Particle Number (PN) - Portable Emissions Measurement Systems (PEMS) : heavy duty vehicles evaluation phase at the Joint Research Centre (JRC).
Date: 2017-01-05
Institutions: Joint Research Centre
Subjects: Joint Research Centre, air quality, atmospheric pollutant, commercial vehicle, metrology, motor vehicle pollution, reduction of gas emissions, research report

Particle Number (PN) - 
Portable  Emissions  Measurement 
Systems (PEMS) 

Heavy 
Vehicles 
Duty 
Evaluation  phase  at  the 
Joint  Research  Centre 
(JRC) 

Barouch  Giechaskiel,  Francesco  Riccobono, 
Pablo Mendoza-Villafuerte, Theodoros Grigoratos 

2016

EUR 28256 EN 

This publication is a Science for Policy report by the Joint Research Centre (JRC), the European Commission’s 
science and knowledge service. It aims to provide evidence-based scientific support to the European policy-
making process. The scientific output expressed does not imply a policy position of the European Commission. 
Neither the European Commission nor any person acting on behalf of the Commission is responsible for the use 
which might be made of this publication. 

Contact information 
Name: Barouch Giechaskiel 
Address: via Fermi 2749, 21027, Ispra (VA), Italy 
E-mail: barouch.giechaskiel@jrc.ec.europa.eu 
Tel.: +39 0332 78 5312 

JRC Science Hub 
https://ec.europa.eu/jrc 

JRC103701 

EUR 28256 EN 

PDF 

ISBN 978-92-79-64019-3 

ISSN 1831-9424 

doi:10.2788/052796 

Luxembourg: Publications Office of the European Union, 2016 

© European Union, 2016 

Reproduction is authorised provided the source is acknowledged. 

How to cite: Giechaskiel B., Riccobono F., Mendoza P., Grigoratos T.;  Particle Number (PN) - Portable Emissions 
Measurement  Systems  (PEMS):  Heavy  Duty  Vehicles  Evaluation  phase  at  the  Joint  Research  Centre  (JRC);  EUR 
28256 EN; doi:10.2788/052796 

All images © European Union 2016 

Title Particle Number (PN) - Portable Emissions Measurement Systems (PEMS): Heavy Duty Vehicles Evaluation 
phase at the Joint Research Centre (JRC) 
Abstract 
JRC  evaluated  the  feasibility  of  using  PN-PEMS  systems  for  Heavy  Duty  Vehicles  (HDV)  applications.  The  main 
evaluation phase took place between February and June 2016. One Compressed Natural Gas (CNG) vehicle and 
three vehicles equipped Diesel Particulate Filters (DPF) and Selective Catalytic NOx Reduction (SCR) were tested. 
The  key  conclusion  of  the  evaluation  phase  is  that  PN-PEMS  testing  for  HDV  is  feasible.  However,  low  ambient 
temperatures  were  challenging  for  the  instruments  regarding  their  robustness.  Re-testing  of  the  commercial 
instruments in September with a DPF and SCR equipped vehicle showed that most of the issues were resolved. 
The  PN-PEMS  instruments  measurement  uncertainty  is  around  30%  at  the  moment.  Similar  uncertainty  (35%) 
was found when comparing the best performing system with the reference system at the dilution tunnel (CVS); 
i.e. PEMS method uncertainty. 

Table of contents 

Acknowledgements ................................................................................................ 1 

Executive summary ............................................................................................... 2 

1 

Introduction .................................................................................................... 6 

2  Experimental methods...................................................................................... 8 

2.1  VELA 7 facilities and setup .......................................................................... 8 

2.2  Reference PN systems .............................................................................. 11 

2.3  PN-PEMS ................................................................................................. 12 

2.4  Sampling position influence ....................................................................... 14 

2.5  Test cycles .............................................................................................. 15 

2.6  Protocol .................................................................................................. 16 

2.7  Calculations ............................................................................................. 16 

3  Main evaluation Phase: Reference systems ....................................................... 20 

3.1  Emission levels ........................................................................................ 20 

3.2  PMP_CVS vs. PMP_TP ............................................................................... 22 

3.3  Cold start ................................................................................................ 26 

3.4  Sub-23 nm fraction .................................................................................. 28 

4  Main evaluation phase: PN-PEMS #1: AVL ........................................................ 34 

4.1  General ................................................................................................... 34 

4.2  Robustness ............................................................................................. 34 

4.3  Accuracy ................................................................................................. 34 

4.4  Real time measurements........................................................................... 36 

4.5  Conclusions ............................................................................................. 40 

5  Main evaluation phase: PN-PEMS #2: HORIBA (mod NPET) ................................. 41 

5.1  General ................................................................................................... 41 

5.2  Robustness ............................................................................................. 41 

5.3  Tilting ..................................................................................................... 42 

5.4  Accuracy ................................................................................................. 43 

5.5  Real time measurements........................................................................... 45 

5.6  Regeneration ........................................................................................... 48 

5.7  Comparison of Horiba units ....................................................................... 49 

5.8  Conclusions ............................................................................................. 49 

6  Main evaluation phase: PN-PEMS #3: TESTO (NanoMet 3) .................................. 51 

6.1  General ................................................................................................... 51 

6.2  Robustness ............................................................................................. 51 

6.3  Accuracy ................................................................................................. 51 

 
 
 
 
 
6.4  Real time measurements........................................................................... 53 

6.5  Conclusions for PN-PEMS #3 ..................................................................... 57 

7  Main evaluation phase: PN-PEMS #6: SHIMADZU .............................................. 58 

7.1  General ................................................................................................... 58 

7.2  Robustness ............................................................................................. 58 

7.3  Accuracy ................................................................................................. 58 

7.4  Real time measurements........................................................................... 59 

8  On-road tests ................................................................................................ 63 

10 

Second evaluation phase ............................................................................. 65 

10.1 

10.2 

10.3 

10.4 

10.5 

10.6 

10.7 

10.8 

PMP_CVS vs. PMP_TP ........................................................................... 65 

Sub-23 nm fraction .............................................................................. 66 

PN-PEMS #1: AVL MOVE ....................................................................... 68 

PN-PEMS #2: HORIBA OBS-ONE ............................................................ 71 

PN-PEMS #3: TESTO NANOMET 3 .......................................................... 72 

PN-PEMS #6: SHIMADZU NanoPEM-10 ................................................... 74 

PN-PEMS #7: MAHA ............................................................................. 75 

Regeneration ....................................................................................... 76 

11 

12 

Comparison with the CVS ............................................................................. 77 

Calibration of PN-PEMS ................................................................................ 79 

12.1 

12.2 

12.3 

12.4 

Leak check .......................................................................................... 79 

Zero check .......................................................................................... 79 

Penetration efficiency requirements ........................................................ 80 

Volatile Removal Efficiency .................................................................... 80 

13 

14 

15 

Theoretical evaluation of the measurement uncertainty ................................... 81 

Suggested technical specifications of PN-PEMS ............................................... 83 

Conclusions ................................................................................................ 89 

References ......................................................................................................... 91 

List of abbreviations and definitions ....................................................................... 93 

List of figures ...................................................................................................... 95 

List of tables ..................................................................................................... 100 

 
 
 
 
Acknowledgements 

The  authors  would  like  to  acknowledge  ACEA  for  providing  some  of  the  vehicles  and  in 
particular the following companies that supported the tests (in alphabetical order):  

•  DAF (H. Voets)  

•  Daimler (F. Zobel, J. Luther, M. Berner) 

•  Scania (H.-L. Karlsson, S. Andersson) 

•  Volvo-Renault (G. Wabinski, G. Rebours, M. Hygrell, C. Delacroix) 

Particular thanks to AMSA, Milano (R. Terenghi) for providing the CNG vehicle of this 
study.  

The support of following companies is very appreciated: 

•  AVL (A. Mamakos) 
•  Horiba (J. Danzer) 
•  Maha (A. Trommer) 
•  Shimadzu (H. Okuda) 
•  Testo (L. Cachon, S. Gerkens) 

We are gratefully thankful to the technical staff for the execution of the tests in such a 
short period of time: M. Cadario, A. Zappia, A. Bonamin. 

Special thanks to M. Schwelberger from Daimler for his assistance and evaluation of the 
data for the second evaluation phase. 

We  would  also  like  to  acknowledge  H.  Bacher  (BMW),  S.  Carli  (VW)  and  H.-L.  Karlsson 
for their comments on the report. 

1 

 
 
 
 
 
Executive summary 

Policy context  

New  emission  standards  (Euro  VI)  were  introduced  in  Europe  in  2013  for  heavy-duty 
engines. Euro VI legislation includes a Portable Emissions Measurement System (PEMS) 
based  test  at  type  approval,  followed  by  an  on-road  in-service  conformity  (ISC)  test  of 
the heavy-duty vehicle (HDV), which is devised as a measure to verify the emissions of 
the vehicle through its useful life. The gaseous pollutants NOx, HC and CO are assessed 
with  PEMS.  For  many  years  Particulate  Matter  (PM)  PEMS  testing  was  evaluated  (i.e. 
collecting  mass  onto  a  paper  filter),  but  due  to  its  inadequate  sensitivity  and  resulting 
low  benefit  vs.  envisaged  costs,  there  were  many  concerns  for  its  introduction  into  the 
regulation. In September 2015 it was decided to evaluate the (PN) method (i.e. real time 
counting  of  the  number  of  solid  particles)  for  ISC.  In  the  beginning  of  2016,  the 
Commission  adopted  a  new  Regulation  introducing  measurement  of  Particle  Number 
(PN) during the type-approval assessment as from September 2018.  

The  kick-off  meeting  for  the  PN-PEMS  for  Heavy  Duty  Vehicles  Pilot  Study  was  held  in 
Ispra  (Italy)  on  the  22nd  of  October  2015.  After  the  kick-off  meeting,  DG-GROW 
requested  JRC  to  conduct  a  feasibility  study  of  using  PN-PEMS  for  HDV  (AA  2016). 
Although  JRC  did  already  in  2014  and  2015  the  feasibility  study  of  PN-PEMS  for  light-
duty  vehicles  (Riccobono  et  al.  2014,  Giechaskiel  et  al.  2014,  2015a),  for  HDV  wider 
conditions had to be  examined (e.g. CNG  vehicles, -7°C to +35°C, regenerations etc.). 
JRC evaluated four  PN-PEMS instruments (based on the light-duty specifications) in the 
lab  and  on  the  road  from  February  until  June  2016  (main  evaluation  phase).  In 
September 2016 five commercial instruments were further evaluated (second evaluation 
phase). The second evaluation phase was conducted in order to check the improvements 
of  the  systems  for  the  exhaust  of  heavy-duty  vehicles.  ACEA  provided  some  of  the 
vehicles  tested.  Instrument  manufacturers  provided  the  PN-PEMS  which  were  based  on 
the  draft  technical  specifications  of  the  light-duty  RDE  regulation  (to  be  voted  as  a  3rd 
package until at end of 2016). 

This report summarizes the findings of the JRC evaluation, which are useful not only for 
the  HDV  regulation  but  also  for  the  upcoming  light-duty  vehicles  RDE  regulation 
regarding robustness at low and high ambient temperatures and regeneration events. 

Key conclusions  

The  key  conclusion  of  the  evaluation  phase  is  that  available  PN-PEMS  are  technically 
robust (e.g. for regenerations, urea particles) and testing with the equipment is feasible 
for  HDV.  However,  low  ambient  temperatures  were  challenging  for  the  instruments 
regarding  their  robustness.  Re-testing  of  the  commercial  instruments  showed  that  for 
most  of  the  instrument  most  of  the  issues  were  resolved.  The  PN-PEMS  instruments 
measurement  uncertainty  is  around  ±30%  (at  the  emission levels  of  6x10^11  p/kWh), 
and  is  in-line  with  the  theoretically  expected  from  the  technical  specifications  of  the 
instruments.  Slightly  higher  uncertainty  (±35%)  was  found  by  comparing  the  best 
performing instruments with the reference system at the full dilution tunnel (CVS). This 
reflects  the  PN-PEMS  procedure  uncertainty,  which  includes  the  PN-PEMS  instrument 
uncertainty). 

Quick guide / Experimental 

Tests  were  conducted  at  the  facilities  of  JRC  (VELA  7).  Six  of  the  vehicles  tested  were 
trucks  (one  of  category  N2  and  five  N3)  equipped  with  the  latest  technology  of 
aftertreatment  devices  like  Diesel  Particulate  filters  (DPF)  and  Selective  Catalyst 

2 

 
 
 
 
 
 
Reduction  of  NOx  (SCR).  One  vehicle  was  garbage  collector  with  a  CNG  (Compressed 
Natural Gas) engine. All vehicles tested were Euro VI certified. The test cycles consisted 
of  cycles  similar  to  the  type  approval  cycles,  but  also  long  cycles  similar  to  those 
conducted during the In-Service Conformity (ISC). Different load steady state points for 
the validation of CO2 predicted by VECTO were also tested. 

The  PN-PEMS  were  sampling  from  the  tailpipe.  The  climatic  room  was  adjusted  at 
temperatures  between  -7°C  and  +35°C.  All  CO2  related  tests  were  conducted  at  20°C. 
The exhaust gas was connected to the full dilution tunnel where the reference PN system 
was measuring (as in the HDV regulation) (always at 20°C). In addition a reference PN 
system was connected  to the tailpipe to investigate the uncertainties introduced by the 
sampling  location.  However,  the  PN  system  at  the  tailpipe  was  close  to  the  dilution 
tunnel  thus  pressure  pulsations,  thermophoretic  and  diffusion  losses,  agglomeration 
effects  etc.  had  probably  a  small  effect  at  this  system  than  at  the  PN-PEMS.  This 
instrument was always at 20°C in order to exclude any temperature effects. 

From  the  four  PN-PEMS  that  were  tested  at  the  main  evaluation  phase,  three  had  a 
particle  detector  based  on  the  Diffusion  Charging  (DC)  principle  and  one  on  the 
Condensation Particle Counter (CPC) as in the reference systems. In the final evaluation 
phase three DC and two CPC based instruments were tested. 

The differences between PN-PEMS and the reference PN system at the tailpipe give the 
measurement uncertainty of the PN-PEMS. The difference between the two reference PN 
systems  gives  in  a  degree  the  uncertainty  of  the  location  (i.e.  EFM  uncertainty,  time 
misalignment,  particle  losses  etc.).  Comparison  of  the  PN-PEMS  with  the  reference 
system at the dilution tunnel gives the uncertainty of the PN-PEMS procedure. 

Main findings 

The findings of the main evaluation phase are: 

•  The  (integrated)  emission  levels  of  the  lab  ISC  cycles  and  on-road  tests  of  the 
DPF  equipped  vehicles  were  <6x10^11  p/kWh  (the  current  Euro  VI  limit) 
measured  with  the  reference  system  at  the  dilution  tunnel  (PMP_CVS).  Higher 
emissions were observed only during some of the high load cycles, where passive 
regeneration occurred, and during some cold start cycles after regeneration. 
•  For two vehicles that were tested for a period of >1 month, for each of them the 

‘mean’ emissions were 5.3x10^11 p/kWh and 2.6x10^11 p/kWh. 

•  The  two  PN  reference  systems;  one  connected  to  the  dilution  tunnel  with 
Constant Volume Sampling (CVS) as required by the legislation and the other at 
the tailpipe, had differences within ±15%. The small difference between the two 
reference  systems  at  different  sampling  locations  indicated  that  the  measured 
emissions  were  most  probably  accurate  enough.  Calibration  uncertainties  could 
further  increase  this  value  by  another  10%  for  other  cases.  The  system  at  the 
tailpipe was considered the basis of comparisons in order to evaluate mainly the 
measurement uncertainty of the instruments and not uncertainties of the exhaust 
flow meter or the time misalignment. 

•  The  PN  system  at  the  tailpipe  was  close  to  the  dilution  tunnel  thus  pressure 
pulsation,  thermophoretic  and  diffusion  losses,  agglomeration  effects  etc.  had 
probably a small effect. Installation of the PN system directly at the tailpipe of the 
heavy-duty  vehicles  could  result  in  higher  emissions  compared  to  the  system  at 
the dilution tunnel.   

•  The fraction of sub-23 nm particles of the DPF equipped vehicles was low (<10%) 
for integrated emission levels >3x10^11 p/kWh. For lower emission levels it was 
higher: the most possible explanation is formation of small nanoparticles from the 
injected urea. There were also indications that some of the difference was due to 
lower  detection  efficiency  of  these  particles  of  the  23  nm  CPC  (Condensation 
Particle Counter)  of the reference system.  In absolute levels the  emissions even 

3 

 
 
 
considering these sub-23 nm particles remained well below 6x10^11 p/kWh. For 
the CNG engine the sub-23 nm fraction was 30-50% for the hot cycles and even 
higher (double) at cold start part of the cycles.  

•  The best performing instrument at temperatures >0°C was a CPC (Condensation 
Particle  Counter)  based  instrument.  It  had  differences  to  the  tailpipe  reference 
system  within  25%.  The  real  time  signals  also  matched  very  well  with  the 
reference system. The detection limit (<1x10^9 p/kWh) was comparable with the 
reference  system  and  could  easily  measure  the  very  low  emissions  of  DPF 
equipped vehicles. It had no issues during regeneration events (both passive and 
active) and measured accurately. At low ambient temperatures it showed  spikes 
and then stopped working. This system was not tested with the CNG vehicle. 
•  The best performing DC (Diffusion Charging) based instrument had differences on 
the order of 30% with the reference system. The real time signals matched quite 
well with the tailpipe reference system. The detection limit was around 1x10^11 
p/kWh.  The  system,  which  has  specifications  5-30°C,  had  warnings  and  errors 
outside  this  temperature  range  (it  also  degraded  fast  when  it  was  used  at  low 
ambient temperature). 

•  The  other  two  DC  based  instruments  had  issues  and  the  agreement  with  the 

reference systems was not satisfactory. 

The  findings  of  the  second  evaluation  phase  of  the  updated  instrument  with  a  DPF 
equipped vehicle are: 

•  The  best  performing  instrument  of  the  main  evaluation  phase  (CPC  based)  was 
also the best performing instrument in the second phase. It had differences to the 
reference  system  within  15%  (integrated  results  over  a  cycle).  It  also  had 
excellent  agreement  of  the  real  time  signals  with  the  tailpipe  reference  system. 
Again at low ambient temperatures showed artificial spikes. 

•  The second CPC-based system had an offset of 30% (measuring lower) compared 
to the tailpipe reference system (bias). The differences from the mean had small 
variability of 12% (precision, expressed as standard deviation of the differences). 
•  The  best  performing  DC-based  system  of  the  first  phase  showed  similar 
behaviour  as  in  the  first  phase.  The  measurements  above  the  limit  agreed 
perfectly  with  the  tailpipe  reference  system  (differences  within  10%).  The 
measurements  >1x10^11  p/kWh  were  around  50%  higher  than  the  reference 
system at the tailpipe. Although the system is specified for temperatures >5°C, it 
could  measure  accurately  and  without  warning  also  at  0°C.  The  -7°C  tests  were 
also possible by putting the instrument in the cold room half an hour before the 
test (i.e. not leaving it overnight at -7°C). 

•  One  of  the  DC-based  systems  that  had  issues  in  the  main  campaign  had  very 
good  results  in  the  second  phase.  The  results  were  within  20%  of  the  tailpipe 
reference  instrument  for  emission  levels  >1x10^11  p/km.  There  were  no  issues 
for low or high ambient temperatures.  

•  One  DC-based  system  didn’t  have  good  results  also  in  the  second  phase. 
Calibration in the laboratory showed that this system was not compliant with the 
draft  technical  specifications.  It  is  not  clear  why  the  real  time  signals  matched 
quite well with the reference system but only after applying a correction factor. 

Related and future JRC work  

Based  on  the  results  of  the  evaluation  phase,  OEMs  can  start  gaining  their  own 
experience.  Testing  with  cracked  DPF,  low  ambient  temperatures,  biofuels  etc  is  also 
highly  recommended.  JRC  can  support  in  this  direction,  especially  the  testing  of  CNG 
engines where more experience with PN-PEMS would be desirable. 

What hasn’t been investigated in this report is the sensitivity of the PN-PEMS to shocks, 
vibration,  aging,  variability  in  temperature  and  air  pressure  as  well  as  electromagnetic 

4 

 
 
 
interferences  and  other  impacts  related  to  on-road  vehicle  and  PN-PEMS  operation. 
Dedicated tests should be conducted. 

5 

 
 
 
 
 
 
1  Introduction 

New  emission  standards  (Euro  VI)  were  introduced  in  Europe  in  2013  for  heavy-duty 
vehicles  (HDV).  The  Euro  VI  Regulation  (EC)  No  595/2009  and  the  implementing 
Regulation (EC) 582/2011 introduced a procedure for PEMS testing as a mandatory part 
of  the  type  approval legislation in  order  to  check  the  conformity  of  heavy-duty  engines 
with  the  applicable  emissions  certification  standards  during  the  normal  life  of  those 
engines: the so-called “In Service Conformity” (ISC) requirements. In addition, Euro VI 
engines also have to verify the off-cycle in-use emissions already at type approval (PEMS 
demonstration  test).  At  the  moment  only  the  gaseous  pollutants  NOx,  HC  and  CO  are 
required  with  PEMS.  No  Particulate  Matter  (PM)  requirement  was  introduced  as  there 
were no instruments that could measure PM in real time. 

