CEN/TS 17660-1:2021
(Main)Air quality - Performance evaluation of air quality sensor systems - Part 1: Gaseous pollutants in ambient air
Air quality - Performance evaluation of air quality sensor systems - Part 1: Gaseous pollutants in ambient air
This document specifies the general principles, including testing procedures and requirements, for the classification of performance of low-cost sensor systems for the monitoring of gaseous compounds in ambient air at fixed sites. The classification of sensor systems includes tests that are performed under prescribed laboratory and field conditions.
The procedure described is applicable to the determination of the mass concentration of air pollutants. The pollutants that are considered in this document are the gaseous pollutants regulated under Directive 2008/50/EC (O3, NO/NO2/NOx, CO, SO2 and benzene) in the range of concentrations expected in ambient air.
This document provides a classification that is consistent with the requirements for indicative measurements and objective estimation defined in Directive 2008/50/EC. In addition, it provides a classification for applications (non-regulatory measurements) that require more relaxed performance criteria.
This document applies to sensor systems used as individual systems. It does not apply to sensor systems as part of a sensor network. However, for some applications (e.g. in cities) sensor systems are deployed as part of a sensor network. Annex A gives information on the use of sensor systems as nodes in a sensor network.
This document gives guidance on the testing of CO2 sensor systems in Annex B since, although not listed in Directive 2008/50/EC, CO2 is an interesting indicator as proxy for activities involving combustion processes or for CO2 evaporation from soil or water.
Luftbeschaffenheit - Leistungsbewertung von Luftqualitätssensorsystemen - Teil 1: Gasförmige Schadstoffe in der Außenluft
Dieses Dokument legt allgemeine Grundsätze einschließlich Prüfverfahren und Prüfanforderungen für die Klassifizierung der Leistung von kostengünstigen Sensorsystemen für die Überwachung gasförmiger Stoffe in der Außenluft an festen Standorten fest. Die Klassifizierung von Sensorsystemen beinhaltet Prüfungen, die unter vorgeschriebenen Labor- und Feldbedingungen durchgeführt werden.
Das beschriebene Verfahren ist für die Bestimmung der Massenkonzentration von Schadstoffen in der Luft anwendbar. Die in diesem Dokument betrachteten Schadstoffe sind die in der Richtlinie 2008/50/EG geregelten gasförmigen Schadstoffe (O3, NO/NO2/NOx, CO, SO2 und Benzol) in dem in der Außenluft erwarteten Konzentrationsbereich.
Dieses Dokument bietet eine Klassifizierung, die mit den Anforderungen an orientierende Messungen und objektive Schätzungen in der Richtlinie 2008/50/EG konsistent ist. Darüber hinaus liefert es eine Klassifizierung für Anwendungen (nicht-geregelte Messungen) die entspanntere Leistungskriterien erfordern.
Dieses Dokument gilt für einzeln verwendete Sensorsysteme. Es gilt nicht für Sensorsysteme als Teil eines Sensornetzwerks. Für einige Anwendungen (z. B. in Städten) werden Sensorsysteme jedoch als Teil eines Sensornetzwerks eingesetzt. Anhang A enthält Informationen zur Nutzung von Sensorsystemen als Knoten in einem Sensornetzwerk.
Dieses Dokument bietet eine Anleitung zur Prüfung von CO2-Sensorsystemen in Anhang B, da CO2, auch wenn es nicht in Richtlinie 2008/50/EG aufgeführt ist, ein interessanter Indikator stellvertretend für Aktivitäten ist, die Verbrennungsprozesse beinhalten, oder für die Verdunstung von CO2 aus Erdreich oder Wasser.
Qualité de l'air - Évaluation des performances des systèmes capteurs de la qualité de l'air - Partie 1: Polluants gazeux dans l'air ambiant
Le présent document spécifie les principes généraux, y compris les modes opératoires d'essai et les exigences, pour la classification des performances des systèmes capteurs à faible coût dans le cadre de la surveillance des composés gazeux dans l'air ambiant sur des sites fixes. La classification des systèmes capteurs comprend des essais réalisés dans des conditions prescrites en laboratoire et sur le terrain.
Le mode opératoire décrit est applicable à la détermination de la concentration massique des polluants atmosphériques. Les polluants pris en considération dans le présent document sont les polluants gazeux réglementés par la Directive 2008/50/CE (O3, NO/NO2/NOx, CO, SO2 et benzène) dans la plage de concentrations attendues dans l'air ambiant.
Le présent document fournit une classification qui est cohérente avec les exigences de mesures indicatives et d'estimation objective définies dans la Directive 2008/50/CE. En outre, il fournit une classification pour les applications (mesures non réglementaires) qui exigent des critères de performance plus souples.
