SIST EN 50271:2018
(Main)Electrical apparatus for the detection and measurement of combustible gases, toxic gases or oxygen - Requirements and tests for apparatus using software and/or digital technologies
Electrical apparatus for the detection and measurement of combustible gases, toxic gases or oxygen - Requirements and tests for apparatus using software and/or digital technologies
This European Standard specifies minimum requirements and tests for electrical apparatus for the detection and measurement of combustible gases, toxic gases or oxygen using software and/or digital technologies.
This European Standard is applicable to fixed, transportable and portable apparatus intended for use in domestic premises as well as commercial and industrial applications.
This European Standard does not apply to external sampling systems, or to apparatus of laboratory or scientific type, or to apparatus used only for process control purposes.
This European Standard supplements the requirements of the European Standards for the detection and measurement of flammable gases and vapours (e.g. EN 60079 29 1, EN 60079-29-4, EN 50194 1, EN 50194 2), toxic gases (e.g. EN 45544 series, EN 50291 1, EN 50291 2) or oxygen (e.g. EN 50104).
NOTE 1 These European Standards will be mentioned in this European Standard as "metrological standards".
NOTE 2 The examples above show the state of the standardisation for gas detection apparatus at the time of publishing this European Standard. There may be other metrological standards for which this European Standard is also applicable.
This European Standard is a product standard which is based on EN 61508 series. It covers part of the phase 10 "realisation" of the overall safety life cycle defined in EN 61508 1.
Additional requirements are specified if compliance with safety integrity level 1 (SIL 1) according to EN 61508 series is claimed for fixed or transportable apparatus for low demand mode of operation.
NOTE 3 Compliance with safety integrity level 1 (SIL 1) for portable apparatus is not considered because portable apparatus cannot make an automatic executive action.
It is recommended to apply this European Standard for apparatus used for safety applications with SIL-requirement 1 instead of EN 50402. However, the technical requirements of EN 50271 and EN 50402 are the same for SIL 1.
NOTE 4 For apparatus used for safety applications with SIL-requirements higher than 1 EN 50402 is applicable.
Elektrische Geräte für die Detektion und Messung von brennbaren Gasen, giftigen Gasen oder Sauerstoff - Anforderungen und Prüfungen für Warngeräte, die Software und/oder Digitaltechnik nutzen
Diese Europäische Norm legt Mindestanforderungen und Prüfungen für elektrische Geräte für die Detektion und Messung von brennbaren Gasen, toxischen Gasen oder Sauerstoff fest, die Software und/oder Digitaltechnik nutzen.
Diese Europäische Norm ist anwendbar auf ortsfeste, transportable und tragbare Geräte, die für die Verwendung in Wohnhäusern oder in gewerblichen oder industriellen Anwendungen vorgesehen sind, sowie auf deren softwaregesteuertes sicherheitsrelevantes Zubehör.
Diese Europäische Norm gilt nicht für externe Entnahmesysteme, die kein Zubehör sind, oder für Labor- oder wissenschaftliche Geräte sowie für Geräte, die nur zur Prozesssteuerung eingesetzt werden.
Diese Europäische Norm ergänzt die Anforderungen der Europäischen Normen für die Detektion und Messung von brennbaren Gasen und Dämpfen (z. B. EN 60079 29 1, EN 60079 29 4, EN 50194 1, EN 50194 2), toxischen Gasen (z. B. Reihe EN 45544, EN 50291 1, EN 50291 2) oder Sauerstoff (z. B. EN 50104).
ANMERKUNG 1 Auf diese Europäischen Normen wird im Text als "messtechnische Normen" Bezug genommen.
ANMERKUNG 2 Die oben genannten Beispiele stellen den Stand der Normung für Gaswarngeräte zum Zeitpunkt der Veröffentlichung dieser Europäischen Norm dar. Es können weitere messtechnische Normen bestehen, auf die diese Europäische Norm ebenfalls anwendbar ist.