The PM-PEMS Evaluation Program was launched in 2008 by the European Commission to 
assess the potential of  portable instruments to measure particulate emissions on-board 
of  vehicles.  The  PM-PEMS  program  was  a  voluntary  program,  receiving  contributions 
from  the  European  Joint  Research  Centre  (JRC),  some  portable  emissions  instrument 
manufacturers  (AVL,  Sensors  Inc,  Horiba)  and  the  European  association  of  heavy-duty 
engines manufacturers (ACEA). 

The  laboratory  evaluation  program  at  JRC  identified  and  recommended  the  candidate 
principles  for  PM  measurements:  A  filter  holder  for  the  measurement  of  the  PM  of  the 
trip plus a real time sensor to ‘convert’ the PM to a second by second PM signal (Bonnel 
et al. 2010, Mamakos et al. 2011a, b, 2013).  

To  support  the  PM-PEMS  Pilot  Program,  JRC  conducted  a  Pre-Pilot  Program  with  the 
collaboration  of  one  of  the  ACEA’s  member,  IVECO,  and  PM  instrument  manufacturers. 
The  aim  of  this  activity  was  to  look  into  all  the  logistic  necessary  to  mount  both  the 
gaseous  and  PM-PEMS  equipment  in  a  HDV,  and  to  check  for  the  system  good 
functioning (Mendoza et al. 2015). The Pre-Pilot program was run at the JRC Vela 7 and 
on-road  around  the  JRC  Ispra  site.  One  gaseous  PEMS  and  four  candidate  PM-PEMS 
instruments were operated together on the same vehicle and the experience was shared 
with all the participants on the PM-PEMS Pilot program.  

The  second  phase  of  the  process  was  launched  with  the  on-road  measurement  of  PM 
with  the  updated  instrumentation  recommended  in  the  validation  program  (PM-PEMS 
Pilot  Program).  This  was  a  manufacturer-run  with  several  members  of  ACEA  and 
member  states  supplying  test  data  from  different  locations  with  support  of  test 
equipment suppliers and JRC (Perujo & Mendoza 2015). 

The  main  conclusions  of  the  PM-PEMS  Evaluation  Program  were  that  PM-PEMS 
measurement instruments are ready, the analysis can follow the procedure performed to 
analyse  the  gaseous  pollutants,  but  concerns  were  raised  for  regeneration  events  and 
most  importantly  about  the  detection  limit  of  the  method  and  the  resulting  low  benefit 
vs. envisaged costs (Perujo et al. 2015). 

The  (solid)  Particle  Number  (PN)  method  due  to  its  superior  sensitivity  was  thought  as 
an  alternative  already  in  2009,  although  there  were  no  available  instruments  at  that 
time (Giechaskiel et al. 2011). 

At the end of September 2015, in a HDV-PEMS meeting, it was decided to evaluate the 
Particle  Number  (PN)  method.  The  kick-off  meeting  for  the  PN-PEMS  for  Heavy  Duty 
Vehicles Pilot Study was held in Ispra (Italy) on the 22nd October 2015. This study was 
the  outcome  of  discussions  within  the  HDV-PEMS  group  and  the  opinion  expressed  by 
Member  States  to  proceed  fast  with  the  validation in  the  Heavy  Duty  Vehicles  of  a  PN-
PEMS measurement and protocol. In the beginning of 2016, the Commission adopted a 

6 

 
 
 
 
 
new  Regulation  introducing  measurement  of  Particle  Number  (PN)  during  the  type-
approval assessment as from September 2018. 

The suggested overview of the study was: 

Phase I (Months 1-2): Technical specifications 

Definition  of  draft  technical  specifications  (based  on  the  findings  of  the  light-duty 
vehicles  evalaution  program).  Agreement  on  test  plan  and  availability  of  vehicles  and 
instruments.  

Phase II (Months 3-8): Evaluation at the JRC 

Experimental  evaluation  at  the  JRC  both  in  the  laboratory  (HDV  Chassis  Dyno)  and  on 
the  road.  At  least  two  PN-PEMS  (based  on  condensation  particle  counter  (CPC)  and 
diffusion  charger  (DC)  principles)  should  be  measuring  in  parallel  with  the  reference 
instruments at the tailpipe and the dilution tunnel. 

The vehicles would be provided by ACEA and they should be at least one N2, one N3 and 
one M3 (all Euro VI). If more Euro 6 vehicles would be available they could be added and 
tested.  The  vehicles  should  be  equipped  with  the  most  typical  after-treatment  devices, 
e.g. DPF, SCR. Regenerations should be possible to be triggered. 

The ambient temperatures should cover at least 0°C to 35°C (with possible extension to 
lower  temperatures).  The  test  cycles  should  be  type-approval  equivalent,  and  ISC 
similar. 

Phase III (Months 5-12): PN validation program 

Independent evaluation from participants (OEMS, MS) to the programme. A wide range 
of  vehicles  should  be  covered  with  special  attention  to  CNG  engines,  dual  fuel,  hybrids 
etc.  The  ambient  conditions  should  cover  a  wide  range  (0°C  to  35°C,  with  possible 
extension  to  lower  temperatures).  Two  PN-PEMS  instruments  measuring  in  parallel  is 
obligatory. 

After the kick-off meeting of the HDV PN-PEMS evaluation program at the end of October 
2015,  DG-GROW  requested  JRC  to  conduct  the  feasibility  study  of  using  PN-PEMS  for 
HDVs  (AA  2016).  JRC  did  in  2014  and  2015  the  feasibility  study  of  PN-PEMS  for  light-
duty vehicles (Riccobono et al. 2014, Giechaskiel et al. 2014, 2015a) and ran an inter-
laboratory correlation exercise with two PN-PEMS (Riccobono et al. 2016). For HDV wider 
conditions  (-7°C  to  +35°C,  regenerations  etc.)  and  different  technologies  than  at  the 
light-duty  vehicles  (e.g.  CNG  vehicles,  DPF  vs  GDIs)  had  had  to  be  examined.  JRC 
evaluated  some  PN-PEMS  instruments  in  the  lab  and  on  the  road  from  February  until 
June 2016. In September 2016 the updated instruments were tested. This phase was a 
transition  between  the  JRC  evaluation  phase  and  the  OEMS  validation  phase,  because 
the OEM actively participated at the evaluation of the results. ACEA provided some of the 
vehicles  tested.  Instrument  manufacturers  provided  the  PN-PEMS  which  were  based  on 
the  draft  technical  specifications  of  the  light-duty  RDE  regulation  (to  be  voted  as  a  3rd 
package at the end of 2016). 

This report summarizes the findings of the JRC evaluation, which are useful not only for 
the  HDV  regulation  but  also  for  the  upcoming  light-duty  vehicles  RDE  regulation 
regarding robustness at low and high ambient temperatures and regeneration events. 

7 

 
 
 
 
 
 
 
 
2  Experimental methods 

Due to the urgency of the PN-PEMS project, it was combined with other projects. Table 1 
summarizes  the  projects  that  were  running  in  parallel  and  the  tested  vehicles.  The 
vehicles included N2 and N3 trucks and a CNG garbage collector. 

In this report only the PN-PEMS results will be discussed. 

Table 1: Overview of projects and tested vehicles (all Euro VI). 

No  Vehicle (approximate) 

Period 

PN-PEMS 

PMP 

Cold start  CO2 

1 

2 

3 

4 

5 

6 

7 

8 

Truck N3, 13L, 340 kW 

February 

Garbage collector, CNG  March 

Truck N3, 13L, 340 kW  Mid March 

Truck N3, 8L, 240 kW 

Mid April 

Truck N2, 5L, 180 kW 

Mid May 

Truck N3, 8L, 240 kW 

June 

Truck N3, 13L, 340 kW 

End June 

Truck N3, 13L, 340 kW  Mid September 

Y 

Y 

Y 

N 

Y 

Y 

N 

Y 

Y 

Y 

Y 

Y 

Y 

Y 

Y 

Y 

Y 

N 

Y 

N 

Y 

N 

N 

Y 

Y 

N 

Y 

N 

N 

Y 

Y 

Y 

2.1  VELA 7 facilities and setup 

Chassis dyno measurements were performed at the Heavy Duty Chassis dynamometer of 
the Vehicle Emissions Laboratory (VELA 7) of the European Commission’s Joint Research 
Centre (JRC). Figure 1 shows an overview of the VELA 7 facilities. 

The  two  roller  chassis  dynamometer  (Zoellner  GmbH,  Germany)  has  been  designed  to 
host  even  4-wheel  drive  heavy-duty  vehicles  (trucks  and  buses)  of  up  to  30  tons  in 
weight, 12 m in length, and 5 m in height. Maximal test speed is set at 150 km/h. The 
test cell can be conditioned between -30°C and +50°C with relative humidity of 15-95% 
providing  the  ability  to  test  vehicles  under  extreme  conditions.  The  constant-volume 
sampler (CVS) for full exhaust dilution (AVL, Graz, Austria) is equipped with 4 Venturis 
of  10,  20,  40,  and  80  m3/min  in  order  to  achieve  a  maximum  air  flow  of  150  m3/min. 
Dilution  air  is  taken  from  the  test  cell,  conditioned  to  22°C,  and  filtered  through  high-
efficiency  particulate  air  (HEPA)  and  activated  charcoal  filters.  The  climatic  test  cell  of 
VELA  7  has  an  air  circulation  system  that  provides  enough  number  of  cell  air  changes 
(≥15) in order to allow the testing of vehicles fueled with different types of fuels. 

An AVL i60 AMA 4000 system was used for the analysis of gaseous emissions. A Heated 
for  measuring  exhaust  gas 
Flame  Ionization  Detector  (HFID)  was  employed 
concentrations  of  THC  and  CH4.  A  Heated  Non-Dispersive  Infrared  sensor  (NDIR)  was 
used for CO2 and CO emissions. A Heated ChemiLuminescence Detector (CLD) measured 
exhaust  NOx.  Pollutants  were  measured  downstream  of  the  exhaust  aftertreatment 
system of the truck.  

8 

 
 
 
 
 
 
Climatic room
-7oC to +35oC

Gas 
PEMS

AMA

PMP_TP

PN-
PEMS

FTIR

Dilution tunnel

Control room

Controlled temperature  
room 20oC

PMP_CVS

Figure 1: VELA 7 facilities. 

The  Gas-PEMS  system  used  both  in  the  lab  and  on-road  was  the  Semtech-DS 
manufactured  by  Sensors,  Inc.  and  it  consisted  of  tailpipe  attachment,  heated  exhaust 
lines, an exhaust flow meter (EFM) (4’’ or 5’’ depending on the vehicle tested, see Table 
3),  exhaust  gas  analyzers,  data  logger  to  vehicle  network,  a  global  positioning  system 
(GPS),  and  a  weather  station  for  ambient  temperature  and  humidity.  All  data  was 
recorded  at  a  frequency  of  1  Hz  and  the  whole  system  added  further  ~100  kg  of 
instrumentation to the vehicle. A generator was used to produce current for the needs of 
the  PEMS.  The  Semtech  DS  measured  exhaust  gas  concentrations  of  unburned 
hydrocarbons  (THC)  by  HFID,  carbon  monoxide  (CO)  and  carbon  dioxide  (CO2)  by  a 
NDIR, and nitrogen monoxide (NO) and nitrogen dioxide (NO2) by a non-dispersive ultra-
violet  sensor  (NDUV).  The  oxides  of  nitrogen  (NOx)  were  calculated  by  the  sum  of  the 
concentrations  of  NO  and  NO2.  The  measurement  principles  and  accuracy  from  the 
Semtech DS were in-line to those described by current legislation for this type of testing. 
As  a  standard  procedure,  test  runs  preparation  included  routine  calibration  of  pollutant 
analyzers (zero and span of gases). 

The AVL SESAM FTIR (Fourier Transform  Infrared spectrometer) was  used to monitor a 
selection  of  unregulated  gaseous  emission,  including  nitrogen  species  like  nitric  oxide 
(NO), nitrogen dioxide (NO2), nitrous oxide (N2O), NH3, and oxygenated compounds like 
formaldehyde, acetaldehyde, and ethanol. The instrument created an infrared broadband 
spectrum that was used to detect the spectral information about the exhaust gas sample 
for all gas components  simultaneously. The absorption spectrum (intensity/wavelength) 
was  calculated  from  the  measured  interferograms  (intensity/time)  by  means  of  the 
Fourier transformation.  

9 

 
 
 
 
 
The  calculation  of  the  engine  work  output  over  each  sub-cycle  was  based  on  the 
instantaneous engine torque and rpm values which were recorded via the vehicle’s OBD 
(On-Board-Diagnostics) system as well as on the nominal torque for each truck. A cross 
validation with the instantaneous work values retrieved from the chassis dyno system or 
a  torquemeter  installed  either  at  the  shaft  or  at  the  wheels  was  also  performed  and 
confirmed  the  accuracy  of  the  calculation.  The  ratio  of  work/distance  for  the  various 
cycles  and  vehicles  can  be  seen  in  Table  2.  With  the  exception  of  the  SICO  cycles  the 
ratio was close to one. These ratios were used to convert p/km to p/kWh when no OBD 
(power) data existed. 

Table 2: Ratio of work to distance for various cycles and vehicles. 

kWh/km 

V1 

V2 

V3 

V4 

V5 

V6 

V7 

ISC 

1.00 

0.90 

1.27 

0.78 

1.53 

WHVC 

1.10 

0.78 

1.49 

1.01 

1.41 

SICO 

2.54 

1.89 

2.76 

On-road 

1.10 

1.17 

No  gaseous  pollutants  results  will  be  presented  in  this  report,  with  a  few  exceptions 
where PN behavior is discussed. 

Figure 2: Example of a vehicle and the PEMS in the climatic room. 

10 

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
2.2  Reference PN systems 

A  PN  measurement  system  compliant  with  the  heavy  duty  engines  (UN-ECE  Reg.  49) 
regulations was used (AVL APC 489) at the dilution tunnel (Giechaskiel et al. 2010).  

The Volatile Particle Remover (VPR) of the system consists of a hot dilution (HD) at 150 
°C  and  an  evaporation  tube  (ET)  at  350  °C.  The  system  was  calibrated  by  the 
manufacturer and the dilution including the particle losses (as average of 30, 50 and 100 
nm)  is  called  Particle  number  Concentration  Reduction  Factor  (PCRF).  Typically,  a 
primary PCRF of 25 and a secondary of 10 were used. 

Downstream  of  the  thermal  pre-treatment  system  a  TSI  butanol  CPC  3790  with  50% 
counting efficiency at 23 nm (d50%=23 nm) is measuring. In parallel a TSI butanol CPC 
3772  (d50%=10  nm)  is  used  in  order  to  investigate  the  presence  of  particles  <23  nm. 
Note  that  HD+ET  with  a  CPC  d50%=23  nm  is  the  protocol  defined  in  the  Particle 
Measurement Program  (PMP) and used for the regulatory measurements. From now on 
this system will be mentioned as PMP_CVS.  

Figure  3:  Typical  setup  of  the  reference  systems  in  the  controlled  temperature  dilution 
tunnel room. 

The instrument used to measure (solid) PN emissions from the tailpipe was the Nanomet 
1 from Testo which is compliant with UNECE Regulation 49. The instrument consists of a 
hot dilution at 150 °C,  an evaporation tube at  350 °C, a secondary dilution at ambient 
temperature and a CPC (TSI 3790) with d50%=23 nm. The Particle number Concentration 

11 

 
 
 
 
 
Reduction Factor (PCRF) chosen was approximately 720 (primary 180 and secondary 4), 
as  given  by  the  manufacturer.  This  value,  which  was  used  in  the  calculations  for  this 
report, is 10% higher than our measured PCRF in the lab with monodisperse aerosol of 
30 nm, 50 nm and 100 nm soot particles. From now on this system will be mentioned as 
PMP_TP.  This  system  was  not  placed  in  the  climatic  chamber  but  was  connected  just 
before  the  mixing  of  the  exhaust  gas  with  the  dilution  air  in  the  dilution  tunnel  room. 
This way it was always measuring at 20°C ambient temperature and thus unaffected by 
changes of the climatic room temperature. On the other hand, as this system was close 
to  the  dilution  tunnel,  pressure  pulsation,  thermophoretic  and  diffusion  losses, 
agglomeration  effects  etc.  had  probably  a  small  effect.  Installation  of  the  PN  system 
directly  at  the  tailpipe  of  the  heavy-duty  vehicles  could  result  in  higher  emissions 
compared  to  the  system  at  the  dilution  tunnel.  Thus  the  differences  between  the  two 
systems at tailpipe and dilution tunnel could be higher in other cases. 

For  our  setup  (9  m  tubing  in  the  climatic  room  plus  6  m  insulated  in  the  controlled 
temperature  dilution  tunnel  room  of  120mm)  the  mean  residence  time  was  1  s  for  the 
HDV  measured  (mean  flow  rate  around  7  m3/min)  and  thus  the  diffusion  losses 
negligible.  The  thermophoretic  losses  should  be  <15%  as  the  exhaust  temperatures  at 
20°C ambient temperature were around 250°C. The agglomeration losses should also be 
negligible due to the low levels of the DPF equipped vehicles. 

2.3  PN-PEMS 

The  PN-PEMS  were  connected  to  the  tailpipe  after  the  exhaust  flow  meter  EFM  (Figure 
4). 

PN-PEMS  #1  (AVL)  consists  of  a  VPR  and  a  DC  (modified  particle  detector,  Partector, 
from Naneos). The VPR is connected to the tailpipe with a short (0.9  m) heated line at 
150°C. The VPR consists of a two stage dilution with an evaporation tube and a catalytic 
stripper in between (both set at 300°C). The primary dilution is 2:1, and the secondary 
5:1  (3:1  in  the  second  evaluation  phase).  For  the  upstream  dilution  the  dilution  air  is 
heated  at  150°C.  The  downstream  dilution  is  performed  with  dilution  air  at  60°C,  to 
minimize  nucleation  potential.  The  diluted  sample  is  transferred  to  the  DC  in  a  1.3  m 
heated line at 60°C. The sampling rate is 0.7 l/min. A sample probe heater at 100°C was 
added at the second evaluation phase (Figure 5). 

PN-PEMS #2 (modified NPET, HORIBA) consists of a VPR and a CPC. The VPR consists of 
two cold dilution stages with a dilution ratio of 10:1 each and a heated catalytic stripper 
at 350°C in between. The first diluter utilizing dried dilution air is located directly at the 
sample  probe  followed  by  a  4  m  heated  line  at  60°C  that  brings  the  diluted  aerosol  to 
the  main  cabinet.  Downstream  of  the  VPR  an  isopropyl  alcohol-based  CPC  with  d50%  at 
23  nm  is  used  to  detect  the  particles.  The  CPC  is  optimized  for  on-road  measurements 
and  has  an  environmental  operating  temperature  ranging  from  -10°C  to  +40°C.  At  the 
second evaluation phase the commercial version OBS-ONE-PN was used. 

PN-PEMS  #3  (Nanomet  3-PS,  Testo  AG)  consists  of  a  VPR  and  a  DC  (Diffusion  Size 
Classifier miniature, DiSC mini). The VPR consists of a heated sampling line at 100°C, a 
heated rotating disk diluter (primary and total PCRF used in this campaign around 30 as 
calibrated  by  the  manufacturer),  and  an  evaporation  tube  at  300°C.  A  unique 
characteristic  of  the  device  is  that  the  DC  has  two  electrometers  and  can  estimate  a 
mean  particle  size  based  on  their  ratio.  The  charged  particles  first  flow  through  a 
diffusion stage. Some of the particles are captured in this stage and generate a current 
Idiff, while the remaining particles flow into a second stage that is equipped with a HEPA 
filter.  Here,  all  particles  are  captured,  and  a  current  Ifilter  is  measured  with  an 
electrometer.  The  ratio  Ifilter/Idiff  is  a  measure  of  the  average  particle  size,  because 
smaller  particles  undergo  larger  Brownian  motion,  and  are  therefore  more  likely  to  be 
captured  in  the  diffusion  stage.  The  instrument  gives  particle  number  concentration 
based on the currents it measures and an estimated mean particle size. 

12 

 
 
 
PN-PEMS #4 (PPS, Pegasor): No unit was delivered to JRC for the HDV campaign. 

PN-PEMS #5 (Sensors): No unit was delivered to JRC for the HDV campaign. 