Le présent document s'applique aux systèmes capteurs utilisés en tant que systèmes individuels. Il ne s'applique pas aux systèmes capteurs faisant partie d'un réseau de capteurs. Cependant, pour certaines applications (par exemple dans les villes), les systèmes capteurs sont mis en œuvre dans le cadre d'un réseau de capteurs. L'Annexe A donne des informations concernant l'utilisation des systèmes capteurs en tant que nœuds dans un réseau de capteurs.
L'Annexe B du présent document fournit des recommandations relatives aux essais des systèmes capteurs de CO2. En effet, bien qu'il ne figure pas dans la Directive 2008/50/CE, le CO2 est un indicateur intéressant pour les activités impliquant des processus de combustion ou pour l'évaporation du CO2 du sol ou de l'eau.
Kakovost zraka - Vrednotenje lastnosti senzorskih sistemov za kakovost zraka - 1. del: Plinasta onesnaževala v zunanjem zraku
Ta tehnična specifikacija (TS) opisuje splošna načela, vključno s preskusnimi postopki in zahtevami, za vrednotenje lastnosti nizkocenovnih senzorskih sistemov za spremljanje plinastih spojin v zunanjem zraku na fiksnih mestih. Vrednotenje senzorskih sistemov vključuje preskuse, ki se izvajajo v predpisanih laboratorijskih in/ali terenskih pogojih.
Ta tehnična specifikacija ni namenjena za preskušanje senzorskih sistemov, ki se uporabljajo za mobilne naprave, za preskušanje omrežij senzorskih vozlišč ali za nadzor zraka v zaprtih prostorih, čeprav je njihov potencialni pomen priznan in bi lahko bili predmet prihodnjih tehničnih specifikacij.
Nizkocenovni senzorji temeljijo na več principih delovanja, tako so lahko npr. amperometrični senzorji, kovinski oksidi, optični senzorji (infrardeča absorpcija) itd. Vendar imajo senzorji v primerjavi s tradicionalnimi referenčnimi metodami nekaj skupnih lastnosti glede njihove prenosljivosti in nizke cene. Običajno lahko senzorji neprekinjeno spremljajo onesnaženost zraka in imajo kratek odzivni čas, ki se giblje od nekaj deset sekund do nekaj minut.
Opisani postopek je uporaben za določanje masne koncentracije onesnaževal zraka. Onesnaževala, ki so obravnavana v tej tehnični specifikaciji:
– plinasta onesnaževala v skladu z direktivami 2008/50/ES: O3, NO2 in NO, CO, SO2 ter benzen v območju pričakovanih koncentracij v zunanjem zraku;
– CO2 kot približek za dejavnosti, ki vključujejo procese zgorevanja ali izhlapevanje CO2 iz zemlje ali vode.
Pri uporabi trenutnih tehničnih specifikacij se pri vrednotenju senzorjev upoštevajo pragovi, omejitve in povprečni čas, ki so opredeljeni v Direktivi o kakovosti zraka (2008/50/ES)[1]. Na splošno direktiva določa mejne vrednosti, sestavljene iz letnega povprečja, ki se izračuna s povprečenjem ur. Pri senzorjih je morda uporabno izbrati krajši čas povprečenja.
Da bi se lahko zanesli na rezultate preskusov tega protokola, bodo morali bodoči uporabniki zagotoviti, da bodo senzorji implementirani z enako konfiguracijo kot senzor, predložen v ta protokol. To lahko vključuje: enako napajanje, pridobivanje podatkov, obdelavo podatkov, identično vzorčenje/zaščitno ohišje in pogostost umerjanja. Senzor mora biti podvržen enakemu režimu zagotavljanja in nazora kakovosti (QA/QC) ter vzdrževanju kot med preskusi. Poleg tega je močno priporočljivo, da se meritve senzorjev redno primerjajo vzporedno z referenčno metodo.
Za namene te tehnične specifikacije so senzorski sistemi bistveno cenejši od referenčnih metod za isto onesnaževalo.
General Information
Standards Content (Sample)
SLOVENSKI STANDARD
01-marec-2022
Kakovost zraka - Vrednotenje lastnosti senzorskih sistemov za kakovost zraka - 1.
