EMC FLEX BLOG A site dedicated to Automotive EMC Testing for Electronic Modules

CISPR 25:2021 6.4.3 Test procedure ... The current probe shall be mounted around the complete harness (including all wires). If the EUT has multiple connectors on the unit resulting in multiple wire bundles, the test plan shall define which wires shall be included in the probe for measurement. In the absence of any definition, measurements shall be made for each bundle (connector) separately as well as combined (i.e. all together).

CISPR 25:2021 6.4.2.2 Location of the test harness: …. The test harness wires shall be nominally parallel and adjacent unless otherwise defined in the test plan.

We normally want to capture noise from wire-to-wire coupling, that’s why all wiring must run parallel and adjacent along the test harness except for the portion of wire/connector with CE-I probe clamped on it. Scenario #1 below shows the correct test harness and wiring layout.

Scenario #2 is incorrect since CISPR 25 require "parallel and adjacent" wiring. CISPR 25 does not define a minimum or maximum distance between the wires included in the test harness.

Christian Rosu

The goal is to EMC validate DUT's Hardware Design assuming that DUT's Software was developed to serve the DUT's Hardware. Following a successful EMC validation, the DUT software may be subject to multipe updates and upgrades to serve the original hardware design w/o altering the outcome of overall product EMC validation.

DUT's software is used to exercise and monitor I/O lines and functions. The use of DUT production software should not be mandatory since may not be finalized prior to validation. The use of specialized DUT software is recommended since the production software may not be efficient enough to otimize the EMC testing time. The use of specialized DUT software is allowed provided that:

1) SW diagnostic timers are set to minimum detection values such that during the maximum 2-second RF exposure time all DUT response error flags are being captured and reported. Using production intent software would extend the DUT activation dwell time beyond 10 seconds such that long duation functions and/or sequential activation of various functions becomes possible.

2) DUT's state and fault conditions are reported directly via communication bus or indirectly via cyclying the outputs (e.g. changes to PWM duty cycle, monitoring LED flash rate, inadvertent status change).

3) DUT monitored data, I/O status values, analog input voltages, operating state are queried via parameter requests to ensure bi-directional communication during RF Immunity. Monitoring functional status via DUT scheduled or periodic broadcast messges is not recommended.

Module to Vehicle Interface Connector and User Interface I/O

• directly via communication bus
• indirectly via cyclying the outputs (e.g. changes to PWM duty cycle, monitoring LED flash rate, inadvertent status change) 

• directly via Fiber Optic system
• indirectly via loop back method (e.g. monitoring the simulated load using a DUT input)

• directly via communication bus
• indirectly via cyclying the outputs (e.g. changes to PWM duty cycle, monitoring LED flash rate, inadvertent status change).

• directly via Fiber Optic system
• indirectly via loop back method (e.g. monitoring the simulated load using a DUT input)

• The analog properties of the bus electrical signal (e.g. V_dominant, V_recessive, etc. must be validated during RF immunity.
• This may require special software to decrease the data rate to be within the bandwidth limitations of analog fiber-optic transmitters.

• Received signals must be set to 3 dB above specified minimum sensitivity level.
• The RF level is to be established with DUT installed in test chamber.
• Bit Error Rate (BER) is the preferred metric with an acceptance threshold set by RF device specifications. 
• BER must be monitored directly through the communication bus via parameter requests (never via scheduled, or periodic, broadcast messages).
• Transmitted signals must be monitored by an appropriate RF receiver, again monitoring BER, acceptable threshold set by RF device specifications.