PN-PEMS  #6  (NanoPEM-10,  Shimadzu)  is  a  6  stage  electro  mobility  analyser  without 
sheath flow. The cut-off size is 23 nm. For the tailpipe tests, the sample was drawn into 
a  heater  (350°C)  and  diluted  10  times  (DF=10).  Then  it  was  drawn  through  a  heated 
line  (190°C)  to  the  main  unit.  The  total  concentration  [p/cm3]  was  given  by  the 
manufacturer’s software. 

PN-PEMS #7 (MAHA-AIP GmbH & Co.) consists of a VPR and a CPC, thus is very similar 
to  a  PMP  system.  It  has  a  short  sampling  line  (0.5  m)  heated  at  100°C.  The  primary 
diluter is an orifice diluter also heated at >100°C, with a dilution of approximately 100. 
The  evaporation  tube  is  kept  at  300°C,  then  a  secondary  dilution  follows  at  ambient 
temperature  (dilution  approximately  10:1).  The  CPC  is  a  3007  TSI  CPC  with  saturator 
and  condenser  temperatures  adjusted  to  obtain  a  cut-off  at  23  nm.  The  unit  was 
available only at the second evaluation phase. 

The calibration results of the PN-PEMS at JRC can be seen in the Chapter 12. 

Figure 4: Example of setup of PEMS (main evaluation phase). 

13 

 
 
 
 
 
Figure  5:  Example  of  setup  of  PN-PEMS  (second  evaluation  phase).  On  the  right  the 
positioning of the sampling probes. Probes facing away from the flow. 

2.4  Sampling position influence 

A  limited  number  of  tests  were  conducted  with  PN-PEMS  #2  at  the  end  of  the  main 
evaluation campaign sampling from the centerline or from the tube wall (no probe). The 
differences of the PN-PEMS from the PMP system at the tailpipe can be seen in Figure 6. 
It seems that lower concentration is measured when there is no probe. The topic was not 
investigated  in  detail  but  indicates  that  a  probe  should  be  used  when  particles  are 
sampled. All systems in this report where  connected to the tailpipe with a probe in the 
tube reaching the centreline (but facing away from the flow). 

In the second phase the probes had a distance of 1.5 tube diameters (approximately 15 
cm)  to  each  other  and  with  an  angle  of  75  degrees  to  each  other.  In  order  to  confirm 
that  there  was  no  influence  of  the  sampling  the  first  instrument  (PN-PEMS  #2)  was 
moved  to  the  last  position  and  then  at  the  first  again.  The  normalized  to  the  reference 
instrument  results  can  be  seen  in  Figure  7.  There  is  no  measureable  effect  from  the 
sampling location. Similarly small or no influence is expected by the location for the main 
evaluation phase. 

14 

 
 
 
 
 
Figure 6: Effect of sampling probe. 

Figure  7:  Influence  of  position  on  results.  See  Figure  5:  Front  refers  to  position  of  PN-
PEMS #2 and Back refers to position of PN-PEMS #7. 

2.5  Test cycles 

Various test cycles were tested in the laboratory: 

15 

 
 
 
 
 
 
•  WHVC (World Harmonized Vehicle Cycle) that is the equivalent of the engine 
World  Harmonized  Test  Cycle  (WHTC)  to  a  vehicle  cycle  for  the  chassis 
dynamometer. The duration of the WHVC test is 1800 s. The test includes three 
segments, representing urban, rural and motorway driving. No slopes were added 
in most of the cases, thus the work  of this cycle in many cases was  different to 
the type approval work of the WHTC. 

•  Regional Delivery which is a distance-based cycle where the actual speed of the 
vehicle at any moment in time is produced by the simulator, and is a function of 
the  vehicle  characteristics  (weight,  resistances,  and  available  power)  and  the 
modeled  behavior  of  the  driver.  Such  an  approach  is  considered  much  more 
realistic  for  evaluating  the  performance  of  a  multitude  of  different  HDV  without 
overlooking  their  optimal  performance  conditions.  In  order  to  match  realistic 
conditions  more  closely,  the  Regional  Delivery  cycle  features  additionally  the 
slope as a function of the traveled distance.  

•  SICO: Constant Speed test with predefined combinations of engine rpm and real 
time  measured  wheel  torque  (predefined  test  cycle  in  VECTO  consisting  of 
constant  speeds  for  optional  later  validation  of  the  CO2  result  produced  for  a 
HDV). 

•  ISC  (In-Service-Conformity)  cycle  which  consists  of  urban  (30%/15%),  rural 
(30%/30%)  and  motorway  (40%/55%)  parts  of  approximately  150  km  (>2.5  h 
duration)  in  this  order  (percentages  excluding  idle  as  time/distance  shares)  for 
the  N3  vehicles.  For  the  N2  vehicle  the  shares  were  urban  (45%/25%),  rural 
(25%/30%)  and  motorway  (30%/45%).  In  the  second  evalaution  phase  an  ISC 
that  consisted  of  rural  (25%/10%),  motorway  (15%/20%)  and  urban  and  rural 
(25%/25%) and motorway (40%/45%) parts was also used for the N3 vehicle. 

The on-road tests around the JRC site were performed to simulate real-world emissions. 
A mixed route  of total distance of approximately 200 km which consists of urban,  rural 
and  highway  parts  was  driven  during  on-road  test.  The  scope  was  to  obtain  a  mix  of 
operating conditions similar to those of the chassis dynamometer tests. Cold start in the 
following figures refers to the first 1200 s of the ISC cycle (when the engine was cold). 

For the on-road tests only the gas PEMS was used with the 5’’ EFM and one or two PN-
PEMS (#2 always and #1 or #3). 

2.6  Protocol 

The test protocol can be seen in Table 3 and the tests conducted in Table 4. 

2.7  Calculations 

For  the  systems  at  the  CVS,  the  CVS  flow  rate  and  the  work  produced  were  used  to 
calculate  the  emissions  in  p/kWh.  For  the  systems  at  the  tailpipe,  the  particle 
concentration was time aligned with the exhaust flow rate and then they were multiplied 
with each other. The sum was divided with the work to give p/kWh. The exhaust flow in 
all  tests  presented  was  estimated  from  the  difference  of  the  total  flow  of  the  dilution 
tunnel minus the dilution air flow. These flows were inter-calibrated weekly. 

The  flow  rate  extracted  by  the  instruments  was  approximately  20-30  lpm  (11  lpm  the 
gas analyzer, 6.5 lpm the FTIR, 1-10 lpm the PN-PEMS). This flow is <1% of the mean 
vehicles’  flow  rate  during  a  test  (<2%  at  idle).  And  was  not  considered  in  the 
calculations. 

For many tests the exhaust flow meter (EFM) was connected to the tailpipe and the flow 
rates  measured  by  the  EFM  and  the  estimated  by  the  CVS  were  compared  (Figure  8). 

16 

 
 
 
 
The flow rate of the EFMs (both 4’’ or 5’’) was also used to estimate the emissions of the 
PMP-TP. The cycle average results had less than 5% difference. Thus no correction was 
applied to the flowrate. 

Table 3: Testing period of PN emissions and available PN-PEMS instrumentation. 

Period 

V1 

#1 

#2 

#3  #6 

EFM  Comments 

3/2-29/2 

Lab 

Y 

Y1, Y2  Y1 

7/3-11/3 

On-road  N 

14/3 

Lab 

N 

Y2 

Y2 

Y1 

Y1 

N 

N 

N 

5’’ 

27 tn 

5’’ 

27 tn 

5’’ 

regeneration 

V2 

16/3-23/3 

Lab 

N 

N 

Y2 

Y 

4’’ 

20 tn, <3000 km 

V3 

24/3-1/4 

Lab 

8/4-12/4 

Lab 

13/4-15/4 

Lab 

N 

Y 

Y 

21/4-6/5 

On-road  Y 

12/5 

Lab 

Y 

V4 

N 

Y3 

Y3 

Y3 

Y3 

Y2 

N 

N 

N 

N 

Y 

Y 

Y 

N 

N 

4’’ 

20 tn, low temp, no OBD 

4’’ 

27 tn, torquemeter 

N 

27 tn, torquemeter* 

5’’ 

27 tn 

5’’ 

27 tn, repeat 

28/4-4/5 

Lab 

N 

N 

N 

N 

N 

Only CVS 

V5 

18/5-31/5 

Lab 

Y 

Y3 

N 

Y 

4’’ 

9 tn 

V6 

9/6-13/6 

Lab 

N 

Y3 

N 

N 

4’’ 

13 tn 

V7 

27/6-28/6 

Lab 

N 

N 

N 

N 

5’’ 

CVS 

V8 

5/9-16/9 

Lab 

Y2 

Y4 

Y3 

Y2 

5’’ 

27 tn, PN-PEMS #7 

* 12/4 Error: Exhaust gas System Faulty (then warning). 16/4 repair at official workshop 

17 

 
 
 
 
 
Table 4: Test cycles for each vehicle and number of repetitions. 

Cycle 

-7°C 

0°C 

10°C 

20°C 

35°C 

Cold 

V1 

ISC 

3 

WHVC 

Various 

On-road 

2 

1 

V2 

ISC 

1 

1 

WHVC 

Various 

V3 

ISC 

WHVC 

Various 

On-road 

V4 

ISC 

Various 

V5 

ISC 

WHVC 

V6 

WHVC 

Various 

V7 

WHVC 

Various 

V8 

ISC 

WHVC 

Various 

1 

1 

4 

3 

2 

2 

4 

1 

2 

2 

1 

2 

1 

1 

1 

1 

2 

2 

10 

15 

2 

2 

1 

8 

24 

5 

2 

2 

4 

3 

5 

3 

9 

2 

4 

5 

4 

7 

0 

2 

3 

0 

0 

2 

2 

0 

3 

2 

0 

3 

2 

0 

0 

1 

0 

6 

0 

0 

5 

1 

1 

18 

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Figure  8:  Example  of  comparison  of  exhaust  flow  estimated  from  the  dilution  tunnel 
(CVS) and an exhaust flow meter (EFM) (201604010_1_ISC). 

19 

 
 
 
 
 
 
 
3  Main evaluation Phase: Reference systems 

3.1  Emission levels 

An example of the emission levels of different cycles for vehicle V1 can be seen in Figure 
9.  The  emission  levels  of  the  on-road  tests  and  the  hot  cycles  are  <1x10^11  p/kWh. 
Higher  emissions  were  measured  during  the  SICO  tests  when  the  DPF  was  passively 
regenerating. High emissions were also measured during some cold WHVCs; the level of 
the  cold  start  probably  has  to  do  with  the  DPF  fill  state  from  the  tests  the  day  before. 
Summing  up  the  emissions  during  a  period  of  approximately  one  month  gave  emission 
levels of 5.3x10^11 p/kWh for vehicle V1. Similarly for vehicle V3 the emissions during a 
period of one and a half months were approximately 2.6x10^11 p/kWh. 

Figure 9: Emission levels of V1 for various cycles. Error bars indicate max-min values. 

The tests were conducted depending on the needs of the various projects and thus there 
was  no  dedicated  protocol  to  ensure  similar  DPF  fill  state  and  testing  conditions.  Thus 
the repeatability of the measurements was not good, as seen in Figure 9. An example of 
continuously running Regional Delivery cycles can be seen in Figure 10. Between the two 
days two WHVC cycles were also conducted. The emissions were low, but then at one of 
the  cycles  the  DPF  regenerated  and  the  emissions  were  high.  The  emissions  remained 
high during the next cycle due to the low soot cake in the DPF. The bad repeatability (big 
error bars) of the measurements has no effect on the conclusions of this report: All PN-
PEMS were measuring in parallel with the reference PN systems and the differences are 
evaluated on a cycle by cycle basis. 

20 

 
 
 
 
 
 
 
Figure 10: Repeatability of Regional Delivery Cycles. 

The emission levels of all vehicles for some test cycles can be seen in Figure 11. Vehicle 
V2 (CNG) had high emissions probably because it was new and there were oil particles. 
The  rest  vehicles  (all  DPF  equipped)  were  below  the  6x10^11  p/kWh  limit  with  a  few 
cold  start  WHVC  exceptions;  these  cold  start  WHVCs  were  conducted  the  day  after  the 
SICO cycles which generated the DPF and thus the DPF efficiency was relatively low. The 
important message from this figure is that a wide range of emissions was examined. 

Figure 11: Emission levels at different cycles of different vehicles. 

21 

 
 
 
 
 
3.2  PMP_CVS vs. PMP_TP 

The  correlation  of  the  PMP_TP  to  the  PMP_CVS  can  be  seen  in  the  following  figures  for 
the  various  vehicles  (Figure  12  for  vehicle  V1,  Figure  13  for  vehicle  V2,  Figure  14  for 
vehicle V3, Figure 15 for vehicle V5). In general, the agreement is within 15% with only 
a  few  cases  exceeding  this  difference  and  there  is  no  dependency  of  the  ambient 
temperature  in  the  climatic  room,  as  it  should,  because  the  PMP_TP  was  installed  in  a 
room with controlled temperature of 20°C. 

Figure  12:  Correlation  of  PMP_TP  to  PMP_CVS  for  vehicle  V1.  Blue  points  tests  at  -7°C, 
red points tests at +35°C. 

Figure  13:  Correlation  of  PMP_TP  to  PMP_CVS  for  vehicle  V2.  Blue  points  tests  at  -7°C, 
red points tests at +35°C. 

22 

 
 
 
 
Figure  14:  Correlation  of  PMP_TP  to  PMP_CVS  for  vehicle  V3.  Blue  points  tests  at  -7°C, 
red points tests at +35°C. The two outliers will be discussed separately. 

Figure  15:  Correlation  of  PMP_TP  to  PMP_CVS  for  V5.  Blue  points  tests  at  -7°C,  red 
points tests at +35°C. 

If the reference system was connected close to the vehicles and not the dilution tunnel 
probably  the  differences  would  be  higher  (higher  influence  from  pressure  fluctuations, 
thermophoretic or diffusion losses and agglomeration). 

23 

 
 
 
 
 
 
Bigger differences than 15% were observed when the concentrations were very low and 
the  total  emissions  were  <10^10  p/kWh  (Figure  15).  In  this  case  the  relatively  high 
background  of  the  CVS  results  in  a  detection  limit  of  the  CVS  around  5x10^9  p/kWh 
(<100 p/cm3 at the CVS). This can be seen in Figure 16 where a cold start ISC cycle is 
shown. At the cold start part the PMP_TP is measuring 30% higher (one of the few cases 
that the ±15% was exceeded) than the PMP_CVS, while in the last hot part 92% lower.  

Figure  16:  Real  time  comparison  of  PMP_CVS  and  PMP_TP  over  a  long  cycle  in  the  lab 
(Example vehicle V5) (20160520_1_ISC_-7°C). 

Special  discussion  need  the  two  outliers  of  Figure  14.  These  tests,  which  happened  on 
the same day, showed low emissions with the PMP_TP but high with the PMP_CVS. The 
real  time  signals  are  shown  in  Figure  17  and  Figure  18.  The  high  emissions  are  due  a 
spike  during  an  acceleration  at  the  PMP_CVS  test  at  both  cases.  There  is  no  clear 
explanation for this behaviour. It could be a re-nucleation effect in the dilution tunnel as 
the exhaust gas cools down that couldn’t be completely removed in the evaporation tube 
of  the  PMP  system.  The  PMP  system  at  the  tailpipe  samples  hot  exhaust  thus  this 
nucleation  did  not  happened.  The  PN-PEMS  also  didn’t  show  this  high  concentration  of 
particles. These two tests were not considered in the analysis and comparison of the CVS 
results. 

24 

 
 
 
 
 
 
Figure 17: Real time comparison of PMP_TP and PMP_CVS (20160411_01_WHVC). 

Figure 18: Real time comparison of PMP_TP and PMP_CVS (20160411_04_Region.Del.). 

25 

 
 
 
 
 
 
 
 
3.3  Cold start 

Examples of cold start emissions (first 1200 s) with the PMP_CVS and PMP_TP systems 
are shown in Figure 19 for vehicle V1, Figure 20 for vehicle V3 and Figure 21 for vehicle 
V5. A summary of the differences of the PMP_TP and PM_CVS systems at the cold part of 
the cycle and the hot part is given in Table 5. The difference of PMP_TP from PMP_CVS is 
lower at the cold part than in the hot part, with a few exceptions that the emissions are 
below the background levels. This is in contrast to the light-duty exercise where the cold 
start  emissions  where  in  general  higher  at  the  tailpipe  than  at  the  CVS.  Part  of  this 
difference  can  be  explained  by  the  position  of  the  PMP_TP  system.  In  the  light-duty 
exercise it was connected directly at the end of the vehicle’s tailpipe, while in the heavy-
duty exercise just before the CVS. Thus diffusion and agglomeration between the system 
at the tailpipe and the dilution tunnel were more significant in the light-duty exercise.  

Table 5: Difference of PMP_TP to PMP_CVS for the cold part and hot part of the ISC cycle 
at different ambient temperatures. 

Vehicle 

V1 

V3 

V5 

Temperature 

-7°C 

20°C 

-7°C 

20°C 

-7°C 

20°C 

Cold start 

-10% 

-15% 

+9% 

+17% 

+30% 

-7% 

Hot part 

+15% 

+5% 

+34% 

+43% 

-43%* 

-20% 

* due to higher background of the CVS 

Figure  19:  Comparison  of  PMP_TP  with  PMP_CVS  at  the  cold  part  of  a  cycle  (V1) 
(20160217_01_ISC_-7°C). 

26 

 
 
 
 
 
Figure  20:  Comparison  of  PMP_TP  with  PMP_CVS  at  the  cold  part  of  a  cycle  (V3) 
(20160331_01_ISC_-7°C). 

Figure  21:  Comparison  of  PMP_TP  with  PMP_CVS  at  the  cold  part  of  a  cycle  (V5) 
(20160520_01_ISC_-7°C). 

27 

 
 
 
 
 
 
3.4  Sub-23 nm fraction 

The sub-23 nm fraction was estimated by comparing the concentrations of a 10 nm CPC 
and the 23 nm CPC measuring in parallel downstream of the VRP of the PMP_CVS. This 
fraction might not be representative of the true sub-23 nm emissions as the losses <30 
nm are not properly considered in the established regulated procedure. 

Figure 22, Figure 24, and Figure 26 show the fraction as a function of the emission levels 
for the DPF equipped vehicles V1, V3 and V5 respectively. Figure 28 shows for the CNG 
vehicle  V2.  For  the  DPF  equipped  vehicles  the  fraction  is  low  at  high  concentrations 
(<10%).  However,  quite  often  it  was  high  at  low  concentrations  (<1x10^11  p/kWh). 
Some possible reasons are: 

•  Drift  of  the  23  nm  CPC  (highly  unlikely  in  this  case,  as  the  pulse  height  was 

monitored) (Figure 23). 

•  Low  measured  concentration  that increases  the  measurement  uncertainty  of  the 

CPCs (see Figure 25 and Table 6). 

•  Formation of particles due to urea injection (Figure 27).  
•  Potential material effect on the counting efficiency of the 23 nm CPCs. 

For  the  CNG  vehicle  V2  (Figure  28)  the  assumption  is  that  these  are  oil  particles  (or 
residuals) that have survived the evaporation tube temperature (350°C). Typically their 
size is around 20 nm thus a high fraction is measured at all tests. During cold start the 
fraction is even higher (Figure 29). One could argue that these particles are re-nucleated 
particles  downstream  of  the  evaporation  tube.  Dedicated  tests  at  different  PCRF  (250 
and  2500)  didn’t  show  any  difference  on  the  measured  levels  (within  experimental 
uncertainty) indicating that the re-nucleation, if any, should be minimum. Note that 10% 
effect  from  changing  the  PCRF  is  at  the  high  end  of  acceptable  calibration  uncertainty, 
but  it  should  be  mentioned  that  the  used  PCRF  2500  (250x10)  is  not  calibrated  by  the 
manufacturer and it was set only to have a 10 fold increase of the PCRF. 

Figure 22: Sub-23 nm fraction of V1. 

28 

 
 
 
 
Figure 23: Real time concentration signals of the two CPCs. Concentrations refer to the 
CVS (20160224_01_WHVC cold). 

Figure 24: Sub-23 nm fraction of V3. 

29 

 
 
 
 
 
Figure  25:  Typical  measured  raw  concentration  of  CPCs  (emissions  around  5x1010 
p/kWh) (20160512_02_Region.Del.). 

Table 6: Count statistics error (n0.5/n) of a CPC based on the measured concentration n. 

 Concentration [p/cm3]
 Uncertainty

1

100%

10

32%

100

10%

1000

3%

10000

1%

Figure 26: Sub-23 nm fraction of V5. Red squares are cold start tests (i.e. first 1200 s). 

30 

 
 
 
 
 
 
Figure 27: Real time concentrations of a) 10  nm and  23  nm PN and  b) NOx. In panel b 
the speed profile is also shown. Vehicle V5.  

31 

 
 
 
Figure 28: Sub-23 nm fraction of V2. 