del: Plinasta onesnaževala v zunanjem zraku
Air quality - Performance evaluation of air quality sensor systems - Part 1: Gaseous
pollutants in ambient air
Luftbeschaffenheit - Leistungsbewertung von Luftqualitäts-sensorsystemen - Teil 1:
Gasförmige Schadstoffe in der Außenluft
Qualité de l'air - Évaluation des performances des systèmes capteurs de la qualité de
l'air - Partie 1: Polluants gazeux dans l'air ambiant
Ta slovenski standard je istoveten z: CEN/TS 17660-1:2021
ICS:
13.040.20 Kakovost okoljskega zraka Ambient atmospheres
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
CEN/TS 17660-1
TECHNICAL SPECIFICATION
SPÉCIFICATION TECHNIQUE
December 2021
TECHNISCHE SPEZIFIKATION
ICS 13.040.20
English Version
Air quality - Performance evaluation of air quality sensor
systems - Part 1: Gaseous pollutants in ambient air
Qualité de l'air - Évaluation des performances des Luftbeschaffenheit - Leistungsbewertung von
systèmes capteurs de la qualité de l'air - Partie 1: Luftqualitäts-sensorsystemen - Teil 1: Gasförmige
Polluants gazeux dans l'air ambiant Schadstoffe in der Außenluft
This Technical Specification (CEN/TS) was approved by CEN on 17 October 2021 for provisional application.
The period of validity of this CEN/TS is limited initially to three years. After two years the members of CEN will be requested to
submit their comments, particularly on the question whether the CEN/TS can be converted into a European Standard.
CEN members are required to announce the existence of this CEN/TS in the same way as for an EN and to make the CEN/TS
available promptly at national level in an appropriate form. It is permissible to keep conflicting national standards in force (in
parallel to the CEN/TS) until the final decision about the possible conversion of the CEN/TS into an EN is reached.
CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and
United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2021 CEN All rights of exploitation in any form and by any means reserved Ref. No. CEN/TS 17660-1:2021 E
worldwide for CEN national Members.
Contents Page
European foreword . 4
Introduction . 5
1 Scope . 6
2 Normative references . 6
3 Terms and definitions . 6
4 Symbols and abbreviations . 12
4.1 Symbols . 12
4.2 Abbreviations . 16
5 Principle of the evaluation . 16
5.1 Introduction to the methodology . 16
5.2 General objective. 18
5.3 Protocol . 18
5.4 Initial requirements . 20
5.5 Test infrastructure . 20
5.6 Test results and classification . 21
5.7 Sensor system design changes . 21
5.8 List of tests to be performed . 22
5.9 Normal test conditions . 24
6 Performance requirements . 24
6.1 Data quality objectives . 24
6.2 Performance requirements . 25
7 General requirements for the performance of tests . 27
7.1 General requirements for testing . 27
7.2 Exposure chamber for laboratory experiments . 28
7.3 Averaging time and repetitions of readings for each laboratory test . 29
8 Pre-test of sensor system under controlled conditions (Step 1) . 29
8.1 General . 29
8.2 Response time . 30
8.3 Evaluation of lack of fit . 31
8.4 Repeatability . 33
9 Extended list of laboratory tests (Step 2) . 34
9.1 Long-term drift . 34
9.2 Cross-sensitivities to gaseous interfering compounds . 36
9.3 Temperature and humidity effects . 39
9.4 Memory effect of main gas, humidity and temperature . 42
9.5 Wind velocity effect . 43
9.6 Atmospheric pressure effect . 43
9.7 Electromagnetic fields effects . 44
9.8 Power supply and battery effects . 44
9.9 Evaluation of data quality objective of the laboratory experiments . 44
10 Field tests (Step 3 or Step 4). 45
10.1 General . 45
10.2 Selection of air quality monitoring station . 45
10.3 Installation . 46
10.4 Deployment and on-going quality control during field tests . 47
10.5 Evaluation of the uncertainty of the sensor system measurement . 47
11 Classification based on the test results . 51
11.1 General . 51
11.2 11.2 Evaluation of the pre-test (Step 1) . 51
11.3 Evaluation of laboratory test (Step 2, if applicable) . 52
11.4 Evaluation of field tests (Step 3, if step is carried out; Step 4 otherwise) . 52
11.5 Final classification . 53
12 Test report . 53
Annex A (informative) Co-location of sensors, deployment and management of a network
of sensor systems . 58
Annex B (informative) Guidance on the testing of CO sensor systems . 62
Annex C (informative) Guidance for the design of an exposure chamber . 65
Annex D (informative) Evaluation of the effect of wind velocity on the sensor system
measurements . 67
Annex E (normative) Evaluation of the effect of atmospheric pressure on the sensor system
measurements . 68
Annex F (informative) Evaluation of the effect of electromagnetic fields on the sensor
system measurements . 70
Annex G (informative) Air composition in different outdoor type of sites . 71
Annex H (informative) Selecting the climate for a field trial site . 74
Annex I (normative) Ordinary least square regression formulae . 76
Annex J (normative) Values for u bs, RM . 78
( )
Annex K (informative) Example of determination of measurement uncertainty . 81
Bibliography . 86
European foreword
This document (CEN/TS 17660-1:2021) has been prepared by Technical Committee CEN/TC 264 “Air
quality”, the secretariat of which is held by DIN.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN shall not be held responsible for identifying any or all such patent rights.
