more than 30 years, the automotive industry has been accustomed
to the e-mark and type approval of motor vehicles sold into the
European Union. Since October 1, 2002, however, manufacturers
of aftermarket electronic
1. Example of an e-mark.
intended for use in vehicles were also required to obtain formal
type approval for these products prior to placing them on the
market. All such products are required to carry an e-mark and
to comply with European vehicle legislation in order to be legally
fitted inside a vehicle.
testing and approvals regime required for e-marking is very different
from that normal for CE marking. This has come as a surprise to
some electronics manufacturers more familiar with the latter.
This article attempts to provide a basic understanding of e-marking
automotive electronic products, principally to readers already
familiar with the process of CE marking electronic goods, particularly
information technology (IT) products.
Since 1970, cars and trailers sold in Europe have required formal
type approval and e-marking.1 On January 1, 1996, European
Commission Directive 95/54/EC extended these requirements to cover
in-vehicle electronic subassemblies (ESAs) by defining acceptable
4 The Netherlands
I. Codes for member states granting the type approvals.
criteria for the electromagnetic emissions and susceptibility
of such devices.2
the directive, ESAs are defined in two distinct groups: (i) components
and (ii) separate technical units (STUs). STUs are specific to
a given make of vehicle and are usually fitted by the vehicle
manufacturer. Aftermarket electronic products fall into the category
termed components that may be fitted to differing makes and models
of vehicles. Article 2 of 95/54/EC requires all ESAs to comply
with the legislation and to be appropriately e-marked.
October 1, 2002, member states may refuse the sale or entry into
service of noncompliant or improperly marked products. Specifically
in the UK, national implementation of 95/54/EC into the nation's
EMC limits and test methods all defined in legislation
Develop compliant product.
Submit product for formal type approval.
Apply e-mark and sell.
Select appropriate EMCcriterion, identify applicableEMC
standards, decide on route to compliance.
Develop compliant product.
Submit TFC, submit for third-party testing.
conformity, apply CE mark, and sell.
95/54/EC is the core directive for vehicles. Additional
European legislation applies to some classes of vehicles;
for example, for motorcycles apply 97/24/EC, for tractors
apply directive 2000/2/EC.
Optional, depending on chosen route to compliance.
II. Comparison of the CE marking and e-marking processes
Use regulations has made it a criminal offense to use a car with
a non-e-marked part fitted. It is essential, therefore, for manufacturers
of aftermarket electronic products intended for vehicle use to
comply with the regulations.
example of an e-mark is shown in Figure 1. It comprises the lowercase
letter e followed by a country code number in a square box. The
number identifies the EU member state granting type approval (see
Table I). The major difference between e-marking and CE marking
is the route to approval. For CE marking, manufacturer self-declaration
is the norm, whereas the only route to compliance with the Automotive
Directive is formal type approval. Each of the EU member states
listed in Table I has a national body responsible for issuing
type approval certificates. In the UK, for example, this body
is the Vehicle Certification Agency (VCA).3
number placed adjacent to the e-mark in Figure 1 is the base approval
number issued by the approval body and printed on the type approval
certificate. The first two digits indicate the sequence number
assigned to the most recent amendment of directive 72/245/EEC.4
For the Automotive Directive 95/54/EC, the sequence number is
2. ESA EM radiation limits.
EEC type-approval mark must be affixed to the main body of an
ESA in such a way that it is clearly legible and indelible. It
need not be visible once the ESA is fitted within a vehicle.
e-Marking Process for ESAs
must comply with myriad legislation covering such areas as environmental
impact, road safety, and crash protection (to name but a few),
whereas e-marking for aftermarket ESAs is all about electromagnetic
compatibility (EMC). Table II contrasts the processes of compliance
between the Automotive and EMC Directives.5
with the EMC Directive usually involves selecting and applying
standards from the ever-growing, ever-changing list published
in the Official Journal of the European Communities. For the Automotive
Directive, the process is simplified (in principle) because the
directive contains within it all the test methods and limits necessary
and their representatives should note, however, that 95/54/EC
compliance does not absolve them from compliance with other applicable
European legislation. For example, a product that can be fitted
in a vehicle or used at home must comply with both the Automotive
and EMC Directives. If a product contains a radio transmitter,
it must also comply with the R&TTE Directive, and so on. In
all cases, a product must be safe when used as intended and should
not impair a driver's ability to properly control the vehicle.
and Test Methods
within the body of the Automotive Directive are the test methods
and limits applicable to the electromagnetic emissions and susceptibility
of both vehicles and ESAs. The test method for ESAs is based on
CISPR 25 and differs considerably from the familiar EN 55022 and
EN 55024, as the following comparison shows.68
Emissions. The Automotive Directive 95/54/EC contains no requirement
to test the conducted emissions from automotive ESAs. This is
because the legislation for ESAs is derived from that for vehicles
and vehicles don't normally feature connecting cables. The argument
placed 50 mm above fixed table with conducting surface,
1 m above reference plane (ground plane).