Figure 29: Typical measured concentration of CPCs (emissions around 4x1012 p/kWh for 
the  whole  cycle  and  1.5x1013  p/kWh  for  the  cold  start  part).  Cold  start  at  0°C 
(20160323_01_ISC cold_0°C). 

32 

 
 
 
 
 
 
Figure  30:  Difference  of  PMP_CVS  from  PMP_TP  with  different  PCRFs.  Exact  levels  not 
known  due  to  lost  OBD  signal.  Based  on  the  distance  the  emission  levels  should  be 
around 5x10^12 p/kWh. 

33 

 
 
 
 
 
 
4  Main evaluation phase: PN-PEMS #1: AVL 

4.1  General 

PN-PEMS #1 was available with vehicle V1. It was returned to the manufacturer to check 
the device and then it was used with vehicle V3 and V5.  

4.2  Robustness 

In  general  the  device  didn’t  have  any  issues  during  cold  or  hot  ambient  temperature 
tests.  No  indication  of  wear  either.  However,  the  results  were  not  satisfactory:  the 
device  didn’t  have  good  correlation  with  the  reference  systems  indicating  sensitivity  to 
pressure, humidity or particle size that will be discussed in the paragraphs below. 

4.3  Accuracy 

The comparison of PN-PEMS #1 with the PMP_TP for vehicle V1 can be seen in Figure 31. 
In  general  there  is  a  100%  overestimation  of  the  emissions  with  some  points 
overestimating the emissions one order of magnitude. These tests and five tests at -7°C 
which are not plotted had spikes of very high concentration. 

Figure  31:  Comparison  of  PN-PEMS  #1  with  PMP_TP  for  vehicle  V1.  Green  points  are 
tests at ambient temperature of 20°C. Blue points are tests at ambient temperature of -
7°C  (5  tests  had  artificial  high  spikes  and  are  not  plotted).  Red  points  are  tests  at 
ambient temperature of 35°C. 

The  results  with  vehicle  V3  were  not  better  (Figure  32).  Although  there  were  many 
points within 50%, there were others that were overestimating the emissions one order 
of magnitude. Similar behaviour was observed with V5 (Figure 33). 

34 

 
 
 
 
 
 
 
 
It is important to mention though that the low or high ambient temperature tests didn’t 
cause  any  problems  to  the  device.  The  possible  reasons  of  the  high  deviations  are 
discussed in the real time graphs in the next paragraph. 

Figure  32:  Comparison  of  PN-PEMS  #1  with  PMP_TP  for  vehicle  V3.  Green  points  are 
tests  at  ambient  temperature  of  20°C.  A  test  at  -7°C  is  shown  (blue  point)  and  one  at 
+35°C (red point); no more tests were conducted at extended ambient temperatures. 

Figure 33: Comparison of PN-PEMS #1 with PMP_TP for vehicle V5. 

35 

 
 
 
 
 
 
4.4  Real time measurements 

An example of a real time measurement of  PN-PEMS #1  versus the PMP_TP for vehicle 
V1  can  be  seen  in  Figure  34.  At  high  concentrations  (e.g.  cold  start)  the  agreement  is 
good.  Then  the  PN-PES  has  more  spikes  that  reach  100000  p/cm3.  At  the  end  of  the 
cycle the PN-PEMS is measuring higher than the PMP_TP. Over this specific portion of the 
cycle the 10 nm CPC also registered more particle counts and this issue will be discussed 
in  a  later  section.  This  was  a  test  with,  on  average,  good  agreement  between  the  two 
systems (36%). 

Figure  34:  Real  time  comparison  of  PN-PEMS  #1  with  PMP_TP  over  a  cold  start  WHVC 
(vehicle  V3)  (20160411_01_WHVC  cold).  Difference  over  the  cycle  36%  (level 
3.3x10^11 p/kWh). 

Another example during a SICO test with steady state points of high load can be seen in 
Figure  35.  The  PMP_CVS  of  both  the  23  nm  and  10  nm  CPCs  are  also  given.  The 
pressure  at  the  particle  detector  of  PN-PEMS  is  given  in  the  second  panel.  The  relative 
humidity at the detector was 10% to 16% and thus it is not plotted. A small dependency 
on  the  pressure  and/or  size  of  particles  can  be  seen.  The  most  important  is  that  the 
rapid  pressure  changes  result  in  huge  spikes  that  affect  the  results.  In  this  example 
without the spikes the difference of the PN-PEMS from the PMP_TP is 30%, but including 
the  spikes  is  100%.  It  should  be  noted  though  that  high  pressure  increases  are  not 
expected  at  typical  chassis  dynamometer  testing  and  not  on  the  road.  Another 
interesting observations is that the higher  emissions recorded by the PN-PEMS coincide 
with periods were the 10 nm CPC is also measuring higher. As the efficiency of the PN-
PEMS for small particles is very low (<10% see Calibration chapter 11) it is possible that 
these  particles  are  bigger  that  the  23  nm  CPC  cannot  detect  due  to  their  structure  or 
chemical composition.  

36 

 
 
 
 
 
Figure 35: Real time comparison of PN-PEMS #1 with PMP_TP over a SICO test (vehicle 
V3) (20160512-01-SICO). 

An  ISC  cycle  is  given  in  Figure  36.  The  emission  levels  are  7.5x10^9  p/kWh.  The  PN-
PEMS is measuring higher than the PMP_TP because the emissions of the vehicle are at 
the background levels of the PN-PEMS. Nevertheless, this background level is quite close 
to the background level of the PMP_CVS system. In this example there are two spikes of 
the PN-PEMS system that result in high average emissions for the cycle, close at the PN 
emissions limit of 6x10^11 p/kWh. These two spikes are probably the result of a droplet 
entering the system,  as the  relative humidity at the detector of the PN-PEMS increases 
suddenly (without obvious reason from the engine operation). The difference of the PN-
PEMS to the PMP_TP is around 100% at the first part (first 1000 s) or the high emitting 
part of the cycle (around 4400-5400 s). At the low emissions parts of the cycle the PN-
PEMS  is  measuring  6  times  higher,  but  in  absolute  levels  the  difference  is  very  small. 

37 

 
 
 
 
 
The overall emissions are 7.5x10^9 p/kWh, the PN-PEMS measures 5x10^11 p/kWh or 
2x10^10 p/kWh without these two spikes.   

Figure 36: Real time comparison of PN-PEMS #1 with PMP_TP over an ISC cycle (vehicle 
V5) (20160519-01_ISC cold). 

Another  example  with  good  agreement  at  the  cold  start,  but  noisy  signal  afterwards  is 
given  in  Figure  37.  In  this  case  the  ambient  temperature  was  -7C.  Although  the 
difference is 20% at the cold start the PN-PEMS is measuring 18 times higher at the rest 
part of the cycle. The average cycle difference though is only 32%. Probably in this test 
there  were  condensates  actually  frozen  at  the  inlet  and  causing  this  behaviour;  the 
pressure downstream of the orifices of the device was not constant as it should be, but 
fluctuating. 

In Figure 38, where the emissions are high, the difference of the PN-PEMS to the PM_TP 
is 10%. 

38 

 
 
 
 
 
 
 
PMP_CVS PMP_TP PN-PEMS Diff to TP
1.18E+12 1.54E+12 1.24E+12
-19%
4.59E+09 2.61E+09 4.90E+10 1781%
32%
6.83E+10 8.65E+10 1.14E+11

Cold
Rest
All

Figure 37: Real time comparison of PN-PEMS #1 with PMP_TP over a cold start WHVC at 
-7°C (vehicle V5). (20160529_01_ISC cold_-7°C) 

Figure  38:  Real  time  comparison  of  PN-PEMS  #1  with  PMP_TP  over  a  cold  start  WHVC 
(vehicle V3) (20160415_01_WHVC cold_-7°C) 

39 

 
 
 
 
 
4.5  Conclusions 

The conclusions for PN-PEMS #1 in the main evaluation phase are: 

Only for high concentration levels (e.g. during cold start) the correlation of PN-PEMS to 
PMP_TP is good (within 30%). 

Very high differences were observed very often at low emission levels. One reason could 
be  the  sensitivity  to  particles  smaller  than  23  nm,  although  highly  unlikely.  The  main 
reason  though  was  high  spikes  which  probably  originated  from  pressure  fluctuations 
and/or droplets entering the system. 

It  seems  that  the  ambient  temperature  doesn’t  have  any  direct  effect  at  the  device. 
Indirectly  it  can  affect  the  emissions  by  droplets  and  condensation  upstream  of  the 
system that can create spikes.  

No indication in the data file of errors or warnings. However this is not the case for the 
complete PEMS unit, which is logging all warnings and errors. 

40 

 
 
 
 
 
 
5  Main evaluation phase: PN-PEMS #2: HORIBA (mod NPET) 

5.1  General 

PN-PEMS #2 was available with vehicles V1 (unit PN-PEMS #2a and #2b), V3 (PN PEMS 
#2c), V5 (PN PEMS #2c) and V6 (PN-PEMS #2c).  

5.2  Robustness 

During the evaluation phase three units were tested. One of them was the light-duty unit 
(PN-PEMS #2a) and was available only for a limited time. 

PN-PEMS  #2b  (solid  diamonds  in  Figure  39)  had  a  good  agreement  with  the  reference 
system  at  the  tailpipe  (within  25%)  (vehicle  V1).  However,  after  the  tests  at  low 
ambient  temperature  the  difference  drifted  to  -20%  to  -30%  and  remained  at  those 
levels  for  all  tests  (even  at  20°C).  During  those  low  ambient  temperature  tests  the 
instrument  showed  some  errors.  The  on-road  tests  were  done  without  any  errors  from 
the device. This unit failed at the first test with vehicle V2 and was sent back for repair. 

PN-PEMS #2c (open squares) was within 20% of the PMP_TP and remained at this level 
for  all laboratory  before  and  after  on-road  tests  (including  a  few  low  temperature  tests 
before  the  on-road  tests).  With  vehicle  V3  the  differences  remained  within  20%  (open 
triangles).  However  during  the  low  ambient  temperature  tests  some  errors  appeared. 
With  the  next  vehicle  V6  (open  circles)  the  differences  were  up  to  -40%.  After  a  few 
tests the system stopped working. 

Figure 39: Evaluation over measuring time of PN-PEMS #2. Solid diamonds are unit PN-
PEMS  #2b  with  vehicle  V1.  Open  symbols  are  unit  PN-PEMS  #2c  with  vehicle  V3  (open 
squares), V5 (open triangles) and V6 (open circles). 

41 

 
 
 
 
 
 
 
The main conclusion is that the system is not very robust at low ambient temperatures. 
It  needs  to  be  mentioned  that  HORIBA´s  modified  NPET,  which  is  prototype,  was  a 
concept study to prove the feasibility of the system design with respect to accuracy and 
robustness  in  mobile  applications.  Further  improvements  regarding  robustness  against 
low ambient temperatures were introduced in the final product, namely the OBS-ONE-PN 
(On-Board  System  for  Particle  Number  measurements).  Some  of  these  improvements 
will be discussed in this report in the real time measurements section. 

5.3  Tilting  

The  CPC  of  the  PN-PEMS  #2c  was  evaluated  regarding  the  stability  of  its  counting 
efficiency on tilting the instrument and shaking. Only this system was checked as it was 
the  only  PEMS  CPC-based  system  available  at  that  time.  No  DC-based  system  was 
checked as there were no concerns regarding tilting for this technology. 

The setup was the typical calibration set up: A soot generator (APG from AVL) produced 
thermally stable particles which were classified in a Differential Mobility Analyzer 3080L 
from  TSI.  The  monodisperse  aerosol  was  sent  to  a  reference  CPC  (3025A  from  TSI),  a 
PMP  CPC  (3790  from  TSI)  (but  not  any  of  those  used  in  the  current  measurement 
campaign) and the isopropanol CPC of the PEMS. For these tests the dilution and thermal 
pre-treatment system of the PN-PEMS was bypassed, thus the monodisperse aerosol was 
connected  directly  to  the  inlet  of  the  CPC.  For  this  reason  the  results  of  the  PN-PEMS 
were divided with the PCRF. The PMP CPC was kept at a fixed position without any tilting 
or shaking, as control unit. 

The results are shown in Figure 40.  The PMP CPC has low counting efficiency at 23 nm 
(30%)  and  reaches  approximately  95%  at  100  nm.  The  PEMS  CPC  has  65%  counting 
efficiency at 23 nm and 90% at 100 nm. The absolute levels of the counting efficiencies 
should be considered with care as they were estimated by the PEMS result divided with 
the (estimated) PCRF of the unit. In addition, it’s not known how the experimental setup 
(opened device and connecting directly to the PEMS CPC) has affected the instrument. 

Figure 40: Stability of the CPC of PN-PEMS #2 at vibration and tilting at different angles. 

42 

 
 
 
 
 
Tilting  the  instrument  for  around  2  min  had  a  small  effect  on  the  counting  efficiencies; 
they  were  slightly  higher  or  lower  at  the  23  nm  size.  The  effect  on  the  counting 
efficiencies was in the range of 5% at 23nm during extreme tilting (+25° slope, which is 
above  the  specification  of  the  manufacturer))  and  it  was  a  little  bit  smaller  at  100  nm. 
The  efficiencies  during  strong  shaking  of  the  instrument  were  also  within  the 
experimental  uncertainty.  This  information  in  addition  to  the  vibration  testing  of  the 
instrument manufacturer indicate that the instrument can be  considered robust  enough 
for the on-road tests. 

5.4  Accuracy 

The comparison  of PN-PEMS #2b  with the PMP_TP for  vehicle V1 can be seen in Figure 
41. All green points (i.e. at temperatures between around 20°C) are within ±25%.  

Figure  41:  Comparison  of  PN-PEMS  #2b  with  PMP_TP  for  vehicle  V1.  Green  points  are 
tests at ambient temperature of 20°C. At different temperatures the system had errors. 
Only for illustrative purposes a test at -7°C is shown (blue point) and one at +35°C (red 
point). Dotted lines show the ±15% differences from the 1:1 line. 

The  comparisons  of  PN-PEMS  #2c  with  PMP_TP  for  vehicles  V3  and  V5  are  shown  in 
Figure  42  and  Figure  43  respectively.  The  differences  are  within  15%.  With  vehicle  V3 
only  a  limited  number  of  tests  at  extended  ambient  conditions  were  conducted.  These 
tests were still within the 15% differences that was observed at the 20°C tests.  

Different  ambient  temperatures  were  examined  with  vehicle  V5.  The  tests  at  -7°C  and 
0°C with high emissions were again within 15% from the PMP_TP. The tests with lower 
concentrations  had  big  (relatively)  differences.  As  it  will  be  shown  in  the  real  time 
graphs,  there  were  spikes  that  artificially increased  the  concentration.  The  +35°C  tests 
were  lower  than  the  PMP_TP  system.  It  is  not  clear  though  if  this  has  to  do  with  the 
temperature or because these tests were after the low temperature tests and there was 
a small drift (see discussion in robustness). 

43 

 
 
 
 
 
 
Figure  42:  Comparison  of  PN-PEMS  #2c  with  PMP_TP  for  vehicle  V3.  Green  points  are 
tests  at  ambient  temperature  of  20°C.  A  test  at  -7°C  is  shown  (blue  point)  and  one  at 
+35°C  (red  point);  no  more  tests  were  conducted  at  extended  ambient  temperatures. 
Dotted lines show the ±15% differences from the 1:1 line. 

Figure  43:  Comparison  of  PN-PEMS  #2c  with  PMP_TP  for  vehicle  V5.  Dotted  lines  show 
the ±15% differences from the 1:1 line. 

44 

 
 
 
 
 
 
5.5  Real time measurements 

Some  real  time  comparisons  with  the  PMP_TP  and  PMP_CVS  systems  are  shown  in 
Figure 44 and Figure 45 where an excellent agreement is shown. This agreement holds 
true even for cold start (Figure 46).  

Figure  44:  Real  time  comparison  of  PN-PEMS  #2c  with  PMP_TP  over  a  cold  WHVC 
(vehicle V3) (20160411_1_WHVC cold). 

Figure 45: Real time measurements with vehicle V1 (20160204_3_cycle-steady). 

45 

 
 
 
 
 
 
Figure  46:  Real  time  comparisons  at  cold  start  with  vehicle  V1  (20160205_1_WHVC 
cold). 

In 10 tests at extended temperature conditions with vehicle 1, e.g. at low (≤0°C) or high 
ambient  temperatures  (35°C),  the  PN-PEMS  #2b  had  several  errors  such  as  CPC  flow 
error, CPC bypass flow error, optics temperature error or dilution ratio error. These tests 
are not shown in (Figure 41). One of these tests is shown only for illustrative purposes 
(Figure 47). There are many spikes of high concentration that would result in emissions 
>6x10^11  p/km.  The  root  cause  of  these  spikes  is  unclear  but  according  to  the 
instrument manufacturer there are several possible explanations: 

(1) 
Electrical noise due to ice formation on the CPC detector board: PN-PEMS #2 was 
not  actively  controlling  the  cabinet  temperature.  The  OBS-ONE-PN  production  version 
contains  an  active  control  of  the  cabinet  temperature  by  means  of  shutting  down  the 
cooling fans at a certain ambient temperature to avoid cabinet temperatures below 0°C. 

(2)  Water condensation in the sample line due to either an exceedance of the water 
storage  capacity  of  the  dryer  for  the  dilution  air  or  cold  spots  somewhere  in  the  main 
cabinet. The OBS-ONE-PN keeps the cabinet temperature above 0°C under all conditions 
as described above. Furthermore a humidity sensor was implemented in the dilution air 
line  to  give  an  indication  about  the  remaining  water  storage  capacity  of  the  desiccant 
dryer. The mod. NPET did not had these functions.  

Formation  of  isopropyl  alcohol  particles  in  the  CPC  optics  block.  The  mod.  NPET 
(3) 
controls the optics temperature so that the temperature is kept a few degrees above the 
condenser temperature in order to avoid condensation of isopropyl alcohol in the optics 
block. Nevertheless the upper temperature limit is not controlled (this function has been 
implemented  in  the  OBS-ONE-PN  production  version)  which  might lead  to  nucleation  of 
isopropyl alcohol particles. 

46 

 
 
 
 
 
Figure  47:  Real  time  measurements  over  a  WHVC  at  ambient  temperature  of  0°C 
(20160225_1_WHVC cold 0°C). Vehicle V1. 

The  PN-PEMS  #2c  could  measure  one  WHVC  cold  start  test  at  -7°C  without  any  issues 
(Figure 48). However, during an ISC cycle at -7°C spikes appeared probably due to one 
of  the  reasons  discussed  above.  The  first  spike  appeared  approximately  after  6h  of 
operation at -7°C (Figure 49). Note that approximately after 4h the wick was exchanged 
by another fully charged wick (PN-PEMS #2 does not have a reservoir of liquid working 
fluid, but a charged CPC wick only. This wick needs to be recharged in isopropyl alcohol 
after approximately 4 hours). 

Figure  48:  Real  time  measurements  over  a  WHVC  at  ambient  temperature  of  -7°C  with 
vehicle V3 (20160415_01_WHVC cold at -7°C). 

47 

 
 
 
 
Figure  49:  Real  time  measurements  over  an  ISC  cycle  at  ambient  temperature  of  -7°C 
with vehicle V5 (20160520_2_ISC -7°C). 

In  this  case  the  effect  on  absolute  emissions  was  small.  The  ‘true’  emissions  as 
measured  by  the  PMP_TP  were  1.7x10^8  p/kWh,  the  emissions  measured  by  the 
PMP_CVS  system  were  3.2x10^9  p/kWh  due  to  the  CVS  background  and  the  PN-PEMS 
#2c  measured  5.0x10^9  p/kWh  due  to  the  spikes.  The  spikes  in  this  case  were  up  to 
5x10^5 p/cm3 and not 2x10^6 p/cm3 like in Figure 47. 

5.6  Regeneration 

All  vehicles  tested  (except  V2  which  was  a  CNG  one)  had  DPFs  and  they  regenerated 
passively.  Only  in  a  few  tests  where  high  loads  and  exhaust  gas  temperatures  were 
experienced  (SICO  tests)  the  instruments  were  really  challenged  regarding  high 
temperatures. For  one  test it was possible to actively regenerate the DPF with the help 
of the OEM. The results of this test can be seen in Figure 50. The regeneration starts at 
approximately time 3000 s and lasts until time 7500 s. The first 3000 s the engine was 
off  or  idling  (“missing”  data  of  the  PN-PEMS  #2b  in  the  first  3000s  are  related  to  zero 
emissions  which  cannot  be  plotted  in  log  scale).  The  emissions  at  the  tailpipe  are 
approximately  10^5  p/cm3.  The  PN-PEMS  #2b  measures  as  the  PMP_TP  without  any 
indication of malfunctioning. Note that the PN-PEMS was connected at the tailpipe and it 
was  installed  inside  the  vehicle  (immediately  after  the  on-road  tests).  Thus  it  was 
experiencing  very  high  exhaust  gas  temperatures  (425°C).  The  PMP_TP  was  connected 
just  before  the  CVS  mixing  point  thus  the  temperatures  were  much  lower.  The  final 
result  of  the  PN-PEMS  was  -30%  compared  to  the  PMP_TP  in  agreement  with  previous 
tests  that  had  differences  of  around  -25%.  The  conclusion  is  that  the  PN-PEMS  can 
measure during regeneration events without any wear issues. 