MCU Connector “Internal” I/O 

• MCU Analog Input is set to nominal operating value/condition for the specified test mode with the value reported either directly via the DUT communications bus or, indirectly through the DUT monitoring the input and changing the state of an output in a known, pre-determined manner. These functions are based on internal Printed Circuit Board (PCB) operating conditions and are not expected to
  be controlled or changed during testing; it is not necessary to force a mid-value for these inputs as with vehicle harness interface I/O.
• Digital Input - Non-dynamic (Steady State I/O). Examples include feedback fault indication, over/under current monitoring via discrete comparator circuit, etc. The input is set to the nominal operating value/condition for the specified test mode with the value reported either directly via the DUT communications bus or, indirectly through the DUT monitoring the input and establishing the state of an output in a known, pre-determined manner. Not to include reset, address/data lines and communication between the microprocessor and electronically erasable programmable read-only memory (EEPROM), etc.
• Digital State Input - Dynamic Cycling I/O. Requires state change between asserted to non-asserted back to asserted states during radiated immunity RF “on” exposure, reported directly by communication or indicate indirectly via output state change by detected input. Reset, address/data lines and communication between the micro and EEPROM are not included. The following MCU I/O types do not require direct monitoring since are indirectly monitored by the inherent operation of the device: Discrete outputs, Analog outputs, Internal communication bus.

Christian Rosu

Reference: Automotive OEM EMC specs

The latest revision of CISPR 25 is looking into various types of Artificial Networks used in today's automotive EMC.

1. Artificial Network (AN): used for LV power supplies;
2. High Voltage Artificial Network (HV-AN): used for high voltage d.c. power supplies;
3. Direct Current charging Artificial Network (DC-charging-AN): used for d.c. power supplies;
4. Artificial Mains Network (AMN): used for a.c. power mains;
5. Asymmetric Artificial Network (AAN): used for signal/control port lines and/or wired network port lines.

1. Artificial Network (AN)

Measurement ports of HV-AN(s) must be terminated with a 50 Ω load. The HV-AN impedance ZPB (tolerance ± 20 %) in the measurement frequency range of 0.1 MHz to 100 MHz. This table above shows the nominal impedance and upper/lower tolerances in tabular form. It is measured between the EUT HV and ground terminals with a 50 Ω load on the measurement port and with the supply line HV and ground terminals short circuited.

2. High Voltage Artificial Network (HV-AN)

3. Direct Current charging Artificial Network (DC-charging-AN)

4. Artificial Mains Network (AMN)

Power mains must be applied to the vehicle through 50 μH/50 Ω AMN(s). The DC resistance between the ground of the AMN measurement port and the ground plane must not exceed 2,5 mΩ.

5. Asymmetric Artificial Network (AAN)

Christian Rosu

2021-06-22

An incorrect DUT grounding scheme can easily make the difference between compliance and non-compliance to CISPR 25 CEI limits. Sometimes we have to evaluate CEI from two modules, one used as DUT and the other one used as DUT's load (e.g. Module #1 is a PWM maker while Module #2 is an LEDs Lamp).

Christian Rosu, 2021-06-09

A/C = Air Conditioning
A/F = Air/Fuel Ratio
A/T = Automatic Transmission or Transaxle
ABS = Antilock Braking System
ABSV = Air Bypass Solenoid Valve
AC = Alternating Current
ACTS = Air Charge Temperature Sensor
AFC = Air Flow Control
AFM = Air Flow Meter
AFS = Air Flow Sensor
ALCL = Assembly Line Communications Link
ALDL = Assembly Line Data Link
APS = Absolute Pressure Sensor
APS = Atmospheric Pressure Sensor
ASDM = Airbag System Diagnostic Module
ATDC = After Top Dead Centre
ATF = Automatic Transmission Fluid
ATS = Air Temperature Sensor
AWD = All Wheel Drive

B+ = Battery Positive Voltage
BARO = Barometric Pressure
BAT = Battery
BCM = Body Control Module
BHP = Brake Horse Power
BMAP = Barometric/Manifold Absolute Pressure Sensor
BPS = Back pressure Sensor
BPT = Back Pressure Transducer
BTDC = Before Top Dead Centre
Btu = British Thermal Units