This document is Part 1 of a series of documents published under the general title Air quality —
Performance evaluation of air quality sensor systems.
Part 1 covers the performance evaluation of air quality sensor systems for gaseous pollutants in ambient
air.
Part 2 covers the performance evaluation of air quality sensor systems for particulate pollutants in
ambient air.
Any feedback and questions on this document should be directed to the users’ national standards body.
A complete listing of these bodies can be found on the CEN website.
According to the CEN-CENELEC Internal Regulations, the national standards organisations of the
following countries are bound to announce this Technical Specification: Austria, Belgium, Bulgaria,
Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland,
Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Republic of
North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the United
Kingdom.
Introduction
Sensor systems are generally seen as emerging measuring devices for the monitoring of air quality.
Sensor systems provide a fast and low-cost alternative to the reference methods as defined in Directive
2008/50/EC on ambient air quality and cleaner air for Europe [1]. Sensor systems could allow for air
pollution monitoring at a lower cost and with a higher spatial density than with the reference methods.
They also allow for new air pollution applications when coupled with the global positioning system (GPS),
global system for mobile communications (GSM) and smartphones including monitoring in complex
topographies, at traffic junctions, in street canyons, at remote sites and for citizen science studies; e.g.
monitoring around sensitive receptors, schools, or parks.
Sensor systems are making use of one or more low-cost sensors that are based on several principles of
operations, e.g. amperometric sensors, metal oxides, optical sensors (infra-red absorption). However,
sensor systems share some common features regarding their portability and low-cost compared to
traditional reference methods. Typically, sensor systems are able to continuously monitor air pollution,
with fast response times ranging between a few tens of seconds and a few minutes.
Currently, the use of sensor systems for air quality monitoring is limited by the occasional low accuracy
of measurements that they can achieve. Additionally, there was no unambiguous protocol of evaluation
of sensor systems with a structured metrological approach, able to ensure traceability from sensor
system measurements to national and international standards. A protocol will enable exhaustive and
transparent evaluations of sensor systems that can be an important step to include sensor system
measurements into the monitoring of air quality for regulatory and non-regulatory purposes.
The protocol presented in this document applies to sensor systems and supports the requirements of
Directive 2008/50/EC. The presented procedure evaluates if the measurement uncertainty defined in
Directive 2008/50/EC as data quality objectives for indicative measurements and for objective
estimation is met. However, the protocol additionally allows for a less demanding evaluation of the
performance of sensor systems for non-regulatory measurements.
The protocol applies to sensor systems as individual measurement devices. This protocol does not apply
to sensor systems as nodes in a sensor network. Annex A gives information on the use of sensor systems
in sensor networks.
This document defines common procedures and requirements for the evaluation of the performance of
sensor systems to facilitate mutual recognition by the relevant bodies or stakeholders and thereby
minimise both administrative and cost burdens on manufacturers. It does not describe the roles and
responsibilities of manufacturers, test laboratories and relevant bodies under these procedures.
In addition to the gaseous pollutants regulated in Directive 2008/50/EC, carbon dioxide is considered in
the scope of this protocol although this compound is not listed in Directive 2008/50/EC. Consequently,
there is no data quality objective for carbon dioxide. The World Health Organisation (WHO) has not set
any guidelines for carbon dioxide. However, there is a growing interest in monitoring carbon dioxide in
ambient air with sensor systems.
1 Scope
This document specifies the general principles, including testing procedures and requirements, for the
classification of performance of low-cost sensor systems for the monitoring of gaseous compounds in
ambient air at fixed sites. The classification of sensor systems includes tests that are performed under
prescribed laboratory and field conditions.
The procedure described is applicable to the determination of the mass concentration of air pollutants.
The pollutants that are considered in this document are the gaseous pollutants regulated under Directive
2008/50/EC (O , NO/NO /NO , CO, SO and benzene) in the range of concentrations expected in ambient
3 2 x 2
air.
This document provides a classification that is consistent with the requirements for indicative
measurements and objective estimation defined in Directive 2008/50/EC. In addition, it provides a
classification for applications (non-regulatory measurements) that require more relaxed performance
criteria.
This document applies to sensor systems used as individual systems. It does not apply to sensor systems
as part of a sensor network. However, for some applications (e.g. in cities) sensor systems are deployed
as part of a sensor network. Annex A gives information on the use of sensor systems as nodes in a sensor
network.