Diese Europäische Norm stellt eine Produktnorm auf Grundlage der Reihe EN 61508 dar. Sie deckt Teile der Phase 10 "Realisierung" des in EN 61508 1 definierten Gesamt-Sicherheitslebenszyklus ab.
Zusätzliche Anforderungen sind festgelegt, wenn eine Übereinstimmung mit dem Sicherheits-Integritätslevel 1 (SIL 1) nach der Reihe EN 61508 für ortsfeste oder transportable Geräte in der Betriebsart mit niedriger Anforderungsrate angegeben wird.
Diese können ebenso auf tragbare Geräte angewendet werden, die eine automatische Schalthandlung ausführen können.
Es wird empfohlen, diese Europäische Norm für Geräte zum Einsatz in sicherheitsgerichteten Anwendungen mit SIL-Anforderung 1 anstelle der EN 50402 anzuwenden. Die technischen Anforderungen der EN 50271 und der EN 50402 sind jedoch für SIL 1 gleich.
ANMERKUNG 3 Für Geräte zum Einsatz in sicherheitsgerichteten Anwendungen mit SIL-Anforderungen größer als 1 ist die EN 50402 anwendbar.
Appareils électriques de détection et de mesure des gaz combustibles, des gaz toxiques ou de l'oxygène - Exigences et essais pour les appareils utilisant un logiciel et/ou des technologies numériques
La présente Norme européenne spécifie les exigences minimales et les essais pour les appareils électriques de détection et de mesure de gaz combustibles, de gaz toxiques ou d'oxygène qui utilisent un logiciel et/ou des technologies numériques.
La présente Norme européenne s’applique aux appareils fixes, transportables et portables destinés à être utilisés dans des locaux à usage domestique ainsi qu’à applications commerciales et industrielles et leurs accessoires contrôlés par des logiciels relatifs à la sécurité.
La présente Norme européenne ne s’applique ni aux systèmes d’échantillonnage externe qui ne sont pas des accessoires, ni aux appareils de laboratoire ou à vocation scientifique, ni aux appareils utilisés uniquement à des fins de maîtrise des processus.
La présente Norme européenne complète les exigences des Normes européennes pour la détection et le mesurage des vapeurs et des gaz inflammables (par exemple, l’EN 60079-29-1, l’EN 60079-29-4, l’EN 50194-1, l’EN 50194-2), des gaz toxiques (par exemple, la série EN 45544, l’EN 50291-1, l’EN 50291-2) ou de l’oxygène (par exemple, l’EN 50104).
NOTE 1: Dans la présente Norme européenne, ces Normes européennes sont appelées « normes métrologiques ».
NOTE 2: Les exemples susmentionnés présentent l'état de la normalisation pour les appareils de détection de gaz au moment de la publication de la présente Norme européenne. La présente Norme européenne peut également s’appliquer à d’autres normes métrologiques.
La présente Norme européenne est une norme de produit fondée sur la série EN 61508. Elle traite en partie de la phase 10 « réalisation » du cycle de vie de sécurité globale définie dans l’EN 61508-1.
Des exigences supplémentaires sont spécifiées si la conformité au niveau d'intégrité de sécurité 1 (SIL 1) conformément à la série EN 61508 est revendiquée pour un appareil fixe ou transportable pour un mode de fonctionnement à faible sollicitation. Elles s’appliquent également aux appareils portables pouvant exécuter une action automatique.
Il est recommandé d’appliquer la présente Norme européenne plutôt que l’EN 50402 pour des appareils utilisés dans des applications de sécurité exigeant le niveau de sécurité 1 (SIL 1). Toutefois, les exigences techniques de l’EN 50271 et de l’EN 50402 sont identiques pour le niveau SIL 1.
NOTE 3: Pour des appareils utilisés dans des applications de sécurité exigeant un SIL supérieur à 1, l’EN 50402 s’applique.