C = Celsius
C3I = Computer Controlled Coil Ignition
CALPAK = Calibration Pack
CAN = Controller Area Network
CANP = Canister Purge Solenoid Valve
CAS = Crank Angle Sensor
CC = Cubic Centimetres
CDI = Capacitor Discharge Ignition
CEAB = Cold Engine Air Bleed
CECU = Central Electronic Control Unit
CER = Cold Enrichment Rod
CESS = Cold Engine Sensor Switch
CFI = Central Fuel Injection
CFI = Continuous Fuel Injection
cfm = Cubic Feet Per Minute
CID = cylinder identification sensor
CID = Cubic Inch Displacement
CIS = Continuous Injection System
CKP = Crankshaft Position Sensor
CMP = Camshaft Position Sensor
CO = Carbon Monoxide

CO2 = Carbon Dioxide

COP = Coil On Plug ignition

CPI = Central Port Injection

CPU = Central Processing Unit

CSSA = Cold Start Spark Advance

CSSH = Cold Start Spark Hold

CTS = Coolant Temperature Sensor

CTVS = Choke Thermal Vacuum Switch

CVR = Control Vacuum Regulator

dB = Decibels

DC = Direct Current

DEFI = Digital Electronic Fuel Injection

DFS = Deceleration Fuel Shutoff

DIS = Distributorless Ignition System

DIS = Direct Ignition System

DLC = Data Link Connector

DOHC = Double OverHead Camshaft

DTC = Diagnostic Trouble Code

DVOM = Digital Volt Ohm Meter

E2PROM = Electrically Erasable Programmable Read Only Memory

EACV = Electronic Air Control Valve

EBCM = Electronic Brake Control

Module EBM = Electronic Body Module

ECA = Electronic Control Assembly

ECM = Engine Control Module

ECT = Engine Coolant Temperature

ECU = Electronic Control Unit

EDIS = Electronic Distributorless Ignition System

EEPROM = Electronically Erasable Programmable Read Only Memory

E2PROM = Electronically Erasable Programmable Read Only Memory

EFC = Electronic Fuel Control

EFCA = Electronic Fuel Control Assembly

EFI = Electronic Fuel Injection

EGO = Exhaust Gas Oxygen Sensor

EGR = Exhaust Gas Recirculation

EGRPS = EGR Valve Position Sensor

EGRT = EGR Temperature

EI = Electronic Ignition

EMI = Electromagnetic Interference

EMR = Electronic Module Retard

EOS = Exhaust Oxygen Sensor

EOBD = European Onboard Diagnostics

EPOS = EGR Valve Position Sensor

EPROM = Erasable Programmable Read Only Memory (chip)

ESC = Electronic Spark Control

EST = Electronic Spark Timing

EVAP = Evaporative Emission System

EVP = EGR Valve Position Sensor

F = Fahrenheit

FBC = Feedback Carburettor System

FBCA = Feedback Carburettor Actuator

FCS = Fuel Control Solenoid

FDC = Fuel Deceleration Valve

FI = Fuel Injection

FLS = Fluid Level Sensor

ft.lb. = Foot Pound

FWD = Front-Wheel Drive

gal = Gallon

GDI = Gasoline Direct Injection

GEN = Generator

GND = Ground

GPM = Grams Per Mile

GVW = Gross Vehicle Weight

H20 = Water HC = Hydrocarbon

HEGO = Heated Exhaust Gas Oxygen Sensor

HEI = High Energy Ignition

Hg = Mercury

HO2S = Heated Oxygen Sensor

hp = Horsepower

HT = High Tension

IAC = Idle Air Control

IAT = Intake Air Temperature

IATS = Intake Air Temperature Sensor

IC = Integrated Circuit

ICM = Ignition Control Module

ICS = Idle Control Solenoid

ID = Inside Diameter

IFI = Indirect Fuel Injection

IGN = Ignition

ISC = Idle Speed Control

ISO = International Standards Organization

ITCS = Ignition Timing Control System

ITS = Idle Tracking Switch

JAS = Jet Air System kHz = Kilohertz

Km = Kilometres

KOEC = "Key On, Engine Cranking"

KOEO = "Key On, Engine Off"

KOER = "Key On, Engine Running"

kPa = Kilopascals

KS = Knock Sensor

KV = Kilovolts

L = Litres lb.