This document gives guidance on the testing of CO sensor systems in Annex B since, although not listed
in Directive 2008/50/EC, CO is an interesting indicator as proxy for activities involving combustion
processes or for CO evaporation from soil or water.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
EN ISO 14956:2006, Air quality — Evaluation of the suitability of a measurement procedure by comparison
with a required measurement uncertainty (ISO 14956:2002)
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— IEC Electropedia: available at http://www.electropedia.org/
— ISO Online browsing platform: available at http://www.iso.org/obp
3.1
ambient air
outdoor air in the troposphere where provisions concerning health and safety at work apply and to which
members of the public do not have regular access
[SOURCE: Directive 2008/50/EC]
Note 1 to entry: This does not include workplaces defined by Directive 89/654/EC.
3.2
sensor
individual sensor
chemical cell or physical unit that produces an analytically useful signal by detecting or measuring the
analyte
3.3
sensor system
sensor node
single integrated set of hardware that uses one or more sensors to detect and/or measure a chemical
concentration or quantity that is able to supply real time measurements
Note 1 to entry: The term “instrument” has a very similar definition, but many researchers are typically referring
to a reference grade device when using the word “instrument”.
Note 2 to entry: All the tests that are intended in this document are designed for sensor systems only.
Note 3 to entry: Sensor systems contain a number of common components in addition to the basic sensing or
analytical element that is used for detection. Common core components and functions can include:
— sensing element or detector (actually the sensor);
— sampling capability (active or passive sampling);
— power systems, including batteries;
— analogue to digital conversion;
— signal processing;
— local data storage;
— data transmission;
— housing or casing.
3.4
class 1 sensor system
measuring device delivering data that are at minimum consistent with the data quality objectives of
indicative measurements
Note 1 to entry: The term “indicative measurement” refers to the definition in Directive 2008/50/EC and not to
the performance of the sensor system.
3.5
class 2 sensor system
measuring device delivering data that are at minimum consistent with the data quality objectives of
objective estimations
Note 1 to entry: The term “objective estimation” refers to the definition in Directive 2008/50/EC and not to the
performance of the sensor system.
3.6
class 3 sensor system
measuring device delivering data that comply with a relaxed target measurement uncertainty, but are
not formally associated with any mandatory data quality objective
Note 1 to entry: Relaxed target measurement uncertainty are given in Table 3.
3.7
exposure chamber
volume that can be sealed with controlled conditions of temperature, humidity and test gas volume
fraction, used for performing the test on the sensor system
3.8
averaging period
period of time for which a limit value is associated
Note 1 to entry: For this document, the averaging period for field measurements is default to 1 h if the averaging
period in Directive 2008/50/EC is greater than 1 h.
3.9
independent measurement
measurement that is not influenced by a previous individual measurement, by separating two individual
measurements by at least four response times
3.10
individual measurement
measurement averaged over a time period equal to the response time of the sensor system
[SOURCE: adapted from EN 14211:2012, 3.15]
Note 1 to entry: This definition differs from the meaning of the concept “individual measurement” in Directive
2008/50/EC.
3.11
cold start
initial start after a shutdown or a long maintenance
Note 1 to entry: While the durations can vary, typically a cold start follows a shutdown of at least 48 h (2 days or
more).
3.12
warm start
restart after a short maintenance period of typically 1 h
3.13
hot start
restart after a shutdown period of a few minutes
3.14
shelf life
maximum storage period before use as stated by the manufacturer
3.15
zero gas
gas or gas mixture used to produce the zero response of a given analytical procedure or measuring device
for a given range of content
[SOURCE: ISO 7504:2015, 4.6]
3.16
calibration
operation that, under specified conditions, in a first step, establishes a relation between the quantity
values with measurement uncertainties provided by measurement standards and corresponding
indications with associated measurement uncertainties and, in a second step, uses this information to
establish a relation for obtaining a measurement result from an indication
[SOURCE: JCGM 200:2012, 2.39]
Note 1 to entry: A calibration can be expressed by a statement, calibration function, calibration diagram,
calibration curve, or calibration table. In some cases, it can consist of an additive or multiplicative correction of the
indication with associated measurement uncertainty. Calibration should not be confused with adjustment of a
measuring system, often mistakenly called “self-calibration”, nor with verification of calibration.
Note 2 to entry: This document does not describe the process of calibration of sensor systems.
3.17
drift
continuous or incremental change over time in measurement, due to changes in properties of a sensor
system
Note 1 to entry: The drift is related neither to a change in a quantity being measured nor to a change of any
recognized influence quantity.
3.18
memory effect
effect of previous values of the measurand on the current measurement results
[SOURCE: EN ISO 9169:2006, 2.1.21]
Note 1 to entry: Memory effect can be quantified by the difference between the upscale and downscale
measurements starting from fixed lower and upper measurement values.
3.19
detection limit
limit of detection
measured quantity value, obtained by a given measurement procedure, for which the probability of
falsely claiming the absence of a component in a material is β, given a probability α of falsely claiming its
presence
Note 1 to entry: IUPAC recommends default values for α and β equal to 0,05.
