplify (e.g. surrogate data, focus on
what’s new, etc)
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Traditional vs PAR Summary
Stage
1. Analysis
Traditional
PAR
1. Define Requirements
1. Define Requirements
2. Expertise Distributed – Analysis Piecemeal
2. Multi-Disciplined Perspective (Broad
Experience).
3. Little Synergy to Identify Weaknesses.
3. Identifying Weaknesses Critical - Where
to Focus.
2. Development
1. Not Required or Limited.
1. Main Focus - More Important than DV
2. Waiting for DV to Detect Concerns.
2. Formalized Series of Simple Tests.
3. Low Cost, Minimal Lab Facilities.
4. Typically Takes 3 days.
5. Failure is Good - Maximizes Information
6. Identifies Concerns Early.
3. Validation
1. Cookbook Test Procedures.
1. Small Sample Size.
2. Late in Program
2. More of Systems Approach.
3. Large Sample Sizes.
3. Heavy Use of Surrogate Data.
4. "Test for Success", Feel Good Results.
4. More Focused on Weaknesses.
5. Limited "Play Time" to Find Customer Issues.
5. Key Life Test Looking at Degradation (Not Failure).
6. Software Validation Under Pristine Conditions
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Description
Approach
Surrogate Data
Cost, Test Time
Effectiveness
Test for Success
Sample Size
Monitoring
Test Configuration
Time Compression
where Possible
EMC Testing
Item
1
2
3
4
5
6
7
8
9
10
Done separately
at room temp.
Not applied
sufficiently
Artificial loads,
minimal interfaces
Limited
Large
Majority of tests
Minimal
Expensive, Long
Varies
Traditional
Process
Cookbook
Supplemented by more realistic Conducted Immunity testing
in Development Stage. Reference SAE J2628
Example: Reduce dwell times on thermal cycling/shock.
Measure DUT board temp and set dwells to stabilization + 5
minutes. Use surrogate data to only run the test required to
verify the unknown.
Sub-system with realistic loads and interfaces (allowed by
reduced sample size).
Continuous monitoring (allowed by smaller sample size)
Smaller, reduced facilities with the focus on what’s
needed to verify the unknown.
Some but also generates variable data (test to failure or
measuring degradation).
More effective. Aimed at contemporary issues
Focused on what is unknown.
Potential to reduce by 50% or more.
Maximize to reduce non value testing.
Tailored test plan utilizing historical data, analysis and
development testing to focus on potential product
weaknesses and changes.
Intelligent Testing Process
Actual Example Plan
Note - Although PAR much shorter, plan is better
(customized to address many issues not in original)
OEM Original Request
PAR - OEM Approved
Analysis
Moderate
Similar but also Developed
Focused Test Plan
Development Test Time
No
24 hr (3 X 8 hr)
DV Sample Size
12
6
DV Cumulative Test Time
3000 hr
400 hr
Key Life Test Time
4800 hr
300 hr
Overall Total Test Time
7800 hr
700
Note: software validation,
EMC additional
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PAR Support Hardware
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Product Assurance Robustness (PAR) Tester
•
Based on real world issues often missed in typical
Product Assurance/Validation process.
•
Uses simple, low cost techniques and includes many
functions in one package (does not require a test
laboratory environment).
•
Makes it practical for Hardware-Software Robustness
and Design Margin testing throughout the design
process. Enables early detection of issues and a
lean testing process.
•
Capability to do many OEM, ISO, etc Conducted
Immunity EMC tests.
•
Recreates “real world” transient events (unlike the
unrealistic simulations of ISO 7637).
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PAR Tester Cont’d
•
Creates other waveforms via a 2 channel Arbitrary
Waveform Generator (AWG) and 2 channel DC power
amplifier. Fast waveforms use the Electronic Switch
module.
•
Evaluates non ideal DUT switch signal inputs via a 4
channel switch simulator that creates random noise
on switch transitions. Also simulates non ideal switch
impedances.
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1. DC Power Amplifiers:
a. Power Op Amps - switching power supplies.
b. 0-20 KHz, 0-24 volts.
c. Two Channels (150 and 50 watts)
2. Arbitrary Waveform Generator (AWG):
a. 2 channels
b. PC Controlled via USB
c. Easy to use waveform editor.
3. Electronic Switch, DC voltage source
a. 1us rise/fall time
b. Capability = 10 amps
c. Voltage Source = 1.5 - 20 volts, 1.5 amp (Higher
currents available via DC Amp)
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4. Transient Generator: Uses inductors and relays
(including chattering relay) to simulate vehicle
Transients per SAE J2628 and Ford EMC spec.
5. Switch Noise Simulator:
a. Creates random bounce at switch transitions
(adjustable)
b. 4 channels, separate or simultaneous activation.
c. Includes non ideal switch impedances.
Contents: Rack Assembly, Enclosure (pull handle,
wheels), DC Amps, Electronic Switch, Switch Noise
Simulator, Transient Generator, AWG, Waveform files,
User manual. Weight approx 30 lbs
Contact:
Arnie Nielsen, (248) 305-8264, [email protected]
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