ft. = Pound Feet

LCD = Liquid Crystal Display

LED = Light Emitting Diode

LHD = Left-Hand Drive

LTFT = Long Term Fuel Trim

LWB = Long Wheel-Base

MAF = Mass Air Flow

MAP = Manifold Absolute Pressure

MAT = Manifold Air Temperature

MCS = Mixture Control Solenoid

MCT = Manifold Charge Temperature

MFI = Multi Port Fuel Injection

MIL = Malfunction Indicator Light

mm = Millimetres

MPFI = Multi Point Fuel Injection

MPG = Miles Per Gallon

MPH = Miles Per Hour

MPI = Multi Port Injection

MPV = Multi-Purpose Vehicle
ms = Millisecond

mV = Millivolts
Nm = Newton Metres

NOX = Oxides of Nitrogen
NVRAM = Nonvolatile Random Access Memory

O2 = Oxygen
O2S = Oxygen Sensor
OBD = Onboard Diagnostics
OBD I = Onboard Diagnostics One

OBD II = Onboard Diagnostics Two

OD = Outside Diameter
OE = Original Equipment
OEM = Original Equipment Manufacturer

OHC = OverHead Camshaft
OHV = OverHead Valve

OS = Oxygen Sensor

P/B = Power Bakes
P/N = Part Number

PA = Pressure Air
PAIR = Pulsed Secondary Air Injection

PAS = Power-Assisted Steering
PCM = Powertrain Control Module

PCV = Positive Crankcase Ventilation
PECV = Power Enrichment Control Valve

PFI = Port Fuel Injection
PID = Parameter ID
PIP = Profile ignition pickup

PNP = Park/Neutral Switch

PPM = Parts Per Million
PROM = Program Read Only Memory (chip)

PS = Power Steering
PSI = Pounds Per Square Inch

PSP = Power Steering Pressure

pt. = Pint
PTC = Pending Trouble Code

PWR = Power to Weight Ratio

Qt. = Quart
RAM = Random Access Memory

RFI = Radio Frequency Interference

RHD = Right-Hand Drive
ROM = Read Only Memory

RON = Rated Octane Number

RPM = Revolutions Per Minute

RWD = Rear-Wheel Drive
SC = Supercharged
SEFI = Sequential Electronic Fuel Injection

SES = Service Engine Soon (light)
SFI = Sequential Fuel Injection
SIPS = Side Impact Protection System

SOHC = Single Over Head Camshaft

SRS = Secondary Restraint System
SRS = Supplemental Restraint System (air bag)

SRT = System Readiness Test
SS = Speed Sensor
SSI = Solid State Ignition

STFT = Short Term Fuel Trim
SWB = Short Wheel-Base

TACH = Tachometer
TB = Throttle Body
TBI = Throttle Body Injection

TC = Turbocharged
TCC = Torque Converter Clutch
TCM = Transmission or Transaxle Control Module

TD = Turbo Diesel
TDC = Top Dead Centre
TDI = Turbo Direct Injection (A turbo charged direct injected diesel engine)

TIV = Thermactor Idle Vacuum Valve
TKS = Throttle Kicker Solenoid

TPI = Tuned Port Injection
TPP = Throttle Position Potentiometer

TPS = Throttle Position Sensor
TPT = Throttle Position Transducer

TSP = Throttle Solenoid Positioner

TV = Throttle Valve
TVS = Thermal Vacuum Switch

TWC = Three Way Catalyst
TWC+OC = Three Way + Oxidation Catalytic Converter

V = Volts
VAC = Vacuum
VAC = Volts Alternating Current

VAF = Volume Airflow
VAF = Vane Airflow Sensor
VCC = Viscous Converter Clutch

VCM = Vehicle Control Module

VDC = Volts Direct Current
VIN = Vehicle Identification Number

VR = Voltage Regulator
VS = Vehicle Sensor
VSS = Vehicle Speed Sensor

VVC = Variable Valve Control

VVT = Variable Valve Timin
WOT = Wide Open Throttle

Christian Rosu