Note 2 to entry: The abbreviation LOD is sometimes used.
Note 3 to entry: The term “sensitivity” is discouraged for “detection limit”.
[SOURCE: JCGM 200:2012, 4.18]
3.20
repeatability of results of measurements
repeatability
closeness of the agreement between the results of successive measurements of the same measurand
carried out under the same conditions of measurement
Note 1 to entry: These conditions are called repeatability conditions.
Note 2 to entry: Repeatability conditions include:
— the same measurement procedure;
— the same observer;
— the same measuring instrument, used under the same conditions;
— the same location;
— repetition over a short period of time.
Note 3 to entry: Repeatability can be expressed quantitatively in terms of the dispersion characteristics of the
results.
[SOURCE: VIM:1993, 3.6]
3.21
selectivity of a measuring system
selectivity
property of a measuring system, used with a specified measurement procedure, whereby it provides
measured quantity values for one or more measurands such that the values of each measurand are
independent of other measurands or other quantities in the phenomenon, body, or substance being
investigated
[SOURCE: JCGM 200:2012, 4.13]
Note 1 to entry: In chemistry, the measured quantities often involve different components in the system undergoing
measurement and these quantities are not necessarily of the same kind.
Note 2 to entry: In chemistry, selectivity of a measuring system is usually obtained for quantities with selected
components in concentrations within stated intervals.
3.22
sensitivity of a measuring system
sensitivity
quotient of the change in an indication of a measuring system and the corresponding change in a value of
a quantity being measured
Note 1 to entry: Sensitivity of a measuring system can depend on the value of the quantity being measured.
Note 2 to entry: The change considered in a value of a quantity being measured must be large compared with the
resolution.
[SOURCE: JCGM 200:2012, 4.12]
3.23
stability of a measuring instrument
stability
property of a measuring instrument, whereby its metrological properties remain constant in time
[SOURCE: JCGM 200:2012, 4.19]
Note 1 to entry: Stability can be quantified in several ways, e.g. in terms of the duration of a time interval over
which a metrological property changes by a stated amount, or in terms of the change of a property over a stated
time interval.
3.24
uncertainty of measurement
measurement uncertainty
uncertainty
non-negative parameter characterizing the dispersion of the quantity values being attributed to a
measurand, based on the information used
Note 1 to entry: Measurement uncertainty includes components arising from systematic effects, such as
components associated with corrections and the assigned quantity values of measurement standards, as well as the
definitional uncertainty. Sometimes estimated systematic effects are not corrected for, but instead, associated
measurement uncertainty components are incorporated.
Note 2 to entry: The parameter may be, for example, a standard deviation called standard measurement
uncertainty (or a specified multiple of it), or the half-width of an interval, having a stated coverage probability.
Note 3 to entry: Measurement uncertainty comprises, in general, many components. Some of these may be
evaluated by Type A evaluation of measurement uncertainty from the statistical distribution of the quantity values
from series of measurements and can be characterized by standard deviations. The other components, which may
be evaluated by Type B evaluation of measurement uncertainty, can also be characterized by standard deviations,
evaluated from probability density functions based on experience or other information.
Note 4 to entry: In general, for a given set of information, it is understood that the measurement uncertainty is
associated with a stated quantity value attributed to the measurand. A modification of this value results in a
modification of the associated uncertainty.
[SOURCE: JCGM 200:2012, 2.26]
3.25
combined standard measurement uncertainty
standard measurement uncertainty that is obtained using the individual standard measurement
uncertainties associated with the input quantities in a measurement model
[SOURCE: JCGM 200:2012, 2.31]
3.26
expanded measurement uncertainty
expanded uncertainty
product of a combined standard measurement uncertainty and a factor larger than the number one
Note 1 to entry: The factor depends upon the type of probability distribution of the output quantity in a
measurement model and on the selected coverage probability.
Note 2 to entry: The term “factor” in this definition refers to a coverage factor.
Note 3 to entry: Expanded measurement uncertainty is termed “overall uncertainty” in paragraph 5 of
Recommendation INC-1 (1980) (see the GUM) and simply “uncertainty” in IEC documents.
[SOURCE: JCGM 200:2012, 2.35]
3.27
coverage factor
number larger than one by which a combined standard measurement uncertainty is multiplied to obtain
an expanded measurement uncertainty
Note 1 to entry: A coverage factor is usually symbolized k.
[SOURCE: JCGM 200:2012, 2.38]
4 Symbols and abbreviations
4.1 Symbols
For the purposes of this document, the following symbols apply.
NOTE In the following list, all symbols related to the measurement uncertainty of source contributions are
indicated as standard uncertainty, e. g. uX . However, in the text expanded uncertainties of the same source
( )
contributions can be used, e. g. UX .
