A Review of the Ford Motor Company EMC Specification ES-XW7T-1A278-AC

Introduction

The 10^th October 2003 saw the release of the new Ford EMC Specification ES-XW7T-1A278-AC. This new version of the well used and well known Ford “AB” EMC specification presents many challenges for Component / ESA Manufacturers and Test Laboratories alike. Sweeping changes have been introduced to many tests and also factors affecting the pre-requisites and order of tests have been introduced. With the introduction or modification of existing tests, increasing convergence and commonality with other manufacturer’s specifications (notably General Motors) can be seen. It is applicable to those component manufacturers who have signed commercial agreements with Ford Motor Company after 10^th October 2003.

Discussion

In order to highlight the most significant changes, a comparison between old and new is thought to be the most useful approach.

Pre-requisites / Test Plan

From the initiation of the product test plan, right through until the production of the final test report, the AC specification demands change.

To begin with, the AB specification has no explicit requirements regarding Laboratory Accreditation whereas the AC version requires all final testing to be carried out at a Test Laboratory that is accredited under the Automotive EMC Laboratory Recognition Programme – of which Ford Motor Company (FMC) is a founder member.

Test plan documents to the AB specification have to be submitted no later than 60 days to FMC and the test plan must be pre-approved by the FMC EMC department. Documents to the AC specification must be submitted to FMC no later than 20 days prior to testing, although some test plans may not require pre-approval, depending on vehicle brand requirements.

Order of testing is considered for the first time, in that the ESD handling test must be performed before any other testing can take place. It is assumed that all testing must then follow on with the same test sample (the number of which remains a minimum of 2)

Test Considerations

Variations from the old AB specification begin with the standard test harness (this was defined as either 2 meters or 500mm depending on the test). The new AC specification requires a test harness of 1700mm +300 / - 0 mm on most tests. The length has been chosen to be compatible with radiated emissions and immunity tests, and it is permitted for some conducted tests to break-out the Power and Ground wires.

Specific Test Changes

ES-XW7T-1A278-AB

Changes in ES-XW7T-1A278-AC

RI110 (Triplate)

RI111 (Stripline)

RI113 (Parallel Plate)

Tests deleted

RI112 (BCI)

Applicable from 1MHz-400MHz. Stress level and units of measurement changed substantially.

Uses substitution method and 2 probe positions.

RI114 (Free Field - Chamber)

400MHz – 3100MHz to include radar bands.

Stress levels changed substantially (up to 600V/m in some bands!)

Testing of DUT required in 3 orthogonal planes above 1GHz.

Reverberation (mode tuned) method may be used as an alternative to Free Field - Chamber.

RI120 (Parallel Wire Ignition Noise)

Test deleted

RI130 (Parallel Wire Misc Noise)

Test setup modified, test pulse validation required.

RI140 (Magnetic Field)

Essentially unchanged, but test setups are clarified.

RI150 (Charging system noise)

New test

CI210 (Sine Noise)

Terminology changed

e.g. Level 1 = former CI210-A

Level 2 = former CI210-B

Stress levels are elevated at some frequencies.

CI230 (Power Cycling)

CI230 Waveform timing/characteristics modified to match current ignition / starter motor designs.

Tests performed at –40C

CI240 (Load Dump)

Now uses ISO7637 pulse 5 rather than a specific load dump generator. Also specifies use of a non central load dump unless specifically mentioned in the test plan.

CI250 (Ground Shift)

CI250 pulsed test is deleted.

Sine Wave test now uses an amplifier rather than transformer injection.

CI260 (Power Dropout / Recovery)

CI260-E (T>400 used) deleted

CI260-F Circuit changed. Now applicable to more equipment categories. Waveform substantially modified.

Dropout tests applicable to devices that are powered from other modules.

CI270 (DC Voltage Overstress)

CI270 levels unchanged

Applicability now includes passive components. Testing may be minimized or avoided via analysis (requires FMC EMC approval).

Improved clarification of test setup and procedures.

CI280 (ESD)

CI280 substantially changed. Voltage levels changed with more stress levels.

Handling test on connectors requires extension of pins to enable testing.

New tests for I/O circuits (e.g. remote switches, diagnostic connectors)

RE310 (Radiated Emissions)

Requirements separated into 15 discrete frequency bands covering range from 150kHz – 2.5GHz.

Requirements developed for Peak and Quasi-peak detection. Average detection used for some bands.

Measurement system requirements explicitly defined for both swept and stepped receivers.

RE requirements now applicable to electric motors.

New requirements regarding loom layout.

Ambient runs required.

CE410 (Conducted Emissions – Time)

CE410 limits changed to +100/-150volts.

Requirement applicable to all electric motors and inductive devices.

CE420 (Conducted Emissions – Frequency)

CE420 requirements unchanged, but frequency coverage limited to LW, MW and FM broadcast bands

Ambient runs required.

CI220 (Inductive Switching)

Substantially changed to include new transient waveforms produced from switch arcing.

CI220 D/E deleted.

Re-testing

In the AB specification, re-testing requirements (after a failure) were determined informally between the supplier and the FMC EMC department. In the AC specification, there are specific requirements that the supplier must adhere to. The FMC EMC department must pre-approve any proposed deviation to the written requirements for re-testing.

Reporting Issues

The test data for the AC specification has to be recorded in a specific manner for the first time, while a summary of the test data needs to be submitted to FMC EMC department within 5 business days and the full report will need to be presented within 30 business days.

Conclusion

This document is intended as a quick guide to highlight the major changes between the Ford Motor Company ES-XW7T-1A278-AB and ES-XW7T-1A278-AC documents. It is hoped it will be useful to those familiar with the older specification.

It covers aspects mainly of interest to component suppliers, test plan authors and test laboratories. A thorough study of the new document is recommended before embarking on any programme of work. Comprehensive details can, of course, be found in the documents themselves which are available for free download at the Ford EMC Website. http://www.fordemc.com/docs/AC_spec_page.htm

Alex McKay

3C Test Ltd

25/2/2004