Električne naprave za odkrivanje in merjenje vnetljivih plinov, strupenih plinov ali kisika - Zahteve in preskusi za naprave s programsko opremo in/ali digitalno tehnologijo
Ta evropski standard določa minimalne zahteve in preskuse v zvezi z električnimi napravami za odkrivanje in merjenje vnetljivih plinov, strupenih plinov ali kisika z uporabo programske opreme in/ali digitalne tehnologije.
Ta evropski standard se uporablja za nepremične, premične in prenosne naprave, namenjene za uporabo v bivalnih prostorih ter za poslovne in industrijske namene.
Ta evropski standard se ne uporablja za zunanje sisteme vzorčenja, laboratorijske ali znanstvene naprave in naprave, ki se uporabljajo samo za namene nadziranja procesov.
Ta evropski standard dopolnjuje zahteve evropskih standardov za odkrivanje in merjenje vnetljivih plinov ter hlapov (npr. EN 60079 29 1, EN 60079-29-4, EN 50194 1, EN 50194 2), strupenih plinov (npr. skupina standardov EN 45544, EN 50291 1, EN 50291 2) ali kisika (npr. EN 50104).
OPOMBA 1: Ti evropski standardi bodo v tem evropskem standardu navedeni kot »meroslovni standardi«.
OPOMBA 2: Spodnji primeri prikazujejo stanje standardizacije naprav za odkrivanje plina v času objave tega evropskega standarda. Ta evropski standard se morda lahko uporablja tudi za druge meroslovne standarde.
Ta evropski standard je standard za proizvode, ki temelji na skupini standardov EN 61508. Obravnava del »realizacije« 10. faze celotnega varnostnega življenjskega cikla, opredeljenega v standardu EN 61508 1.
Dodatne zahteve so določene, če je za nepremične ali premične naprave, ki delujejo na način z nizkimi zahtevami, navedena skladnost s stopnjo varnostne celovitosti 1 (SIL 1) v skladu s skupino standardov EN 61508.
OPOMBA 3: Skladnost s stopnjo varnostne celovitosti 1 (SIL 1) za prenosne naprave ni obravnavana, ker prenosne naprave ne morejo samodejno izvajati dejanj.
Priporočljivo je, da se ta evropski standard uporablja za naprave, namenjene varnostni uporabi, z zahtevo SIL 1 namesto standarda EN 50402. Vendar tehnične zahteve iz standarda EN 50271 in EN 50402 veljajo tudi za SIL 1.
OPOMBA 4: Za naprave, namenjene varnostni uporabi, z zahtevami SIL, večjimi od 1, se uporablja standard EN 50402.
General Information
Relations
Standards Content (Sample)
SLOVENSKI STANDARD
SIST EN 50271:2018
01-oktober-2018
1DGRPHãþD
SIST EN 50271:2010
(OHNWULþQHQDSUDYH]DRGNULYDQMHLQPHUMHQMHYQHWOMLYLKSOLQRYVWUXSHQLKSOLQRYDOL
NLVLND=DKWHYHLQSUHVNXVL]DQDSUDYHVSURJUDPVNRRSUHPRLQDOLGLJLWDOQR
WHKQRORJLMR
Electrical apparatus for the detection and measurement of combustible gases, toxic
gases or oxygen - Requirements and tests for apparatus using software and/or digital
technologies
Elektrische Geräte für die Detektion und Messung von brennbaren Gasen, giftigen
Gasen oder Sauerstoff - Anforderungen und Prüfungen für Warngeräte, die Software
und/oder Digitaltechnik nutzen
Appareils électriques de détection et de mesure des gaz combustibles, des gaz toxiques
ou de l'oxygène - Exigences et essais pour les appareils utilisant un logiciel et/ou des
technologies numériques
Ta slovenski standard je istoveten z: EN 50271:2018
ICS:
13.230 Varstvo pred eksplozijo Explosion protection
29.260.20 (OHNWULþQLDSDUDWL]D Electrical apparatus for
HNVSOR]LYQDR]UDþMD explosive atmospheres
SIST EN 50271:2018 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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SIST EN 50271:2018
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SIST EN 50271:2018
EUROPEAN STANDARD EN 50271
NORME EUROPÉENNE
EUROPÄISCHE NORM
June 2018
ICS 13.320 Supersedes EN 50271:2010
English Version
Electrical apparatus for the detection and measurement of
combustible gases, toxic gases or oxygen - Requirements and
tests for apparatus using software and/or digital technologies
Appareils électriques de détection et de mesure des gaz Elektrische Geräte für die Detektion und Messung von
combustibles, des gaz toxiques ou de l'oxygène - brennbaren Gasen, giftigen Gasen oder Sauerstoff -
Exigences et essais pour les appareils utilisant un logiciel Anforderungen und Prüfungen für Warngeräte, die Software
et/ou des technologies numériques und/oder Digitaltechnik nutzen
This European Standard was approved by CENELEC on 2017-11-06. CENELEC members are bound to comply with the CEN/CENELEC
Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration.
Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the CEN-CENELEC
Management Centre or to any CENELEC member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by translation
under the responsibility of a CENELEC member into its own language and notified to the CEN-CENELEC Management Centre has the
same status as the official versions.
CENELEC members are the national electrotechnical committees of Austria, Belgium, Bulgaria, Croatia, Cyprus, the Czech Republic,
Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia,
Lithuania, Luxembourg, Malta, the Netherlands, Norway, Poland, Portugal, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden,
Switzerland, Turkey and the United Kingdom.
European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2018 CENELEC All rights of exploitation in any form and by any means reserved worldwide for CENELEC Members.
Ref. No. EN 50271:2018 E
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EN 50271:2018 (E)
Contents
European foreword . 3
Introduction . 4
1 Scope . 5
2 Normative references . 5
3 Terms and definitions . 6
4 Design principles . 8
4.1 Basic requirements . 8
4.1.1 General . 8
4.1.2 Analogue/digital interface . 8
4.1.3 Numerical errors . 8
4.1.4 Measuring operation . 8
4.1.5 Special state indication . 8
4.2 Displays . 9
4.2.1 General . 9
4.2.2 Indication of messages . 9
4.2.3 Indication of measured values . 10
4.3 Software.10
4.3.1 General . 10
4.3.2 Re-used or commercial operating systems . 11
4.3.3 Software requirements . 11
4.3.4 Requirements for software documentation . 12
4.3.5 Requirements for the software development process . 12
4.4 Hardware .20
4.5 Digital data transmission between components of apparatus .20
4.6 Test routines .20
4.7 Instruction manual .22
4.8 Additional requirements for compliance with SIL 1 .23
5 Test of the digital unit .24
5.1 General .24
5.2 Verification of functional concept .25
5.3 Performance test .25
Annex A (normative) Hardware-software integration test .27
A.1 Functional testing/Black-box testing .27
A.2 Equivalence class test with boundary value analysis .27
Annex ZY (normative) Significant changes between this European Standard and
EN 50271:2010 .29
Annex ZZ (informative) Relationship between this European standard and the essential
requirements of Directive 2014/34/EU aimed to be covered .31
Bibliography .32
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EN 50271:2018 (E)
European foreword
This document (EN 50271:2018) has been prepared by CLC/SC 31-9, “Electrical apparatus for the
detection and measurement of combustible gases to be used in industrial and commercial potentially
explosive atmospheres”, of CLC/TC 31, “Electrical apparatus for potentially explosive atmospheres”,
and by CLC/TC 216 “Gas detectors”.
The following dates are fixed:
• latest date by which this document has to be (dop) 2018-12-15
implemented at national level by publication of
an identical national standard or by
endorsement
• latest date by which the national standards (dow) 2021-06-15
conflicting with this document have to
be withdrawn
This document supersedes EN 50271:2010.