48 

 
 
 
 
 
 
Figure 50: Active regeneration test (20160314_regeneration). 

5.7  Comparison of Horiba units 

For  a  short  period  two  units  were  available.  Unit  PN-PEMS  #2a  is  the  light-duty  inter-
laboratory correlation exercise unit. Unit PN-PEMS #2b was the unit for the heavy-duty 
vehicles  evaluation  program.  Both  units  were  measuring  in  parallel.  The  differences  of 
the two untis were within 10-25%; the light-duty unit probably was overestimating as it 
was also measuring higher than the PMP systems both at the tailpipe and the CVS. There 
was  no  particular  tendnecy  or  trend  at  these  tests  to  explain  the  differences;  i.e.  the 
differences couldn’t be explained by emission levels, test type or duration of the test. 

5.8  Conclusions 

The main conclusions for the PN-PEMS #2 from Horiba (modified NPET) are: 

•  Very good correlation with the PMP_TP: Differences within 15% (or 25% with the 

first unit) at 0-20°C. 

•  No issues with engine cold start and regeneration events. 

•  Robust device for mobile applications (no issues with inclination and/ or shaking) 

•  Tendency  of  drift  after  tests  at  low  ambient  temperature.  The  low  ambient 
temperature  tests  had  errors  of  the  optics.  They  also  showed  high  artificial 
spikes. These issues should’t appear in the production version units OBS-ONE-PN 
which have implemented some functionalities to address this topic. 

•  File with no real time errors (only one error for the whole test) as the mod. NPET 
was  operated  by  a  very  basic  software.  A  real  time  error  file  is  implemented  in 
the OBS-ONE-PN control software. 

•  No results are availlable with vehicle V2 (CNG). 

49 

 
 
 
 
 
 
Figure 51: Comparison of two PN-PEMS units with the reference systems. 

50 

 
 
 
 
 
 
 
6  Main evaluation phase: PN-PEMS #3: TESTO (NanoMet 3) 

6.1  General 

PN-PEMS #3 was available with V1 (unit PN-PEMS #3a), V2 (unit PN-PEMS #3b) and V3 
(unit PN-PEMS #3b). 

6.2  Robustness 

During the evaluation phase two units were tested. Both of them had issues and failed. 
The  first  one  was  the  light-duty  unit  (PN-PEMS  #3a).  It  had  already  some  issues  from 
the  inter-laboratory  exercise  (‘offsets  too  high  or  unstable’,  ‘Idiff  out  of  range’).  At  the 
tests at +35°C the error ‘temp. stage out of range’ also appeared. The second unit was 
used with the CNG vehicle V2. A warning appeared at the +35°C tests (‘corona voltage 
out  of  range’)  but  there  was  no  indication  of  malfunctioning  even  at  the  low  ambient 
temperature tests.  

The  same  warning  insisted  with  vehicle  V3.  At  the  -7°C  test  the  error  ‘low  meas.  gas 
pump’  appeared  and  then  the  unit  was  not  functioning  as  the  pump  was  not  sampling 
(the unit was left overnight at -7°C). When the unit was sent back to the manufacturer it 
was  found  that  this  problem  was  due  to  a  kinked  tubing  upstream  of  the  impactor 
module. 

The  conclusion  of  these  tests  is  that  the  unit  was  robust  enough  at  the  temperatures 
specified by the manufacturer (5-30°C). 

6.3  Accuracy 

The comparison of PN-PEMS  #3a with the PMP_TP for vehicle V1 can be seen in Figure 
52. Although many points are missing due to errors and warnings (that existed from the 
beginning  of  the  measurement  campaign),  the  points  that  are  shown  have  a  relatively 
good agreement with the PMP_TP. 

The comparison of the PN-PEMS #3b with the PMP_TP for vehicle V2 is shown in Figure 
53  and  for  vehicle  V3  in  Figure  54.  The  results  are  within  30%  for  emission  levels 
>1x10^11  p/kWh.  Higher  (relative)  differences  can  be  seen  at  lower  levels  where  the 
detection limit of the PN-PEMS is approached. 

The results also show, that as long as there are no errors, the values that are measured 
at  low  or  high  ambient  temperatures  are  accurate  enough,  i.e.  the  differences  to  the 
PMP_TP are similar to the differences observed at 20°C. 

A  point  that  needs  attention  is  the  cold  start.  Depending  on  the  size  of  the  particles 
there  might  an  effect  (i.e.  PN-PEMS  and  PMP_TP  measuring  differently)  (Figure  53)  or 
there  could  be  no  effect  (Figure  54).  This  will  be  shown  better  in  the  real  time 
measurements section. 

51 

 
 
 
 
 
Figure  52:  Comparison  of  PN-PEMS  #3a  with  PMP_TP  for  vehicle  V1.  Green  points  are 
tests at ambient temperature  of 20°C. The blue point is a test at -7°C. Many tests with 
low concentrations are not shown. Dotted lines show the ±15% differences from the 1:1 
line.  

Figure 53: Comparison  of PN-PEMS #3b with PMP_TP for vehicle V2. Dotted lines show 
the ±15% differences from the 1:1 line. 

52 

 
 
 
 
 
 
Figure 54: Comparison  of PN-PEMS #3b with PMP_TP for vehicle V3. Dotted lines show 
the 0-50% differences from the 1:1 line. 

6.4  Real time measurements 

Some  real  time  comparisons  of  PN-PEMS  #3a  with  the  PMP_TP  can  be  seen  in  the 
following  Figures.  Figure  55  and  Figure  56  show  the  PN  emissions  of  P-PEMS  #3a  with 
warnings  or  errors  (offsets  too  high  or  unstable,  Idiff  out  of  range).  The  real  time 
agreement  with  the  PMP_TP  is  not  satisfactory.  For  both  low  (2.5x10^10  p/kWh)  and 
high  (2.5x10^12  p/kWh)  levels.  The  average  result  though  agrees  relatively  well  with 
the PMP_TP. 

The  real  time  comparability  of  PN-PEMS  #3b  (without  any  warnings or  errors)  with  the 
PMP_TP was very good for cold start or hot parts of the cycle at different emission levels 
with vehicle V2 (Figure 57 and Figure 58) or vehicle V3 (Figure 61).  

However there  can be  case where the agreement is not  so good. This is the case for a 
cold start of vehicle V2 where high concentration of small particles were emitted (15-40 
nm  according  to  the  mean  size  estimated  by  the  PN-PEMS  #3b)  or  the  relatively  big 
difference  between  the  23  nm  and  10  nm  CPCs  (Figure  59).  Note  however  that  these 
tests  at  0°C  and  -7°C  were  outside  the  specified  temperature  range  of  the  instrument. 
The hot part had good agreement though (Figure 60). Correcting the second by second 
PN  concentrations  of  the  PN-PEMS  with  the  efficiency  of  a  PMP  system  for  the  size 
estimated  by  the  PN-PEMS  improves  the  correlation  (Figure  59).  In  other  words 
mathematically forcing a PMP efficiency at the PN-PEMS could improve the results. This 
assumption though has to be further evaluated. This function will be implemented in the 
future PN-PEMS units according to the manufacturer. 

53 

 
 
 
 
Figure 55: Real time comparison of PN-PEMS #3a with PMP_TP for vehicle V1. PN-PEMS 
levels  of  2.5x10^10  p/kWh 
range’.  Emission 
had  an  error 
(20160224_1_WHVC cold). 

‘Idiff  out  of 

Figure 56: Real time comparison of PN-PEMS #3a with PMP_TP for vehicle V1. PN-PEMS 
had  a  warning  ‘offset  too  high  or  unstable’  and  an  error  ‘Idiff  out  of  range’.  Emission 
levels of 2.5x10^12 p/kWh (20160224_3_SICO). 

54 

 
 
 
 
 
 
Figure 57: Real time comparison of PN-PEMS #3b with PMP_TP for vehicle V2. Cold start 
(20160321_1_ISC_cold_10°C). 

Figure 58: Real time comparison of PN-PEMS #3b with PMP_TP for vehicle V2. Hot part 
of a long test (20160321_1_ISC_cold_10°C). 

55 

 
 
 
 
 
 
Figure 59: Real time comparison of PN-PEMS #3b with PMP_TP for vehicle V2. Cold start 
at  0°C  (20160323_1_ISC_cold_0°C).  ‘Corr’  means  signal  corrected  with  a  typical  PMP 
penetration efficiency based on the estimated size of the PN-PEMS #3. 

Figure 60: Real time comparison of PN-PEMS #3b with PMP_TP for vehicle V2. Hot part 
of a long test (20160323_1_ISC_cold_0°C). 

56 

 
 
 
 
 
 
Figure 61: Real time comparison of PN-PEMS #3b with PMP_TP for vehicle V3. Cold start 
at -7°C (20160331_01_ISC cold_-7°C). 

6.5  Conclusions for PN-PEMS #3 

The main conclusion for PN-PEMS #3 from Testo (NanoMet 3) were: 

•  The  agreement  with  the  PMP_TP  was  good  (around  30%)  for  emission  levels 
>1x10^11  p/kWh.  Higher  relative  differences  were  observed  for  lower  levels  as 
the unit was approaching its detection limit. 

•  The real time signals were in good agreement with the PMP_TP 
•  The unit when operated outside its specified temperature range (around 5-30°C) 
had warnings and errors that resulted in failure of the device. Typically observed 
warnings and errors were: ‘offsets too high or unstable’ and ‘Idiff out of range’. In 
these cases the real time agreement with the PMP_TP was not good. 

57 

 
 
 
 
 
 
 
7  Main evaluation phase: PN-PEMS #6: SHIMADZU 

7.1  General 

PN-PEMS #6 (prototype) was available with vehicle V2, V3 and V5. The commercial unit 
was available during the second evaluation phase with vehicle V8. 

7.2  Robustness 

There are no warnings and errors in the exported file, thus it is not clear whether there 
were any issues during the campaign. 

7.3  Accuracy 

The comparison of PN-PEMS #6 with the PMP_TP for vehicle V2 can be seen in Figure 62. 
This  was  the  high  emitting  CNG  vehicle.  The  20°C  tests  were  relatively  close  to  the 
PMP_TP. The rest of the tests at sub 0°C, which were conducted afterwards, were 40% 
lower.  Comparing  the  +35°C  and  the  -7°C  it  seems  that  the  temperature  doesn’t  have 
an effect  on the operation of the unit. However why the absolute levels are 40% lower 
it’s not clear; maybe condensates blocked orifices in the device. 

Figure 62: Comparison of PN-PEMS #6 with PMP_TP for vehicle V2. 

The results with the low emitting vehicle V3 can be seen in Figure 63. The scatter of the 
results is high. Figure 64 shows the results for vehicle V5 (all PN_PEMS #6 results in this 
figure were multiplied by 100 to have better agreement with the PMP_TP). 

58 

 
 
 
 
 
 
 
 
Figure 63: Comparison of PN-PEMS #6 with PMP_TP for vehicle V3. 

Figure 64: Comparison of PN-PEMS #6 with PMP_TP for vehicle V5. PN-PEMS #6 results 
were multiplied by 100 for this figure. 

7.4  Real time measurements 

An example of a real time measurement of  PN-PEMS #6  versus the PMP_TP for vehicle 
V2 can be seen in Figure 65 (+35°C) and Figure 66 (-7°C). The agreement is good (after 
correcting with a factor of 2 for better visualization).  

59 

 
 
 
 
 
Figure 65: Real time comparison of PN-PEMS #6 with PMP_TP over a WHVC (vehicle V2) 
(20160321_02_WHVC_+35°C).  PN-PEMS  #6  concentration  was  multiplied  by  2  for 
better visualization. 

Figure 66: Real time comparison of PN-PEMS #6 with PMP_TP over a WHVC (vehicle V2) 
(20160322_01_WHVC_-7°C).  PN-PEMS  #6  concentration  was  multiplied  by  2  for  better 
visualization. 

60 

 
 
 
 
 
 
Real time examples with the low emitting vehicle V3 can be seen in the following figures. 
For vehicle V5, Figure 70 shows that the agreement is not very good. There is an offset 
and the cold start peaks do not match. 

Figure  67:  Real  time  comparison  of  PN-PEMS  #6  with  PMP_TP  over  a  warmup  test 
(vehicle V3) (20160330_01_WHVC_2°C). 

Figure  68:  Real  time  comparison  of  PN-PEMS  #6  with  PMP_TP  (20160411_01_WHVC 
cold) (vehicle V3). 

61 

 
 
 
 
 
 
Figure 69: Real time comparison of PN-PEMS #6 with PMP_TP (20160331_01_ISC_-7°C) 
(vehicle V3). 

Figure  70:  Real  time  comparison  of  PN-PEMS  #6  with  PMP_TP  (vehicle  V5). 
(20160525_01_ISC cold_0°C). PN-PEMS #6 was multiplied by 100. 

62 

 
 
 
 
 
 
 
8  On-road tests 

Figure  71:  Real  time  signal  of  PN-PEMS  during  an  on-road  test  with  vehicle  V1 
(20160309_01_Road).  Emissions  8.0x10^10  (PN-PEMS  #2)  and  7.4x10^10  (PN-PEMS 
#3) p/kWh. 

Figure  72:  Real  time  signal  of  PN-PEMS  during  an  on-road  test  with  vehicle  V3 
(20160427_01_Road).  Emissions  7.5x10^10  (PN-PEMS  #2)  and  1.5x10^11  (PN-PEMS 
#1) p/kWh. 

63 

 
 
 
 
 
 
For  the  on-road  tests  there  was  no  reference  system  installed  on-board.  However,  in 
most cases two PN-PEMS were installed and were measuring simultaneously.  

The  comparison  of  the  real  time  signals  can  be  seen  in  Figure  71  for  PN-PEMS  #2  and 
#3  and  Figure  72  for  PN-PEMS  #2  and  #1.  The  comparability  of  the  two  signals  is 
acceptable and in line with the lab tests: PN-PEMS #2 and #3 were within 10% and this 
reflects  the  good  comparability  they  had  with  the  reference  PMP  system  in  the 
laboratory. PN-PEMS #1 was 50% higher than PN-PEMS #2 and this is also similar to the 
overestimation that the PN-PEMS showed in the laboratory. 

The emission levels that were measured during the on-road tests were close to the ISC 
cycles  in  the  laboratory  (Figure  9  and  Figure  11)  and  also  on  the  expected  range 
(Giechaskiel et al. 2015b). Thus the on-road tests didn’t indicate any special issues with 
the PN-PEMS, or at least in addition to those identified in the laboratory. 

For a few laboratory tests with vehicle V1 the PN-PEMS #2 and #3 were installed on the 
vehicle,  exactly  as  on  the  road.  The  difference  to  the  reference  system  remained  the 
same indicating that having the system inside the vehicle didn’t affect their performance. 

64 

 
 
 
 
 
 
10 Second evaluation phase 

In 

this  phase  commercially  available 

The second evaluation phase was conducted in order to check the improvements of the 
tested. 
instruments. 
Representative of the OEM that provided the vehicle V8 was present, participated in the 
setup and tests, had access to all data, and did the calculations. Thus this phase can be 
considered  as  an  OEM  pre-validation  phase.  The  final  check  of  the  results  and  the 
reporting was still done by JRC. No CNG vehicle was available for this phase. 

instruments  were 

10.1  PMP_CVS vs. PMP_TP 

The correlation of the PMP_TP to the PMP_CVS can be seen in Figure 73. The agreement 
is  excellent  with  a  slope  of  1.01  and  R2=0.99.  The  differences,  with  one  exception,  are 
within  15%  and  there  is  no  dependency  of  the  ambient  temperature  in  the  climatic 
room,  as  it  should,  because  the  PMP_TP  was  installed  in  a  room  with  controlled 
temperature  of  20°C.  As  mentioned  in  the  main  evaluation  phase  the  position  of  the 
tailpipe system close to the dilution tunnel probably masked any effects due to pressure 
pulsations, thermophoresis, diffusion and agglomeration. 

Figure  73:  Correlation  of  PMP_TP  to  PMP_CVS  for  vehicle  V8.  The  red  point  was  not 
considered in the correlation. 

The  real  time  signals  of  the  outlier  of  Figure  73  are  shown  in  Figure  74.  The  high 
difference is due to two high spikes of the system at the dilution tunnel (PMP_CVS). For 
this test an EEPS (Engine Exhaust Particle Sizer) was also connected to the full dilution 
tunnel to measure total particles (i.e. without any thermal pre-treatment). It is evident 
that  the  high  spike  of  the  PMP_CVS  coincides  with  the  increase  of  the  exhaust  gas 
temperature  and  the  increase  of  total  particle  concentration.  Thus  it  can  be  assumed 
that  the  high  spike  of  the  PMP_CVS  system  is  re-nucleation  downstream  of  the 
evaporation tube of the system due to the high concentration of nucleation mode mass 

65 

 
 
 
 
 
 
 
in  the  dilution  tunnel  (estimated  >0.5  mg/m3).  The  PMP_TP  system  didn’t  have  this 
artefact  because  this  nucleation  mode  probably  doesn’t  form  in  the  first  place:  at  the 
tailpipe  the  exhaust  gas  is  sampled  at  high  temperature  before  any  nucleation  mode 
formation. A key message from this figure is that systems should be capable of handling 
masses  of  >0.5  mg/m3.  Thus  the  requirement  in  technical  specifications  of  volatile 
removal efficiency of >1 mg/m3 is the right order of magnitude (alkanes or emery oil). 

Figure 74: Real time comparison of PMP_TP and PMP_CVS (20160914-02_Steady). 

10.2  Sub-23 nm fraction 

The sub-23 nm fraction was estimated by comparing the concentrations of a 10 nm CPC 
and the 23 nm CPC measuring in parallel downstream of the VRP of the PMP_CVS (3772 
from  TSI)  and  PMP_TP  (Airmodus  A20-10nm).  No  correction  was  applied  to  the  10  nm 
CPC  for  the  particle  losses  in  the  PMP  system,  thus  the  fractions  might  be 
underestimated. 

The  sub-23  nm  fraction  for  the  DPF  and  SCR  equipped  vehicle  V8  is  low  (<20%)  at 
concentrations  >1x10^11  p/kWh  (Figure  75).  However,  quite  often  it  was  high  at  low 
concentrations (<1x10^11 p/kWh) and the main assumption is formation of small urea 
particles  (Amanatidis  et  al.  2014);  their  contribution  in  relative  terms  increases  as  the 
absolute  emissions  decrease.  Lower  counting  efficiency  of  the  23  nm  CPC  of  these 
particles due to their chemistry is also another possibility. 

The comparison of the sub-23 nm fractions as measured at the full dilution tunnel by the 
PMP_CVS and the tailpipe by the PMP_TP are shown in Figure 76. The correlation is very 
good  with  a  13%  difference  on  average.  This  difference  could  originate  either  from 
higher losses of sub-23 nm particles in the PMP_TP system or more efficient removal of 
the condensed material. This can happen because the system at the tailpipe theoretically 
never  permits  condensation  of  volatile  material  on  the  particles  as  the  sample 
temperature  is  always  held  above  the  dew  point.  On  the  other  hand  the  system  at  the 
dilution  tunnel  measures  particles  that  condensation  of  volatile  on  them  has  already 
happened. 

66 

 
 
 
 
 
Figure 75: Sub-23 nm fraction of V8. 

Figure  76:  Correlation  of  sub-23  nm  fractions  as  identified  in  the  system  at  the  full 
dilution and the tailpipe. 

67 

 
 
 
 
 
 
 
 
10.3  PN-PEMS #1: AVL MOVE 

PN-PEMS #1b had the following modifications compared to the main evaluation phase:  

•  The dilution ratio was reduced to 6:1 in order to a) increase the sample flowrate 
and reduce the sensitivity of dilution on pressure fluctuations and b) improve the 
noise levels of the device. 

•  The  operating  voltages  of  the  sensor  were  modified  to  reduce  the  counting 
efficiency at small sizes and thus assess whether the device was indeed detecting 
sub-23  nm  particles.  These  specific  settings  were  not  optimal  for  the  size 
dependence efficiency of the device, but were rather focusing on investigating the 
possibility that sub-23 nm particles were actually detected. 

•  A  probe  heater  was  supplied  to  be  installed  on  the  adaptor  used  to  connect  the 
heated line on the  sampling probe, as this was considered by the  supplier to be 
the cold spot that could lead to condensation issues. 

The  results  can  be  seen  in  Figure  77.  There  is  a  slight  overestimation  of  the  emissions 
(17%) but in general the correlation is good (R2>0.97) until emission levels of 1x10^11 
p/kWh. The instrument didn’t have any issues at low or high ambient temperatures.  