placed on nonconducting,rotating table 800 mm abovereference
plane (ground plane).
antenna site 1
m from EUT.
antenna site10 m from EUT (or 3 m and results extrapolated
to 10 m).
fixed throughout test.
rotated 360° during test.
antenna height fixed
antenna height varied
from 1 to 4 m during test.
antenna pointed at midpoint of wiring loom connected
antenna pointed at EUT.
product classes (A and B) with different limit lines.
emission types (broadband and narrowband) with different
limit line applies to allemissions.
and quasi-peak detectors used for narrowband and broadband
detector only used.
supplied via AN (artificial network).
supplied via LISN (line impedance stabilization network).
III. Major differences in test methods between 95/54/EC and
may pollute the wiring it is connected to is apparently ignored.
Given that a vehicle wiring loom is an electrically noisy item,
vehicle manufacturers have traditionally employed the opposite
logic, namely that ESAs should demonstrate a high level of immunity
to conducted interference.
Emissions. Testing of ESAs is described in Sections 6.5 and
6.6 of the Automotive Directive. Specifically, Annexes VII and
VIII describe the test method. The differences compared with EN
55022 are shown in Table III.
limit line used for ESA-radiated emissions (see Figure 2) not
only differs from that used for vehicles but also differs considerably
from the EN 55022 limit line. The directive gives two limits,
one for broadband and another for narrow-band emissions. The concept
of broadband and narrowband emissions may be foreign to those
unfamiliar with automotive testing. Individual emissions are classified
as either narrowband or broadband, depending on their appearance.
Broadband emissions are those characteristic of spark ignition
systems, and narrowband emissions are those characteristic of
microprocessor-based systems. More detail can be found in CISPR
25 Clauses 4.1.4 and 4.1.5.
EN 55022, no distinction is made between EUT classes, and so the
same EUT in the same configuration is tested first against the
broadband and then the narrowband limit.
emissions are very spiky and occur at the harmonic frequencies
of the clocks used in the circuitry contained within the ESA.
This author uses the rule that any other type of emission is broadband.
3. Example of ESA being tested at RadioCAD's Cowden facility.
wishing to be cautious will ensure that all emissions fall well
below the narrowband limit, irrespective of classification. Generally,
free-running, switched-mode power supplies are the most common
source of broadband-type emissions in aftermarket ESAs.
of ESAs with no oscillators operating above 9 kHz can use Clause
8.1, exempting them from narrowband testing altogether. Figure
3 shows an example of an ESA being tested.
Susceptibility. Clauses 8.4 and 8.5 exempt ESAs from having
to meet any specific conducted susceptibility or electrostatic
discharge (ESD) criteria. The legislation places the onus on vehicle
manufacturers to ensure that ESAs are properly immune to conducted
interference. Traditionally, vehicle manufacturers have placed
strict immunity requirements on component suppliers as part of
the procurement process.
of aftermarket ESAs might be tempted to skip susceptibility testing
altogether because there is no legal requirement for it. However,
it is foolhardy to do so. The wiring loom of the average car frequently
generates conducted phenomena far more severe than those encountered
by domestic and commercial electronic products. In the sidebar
on page 42, a good practice is recommended for self-respecting
manufacturers to adopt.
Susceptibility. The radiated immunity requirement for automotive
ESAs is considerably more onerous than for IT products. For example,
the field strength specified for free-field immunity testing is
30 V/m compared with the 3 V/m for EN 55024 Class B. Given the
difficulty in generating uniform fields of this intensity, 95/54/EC
gives three other alternative test methods: stripline, transverse
electromagnetic (TEM), and bulk current injection (BCI). Clause
1.2.1 of Annex IX allows manufacturers full discretion in choosing
which methods to apply, provided that the full frequency range
from 20 MHz to 1 GHz is covered by the chosen method or combination
of methods. Of these methods, stripline is most popular. It is
relatively easy to generate high field strengths over a wide frequency
range with comparatively small amplifiers. Most manufacturers
of aftermarket ESAs dispense with all radiated susceptibility
testing by employing Clause 8.3 of the directive, which states
whose functions are not involved in the direct control of the
vehicle need not be tested for immunity and shall be deemed to
comply with paragraph 6.7 of Annex I and with Annex IX to this
should be noted, however, that vehicle manufacturers procuring
components that do affect the driver's control of the vehicle,
(e.g., antilock braking systems [ABS]), generally insist on much
higher field strengths. Immunity to 100 V/m is a common requirement.