The State of the Art is included in Annex ZY “Significant changes between this European Standard
and EN 50271:2010” which lists all changes to EN 50271:2010.
This document has been prepared under a mandate given to CENELEC by the European Commission
and the European Free Trade Association and covers essential requirements of EU Directive
2014/34/EU.
For the relationship with EU Directive see informative Annex ZZ, which is an integral part of this
document.
3
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EN 50271:2018 (E)
Introduction
This European Standard specifies minimum requirements for functional safety of gas detection
apparatus using software and/or digital technologies and defines criteria for reliability and avoidance of
faults. Functional safety is that part of the overall safety which is related to the measures within the
gas detection apparatus to avoid or to handle failures in such a manner that the safety function will be
ensured.
Gas detection apparatus will fail to function if dangerous failures occur. The aim of this European
Standard is to reduce the risk of dangerous equipment failures to levels appropriate to typical
applications of such apparatus.
Failure to function will also occur if such apparatus are not selected, installed or maintained in an
appropriate manner. In some applications failures of this type will dominate the functional safety
achieved. Users of gas detection apparatus will therefore need to ensure that selection, installation
and maintenance of such apparatus are carried out appropriately. Guidance for the selection,
installation, use and maintenance of gas detection apparatus are set out in EN 60079-29-2 and
EN 45544-4, respectively.
This European Standard does not include requirements for operational availability which will need to
be considered separately.
Regarding the requirements for the software development process, this European Standard specifies
a practical approach to comply with the requirements of EN 61508-3 for SIL 1 without using this
generic standard.
This European standard also specifies additional optional requirements for compliance with SIL 1 in
low demand mode operation. The following apparatus or gas detection systems are not fully covered
by this standard:
– apparatus at SIL 1 when the apparatus or gas detection system contains functionality not covered
by EN 50271
– apparatus at SIL 1 high demand mode operation
– apparatus at SIL 2 and SIL 3;
For such apparatus or gas detection systems the European standard EN 50402 should be used
instead of EN 50271. EN 50402 includes all requirements of EN 50271.
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EN 50271:2018 (E)
1 Scope
This European Standard specifies minimum requirements and tests for electrical apparatus for the
detection and measurement of combustible gases, toxic gases or oxygen using software and/or digital
technologies.
This European Standard is applicable to fixed, transportable and portable apparatus intended for use
in domestic premises as well as commercial and industrial applications and their software-controlled
safety related accessories.
This European Standard does not apply to external sampling systems which are not accessories, or to
apparatus of laboratory or scientific type, or to apparatus used only for process control purposes.
This European Standard supplements the requirements of the European Standards for the detection
and measurement of flammable gases and vapours (e.g. EN 60079-29-1, EN 60079-29-4, EN 50194-
1, EN 50194-2), toxic gases (e.g. EN 45544 series, EN 50291-1, EN 50291-2) or oxygen (e.g.
EN 50104).
NOTE 1 These European Standards will be mentioned in this European Standard as “metrological standards”.
NOTE 2 The examples above show the state of the standardization for gas detection apparatus at the time of
publishing this European Standard. There may be other metrological standards for which this European Standard
is also applicable.
This European Standard is a product standard which is based on the EN 61508 series. It covers part
of the phase 10 “realisation” of the overall safety life cycle defined in EN 61508-1.
Additional requirements are specified if compliance with safety integrity level 1 (SIL 1) according to the
EN 61508 series is claimed for fixed or transportable apparatus for low demand mode of operation.
They can also be applied to portable apparatus which are able to perform an automatic executive
action.
It is recommended to apply this European Standard for apparatus used for safety applications with
SIL-requirement 1 instead of EN 50402. However, the technical requirements of EN 50271 and
EN 50402 are the same for SIL 1.
NOTE 3 For apparatus used for safety applications with SIL-requirements higher than 1 EN 50402 is applicable.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and are
indispensable for its application. For dated references, only the edition cited applies. For undated
references, the latest edition of the referenced document (including any amendments) applies.