( )
a intercept of the regression line
A average of the values y
i
slope of the regression line
b
average of the slope of the regression line at zero and highest test level
b
a
c
intercept of the corrected dataset
C average of the values C
a i
th
i value of the sensor system response
C
i
th
ˆ i value of the concentration estimated using a linear regression
C
i
maximum concentration of interfering compound
C
int,max
minimum concentration of interfering compound
C
int,min
average concentration of the measurements at the highest test level at the beginning
C
s,0
of the drift period
average concentration of the measurements at the highest test level at the end of the
C
s,1
drift period
C value of the sensor system response at tested electromagnetic field level X
emf ,X emf ,1
value of the sensor system response at tested electromagnetic field level
C X
emf ,X emf ,2
C value of the sensor system response at tested atmospheric pressure X
p,X p,1
C value of the sensor system response at tested atmospheric pressure X
p,X p,2
C value of the sensor system response at tested wind velocity X
wv,X wv,1
C value of the sensor system response at tested wind velocity X
wv,X wv,2
average concentration of the measurements at zero level at the beginning of the drift
C
z,0
period
average concentration of the measurements at zero level at the end of the drift period
C
z,1
d slope of the corrected dataset
long-term drift at the highest test level
D
l,s
long-term drift at zero level
D
l,z
maximum long-term drift at the highest test level determined during the 90 days test
D
l,s,max
period
maximum long-term drift at zero level determined during the 90 days test period
D
l,z,max
coverage factor
k
LV, UAT or LAT currently being assessed
L
m
number of repetitions at one and the same concentration level
n
number of measuring points; number of measurements
number of replicate sensor systems
n
s
r
measurement repeatability; repeatability
value of the residual sum of squares resulting from the linear regression;
R
ρ
residual
residual of each average at each concentration level
ρ
c,i
ρ maximum residual of individual ρ
c,i,max c,i
square root of the quadratic sum of the standard deviation of the intercepts for the low
sa
( )
level plus the standard deviations of the intercepts for the high level of the compounds
of interest for temperature and humidity, or the standard deviation of intercepts for
test gas
square root of the quadratic sum of the standard deviation of the slopes for the low
sb
( )
level plus the standard deviations of the slopes for the high level of the compounds of
interest for temperature and humidity, or standard deviation of the slopes for test gas
standard deviation of repeatability
s
r
standard deviation of repeatability of parameter X , given in the performance testing
sX
( )
i
reports of the reference analysers
t
time
response time
t
response time (fall)
t
f
response time (rise)
t
r
two-sided Students t-factor at a confidence level of 1−α , with n−1 degrees of
t
n−1,α
freedom
standard uncertainty of the intercept of a regression line
ua
( )
square of the uncertainty of the intercept of the uncorrected dataset
ua
( )
standard uncertainty of the slope of a regression line
ub
( )
square of the uncertainty of the slope of the uncorrected dataset
ub
( )
standard uncertainty due to long-term drift at the level of the limit value
uD
( )
l, LV
standard uncertainty due to long-term drift at zero level
uD
( )
l, z
uh
( )
X standard uncertainty due to the effect of test gas uh , temperature uh or
( ( )) ( ( ))
X X
c t
humidity uh
( ( ))
X
rh
standard uncertainty due to the memory effect of sensor systems for test gas
uh
( )
X
c
standard uncertainty due to the memory effect of sensor systems for humidity
uh
( )
X
rh
standard uncertainty due to the memory effect of sensor systems for temperature
uh
( )
X
t
standard uncertainty of the tested parameter X
uX
( )
standard uncertainty associated with the influence of atmospheric pressure
uX
( )
p
standard uncertainty associated with the influence of humidity
uX
( )
rh
standard uncertainty associated with the influence of temperature
uX( )
t
standard uncertainty associated with the effect of wind velocity
uX
( )
wv
between reference method standard uncertainty
u bs, RM
( )
between sensor systems standard uncertainty
u bs,s
( )
standard uncertainty associated with the effect of electromagnetic fields
u emf
( )
standard uncertainty associated with the influence of a gaseous interferent
u(int)
standard uncertainty associated with lack of fit
u lof
( )
expanded uncertainty associated with lack of fit
U lof
( )
expanded uncertainty of the field measurements of the sensor system at the value of
U
field,L
LV, UAT or LAT currently being assessed, in units of mass concentrations
expanded uncertainty of the corrected sensor system at the value of LV, UAT or LAT
U
field,corr,L
currently being assessed, in units of mass concentrations
expanded standard uncertainty of the laboratory tests
U
lab
x
value of the reference measurement
th
i x-value (reference measurement)
x
i
average of the values x
x
i
x average of the values x
a i
X tested parameter (test gas X, temperature X, humidity X ,
c t rh
atmospheric pressure X , wind velocity X )
p wv
high level of test gas during interference testing
X
c
t
th
X i value of the tested parameter X (temperature X or humidity X )
i t rh
high level of gaseous interfering compound
X
int
X average of the values X
a i
X maximum value of parameter X (temperature X or humidity X )
max t rh