A Design Example: 12-V Transient Suppression
7637 defi es that the test pulse shown on the left in
Figure 1 be introduced to the EUT battery input via a
series resistor Ri where 0.5 W
< Ri < 4 W.12
This example has added a transorb and an in-line current
limiting resistor RL.
1. Transorb design example.
transorb must be chosen with a break voltage higher than
the charging voltage of the 12-V system. The nominal alternator
charging voltage for a 12-V system is 13.5 V. A 12-V transorb
has a break voltage of 13.3 V. Therefore, a 13-V device
is chosen with a break voltage of 14.4 V to provide some
severity level III, Vp (the peak
transient voltage) is 80 V (Vs +
13.5). For a 13-V transorb, Vc (the
clamping voltage) is about 21.5 V, specified at a current
Ic derived from the device's peak
power Pp (see Table I). Note that
the protected electronics still must safely handle voltages
up to the clamping voltage.
I. Comparison of surface-mount transorbs.
Ic is used to determine a suitable
line resistance. Assume the EUT takes nominally 1 A and
can tolerate a voltage drop of up to 2.5 V across RL.
Therefore, RL = 2.2 W might
be chosen, and an SMBJ13 transorb is specified.
remainder of the example demonstrates that the selection
just made affords woefully inadequate protection. Firstly,
the transient peak power Pp is given
approximation (Pp) is good if the
pulse rise and fall waveforms are roughly linear. In a
system where the fall time dominates, a linear approximation
is more severe than a logarithmic one, giving some safety
margin in the design.
notice that transorb manufacturers quote Pp
for a 1-millisecond pulse. The ISO 7637 load-dump pulse
duration, however, varies from 40 to 400 milliseconds and,
therefore, the transorb power handling has to be derated
using the manufacturer's data. For example, at td
= 100 milliseconds, the SMBJ13's peak power rating falls
to just 38 W.
compensate, rearrange Equation 1, and plug in a value of
Pp = 38 W to obtain Ri:
problem with this arrangement is that ISO 7637 states that
Ri must be 4 W or less. Reducing
Ri will increase the peak transient
power beyond the absolute maximum limits of the selected
transorb. This, in turn, leads to device rupture and the
ESA becoming unprotected from the remainder of the lethal
achieve proper protection, the example requires not one
but two 1500-W SMCJ13 devices in parallel. This gives a
combined Pp @ 100 milliseconds of
188 W and allows Ri to fall as low
as 1.1 W without overstressing the transient protection
circuit. There is some room
now to trade the values of Ri and
RL to reduce the undesirable voltage
drop developed across RL during normal
nothing else, the exercise demonstrates just how rugged
ESAs must be to survive in the automotive environment.
an ESA for Type Approval
manufacturers have an ESA they believe is compliant with 95/54/EC,
the formal type-approval process must begin before that product
can be sold into the EU market. The following assumes that the
United Kingdom VCA has been selected to issue the approval. The
UK VCA publishes guidance notes for manufacturers seeking type
approval. To start the type approval process, manufacturers may
contact the VCA directly.9 Most manufacturers, however,
start by contacting an independent test laboratory recognized
by VCA.10 These may or may not be designated by VCA
as a technical service. Although any competent test house or consultant
can guide a manufacturer through the approval process, only a
technical service is authorized to act on behalf of VCA.
designated technical service or a VCA official will witness formal
testing at the selected laboratory and will ensure that the test
sample and its arrangement are set up for the worst-case condition.
Worst-case selection, particularly with products offered in a
number of variant configurations, alleviates the need to test
all possible permutations. Manufacturers may be required to present
their own EMC test results to assist in worst-case selection.
Manufacturers must submit product documentation in support of
an application. The documentation required is listed in Annex
IIB of the directive 95/54/EC. For successful applications, VCA
issues a type approval certificate containing the base approval
number that the manufacturer will use with the e-mark. VCA asks
for evidence of conformity of production, ensuring that the sample
tested is representative of the mass-produced product. Generally,
production by an ISO 9002 certified factory is taken as
sufficient evidence, although control plans dealing with specific
issues may be needed in addition.
manufacturers also ask for approval to UN-ECE Regulation 10.02,
which is practically identical to 95/54/EC and is accepted by
a large number of countries outside Europe. The difference in
marking is that the UN mark is a capital E whereas the European
mark is a lowercase e. VCA or a designated technical service can
advise on this and other applicable vehicle-legislation issues.
previously mentioned, the Automotive Directive doesn't stipulate
any requirements for the conducted susceptibility of ESAs. Although
not a legal requirement, self-respecting manufacturers will want
to ensure that their products are fit for use inside a vehicle.