EN 50402:2017, Electrical apparatus for the detection and measurement of combustible or toxic gases
or vapours or of oxygen - Requirements on the functional safety of gas detection systems
EN 60079-29-1:2016, Explosive atmospheres - Part 29-1: Gas detectors - Performance requirements
of detectors for flammable gases
EN 61508-1:2010, Functional safety of electrical/electronic/programmable electronic safety-related
systems - Part 1: General requirements
EN 61508-2:2010, Functional safety of electrical/electronic/programmable electronic safety-related
systems - Part 2: Requirements for electrical/electronic/programmable electronic safety-related
systems
EN 61508-3:2010, Functional safety of electrical/electronic/programmable electronic safety-related
systems - Part 3: Software requirements
EN 61508-4:2010, Functional safety of electrical/electronic/programmable electronic safety-related
systems - Part 4: Definitions and abbreviations
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EN 61508-5:2010, Functional safety of electrical/electronic/programmable electronic safety-related
systems - Part 5: Examples of methods for the determination of safety integrity levels
EN 61508-6:2010, Functional safety of electrical/electronic/programmable electronic safety-related
systems - Part 6: Guidelines on the application of IEC 61508-2 and IEC 61508-3
EN 61508-7:2010, Functional safety of electrical/electronic/programmable electronic safety-related
systems - Part 7: Overview of techniques and measures
3 Terms and definitions
For the purposes of this document, the terms and definitions given in EN 60079-29-1:2016 and the
following apply.
3.1
digital unit
part of an electrical apparatus in which data is processed digitally. Analogue-digital(A/D)-converters
and digital-analogue(D/A)-converters as interfaces to analogue units of the apparatus belong to the
digital unit
3.2
special state
all states of the apparatus other than those in which monitoring of gas concentration and/or alarming is
intended, for example the special states of warm-up, calibration mode or fault condition
[SOURCE: EN 60079-29-1:2016, 3.5.4]
3.3
software
intellectual creation comprising the programs, procedures, rules and associated documentation
pertaining to the operation of the digital unit
3.4
failure
termination of the ability of a functional unit to provide a required function or operation of a functional
unit in any way other than as required
[SOURCE: EN 61508-4:2010, 3.6.4, mod.]
3.5
parameters
settings by the manufacturer or user which affect the operation of the apparatus, e.g. changing of the
alarm set points or measuring ranges. Parameter options are included in the hardware and/or software
during design of the apparatus. Changes of parameter settings are not modifications of the software.
In the software several different levels of permission to read or to change parameters may exist
3.6
specified range of input values
range of analogue input values corresponding to the digital output range of an A/D-converter or range
of digital input values corresponding to the analogue output range of a D/A-converter. The minimum
and maximum digital values of the converter are not to be considered to be within the specified range
because minima and maxima correspond to stuck-at faults which have to be detected by the
apparatus (see 4.1.4)
3.7
defined range of input values
range of input values defined by the manufacturer of the apparatus to be valid; the defined range is a
sub-range of the specified range of input values
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3.8
output data
result of the digital data processing, which is used for driving the output interfaces
Note 1 to entry: Output interfaces may be analogue or digital displays, analogue or digital outputs and/or alarm
indicators or relays.