Figure  77:  Comparison  of  PN-PEMS  #1  with  PMP_TP  for  vehicle  V8.  Green  points  are 
tests at ambient temperature of 20°C. Blue points are tests at ambient temperature of -
7°C. Red points are tests at ambient temperature of 35°C. 

The real time signals agree well with the PMP_TP and the high spikes that were observed 
at the main phase disappeared (Figure 78). Thus it is verified that many of these spikes 
were  due  to  condensates  forming  on  the  adaptor  used  to  connect  the  instrument’s 
heated line to the tailpipe and entering into the system. 

68 

 
 
 
 
 
 
Emission  can  be  measured  accurately  over  a  wide  range  of  emissions  (4  orders  of 
magnitude)  (Figure  79).  However  there  can  be  cases  where  the  absolute  levels  have 
differences (e.g. around second 600). In this case the pressure difference was <10 mbar 
thus the reason probably has to do with the nature and size of the particles. On the basis 
of  the  counting  efficiencies  experimentally  determined  (see  Chapter  12),  it  seems 
unlikely that sub-23 nm particles are actually detected by the system.  

A  small  pressure  effect  (absolute  level  and  variation)  might  be  still  present  when  the 
changes are >15 mbar (Figure 80). At this test a high nucleation mode was observed at 
the CVS (see Figure 74), however it’s highly unlikely that the emissions observed by PN-
PEMS #1 were due to inefficient removal efficiency as the calibration tests showed very 
high removal efficiency (see Table 8) or the regeneration tests (to be discussed later in 
Figure  90).  This  would  happen  only  if  the  pressure  change  would  affect  the  residence 
time  in  the  catalytic  stripper  of  the  device,  which  is  unlikely.  As  discussed  in  the  main 
evaluation  phase  it  cannot  be  excluded  that  the  difference  could  also  be  due  to  lower 
detection efficiency of the specific type of particles for the 23 nm CPC. 

Figure  78:  Real  time  comparison  of  PN-PEMS  #1  with  PMP_TP  over  a  hot  start  WHVC 
(vehicle V8) (20160906-05_WHVC hot). Emission levels 1.4x10^11 p/km (PN-PEMS #1 
+83%). 

69 

 
 
 
 
 
Figure  79:  Real  time  comparison  of  PN-PEMS  #1  with  PMP_TP  over  steady  state  points 
(vehicle V8) (20160906_04_Steady). Pressure variation <10 mbar. 

Figure  80:  Real  time  comparison  of  PN-PEMS  #1  with  PMP_TP  over  steady  state  points 
(vehicle V8) (20160914-02_Steady).  

70 

 
 
 
 
 
 
 
10.4  PN-PEMS #2: HORIBA OBS-ONE 

For  the  second  evaluation  phase  the  commercial  unit  OBS-ONE  PN  was  available  (PN-
PEMS  #2d).  The  correlation  was  excellent  (slope  1.05,  R2>0.99)  and  the  differences 
were within ±15% with the exception of the tests at 0°C and -7°C (Figure 81).  

Figure  81:  Comparison  of  PN-PEMS  #2d  with  PMP_TP  for  vehicle  V8.  Green  points  are 
tests  at  ambient  temperature  of  20°C.  Red  points  are  tests  at  ambient  temperature  of 
35°C. All tests at sub-0°C had errors and only one (blue square) is shown for illustrative 
reasons. One test with a probe heater had no errors (blue square). 

The law ambient temperature tests had spikes, like in the main campaign. These spikes 
resulted  in  emission  levels  around  2x10^11  p/km.  It  seems  that  the  insulation  of  the 
tube  was  not  enough  to  avoid  condensation  in  the  tube  between  the  tailpipe  and  the 
instrument,  which  was  longer  than  it  would  be  in  real  applications  due  to  lack  of  the 
appropriate  parts  to  connect  it  directly  (Figure  5).  These  condensates  could  result  in 
many  small  particles  when  heated  inside  the  device.  When  a  heater  was  used  at  the 
sample probe these spikes didn’t appear even during a 3 h test (Figure 82).  

For  tests  at  20°C  the  agreement  with  the  reference  system  at  tailpipe  was  excellent, 
even when high concentration of sub-23 nm particles existed (Figure 83). 

71 

 
 
 
 
Figure 82: Real time comparison of PN-PEMS #2d with PMP_TP over an ISC cycle at -7°C 
(vehicle V8) (20160913-01_ISC_-7°C). With probe heater. 

Figure 83: Real time comparison of PN-PEMS #2d with PMP_TP over steady state modes 
(vehicle V8) (20160914-02-Steady). 

10.5  PN-PEMS #3: TESTO NANOMET 3 

PN-PEMS  #3c  is  basically  the  same  unit  since  2013  with  only  minor  modifications.  The 
results  can  be  seen  in  Figure  84.  The  agreement  with  the  PMP_TP  is  excellent  for 
emission  levels  above  the  emission  limit  6x10^11  p/kWh.  From  1x10^11  p/kWh  to 

72 

 
 
 
 
 
3x10^11 p/kWh the differences are from 0% up to 150% (still the result below 6x10^11 
p/kWh). The reason is that a dilution (PCRF) of 30 was used (instead of 10) and thus the 
uncertainty  which  is  typically  50%  increased  3  times.  This  can  be  seen  on  Figure  85 
where  the  signal  of  PN-PEMS  is  higher  than  the  PMP_TP.  It  can  also  be  seen  that  the 
signal matches better with the 10 nm CPC. 

Figure  84:  Comparison  of  PN-PEMS  #3c  with  PMP_TP  for  vehicle  V8.  Green  points  are 
tests at ambient temperature of 20°C. Blue points are tests at ambient temperature of -
7°C. Red points are tests at ambient temperature of 35°C. 

Figure 85: Real time comparison of PN-PEMS #3c with PMP_TP over an ISC cycle at 22°C 
(vehicle V8) (20160912-01_ISC_22°C). 

73 

 
 
 
 
10.6  PN-PEMS #6: SHIMADZU NanoPEM-10 

The correlation of PN-PEMS #6b with the PMP_TP was not satisfactory (Figure 86). The 
reasons  are  not  clear.  However  applying  a  correction  factor  tests  with  high  emissions 
could match the reference system PMP_TP (Figure 87). 

Figure  86:  Comparison  of  PN-PEMS  #6b  with  PMP_TP  for  vehicle  V8.  Green  points  are 
tests at ambient temperature of 20°C. Blue points are tests at ambient temperature of -
7°C. Red points are tests at ambient temperature of 35°C. 

Figure 87: Real time comparison of PN-PEMS #6b with PMP_TP over steady state points 
(vehicle V8) (20160906-03_Steady) 

74 

 
 
 
 
10.7  PN-PEMS #7: MAHA 

PN-PEMS #7 was tested only in the second evaluation phase. The summary results can 
be  seen  in  Figure  88.  The  agreement  is  in  general  very  good  (R2  almost  0.99)  with  an 
offset  (slope  0.67).  The  device  didn’t  show  any  issues  at  low  or  high  ambient 
temperatures. The real time signal matched perfectly with the PMP_TP (having an offset 
as previously mentioned) (Figure 89). 

Figure  88:  Comparison  of  PN-PEMS  #7  with  PMP_TP  for  vehicle  V8.  Green  points  are 
tests at ambient temperature of 20°C. Blue points are tests at ambient temperature of -
7°C. Red points are tests at ambient temperature of 35°C. 

Figure 89: Real time comparison of PN-PEMS #7 with PMP_TP over a WHVC (vehicle V8) 
(20160906-05_WHVC hot). 

75 

 
 
 
 
10.8  Regeneration 

During  the  second  evaluation  phase  a  regeneration  test  at  80  km/h  was  possible.  The 
results of the instruments that were connected during that test can be seen in Figure 90. 
All  instruments  measured  similarly  with  the  PMP_TP  (PN-PEMS  #6  and  #7  with  the 
offsets that were discussed in the respective paragraphs). After the test no issues were 
observed  with  any  of  the  instruments  confirming  the  findings  of  the  main  evaluation 
phase,  that  the  PN-PEMS  are  robust  enough  during  regenerations  and  in  addition  they 
measure accurately. 

Figure 90: Regeneration test at 80 km/h. 

76 

 
 
 
 
 
 
 
 
11 Comparison with the CVS 

In this chapter the best performing systems will be compared with the reference PMP 
system at the dilution tunnel for all examined vehicles. The differences give an indication 
of the expected uncertainty of the current PN-PEMS procedure.  

Figure 91: Comparison of PN-PEMS #2 with the PMP_CVS. Each point is a test and each 
symbol  is  a  different  vehicle.  Tests  with  errors  (most  at  sub-0°C)  have  been  excluded. 
Lines indicate the 1.35:1, 1:1 an 0.7:1 lines. 

Figure 92: Comparison of PN-PEMS #3 with the PMP_CVS. Each point is a test and each 
symbol  is  a  different  vehicle.  Tests  with  errors  (most  at  sub-0°C)  have  been  excluded. 
Lines indicate the 1.35:1, 1:1 an 0.7:1 lines. 

77 

 
 
 
 
 
 
Figure 91 and Figure 92 present the results for PN-PEMS #2 (V1, V3, V5, V8) and #3 
(V1, V2, V3, V8) respectively. The major conclusions are: 

•  Both systems are within 35%. Only a few exceptions for the CPC-based system 
(#2) and some for the DC-based (#3) as the emissions reach 1x10^11 p/kWh 
approximately which is close to the detection limit. 

•  The uncertainty of PN-PEMS measurement procedure is better than the 50% that 

was found in the light-duty study for levels >1x10^11 p/km. 

The most probable explanation is the small effect of particle dynamics in the tube 
between the vehicle and the dilution tunnel due to the low particle emission levels. 

78 

 
 
 
 
 
 
12 Calibration of PN-PEMS 

During the second evaluation phase the only instrument with a calibration certificate was 
PN-PEMS  #3.  Some  checks  that  are  required  by  the  draft  light-duty  on-road  regulation 
were conducted at JRC. 

12.1  Leak check 

This  is  obligatory.  PN-PEMS  #1  and  PN-PEMS  #6  have  available  an  automated 
underpressure  leak  check,  while  PN-PEMS  #3  a  manual  one.  CPC  based  PN-PEMS  have 
the  HEPA  filter  zero  check  as  leak  check  (but  with  lower  than  5000  p/cm3  limit)  (see 
below). 

12.2  Zero check 

The  zero  check  of  CPC-based  systems  (PN-PEMS  #2  and  #7)  was  almost  0  p/cm3.  The 
zero check of DC-based systems (PN-PEMS #1 and #3) was around 500 p/cm3. PN-PEMS 
#3  though  didn’t  pass  the  limit  of  5000  p/cm3  the  first  time.  PN-PEMS  #6  (DC-based) 
did not pass the zero check. 

Figure 93: Zero and ambient air checks. 

The  ambient  air  check  is  not  required  by  the  PN-PEMS  legislation.  All  systems  though 
measured  higher  than  the  zero  check.  Of  course  ambient  air  concentrations  can  differ 
from  place  to  place  and  over  time;  for  this  reason  it  is  not  required  check  to  evaluate 
proper  operation  of  the  sensors;  nonetheless  it’s  a  good  quality  check  of  the  proper 
operation of the system. 

79 

 
 
 
 
 
 
 
 
 
12.3  Penetration efficiency requirements 

The results of the penetration efficiency checks conducted at JRC can be seen in Table 7. 
Note  that  no  correction  for  multiply  charged  particles  was  applied  that  would  slightly 
affect  the  DC-based  instruments  results  (10%).  PN-PEMS  #2  and  #3  passed  the 
technical  specifications.  PN-PEMS  #1  and  PN-PEMS  #7  could  pass  by  multiplying  by  a 
factor (but outside the permitted 0.9-1.1 range). This factor was in the right direction in 
explaining  some  of  the  differences  observed  in  the  second  evaluation  phase.  PN-PEMS 
#6  had  a  response  as  normal  diffusion  charger  and  was  outside  the  technical 
specifications. 

Table  7:  Penetration  efficiencies.  In  red  non-compliant  values.  ‘Corr’  means  adjusted 
more than 10%. 

dp 
[nm] 

15* 

23 

30 

50 

70 

100 

200 

Specs 

- 

0.2-0.6  0.3-1.2  0.6-1.3  0.7-1.3  0.7-1.3  0.5-2.0 

#1 

#2 

0.01 

0.16 

0.31 

0.68 

0.97 

1.24 

1.71 

Corr. 

0.19 

0.50 

0.67 

0.94 

0.97 

0.99 

- 

Pass 

#3** 

0.07 

0.56 

0.56 

0.97 

1.22 

1.10 

1.03 

Pass 

#6 

#7 

- 

- 

0.13 

0.75 

2.64 

- 

8.94 

- 

Fail 

0.40 

0.68 

0.81 

1.00 

0.80 

Corr. 

* silver particles and high uncertainty 

** DF=30 

12.4  Volatile Removal Efficiency 

The volatile removal efficiency results can be seen in Table 8 of the systems evaluated. 

Table 8: Volatile Removal Efficiency results. In red non-compliant results. 

Number  GMD  mass 

PMP23  PMP10  #1 

#2 

#3*  size  Comments 

p/cm3 

nm  mg/m3  [%] 

[%] 

[%]  [%]  [%]  nm 

8.6E6 

45 

1.1 

100 

100 

100 

100 

100 

- 

required 

1.3E7 

56 

11.5 

100 

99.9 

100 

100 

96.3  10 

extreme 

* DF=30 

80 

 
 
 
 
 
 
 
 
 
 
 
 
13 Theoretical evaluation of the measurement uncertainty 

Figure  94  presents  the  expected  measurement  uncertainty  based  on  estimations  of  the 
uncertainty of the parts that are needed for the calculation of the emissions: 

(cid:1)(cid:2) =

∑ (cid:1)(cid:2), (cid:6)
(cid:7)(cid:8)(cid:9)(cid:10)

(cid:1)(cid:2), (cid:6) = 	 (cid:12)(cid:13)(cid:14),(cid:15)(cid:16)(cid:17)(cid:18)(cid:19),(cid:15)/(cid:21)(cid:18) 

where: 

PN,i     

is the particle number flux [particles/s] 

cPN,i 

 is  the  measured  particle  number  concentration  [#/m3]  normalized  at 0°C 
(time aligned to the exhaust flow) 

qmew,i    

is the measured exhaust mass flow rate [kg/s] 

ρe 

is the density of the exhaust gas [kg/m3] at 0°C 

The  estimated  uncertainty  of  the  parts  are  based  on  the  technical  specifications  of  the 
on-road procedure. The critical parts are: 

Figure 94: Theoretical estimation of PN-PEMS measurement uncertainty. 

The  30%  uncertainty  of  the  PN  analyser  (instrument  uncertainty)  due  to  the  relatively 
wider permitted efficiencies compared to the reference PN instrument at the full dilution 
tunnel  (PMP).  This  uncertainty  refers  to  emission  levels  close  to  the  limit  (6x10^11 
p/kWh) but remains similar until the detection limit of the instruments (around 1x10^11 
p/kWh  for  DC-based  PN-PEMS  and  more  than  one  order  of  magnitude  lower  for  CPC-
based). 

The  20%  uncertainty  due  to  the  particle  dynamics  from  the  vehicle  until  the  sampling 
location  at  the  full  dilution  tunnel  where  the  Euro  emission  limits  are  set.  This 
uncertainty  includes  particle  transformations  due  to  e.g.  agglomeration  and  particle 
losses due to diffusion and thermophoresis. The uncertainty is expected high (i.e. close 

81 

 
 
 
 
 
 
 
 
 
 
to  20%)  at  cold  start  but  lower  during  hot  operation  (i.e.  when  everything  has 
stabilized). 

The theoretical estimation (50%) is a little bit higher than the experimental data (35%), 
probably  due  to  the  smaller  effect  of  the  particle  dynamics  at  the  HDV  emission  levels 
(<1x10^11 p/km). 

82 

 
 
 
 
 
14 Suggested technical specifications of PN-PEMS  

Based  on  the  light  duty  technical  specifications  and  the  existing  PEMS  regulation 
582/2011, the following modifications are recommended. 

Regulation 582/2011 is available at: 

http://eur-lex.europa.eu/legal-content/EN/TXT/PDF/?uri=CELEX:02011R0582-
20140703&qid=1475580169409&from=EN 

Appendix 1 

1. INTRODUCTION 

Replace: ‘The gaseous emissions to …’ with: 

The  pollutants  to  be  measured  from  the  exhaust  of  the  engine  include  the  following 
components: carbon monoxide, total hydrocarbons, nitrogen oxides and particle number 
for diesel engines with the addition of methane for gas engines. 

2.1.1 shall change to 2.1.1a 

2.1.1b Particle analyser to measure the concentration of particle number in the exhaust 
gas 

2.2 Add at the table a line: 

PN concentration (4) cm3 (5) 

Particle analyser 

(4) measured on a wet basis 

(5) at 0°C and 101.3 kPa 

2.4.6. Installation of PN analyser (normally to be added after 2.4.1) 

The installation and operation of the PEMS shall be leak-tight. To avoid the generation of 
particles, connectors shall be thermally stable at the exhaust gas temperatures expected 
during  the  test.  It  is  recommended  not  to  use  elastomer  connectors  to  connect  the 
vehicle exhaust outlet and the connecting tube. Elastomer connectors, if used, shall have 
no contact with the exhaust gas to avoid artefacts at high engine load. 

2.4.7 Sampling of PN emissions 

If particles are measured, the exhaust shall be sampled from the centre of the exhaust 
stream.  If  several  probes  are  used  for  emissions  sampling,  the  particle  sampling  probe 
should  be  placed  upstream  of  the  other  sampling  probes.  The  particle  sampling  probe 
should not interfere with the sampling of gaseous pollutants. The type and specifications 
of the probe and its mounting shall be documented in detail. 

If  particles  are  sampled  and  not  diluted  at  the  tailpipe,  the  sampling line  from  the  raw 
exhaust  sample  point  to  the  point  of  dilution  or  particle  detector  shall  be  heated  to  a 
minimum of 373 K (100 °C). The residence time of the sample in the particle sampling 
line shall be less than 3 s until reaching first dilution or the particle detector. 

All parts of the sampling system from the exhaust pipe up to the particle detector, which 
are in contact with raw or diluted exhaust gas, shall be designed to minimize deposition 

83 

 
 
 
 
 
 
 
 
of  particles.  All  parts  shall  be  made  from  antistatic  material  to  prevent  electrostatic 
effects. 

2.5.5 Checking the PN analyser 

The PEMS shall function free of errors and critical warnings. 

The zero level of the analyser shall be recorded by sampling HEPA filtered ambient air at 
an appropriate sampling point, usually at the inlet of the sampling line. The signal shall 
be  recorded  at  a  constant  frequency  of  at  least  1.0  Hz  averaged  over  a  period  of  2 
minutes;  the  final  concentration  shall  be  within  the  manufacturer’s  specifications,  but 
shall not exceed 5000 particles per cubic-centimetre.  

2.7.6 Checking the PN analyser 

The zero level of the analyser shall be checked and recorded according to point 2.5.5 

3.1.1 (To be added at the end of the paragraph) 

The  PN  analyser  will  be  time  aligned  with  the  rest  gaseous  pollutants  using  the 
transformation time. 

3.6. Calculation of the instantaneous particle number emissions 

The  instantaneous  particle  number  emissions  [particles/s]  shall  be  determined  by 
multiplying  the  instantaneous  concentration  of  the  pollutant  under  consideration 
[particles/cm3] with the instantaneous exhaust mass flow rate [kg/s], both corrected and 
aligned  for  the  transformation  time.  If  applicable,  negative  instantaneous  emission 
values  shall  enter  all  subsequent  data  evaluations.  All  significant  digits  of  intermediate 
results shall enter the calculation of the instantaneous emissions. The following equation 
shall apply: 

(cid:1)(cid:2), (cid:6) = (cid:12)(cid:13)(cid:14),(cid:15)(cid:16)(cid:17)(cid:18)(cid:19),(cid:15)/(cid:21)(cid:18) 

where: 

PN,i    is the particle number flux [particles/s] 

cPN,i 

is the measured particle number concentration [#/m3] normalized at 0°C 

qmew,i   is the measured exhaust mass flow rate [kg/s] 

ρe 

is the density of the exhaust gas [kg/m3] at 0°C (Table 1) 

Appendix 2 

2.5 PN analysers 

2.5.1 General  

The  PN  analyser  shall  consist  of  a  pre-conditioning  unit  and  a  particle  detector.  It  is 
permissible  that  the  particle  detector  also  pre-conditions  the  aerosol.  The  sensitivity  of 
the analysers to shocks, vibration, aging, variability in temperature and air pressure  as 
well as electromagnetic interferences and  other impacts related to vehicle and analyser 
operation shall be limited as far as possible and shall be clearly stated by the equipment 

84 

 
 
 
 
 
 
 
 
 
manufacturer  in  its  support  material.  The  PN  analyser  shall  only  be  used  within  its 
manufacturer's declared parameters of operation. 