X minimum value of parameter X (temperature X or humidity X )
min t rh
minimum value for atmospheric pressure in test conditions
X
p,1
maximum value for atmospheric pressure in test conditions
X
p,2
maximum expected value for atmospheric pressure in real ambient conditions
X
p,max
minimum expected value for atmospheric pressure in real ambient conditions
X
p,min
minimum value for wind velocity in test conditions
X
wv,1
maximum value for wind velocity in test conditions
X
wv,2
maximum expected value for wind velocity in real ambient conditions
X
wv,max
minimum expected value for wind velocity in real ambient conditions
X
wv,min
y
value of the sensor system response
th
i y-value (sensor system response)
y
i
value of the sensor system response for period i of sensor system j
y
i,j
y
average of the values y
i
y average for period i of the n replicate sensor systems;
i s
y average of the values y at the same concentration level;
a i
measured signal
Y
Y sensor system measurement of a gas mixture with test gas level at X and interferent
c c
t t
concentration at high level of the gaseous interfering compound X
int
Y sensor system measurement with test gas level at X and without interferent
c ,0 c
t t
influence quantity of the interferent at the limit value
Y
int
Y influence of the interferent on the sensor system response at test gas level X
int, c c
t t
influence of the interferent on the sensor system response at zero level of the test gas
Y
int,z
sensor system measurement with test gas at zero level and interferent concentration
Y
z
at high level of the gaseous interfering compound X
int
sensor system measurement with test gas at zero level and without interferent
Y
z,0
4.2 Abbreviations
For the purposes of this document, the following abbreviations apply.
AQMS air quality monitoring station (using measurement methods as defined in Directive
2008/50/EC)
AT alert threshold (for protection of human health set in Directive 2008/50/EC)
CL critical level (for the protection of vegetation set in Directive 2008/50/EC)
DQO data quality objective
GPS global positioning system
GSM global system for mobile communications
LAT lower assessment threshold (set in Directive 2008/50/EC)
LOD limit of detection
LV limit value (or target value set in Directive 2008/50/EC)
RH relative humidity
RM reference method
RSS residual sum of squares resulting from the linear regression
SOP standard operating procedure
UAT upper assessment threshold (set in Directive 2008/50/EC)
WLAN wireless local area network
5 Principle of the evaluation
5.1 Introduction to the methodology
The scheme in Figure 1 shows the focus and activities that are part (performance evaluation) and not
part (preparation, deployment) of test procedure specified in this document.
In this document, sensor systems are expected to deliver measurements directly as gas concentrations
(whether they are mixing ratios or mass per unit volume) without the need for calibration as part of this
test procedure.
If calibration is part of the normal operating procedure, then data collected during the performance
evaluation cannot be used to calibrate an individual sensor system. This calibration has to be done in the
preparation phase before providing the sensor systems for performance evaluation. The data of the
performance evaluation (second rectangle in Figure 1) cannot be used for this initial calibration of
individual sensor systems. If the standard operating procedure (SOP) provided by the manufacturer
includes a calibration frequency which is within the time frame of the evaluation, then this is performed
without using the evaluation dataset. The performed calibration during evaluation phase (if part of the
SOP) is reported in the test report and implies that this frequency of calibration is mandatory during
deployment of the sensor system as a Class 1, Class 2 or Class 3 sensor system.
The proposed performance evaluation results in a unique linear correction function (see 10.5.5) that can
be applied to the full dataset and all sensor boxes. During the deployment phase, a sensor system can be
used according to their classification for indicative measurements or objective estimations as defined in
Directive 2008/50/EC. The manufacturer’s deployment and preparation procedures shall be followed
and the SOP used during the performance evaluation has to be applied also during the deployment to be
valid as a Class 1, Class 2 or Class 3 sensor system.
Figure 1 — Scheme of activities that are part of this document (performance evaluation) and not
part of this document (preparation, deployment)
5.2 General objective
This document describes the test protocol and data quality objectives (DQO) for the evaluation and
classification of sensor systems. The aim of the protocol is to have a standardised approach for sensor
system testing and classification. The protocol requires the execution of laboratory tests and field tests
at air quality monitoring stations (AQMS) where sensor systems and reference methods are co-located
and compared. The results of the field tests are representative of the selected type of station and type of
area. Results can be different at other field sites where different air composition and climates can result
in different sensor performances. The protocol includes the evaluation of several variables describing the
sensitivity, selectivity and stability of sensor system measurements.
The classes specified in this document are:
— Class 1 and
...
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