Technical Bulletin

Damped Accelerometers inPedestrian Protection Testing
Version 2.0

9th February 2012
TB 003

TitleVersionDocument NumberAuthor
Date
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Damped Accelerometers in Pedestrian Protection Testing
2.0TB003
Bernard Been, Richard Schram, James Ellway
9th February 2012
Euro NCAP Pedestrian Testing Protocol
Information
ImmediateDamped Accelerometers inPedestrian Protection Testing
Background
Undamped accelerometers can give spurious readings when used in pedestrian
headform impactors, particularly against some parts of a car’s surface. Highfrequency resonance leads to peaks in deceleration and unrepresentative values for
HIC15. The phenomenon occurs most frequently in tests on the windscreen but may
also happen when testing the bonnet surface and front wings.
The issue was first investigated by JARI in 20021 who proposed the use of damped
accelerometers for headform tests.

J-NCAP started using damped accelerometers for pedestrian testing in 2003. The
issue was widely discussed during the development of the ECE global technicalregulation (GTR) for pedestrian protection2. The GTR, published in 2007, requires
the use of damped accelerometers for all child and adult headform tests.
Results presented to the Euro NCAP TWG by BASt in January 2007 confirmed thatundamped accelerometers may not be suitable when testing windscreen areas andcould sometimes give misleading results on the bonnet surface. Since then, the grouphas considered further information regarding the design, suitability and availability of
damped accelerometers.

Decision
Damped accelerometers will be used for all headform and child headform tests(including tests to areas other than the windscreen) for cars to be released in August
2008 and later.

1INF GR/PS/96,

2ECE/TRANS/WP.29/2007/94, July 2007

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Following TWG-09-09-03 it is recommended that accelerometers should have adamping ratio between 0.2 and 0.71 and that the Data Acquisition minimum
measurement range should be set at three times the maximum expected amplitude.
It is also recommended to take countermeasures against noise during pedestrian
testing as follows (TWG-10-06-xx):
 Apply the maximum allowable excitation voltage
 Apply ground wire to the back plate and make sure to remove anodising layer
locally and test ground wire electric conductivity.
o Do not attach the ground wire close to the accelerometer!
 Avoid secondary impact from cables on the bonnet either byo Elastically suspended cable away from the bonnet
o Cushioning of the bonnet in the cable contact area.

The following damped accelerometers have been in use in Euro NCAP laboratories
since 2008:
Endevco 7264G-2K
Kyowa ASE-A-500 SA7
Measurement Specialties 64C-2000-360
Entran EGAS 3

February 2012 Update
In February 2012, concerns have continued to be raised regarding Endevco 7264G
accelerometers reported in document TWG12-02-07. Testing to bonnet top areas
highlighted differences between damped and undamped Endevco 7264G
accelerometers. Signal characteristics and signal offsets after peak G differedconsiderably.

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Subsequently, Euro NCAP has decided that Endevco 7264G accelerometers shallNOT be used for Euro NCAP testing. This is with immediate effect. Euro NCAP
may reconsider this should information be presented to show that modifications to theaccelerometers have removed the observed phenomena.

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