Figure 14.1:  Example of a PN analyser setup: Dotted lines depict optional parts. EFM = 
Exhaust mass Flow Meter, d = inner diameter, PND = Particle Number Diluter. 

Note: Depending on the needs for HDV, the delay time could be possibly increased 

The  PN  analyser  shall  be  connected  to  the  sampling  point  via  a  sampling  probe  which 
extracts a sample from the centreline of the tailpipe tube. If particles are not diluted at 
the tailpipe, the sampling line shall be heated to a minimum temperature of 373 K (100 
°C)  until  the  point  of  first  dilution  of  the  PN  analyser  or  the  particle  detector  of  the 
analyser. The residence time in the sampling line shall be less than 3 s. 

All parts in contact with the sampled exhaust gas shall be always kept at a temperature 
that avoids condensation of any compound in the device. This can be achieved, e.g. by 
heating  at  a  higher  temperature  and  diluting the  sample  or  oxidizing  the  (semi)volatile 
species. 

The PN analyser shall include a heated section at wall temperature ≥573K. The unit shall 
control  the  heated  stages  to  constant  nominal  operating  temperatures,  within  a 
tolerance of ±10 K and provide an indication of whether or not heated stages are at their 
correct  operating  temperatures.  Lower  temperatures  are  acceptable  as  long  as  the 
volatile particle removal efficiency fulfils the specifications of 2.5.4. 

Pressure,  temperature  and  other  sensors  shall  monitor  the  proper  operation  of  the 
instrument during operation and trigger a warning or message in case of malfunction. 

The delay time of the PN analyser shall be ≤5 s. 

The PN analyser (and/or particle detector) shall have a rise time of ≤3.5 s.  

Particle  concentration  measurements  shall  be  reported  normalised  to  273  K  and  101.3 
kpa. If necessary, the pressure and/or temperature at the inlet of the detector shall be 
measured and reported for the purposes of normalizing the particle concentration. 

85 

 
 
 
 
 
PN systems that comply with the calibration requirements of the UNECE Regulations 83 
or 49 or GTR 15 automatically comply with the calibration requirements of this Annex. 

2.5.2 Efficiency requirements 

The  complete  PN  analyser  system  including  the  sampling  line  shall  fulfil  the  efficiency 
requirements of Table 14.1: 

Table 14.1: PN analyser (including sampling line) system efficiency requirements 

Dp [nm]  Sub-23 

23 

30 

50 

70 

100 

200 

E(dp) 

tbd 

0.2-0.6 

0.3-1.2 

0.6-1.3 

0.7-1.3 

0.7-1.3 

0.5-2.0 

Efficiency  E(dp)  is  defined  as  the  ratio  in  the  readings  of  the  PN  analyser  system  to  a 
reference  Condensation  Particle  Counter  (CPC)’s  (d50=10nm  or  lower,  checked  for 
linearity and calibrated with an electrometer) or an Electrometer’s number concentration 
measuring  in  parallel  monodisperse  aerosol  of  mobility  diameter  dp  and  normalized  at 
the same temperature and pressure conditions. The material should be thermally stable 
soot-like  (e.g.  spark  discharged  graphite  or  diffusion  flame  soot  with  thermal  pre-
treatment).  If the  efficiency curve is measured with a different aerosol (e.g.  NaCl), the 
correlation  to  the  soot-like  curve  must  be  provided  as  a  chart,  which  compares  the 
efficiencies obtained using both test aerosols. The differences in the counting efficiencies 
have  to  be  taken  into  account  by  adjusting  the  measured  efficiencies  based  on  the 
provided chart to give  soot-like aerosol efficiencies. Any correction for multiply charged 
particles should be applied and documented but shall not exceed 10%. These efficiencies 
refer to the PN analysers with the sampling line. The PN analyser can also be calibrated 
in parts (i.e. the pre-conditioning unit separately from the particle detector) as long as it 
is proven that PN analyser and the sampling line together fulfil the requirements of Table 
1. The measured signal from the detector shall be >2 times the limit of detection (here 
defined as the zero level plus 3 standard deviations). 

2.5.3 Linearity requirements 

The  linearity  requirements  shall  be  verified  whenever  damage  is  observed,  as  required 
by internal audit procedures or by the instrument manufacturer but no longer than one 
year before the actual test.  

The  PN  analyser  including  the  sampling  line  shall  fulfil  the  following  linearity 
requirements (Table 14.2). 

Table 14.2: Linearity requirements of PN analyser (including sampling line) 

Measurement 
parameter 
/instrument 

|c min (cid:1) (a1 - 1)+ a0| 

Slope a1 

Standard  error 
SEE 

Coefficient 
determination r2 

of 

PN analyser 

≤5% max 

0.85-1.15 

≤10% max 

≥0.950 

The  PN  analyser  including  the  sampling  line  shall  fulfil  the  linearity  requirements  of 
Table  14.2 using monodisperse  soot-like particles. The particle size (mobility diameter 

86 

 
 
 
 
 
 
 
 
or count median diameter) should be larger than 45 nm. The reference instrument shall 
be an Electrometer or a Condensation Particle Counter (CPC) with d50=10 nm or lower, 
verified  for  linearity.  Alternatively,  a  particle  number  system  compliant  with  UNECE 
Regulation 49. 

In addition the differences of the PN analyser from the reference instrument at all points 
checked  (except  the  zero  point)  shall  be  within  15%  of  their  mean  value.  At  least  5 
points  equally  distributed  (plus  the  zero)  shall  be  checked.  The  maximum  checked 
concentration shall be the maximum allowed concentration of the PN analyser. 

If the PN analyser is calibrated in parts, then the linearity can be checked only for the PN 
detector,  but  the  efficiencies  of  the  rest  parts  and  the  sampling  line  have  to  be 
considered in the slope calculation. 

2.5.4 Volatile removal efficiency 

The  system  shall  achieve  >99%  removal  of  ≥30  nm  tetracontane  (CH3(CH2)38CH3) 
particles  with  an  inlet  concentration  of  ≥10,000  particles  per  cubic-centimetre  at  the 
minimum dilution. 

The system shall also achieve a >99% removal efficiency of polydisperse alcane (decane 
or higher) or emery oil with count median diameter >50 nm and mass >1 mg/m3. 

The volatile removal efficiency with tetracontane and/or polydisperse alcane or  oil have 
to be proven  only once for the instrument family. The instrument manufacturer though 
has  to  provide  the  maintenance  or  replacement  interval  that  ensures  that  the  removal 
efficiency  does  not  drop  below  the  technical  requirements.  If  such  information  is  not 
provided, the volatile removal efficiency has to be checked yearly for each instrument. 

Appendix 3 

1.4 PN analyser calibration and verification 

The  leakage  test  shall  be  conducted  in  accordance  with  the  requirements  set  out  in 
paragraph 9.3.4 of Annex 4 to UNECE Regulation 49 

The  response  time  check  of  the  PN  analyser  shall  be  conducted  in  accordance  with  the 
requirements  set  out  in  paragraph  9.3.5  of  Annex  4  to  UNECE  Regulation  49  using 
particles if gases cannot be used. 

1.5 PN validation test 

It  is  highly  recommended  to  check  the  proper  operation  of  the  PN  analyser  every  3 
months conducting a validation test.  

For the validation test, the PN analyser shall be installed and prepared according to the 
requirements of Appendix 1. The validation test shall be conducted in a test bed, as far 
as  applicable,  under  type-approval  conditions  by  following  the  requirements  of  UN/ECE 
Regulation No 49. 

The total work-specific emissions [#/kWh] measured with laboratory equipment shall be 
calculated  following  UN/ECE  Regulation  No  49.  The  emissions  as  measured  with  the 
PEMS  shall  be  calculated  according  to  Appendix  1,  summed  to  give  the  total  PN 
emissions  [#]  and  then  divided  by  the  test  work  [kWh]  as  obtained  from  the  test  bed. 
The  total  work-specific  PN  [#/kWh],  as  determined  by  the  PEMS  and  the  reference 
laboratory system, shall be compared and evaluated against the requirements specified 
in Table 14.3.  

87 

 
 
 
 
 
 
 
Table 14.3: Permissible tolerances 

Parameter [Unit] 

Permissible absolute tolerance 

PN [#/kWh] 

1x10^11  p/kWh  or  50%  of  the  laboratory 
reference whichever is larger 

88 

 
 
 
 
 
 
 
15 Conclusions 

JRC evaluated the feasibility of using PN-PEMS systems for  HDV applications. The main 
evaluation  phase  took  place  between  February  and  June  2016.  One  CNG  vehicle  and 
three  vehicles  equipped  DPF  and  SCR  were  tested.  In  September  commercial  PN-PEMS 
instruments  were  tested  with  a  DPF  and  SCR  equipped  vehicle  (no  CNG  vehicle  was 
available). 

Two  reference  systems  were  used:  One  connected  to  the  full  dilution  tunnel,  as  pre-
scribed  in  the  legislation  (PMP_CVS),  and  one  was  connected  to  the  tailpipe  (PMP_TP). 
Both  were  always  at  constant  ambient  temperature  of  20°C  in  order  to  exclude  any 
temperature effect on their results. However, the location of the tailpipe system close to 
from  pressure  pulsations, 
the  dilution 
thermophoresis, diffusion and agglomeration. The differences between the two systems 
were  within  ±15%.  However,  for  other  cases  calibration  or  exhaust  mass  flow 
uncertainties could further increase this range another 10%. 

reduced  any  effects 

tunnel  probably 

The fraction of sub-23 nm (solid) particles was determined using a CPC with d50% at 10 
nm in parallel with the 23 nm CPC of the PMP_TP. Target was to identify any sensitivity 
of the  PN-PEMS at solid particles <23 nm.  The fraction was relatively high for the CNG 
vehicle  (30-50%)  and  even  higher  (double)  at  cold  start  with  this  vehicle.  For  the  DPF 
and  SCR  equipped  vehicles  the  fraction  was  low  for  emission  levels  >3x10^11  p/kWh 
but  could  reach  100%  at  lower  levels  due  to  the  higher  contribution  of  urea  formed 
nanoparticles. It should be mentioned though that there were indications that the 23 nm 
CPC had lower detection efficiency for these particles. 

The volatile particles were determined by using an EEPS connected directly at the CVS, 
without  any  thermal  pre-treatment.  Generally  there  was  no  separate  nucleation  mode 
with  the  exception  of  regeneration  events  and  high  load  points  where  the  exhaust  gas 
temperature was high. The mass of volatile particles could exceed 0.5 mg/m3.  

Comparing  the  PN-PEMS  with  the  PMP_TP  in  order  to  quantify  the  measurement 
uncertainty of the PN-PEMS instruments only the following conclusions could be drawn: 

PN-PEMS  #2  (HORIBA):  It  was  the  best  performing  instrument  (CPC-based)  at 
temperatures >0°C. It had differences typically within 15% to the reference instrument, 
sometimes up to 25% even for low emission levels close to the background levels of the 
PMP_TP system (1x10^9 p/kWh). Similar differences  were also  observed at the  second 
by second comparisons. It showed no sensitivity to particles smaller than 23 nm, and no 
issues during regeneration events (active and passive) where the temperatures reached 
425°C.  At  low  ambient  temperatures  though  it  degraded  fast,  showed  spikes  and  then 
stopped working. This system was not tested  with the CNG  vehicle.  Calibration tests in 
the laboratory showed that it fully complied with the technical specifications. 

PN-PEMS #3 (TESTO): The differences to the reference system were <30% close to the 
emission  limit  of  6x10^11  p/kWh  or  higher.  The  differences  were  on  the  order  of  50% 
(up to 100% when used with higher dilution ratio) at emission levels close or above its 
detection limit (1x10^11 p/kWh). The real time signals matched quite well the reference 
systems’. It could measure without errors between 5 and 35°C (its specifications are 5-
35°C). At low temperatures though it can degrade fast as the appropriate temperatures 
cannot  be  held.  However  bringing  the  instrument  at  -7°C  half  an  hour  before  the  test 
was  proven  to  be  possible  without  any  errors  and  issues.  Calibration  tests  in  the 
laboratory showed that it fully complied with the technical specifications. 

PN-PEMS #1 (AVL): This DC-based system had issues in the main campaign mainly from 
high spikes that originated from pressure changes and condensates entering the system. 
With  a  probe  heater  the  results  were  very  good  in  the  second  phase.  The  results  were 
within 20% of the reference instrument for emission levels >1x10^11 p/km. There were 
no issues for low or high ambient temperatures or regeneration events. Calibration in the 

89 

 
 
 
lab  confirmed  that  there  was  an  offset  in  its  penetration  efficiency  curve.  The  volatile 
removal efficiency was extremely high (efficient). 

PN-PEMS #6 (SHIMADZU): This DC based system could follow the real time signal of the 
reference system. However the absolute levels had big differences and the reason is not 
clear. Calibration in the lab showed that it didn’t fulfil the technical specifications.  

PN-PEMS  #7  (MAHA):  This  CPC-based  system  had  an  offset  of  30%  (measuring  lower) 
compared  to  the  reference  system  (bias).  The  differences  from  the  median  though  had 
small variability of 12% (precision, expressed as standard deviation of the differences). 
The real time signals matched excellent those of the reference system. In the calibration 
lab similar offset to the reference system was found. 

Concluding,  PN-PEMS  are  ready  to  be  used  for  the  purpose  of  an  assessment  during 
type-approval demonstration. The instruments measurement uncertainty at the moment 
is  on  the  order  of  30%  (even  during  regenerations)  until  the  detection  limits  of  the 
instruments  with  potential  of  reduction  based  on  the  results  of  one  CPC  based  system. 
The  DC  based  systems  have  a  detection  limit  slightly  lower  than  1x10^11  p/kWh;  the 
CPC  based  two  orders  of  magnitude  lower.  Nevertheless,  these  detection  limits  are 
sufficient  for  ISC  testing  given  their  measurement  uncertainty  of  30%.  Similar 
measurement  uncertainty  was  found  during  the  light-duty  vehicles  evaluation  phase 
when comparing to the reference system at the tailpipe. 

The  tests  at  sub-0°C  were  challenging  for  a  few  systems  with  low  sampling  flow  rates. 
They could damage the systems in some cases due to condensates entering the system 
(either  due  to  non-ideal  setup  or  inadequate  heating  capacities).  At  low  temperatures 
the setup is very important to avoid any condensation in the first place. Active heating of 
the adaptor connecting the system to the tailpipe solved the problem. It should be noted 
that some systems could measure at low temperatures without any issues. 

Comparison  of  the  two  PN-PEMS  systems  with  the  PMP  system  at  the  dilution  tunnel 
(PMP-CVS)  for  all  tested  vehicles  showed  that  the  uncertainty  is  <35%  which  is  lower 
than 50% estimated theoretically (and also found in the light-duty evaluation program), 
probably  due  to  lower  particle  dynamics  between  vehicle  and  dilution  tunnel  at  the 
emission levels of HDVs (<1x10^11 p/km). This confirms the suitability of the PN-PEMS 
for measuring the PN emissions of HDV. 

What hasn’t been investigated in this report is the sensitivity of the PN-PEMS to shocks, 
vibration,  aging,  variability  in  temperature  and  air  pressure  as  well  as  electromagnetic 
interferences  and  other  impacts  related  to  on-road  vehicle  and  PN-PEMS  operation. 
Dedicated tests should be conducted. 

In  addition  further  testing  with  cracked  DPF,  low  ambient  temperatures,  biofuels  and 
especially CNG engines where more experience with PN-PEMS would be desirable. 

90 

 
 
 
 
 
 
 
 
References 

AA  (2016).  Administrative  Arrangement  SI2.730104  between  DG  GROW  and  DG  Joint 
Research Centre (DG JRC), Ref. Ares(2016) 1659670 - 07/04/2016 

Amanatidis,  S.,  Ntziachristos,  L.,  Giechaskiel,  B.,  Bergmann,  A.,  Samaras,  Z.  (2014). 
Impact  of  selective  catalytic  reduction  on  exhaust  particle  formation  over  excess 
ammonia events. Environ. Sci. Technol. 48, 11527−11534. 

Bonnel,  P.,  Carriero,  M.,  Forni,  F.,  Alessandrini,  S.,  Montigny,  F.,  Demircioglu,  H.,  & 
Giechaskiel,  B.  (2010).  EUPEMS  PM  Evaluation  Program  -  First  Report”,  JRC  Scientific 
and Technical Report, EUR 24543 EN, ISBN 978-92-79-17031-7 

Giechaskiel,  B.,  Cresnoverh,  M.,  Jörgl,  H.,  and  Bergmann,  A.  (2010).  Calibration  and 
accuracy of a particle number measurement system. Meas. Sci. Technol. 21(4): 045102. 
doi: 10.1088/0957-0233/21/4/045102 

Giechaskiel,  B.,  Massimo,  C.,  Bonnel,  P.,  Schindler,  W.,  Scheder,  D.,  Bassoli  C.,  and 
Niemelä, V. (2011). PEMS feasibility of particulate mass and number measurement with 
portable emission measurement systems (PEMS) for in-use testing, SAE 2011-24-0199. 

Giechaskiel, B., Riccobono, F., & Bonnel, P. (2015a). Feasibility study on the extension of 
the  Real  Driving  Emissions  (RDE)  procedure  to  Particle  Number  (PN):  Experimental 
evaluation  of  portable  emission  measurement  systems  (PEMS)  with  diffusion  chargers 
(DCs)  to  measure  particle  number  (PN)  concentration  Chassis  dynamometer  evaluation 
of  portable  emission  measurement  systems  (PEMS)  to  measure  particle  number  (PN) 
concentration: Phase II. EU JRC report EUR 27451 EN 

Giechaskiel,  B.,  Riccobono,  F.,  Vlachos,  T.,  Mendoza,  P.,  Suarez,  R.,  Fontaras,  G., 
Bonnel,  P.,  Weiss,  M.  (2015b).  Vehicle  emission  factors  of  solid  nanoparticles  in  the 
laboratory  and  on  the  road  using  Portable  Emission  Measurement  Systems  (PEMS). 
Front. Environ. Sci. 3(82), doi: 10.3389/fenvs.2015.00082. 

Mamakos,  A.,  Bonnel,  P.,  Perujo,  A.,  &  Carriero,  M.  (2013).  Assessment  of  portable 
emission  measurement  systems  (PEMS)  for  heavy-duty  diesel  engines  with  respect  to 
particulate matter. Journal of Aerosol Science, 57, 54–70. 