They should, therefore, design and test for immunity to conducted
transients and ESD. The International Organization for Standardization
(ISO) publishes suitable standards for automotive transients and
discharges up to 25 kV, ISO 10605, the ESD standard, is significantly
more severe than the generic IT standard.11 Anyone
who has slid in or out of the driver's seat on a dry day can testify,
however, that vehicle static discharge is a prevalent menace.
Therefore, ISO 10605 seems, to this author at least, reasonable.
7637, the conducted-transient standard, is split into three parts:12
1 and 2 are almost identical, with the same set of transient tests
defined in both, except that the 24-V transients are more severe
and part 2 adds an extra test pulse 1b. Test pulses 1 and 2 are
pretty straightforward switching transients. Pulse 3 is a fast
transient such as what might be generated in mechanical switching.
It is applied directly to the dc power source in Parts 1 and 2,
and indirectly via a coupling clamp in Part 3. The author, experienced
with designing for immunity to transients, found that none of
these pulses presented much of a problem in designing for immunity.
Textbook EMC techniques can readily be used to provide sufficient
4 simulates battery dip during starting. Most ESAs containing
microprocessors reset during the application of this pulse. For
Class C ESAs, a reset during exposure is not a failure, provided
that the EUT recovers following the test. Annex A of ISO 7367
describes the functional classes and severity levels.
author recommends that severity level III, Class C, be applied
in the absence of a specific requirement. Note, however, that
some continental vehicle manufacturers are now suggesting that
ISO 7637, severity level IV, be called up in revisions currently
under consideration to 95/54/EC.
5, the load dump pulse, is a notoriously severe overvoltage surge
peculiar to ISO 7637. The pulse simulates a car battery being
disconnected from a spinning alternator and the resulting long-duration,
high-voltage surge introduced into the 12-V supply line. It is,
therefore, both a reasonably realistic transient and one that
often spectacularly destroys unprotected ESAs.
6 and 7 apply to electronic ignition systems and historic vehicles,
respectively. These are generally ignored.
Dump Protection. Fitting transorb transient suppressors to the
supply line as it enters the ESA is the usual method of providing
load dump protection. Because the load dump pulse is very high
energy, it is essential to design transient suppression circuits
carefully (see example in the sidebar). An alternative method
(used successfully by the author) is the rider circuit. This method
disconnects the ESA electronics from the supply for the duration
of the pulse, which effectively rides out the stormhence,
thanks to Terry Beadman of MIRA UK for his assistance in producing
this article. He can be reached at firstname.lastname@example.org.
"Council Directive on the approximation of the laws of member
states relating to the type approval of motor vehicles and their
trailers," Official Journal of the European Communities (OJ),
no. L 42, 23/2/1970.
"Commission Directive adapting to technical progress Council Directive
72/245/EEC and amending Directive 70/156/EEC," OJ, no.
L 266, 08/11/1995.
Certification Agency, http://www.vca.gov.uk/noframes/
"Council Directive on the approximation of the laws of member
states relating to the suppression of radio interference produced
by spark-ignition engines fitted to motor vehicles," OJ,
no. L 152, 6/7/1972.
"Council Directive on the approximation of the laws of the member
states relating to electromagnetic compatibility," OJ,
no. L 139, 3/5/1989.
25, "Radio disturbance characteristics for the protection of receivers
used on board vehicles, boats, and on devicesLimits and
methods of measurement," International Electrotechnical Commission
55022:1998, "Information technology equipmentRadio disturbance
characteristicsLimits and methods of measurement," CENELEC,
55024:1998, "Information technology equipmentImmunity characteristicsLimits
and methods of measurement," CENELEC, Brussels, 1998.
Type Approval for Electromagnetic Compatibility," VCA Pub TA045,
Revision 4, May 1, 2002, http://www.
"Test Facilities Suitable for Automotive EMC Tests to 95/54/EC,"
VCA Pub TA054, Issue 6, December 11, 2002, http://www.
10605, "Road vehicles, Test methods for electrical disturbances
from electrostatic discharge" (Geneva: International Organization
for Standardization: 2001).
7637, "Road vehicles, Electrical disturbances from conduction
and coupling; Part 1: Passenger cars and light commercial vehicles
with nominal 12 V supply voltage Electrical transient conduction
along supply lines only," 1990; "Part 2: Commercial vehicles with
nominal 24 V supply voltageElectrical transient conduction
along supply lines only," 1990; "Part 3: Vehicles with nominal
12 V or 24 V supply voltageElectrical transient transmission
by capacitive and inductive coupling via lines other than supply
lines," 1995 (Geneva: International Organization for Standardization).
Jarvis is an independent consultant. His company, RadioCAD (www.radiocad.com),
assists clients in designing electronic products for compliance
with European directives and worldwide standards. Jarvis has worked
in the electronics industry since 1983 and specializes in RF design
and EMC. He can be reached at