3.9
output signal
analogue or digital signal which is available at an output interface
3.10
measured value
processed measured signal including physical unit (e.g. % LEL). A measured value may be formed
from a single signal or a combination of several measured signals. The combined measured signals
may represent different physical units, e.g. gas concentration and temperature
3.11
smallest deviation of indication
value which is determined by the applicable metrological standards. In metrological standards the
allowed tolerances for deviation of indication during type testing are given. If there are different
requirements for the tolerances in different applicable metrological standards the smallest tolerance is
the “smallest deviation of indication”
Note 1 to entry: The smallest deviation of indication is basis for the required resolution of measured signals
which use digital transmission and data processing to meet the requirements of the metrological standards when
using digital technologies
[SOURCE: EN 50402:2017, 3.22]
3.12
message
indication on a display which gives an information about the status of the apparatus (e.g. alarm,
special state, warning)
3.13
software component
part of the program that consists of one or several software modules and that can also interact with
other such constructs
3.14
software module
construct that consists of subroutines and/or data declarations and that can also interact with other
such constructs
3.15
safety function of a gas detection apparatus
any function (inclusive from gas sampling to output of the gas detection apparatus) implemented by
the gas detection apparatus which is related to safety as defined by the manufacturer
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4 Design principles
4.1 Basic requirements
4.1.1 General
The metrological standards define performance requirements for gas detection apparatus which have
direct implications on the digital units and software which may be used in such apparatus. This
subclause specifies basic requirements to digital units and software to fulfil the metrological standards.
4.1.2 Analogue/digital interface
The relationship between corresponding analogue and digital values shall be unambiguous. The
output range shall be capable of coping with the defined range of input values. Input values outside
the specified range of the converter shall not result in a valid measured value. A/D- and D/A-converter
quantisation steps shall be chosen so that the requirements in 4.1.3 for the accuracy of data
representation will be fulfilled. The design shall take into account the maximum possible A/D- and D/A-
converter errors.
NOTE This assessment need not include environmental interferences to the A/D- or D/A-converters, e.g.
temperature variation, since environmental testing is covered by the metrological standards.
Outputs at the limits of the specified range of D/A-converters shall result in output signals which are
described as fault signal by the manufacturer.
4.1.3 Numerical errors
Deviations of measured values arising from quantisation, rounding and calculation errors shall be
estimated assuming worst case conditions.
These worst case conditions shall be evaluated in detail. For example, nonlinear behaviour of the
sensor signal with gas concentration, ageing of sensors, varying sensitivities for different gases and
signal variation with temperature, pressure or humidity shall be taken into consideration.
The estimated deviation of measured values shall not be greater than 50 % of the smallest deviation
of indication.
NOTE The deviation of measured values arising from the digital unit will be typically much lower than 50 % of
the smallest deviation of indication. Deviations arising from other sources (e.g. sensor) are expected to be
dominant.
4.1.4 Measuring operation
During data processing the digital unit shall automatically control the specified input data range and
handle range violations. The minimum and maximum digital values of the converter shall not be
considered to be within the specified range in order to detect stuck-at faults.
The software design and verification shall guarantee that range violations for internal and output data
do not occur. Otherwise the digital unit shall automatically control the allowed data ranges and handle
range violations.
During measuring operation, the maximum overall time of four successive updates of the measured
value and all safety relevant output signals shall not exceed the response time t90 of the apparatus or,
for alarm only apparatus, the minimum time to alarm.
NOTE This timing requirement may not be applied to output signals which are explicitly claimed by the
manufacturer to be not safety-relevant.
4.1.5 Special state indication
4.1.5.1 General
It shall not be possible for any interface to an external device to adversely affect a safety function of
the apparatus without the apparatus entering a special state.
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NOTE This includes both hardware and software interfaces.
4.1.5.2 Fixed and transportable apparatus
a) Control units
While a special state is present within the entire gas detection apparatus (i.e. control unit and
external sensors or transmitters) this shall be continuously indicated by a signal. This signal shall
be transmittable except when the apparatus is intended to be used in domestic premises only.
Signals provided for indicating that the entire gas detection apparatus is in the special state “fault”
shall be such that they de-energize when the special state occurs and also on power loss. In the
case of deactivation of alarm devices, e.g. for calibration purposes, it is not required to indicate a
special state by a transmittable signal if the alarm devices are automatically re-enabled within
15 min.
b) Gas detection transmitters intended to be used with control units
The special state “calibration” shall be transmitted to the control unit continuously or the
measured value shall be transmitted during calibration. All other special states shall be
transmitted to the control unit continuously. The test routine according to 4.6 c) is excluded.
c) All other apparatus
A special state shall be continuously indicated by a signal. This signal shall be transmittable
except when the apparatus is intended to be used in domestic premises only. Signals provided for
indicating that the apparatus is in the special state “fault” shall be such that they de-energize
when the special state occurs and also on power loss. In the case of deactivation of alarm
devices, e.g. for calibration purposes, it is not required to indicate a special state by a
transmittable signal if the alarm devices are automatically re-enabled within 15 min.