Mamakos,  A.,  Carriero,  M.,  Bonnel,  P.,  Demircioglu,  H.,  Douglas,  K.,  Alessandrini,  S., 
Forni,  F.,  Montigny,  F.,  &  Lesueur  D.  (2011a).  EU-PEMS  PM  EVALUATION  PROGRAM  - 
Second Report - Study on Post DPF PM/PN Emissions. EUR 24883 EN 

Mamakos,  A.,  Carriero,  M.,  Bonnel,  P.,  Demircioglu,  H.,  Douglas,  K.,  Alessandrini,  S., 
Forni,  F.,  Montigny,  F.,  &  Lesueur  D.  (2011b).  EU-PEMS  PM  EVALUATION  PROGRAM  - 
Third Report – Further Study on Post DPF PM/PN Emissions. EUR 24883 EN 

Mendoza Villafuerte, P., Perujo Mateos del Parque, A., Bonnel, P., Carriero, M., Forni, F., 
& Riccobono, F. (2015).  EU-PEMS  PM Pilot Program:  Testing, data analysis and results. 
Report EUR 27326 EN 

Perujo Mateos del Parque, A., & Mendoza Villafuerte, P. (2015). PEMS emissions testing 
of  heavy  duty  vehicles/engines:  Assessment  of  PEMS  procedures  in  fulfilment  of  article 
14(3) to regulation (EU) 582/2011, EUR 27251 EN 

Perujo  Mateos  del  Parque,  A.,  Bonnel  P.,  &  Mendoza  Villafuerte  P.  (2015).  PEMS  based 
in-service  testing:  Practical  recommendations  for  heavy-duty  engines/  vehicles.  EUR 
27338 EN 

Riccobono,  F.,  Giechaskiel,  B.,  Mendoza,  P.  (2016).  Particle  Number  PEMS  Inter-
Laboratory Comparison Exercise: Performance of PN-PEMS for the extension of the RDE 
test procedure to PN. EU report 28136 EN 

Riccobono,  F.,  Giechaskiel,  B.,  Weiss,  M.,  &  Bonnel,  P.  (2014).  How  to  extend  the  real 
drive  emission  test  procedure  to  particle  number.  Presentation  at  the  18th  ETH 

91 

 
 
 
Conference  on  Combustion  Generated  Nanoparticles,  25th  June  2014,  Zurich, 
Switzerland 

92 

 
 
 
 
List of abbreviations and definitions 

ACEA   

European Automobile Manufacturers' Association 

APC 

CLD 

CNG 

CPC 

CVS 

DC 

DPF 

EC 

EFM 

ET 

FTIR 

GPS 

HDV 

AVL Particle Counter 

ChemiLuminescence Detector 

Compressed Natural Gas  

Condensation Particle Counter 

Constant Volume Sampler 

Diffusion Charger 

Diesel Particuylate Filter 

European Commission 

Exhaust Flow Meter 

Evaporation Tube 

Fourier Transform InfraRed spectrometer 

Global Positioning System 

Heavy Duty Vehicle 

HEPA   

High Efficiency Particulate Air filter 

HFID 

Heated Flame Ionization Detector 

ISC 

JRC 

MS 

NDIR   

NDUV   

OBD 

PCRF   

PEMS   

PM 

PMP 

PN 

RDE 

SCR 

In-Service Conformity 

Joint Research Centre 

Member State 

Non-Dispersive InfraRed sensor 

Non-Dispersive Ultra-Violet sensor 

On-Board Diagnostics 

Particle Number Concentration Reduction Factor 

Portable Emissions Measurement System 

Particulate Matter 

Particle Measurement Programme 

Particle Numbe 

Real Driving Emissions 

Selective Catalytic Reduction 

SICO   

Simplified Constant Speed TEst 

THC 

TP 

UNECE  

VECTO  

VELA   

Total Hydrocarbons 

Tailpipe 

United Nations Economic Commission for Europe 

Vehicle Energy consumption Calculation TOol 

Vehicle Emissions Laboratories 

VPR 

Volatile Particle Remover 

93 

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
WHTC   

WHVC   

World Harmonized Transient Cycle 

World Harmonized Vehicle Cycle 

94 

 
 
 
 
 
List of figures 

Figure 1: VELA 7 facilities. ...................................................................................... 9 

Figure 2: Example of a vehicle and the PEMS in the climatic room. ............................ 10 

Figure  3:  Typical  setup  of  the  reference  systems  in  the  controlled  temperature  dilution 
tunnel room. ...................................................................................................... 11 

Figure 4: Example of setup of PEMS (main evaluation phase). .................................. 13 

Figure  5:  Example  of  setup  of  PN-PEMS  (second  evaluation  phase).  On  the  right  the 
positioning of the sampling probes. Probes facing away from the flow. ....................... 14 

Figure 6: Effect of sampling probe. ........................................................................ 15 

Figure  7:  Influence  of  position  on  results.  See  Figure  5:  Front  refers  to  position  of  PN-
PEMS #2 and Back refers to position of PN-PEMS #7. .............................................. 15 

Figure  8:  Example  of  comparison  of  exhaust  flow  estimated  from  the  dilution  tunnel 
(CVS) and an exhaust flow meter (EFM) (201604010_1_ISC). .................................. 19 

Figure 9: Emission levels of V1 for various cycles. Error bars indicate max-min values. 20 

Figure 10: Repeatability of Regional Delivery Cycles. ............................................... 21 

Figure 11: Emission levels at different cycles of different vehicles. ............................ 21 

Figure 12: Correlation of PMP_TP to PMP_CVS for vehicle V1. Blue points tests at -7°C, 
red points tests at +35°C. .................................................................................... 22 

Figure 13: Correlation of PMP_TP to PMP_CVS for vehicle V2. Blue points tests at -7°C, 
red points tests at +35°C. .................................................................................... 22 

Figure 14: Correlation of PMP_TP to PMP_CVS for vehicle V3. Blue points tests at -7°C, 
red points tests at +35°C. The two outliers will be discussed separately. .................... 23 

Figure  15:  Correlation  of  PMP_TP  to  PMP_CVS  for  V5.  Blue  points  tests  at  -7°C,  red 
points tests at +35°C. ......................................................................................... 23 

Figure  16:  Real  time  comparison  of  PMP_CVS  and  PMP_TP  over  a  long  cycle  in  the  lab 
(Example vehicle V5) (20160520_1_ISC_-7°C). ...................................................... 24 

Figure 17: Real time comparison of PMP_TP and PMP_CVS (20160411_01_WHVC). ..... 25 

Figure 18: Real time comparison of PMP_TP and PMP_CVS (20160411_04_Region.Del.).
......................................................................................................................... 25 

Figure  19:  Comparison  of  PMP_TP  with  PMP_CVS  at  the  cold  part  of  a  cycle  (V1) 
(20160217_01_ISC_-7°C). ................................................................................... 26 

Figure  20:  Comparison  of  PMP_TP  with  PMP_CVS  at  the  cold  part  of  a  cycle  (V3) 
(20160331_01_ISC_-7°C). ................................................................................... 27 

Figure  21:  Comparison  of  PMP_TP  with  PMP_CVS  at  the  cold  part  of  a  cycle  (V5) 
(20160520_01_ISC_-7°C). ................................................................................... 27 

Figure 22: Sub-23 nm fraction of V1. ..................................................................... 28 

Figure 23: Real time concentration signals of the two CPCs. Concentrations refer to the 
CVS (20160224_01_WHVC cold). .......................................................................... 29 

Figure 24: Sub-23 nm fraction of V3. ..................................................................... 29 

Figure  25:  Typical  measured  raw  concentration  of  CPCs  (emissions  around  5x1010 
p/kWh) (20160512_02_Region.Del.). .................................................................... 30 

95 

 
 
 
Figure 26: Sub-23 nm fraction of V5. Red squares are cold start tests (i.e. first 1200 s).
......................................................................................................................... 30 

Figure 27: Real time concentrations of a) 10 nm and 23 nm PN and b) NOx. In panel b 
the speed profile is also shown. Vehicle V5. ............................................................ 31 

Figure 28: Sub-23 nm fraction of V2. ..................................................................... 32 

Figure 29: Typical measured concentration of CPCs (emissions around 4x1012 p/kWh for 
the  whole  cycle  and  1.5x1013  p/kWh  for  the  cold  start  part).  Cold  start  at  0°C 
(20160323_01_ISC cold_0°C). ............................................................................. 32 

Figure  30:  Difference  of  PMP_CVS  from  PMP_TP  with  different  PCRFs.  Exact  levels  not 
known  due  to  lost  OBD  signal.  Based  on  the  distance  the  emission  levels  should  be 
around 5x10^12 p/kWh. ...................................................................................... 33 

Figure  31:  Comparison  of  PN-PEMS  #1  with  PMP_TP  for  vehicle  V1.  Green  points  are 
tests at ambient temperature of 20°C. Blue points are tests at ambient temperature of -
7°C  (5  tests  had  artificial  high  spikes  and  are  not  plotted).  Red  points  are  tests  at 
ambient temperature of 35°C. .............................................................................. 34 

Figure  32:  Comparison  of  PN-PEMS  #1  with  PMP_TP  for  vehicle  V3.  Green  points  are 
tests  at  ambient  temperature  of  20°C.  A  test  at  -7°C  is  shown  (blue  point)  and  one  at 
+35°C (red point); no more tests were conducted at extended ambient temperatures. 35 

Figure 33: Comparison of PN-PEMS #1 with PMP_TP for vehicle V5. .......................... 35 

Figure  34:  Real  time  comparison  of  PN-PEMS  #1  with  PMP_TP  over  a  cold  start  WHVC 
(vehicle  V3)  (20160411_01_WHVC  cold).  Difference  over  the  cycle  36%  (level 
3.3x10^11 p/kWh). ............................................................................................. 36 

Figure 35: Real time comparison of PN-PEMS #1 with PMP_TP over a SICO test (vehicle 
V3) (20160512-01-SICO). .................................................................................... 37 

Figure 36: Real time comparison of PN-PEMS #1 with PMP_TP over an ISC cycle (vehicle 
V5) (20160519-01_ISC cold). ............................................................................... 38 

Figure 37: Real time comparison of PN-PEMS #1 with PMP_TP over a cold start WHVC at 
-7°C (vehicle V5). (20160529_01_ISC cold_-7°C) ................................................... 39 

Figure  38:  Real  time  comparison  of  PN-PEMS  #1  with  PMP_TP  over  a  cold  start  WHVC 
(vehicle V3) (20160415_01_WHVC cold_-7°C) ....................................................... 39 

Figure 39: Evaluation over measuring time of PN-PEMS #2. Solid diamonds are unit PN-
PEMS #2b with vehicle V1. Open symbols are  unit PN-PEMS #2c with vehicle V3 (open 
squares), V5 (open triangles) and V6 (open circles)................................................. 41 

Figure 40: Stability of the CPC of PN-PEMS #2 at vibration and tilting at different angles.
......................................................................................................................... 42 

Figure  41:  Comparison  of  PN-PEMS  #2b  with  PMP_TP  for  vehicle  V1.  Green  points  are 
tests at ambient temperature of 20°C. At different temperatures the system had errors. 
Only for illustrative purposes a test at -7°C is shown (blue point) and one at +35°C (red 
point). Dotted lines show the ±15% differences from the 1:1 line. ............................ 43 

Figure  42:  Comparison  of  PN-PEMS  #2c  with  PMP_TP  for  vehicle  V3.  Green  points  are 
tests  at  ambient  temperature  of  20°C.  A  test  at  -7°C  is  shown  (blue  point)  and  one  at 
+35°C  (red  point);  no  more  tests  were  conducted  at  extended  ambient  temperatures. 
Dotted lines show the ±15% differences from the 1:1 line. ...................................... 44 

Figure  43:  Comparison  of  PN-PEMS  #2c  with  PMP_TP  for  vehicle  V5.  Dotted  lines  show 
the ±15% differences from the 1:1 line. ................................................................ 44 

Figure  44:  Real  time  comparison  of  PN-PEMS  #2c  with  PMP_TP  over  a  cold  WHVC 
(vehicle V3) (20160411_1_WHVC cold). ................................................................ 45 

Figure 45: Real time measurements with vehicle V1 (20160204_3_cycle-steady). ....... 45 

96 

 
 
Figure  46:  Real  time  comparisons  at  cold  start  with  vehicle  V1  (20160205_1_WHVC 
cold). ................................................................................................................. 46 

Figure  47:  Real  time  measurements  over  a  WHVC  at  ambient  temperature  of  0°C 
(20160225_1_WHVC cold 0°C). Vehicle V1............................................................. 47 

Figure 48: Real time measurements over a WHVC at ambient temperature of -7°C with 
vehicle V3 (20160415_01_WHVC cold at -7°C). ...................................................... 47 

Figure  49:  Real  time  measurements  over  an  ISC  cycle  at  ambient  temperature  of  -7°C 
with vehicle V5 (20160520_2_ISC -7°C). ............................................................... 48 

Figure 50: Active regeneration test (20160314_regeneration). ................................. 49 

Figure 51: Comparison of two PN-PEMS units with the reference systems. ................. 50 

Figure  52:  Comparison  of  PN-PEMS  #3a  with  PMP_TP  for  vehicle  V1.  Green  points  are 
tests at ambient temperature of 20°C. The blue point is a test at -7°C. Many tests with 
low concentrations are not shown. Dotted lines show the ±15% differences from the 1:1 
line. ................................................................................................................... 52 

Figure 53:  Comparison  of  PN-PEMS  #3b with PMP_TP for  vehicle V2.  Dotted lines show 
the ±15% differences from the 1:1 line. ................................................................ 52 

Figure 54:  Comparison  of  PN-PEMS  #3b with PMP_TP for  vehicle V3.  Dotted lines show 
the 0-50% differences from the 1:1 line. ................................................................ 53 

Figure 55: Real time comparison of PN-PEMS #3a with PMP_TP for vehicle V1. PN-PEMS 
had  an  error 
levels  of  2.5x10^10  p/kWh 
range’.  Emission 
(20160224_1_WHVC cold). .................................................................................. 54 

‘Idiff  out  of 

Figure 56: Real time comparison of PN-PEMS #3a with PMP_TP for vehicle V1. PN-PEMS 
had  a  warning  ‘offset  too  high  or  unstable’  and  an  error  ‘Idiff  out  of  range’.  Emission 
levels of 2.5x10^12 p/kWh (20160224_3_SICO). ................................................... 54 

Figure 57: Real time comparison of PN-PEMS #3b with PMP_TP for vehicle V2. Cold start 
(20160321_1_ISC_cold_10°C). ............................................................................ 55 

Figure 58: Real time comparison of PN-PEMS #3b with PMP_TP for vehicle V2. Hot part 
of a long test (20160321_1_ISC_cold_10°C). ......................................................... 55 

Figure 59: Real time comparison of PN-PEMS #3b with PMP_TP for vehicle V2. Cold start 
at  0°C  (20160323_1_ISC_cold_0°C).  ‘Corr’  means  signal  corrected  with  a  typical  PMP 
penetration efficiency based on the estimated size of the PN-PEMS #3. ..................... 56 

Figure 60: Real time comparison of PN-PEMS #3b with PMP_TP for vehicle V2. Hot part 
of a long test (20160323_1_ISC_cold_0°C). ........................................................... 56 

Figure 61: Real time comparison of PN-PEMS #3b with PMP_TP for vehicle V3. Cold start 
at -7°C (20160331_01_ISC cold_-7°C). ................................................................. 57 

Figure 62: Comparison of PN-PEMS #6 with PMP_TP for vehicle V2. .......................... 58 

Figure 63: Comparison of PN-PEMS #6 with PMP_TP for vehicle V3. .......................... 59 

Figure 64: Comparison of PN-PEMS #6 with PMP_TP for vehicle V5. PN-PEMS #6 results 
were multiplied by 100 for this figure..................................................................... 59 

Figure 65: Real time comparison of PN-PEMS #6 with PMP_TP over a WHVC (vehicle V2) 
(20160321_02_WHVC_+35°C).  PN-PEMS  #6  concentration  was  multiplied  by  2  for 
better visualization. ............................................................................................. 60 

Figure 66: Real time comparison of PN-PEMS #6 with PMP_TP over a WHVC (vehicle V2) 
(20160322_01_WHVC_-7°C).  PN-PEMS  #6  concentration  was  multiplied  by  2  for  better 
visualization. ...................................................................................................... 60 

Figure  67:  Real  time  comparison  of  PN-PEMS  #6  with  PMP_TP  over  a  warmup  test 
(vehicle V3) (20160330_01_WHVC_2°C). .............................................................. 61 

97 

 
 
Figure  68:  Real  time  comparison  of  PN-PEMS  #6  with  PMP_TP  (20160411_01_WHVC 
cold) (vehicle V3). ............................................................................................... 61 

Figure 69: Real time comparison of PN-PEMS #6 with PMP_TP (20160331_01_ISC_-7°C) 
(vehicle V3). ....................................................................................................... 62 

Figure  70:  Real  time  comparison  of  PN-PEMS  #6  with  PMP_TP  (vehicle  V5). 
(20160525_01_ISC cold_0°C). PN-PEMS #6 was multiplied by 100. .......................... 62 

Figure  71:  Real  time  signal  of  PN-PEMS  during  an  on-road  test  with  vehicle  V1 
(20160309_01_Road).  Emissions  8.0x10^10  (PN-PEMS  #2)  and  7.4x10^10  (PN-PEMS 
#3) p/kWh. ........................................................................................................ 63 

Figure  72:  Real  time  signal  of  PN-PEMS  during  an  on-road  test  with  vehicle  V3 
(20160427_01_Road).  Emissions  7.5x10^10  (PN-PEMS  #2)  and  1.5x10^11  (PN-PEMS 
#1) p/kWh. ........................................................................................................ 63 

Figure  73:  Correlation  of  PMP_TP  to  PMP_CVS  for  vehicle  V8.  The  red  point  was  not 
considered in the correlation. ................................................................................ 65 

Figure 74: Real time comparison of PMP_TP and PMP_CVS (20160914-02_Steady). .... 66 

Figure 75: Sub-23 nm fraction of V8. ..................................................................... 67 

Figure  76:  Correlation  of  sub-23  nm  fractions  as  identified  in  the  system  at  the  full 
dilution and the tailpipe. ...................................................................................... 67 

Figure  77:  Comparison  of  PN-PEMS  #1  with  PMP_TP  for  vehicle  V8.  Green  points  are 
tests at ambient temperature of 20°C. Blue points are tests at ambient temperature of -
7°C. Red points are tests at ambient temperature of 35°C. ...................................... 68 

Figure  78:  Real  time  comparison  of  PN-PEMS  #1  with  PMP_TP  over  a  hot  start  WHVC 
(vehicle V8) (20160906-05_WHVC hot). Emission levels 1.4x10^11 p/km (PN-PEMS #1 
+83%). ............................................................................................................. 69 

Figure  79:  Real  time  comparison  of  PN-PEMS  #1  with  PMP_TP  over  steady  state  points 
(vehicle V8) (20160906_04_Steady). Pressure variation <10 mbar. .......................... 70 

Figure  80:  Real  time  comparison  of  PN-PEMS  #1  with  PMP_TP  over  steady  state  points 
(vehicle V8) (20160914-02_Steady). ..................................................................... 70 

Figure  81:  Comparison  of  PN-PEMS  #2d  with  PMP_TP  for  vehicle  V8.  Green  points  are 
tests  at  ambient  temperature  of  20°C.  Red  points  are  tests  at  ambient  temperature  of 
35°C. All tests at sub-0°C had errors and only one (blue square) is shown for illustrative 
reasons. One test with a probe heater had no errors (blue square). ........................... 71 

Figure 82: Real time comparison of PN-PEMS #2d with PMP_TP over an ISC cycle at -7°C 
(vehicle V8) (20160913-01_ISC_-7°C). With probe heater. ...................................... 72 

Figure 83: Real time comparison of PN-PEMS #2d with PMP_TP over steady state modes 
(vehicle V8) (20160914-02-Steady). ..................................................................... 72 

Figure  84:  Comparison  of  PN-PEMS  #3c  with  PMP_TP  for  vehicle  V8.  Green  points  are 
tests at ambient temperature of 20°C. Blue points are tests at ambient temperature of -
7°C. Red points are tests at ambient temperature of 35°C. ...................................... 73 

Figure  85:  Real  time  comparison  of  PN-PEMS  #3c  with  PMP_TP  over  an  ISC  cycle  at 
22°C (vehicle V8) (20160912-01_ISC_22°C). ......................................................... 73 

Figure  86:  Comparison  of  PN-PEMS  #6b  with  PMP_TP  for  vehicle  V8.  Green  points  are 
tests at ambient temperature of 20°C. Blue points are tests at ambient temperature of -
7°C. Red points are tests at ambient temperature of 35°C. ...................................... 74 

Figure 87: Real time comparison of PN-PEMS #6b with PMP_TP over steady state points 
(vehicle V8) (20160906-03_Steady) ...................................................................... 74 

98 

 
 
Figure  88:  Comparison  of  PN-PEMS  #7  with  PMP_TP  for  vehicle  V8.  Green  points  are 
tests at ambient temperature of 20°C. Blue points are tests at ambient temperature of -
7°C. Red points are tests at ambient temperature of 35°C. ...................................... 75 

Figure 89: Real time comparison of PN-PEMS #7 with PMP_TP over a WHVC (vehicle V8) 
(20160906-05_WHVC hot). .................................................................................. 75 

Figure 90: Regeneration test at 80 km/h. ............................................................... 76 

Figure 91: Comparison of PN-PEMS #2 with the PMP_CVS. Each point is a test and each 
symbol  is  a  different  vehicle.  Tests  with  errors  (most  at  sub-0°C)  have  been  excluded. 
Lines indicate the 1.35:1, 1:1 an 0.7:1 lines. .......................................................... 77 

Figure 92: Comparison of PN-PEMS #3 with the PMP_CVS. Each point is a test and each 
symbol  is  a  different  vehicle.  Tests  with  errors  (most  at  sub-0°C)  have  been  excluded. 
Lines indicate the 1.35:1, 1:1 an 0.7:1 lines. .......................................................... 77 

Figure 93: Zero and ambient air checks. ................................................................ 79 

Figure 94: Theoretical estimation of PN-PEMS measurement uncertainty. ................... 81 

99 

 
 
 
 
List of tables 

Table 1: Overview of projects and tested vehicles (all Euro VI). .................................. 8 

Table 2: Ratio of work to distance for various cycles and vehicles. ............................. 10 

Table 3: Testing period of PN emissions and available PN-PEMS instrumentation. ........ 17 

Table 4: Test cycles for each vehicle and number of repetitions. ............................... 18 

Table 5: Difference of PMP_TP to PMP_CVS for the cold part and hot part of the ISC cycle 
at different ambient temperatures. ........................................................................ 26 

Table 6: Count statistics error (n0.5/n) of a CPC based on the measured concentration n.
......................................................................................................................... 30 

Table  7:  Penetration  efficiencies.  In  red  non-compliant  values.  ‘Corr’  means  adjusted 
more than 10%................................................................................................... 80 

Table 8: Volatile Removal Efficiency results. In red non-compliant results. ................. 80 

100 

 
 
 
 
 
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doi:10.2788/052796 

ISBN 978-92-79-64019-3