In the case of digital data transmission, the term “continuously” is used with the meaning: continually,
at the rate at which the output signal is updated (see 4.1.4).
4.1.5.3 Portable apparatus
The special state “fault” shall be continuously indicated by an optical and audible signal. It is permitted
that the audible signal can be silenced.
If it is not possible to show an indication in all possible fault situations the normal operation of the
apparatus shall be confirmed by a periodic optical and audible output signal (commonly called alive
signal or confidence signal). The time interval between two signals shall not exceed 60 s.
EXAMPLE: A sudden breakdown of battery voltage cannot be indicated without implementing a second
independent power supply.
The special state “warm-up” shall be indicated by an optical and/or audible signal.
The special states “calibration mode” and “parameterization mode” shall be indicated by an optical
signal.
4.2 Displays
4.2.1 General
If a display is provided the requirements of 4.2.2 and 4.2.3 apply.
4.2.2 Indication of messages
If it is intended to indicate messages on a display:
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SIST EN 50271:2018
EN 50271:2018 (E)
a) it shall be possible to display all active messages simultaneously or a consolidated signal shall be
generated (e.g. indicating lights for alarms or fault) and a consolidated message shall be
displayed. It shall be possible to interrogate all active messages;
b) a unique message shall be provided for each individual gas alarm;
c) if no special state is activated, it shall be possible to interrogate the measured values of all gas
sensors.
If a message includes another subsidiary message (e.g. exceeding the 2nd alarm threshold includes
exceeding the 1st alarm threshold) it is sufficient to show the message of higher priority. After
cancelling the higher order message the subsidiary message shall remain if the reason for its
activation still exists.
It is recommended that the manufacturer defines an appropriate set of messages in order to enable
the user an easy identification of alarms, special states, etc.
4.2.3 Indication of measured values
For measured values the displayed unit of measurement and any related sign shall be unambiguous.
Any under-range or over-range measurements shall be clearly indicated according to the requirements
of the metrological standards.
4.3 Software
4.3.1 General
This clause specifies minimum requirements for the software development process which are based
on EN 61508-3. Alternative procedures are permitted provided that the applicable requirements of
EN 61508-3 are fulfilled. Compliance through “proven in use” (Route 2s of EN 61508-3) shall not be
used.
NOTE This standard specifies minimum requirements and does not give additional recommendations (in the
tables of EN 61508-3 and in EN 50402:2017 marked as “R”).
In general, software will consist of device software and, if applicable, an operating system and libraries
(e.g. mathematical functions).
The requirements of this clause shall be applied to the entire software. A distinction between safety-
related and non safety-related software is not made.
New operating systems shall be developed according to 4.3.3 to 4.3.5. Re-used or commercial
operating systems shall comply with 4.3.2.
New device software and libraries shall be developed according to 4.3.3 to 4.3.5.
Bought or re-used software modules which were previously developed according to 4.3.3 to 4.3.5 or
commercial libraries which are only available as object code shall be qualified (see 4.3.5.3.2).
Bought or re-used software modules which are relevant for the basic gas detection functionality (signal
chain from sensor to safety relevant output(s)) or the effectiveness of the test routines (according to
4.6) which were not developed according to 4.3.3 to 4.3.5 shall be treated as new code (Route 3s
according to EN 61508-3, 7.4.2.13). All other bought or re-used software modules shall be qualified
(see 4.3.5.3.2).
Only the requirements of 4.3.3, 4.3.4 a)-e), g), h) and 4.7 shall be applied to so
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