EN 17526:2021+A1:2025

SLOVENSKI STANDARD
01-julij-2025
Nadomešča:
SIST EN 17526:2022
Plinomeri - Plinomer na osnovi termičnega merjenja masnega toka (vključno z
dopolnilom A1)
Gas meter - Thermal-mass flow-meter based gas meter
Gaszähler - Thermische Massendurchflussgaszähler
Compteurs de gaz - Compteur de gaz basé sur un débitmètre massique par effet
thermique
Ta slovenski standard je istoveten z: EN 17526:2021+A1:2025
ICS:
91.140.40 Sistemi za oskrbo s plinom Gas supply systems
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EN 17526:2021+A1
EUROPEAN STANDARD
NORME EUROPÉENNE
April 2025
EUROPÄISCHE NORM
ICS 91.140.40 Supersedes EN 17526:2021
English Version
Gas meter - Thermal-mass flow-meter based gas meter
Compteurs de gaz - Compteur de gaz basé sur un Gaszähler - Thermische Massendurchflussgaszähler
débitmètre massique par effet thermique
This European Standard was approved by CEN on 11 July 2021 and includes Amendment 1 approved by CEN on 15 December
2024.
CEN 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 CEN
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 CEN member into its own language and notified to the CEN-CENELEC Management
Centre has the same status as the official versions.

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, Türkiye 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
© 2025 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN 17526:2021+A1:2025 E
worldwide for CEN national Members.

Contents Page
European foreword . 4
1 Scope . 5
2 Normative references . 5
3 Terms, definitions and symbols . 8
3.1 Terms and definitions . 8
3.2 Symbols . 12
4 Working conditions . 13
4.1 General . 13
4.2 Base conditions . 13
4.3 Flow range . 13
4.4 Maximum working pressure . 14
4.5 Temperature range . 14
4.6 Range of gases . 15
4.7 Installation orientation . 15
5 Metrological performance . 15
5.1 General . 15
5.2 Test mode comparison . 16
5.3 Permissible errors . 17
5.4 Gas-air relationship . 19
5.5 Pressure absorption . 20
5.6 Metrological stability . 21
5.7 Immunity to contaminants in gas stream (dust test) . 22
5.8 Flow disturbances . 25
5.9 Zero flow . 29
5.10 Reverse flow . 30
5.11 Low flow registration (starting flow rate) . 30
5.12 Overload flow rate . 30
5.13 MM - Pulsed (unsteady) flow . 31
6 Construction and materials . 31
6.1 Mechanical interference . 32
6.2 Unauthorized interference . 32
6.3 Robustness of meter case . 33
6.4 Connections . 37
6.5 Resistance to vibration . 42
6.6 Corrosion protection. 44
6.7 Flame retardance of external surfaces . 45
6.8 Requirements for rubber components in the gas path . 46
6.9 Resistance to storage temperature range . 46
6.10 Resistance to toluene/iso-octane vapour. 46
6.11 Resistance to water vapour . 48
6.12 Ageing . 49
7 Optional features . 50
7.1 Pressure measuring point . 50
7.2 Electrical insulating feet (optional) . 51
7.3 Resistance to high ambient temperatures . 51
7.4 Additional functionalities (if fitted) . 53
7.5 Use in hazardous zones . 54
8 Index . 54
8.1 Recording and storage . 54
8.2 Display . 54
8.3 Display functionality . 55
8.4 Non-volatile memory . 56
9 Marking . 57
9.1 All meters. 57
9.2 Two-pipe meters . 57
9.3 Durability and legibility of marking and labels . 58
9.4 Indelibility of marking . 59
10 Software . 59
10.1 Requirements . 59
10.2 Test . 60
11 Communications . 61
11.1 General . 61
11.2 Metrological influence of radio communication function . 61
11.3 Test mode . 62
11.4 Data optical port (optional) . 62
11.5 Galvanic port (optional) . 62
11.6 Diagnostics . 62
12 Battery . 64
12.1 General . 64
12.2 Additional requirements . 64
13 Immunity to electromagnetic disturbances . 64
13.1 General . 64
13.2 Electrostatic discharge . 65
13.3 Radio frequency electromagnetic field . 65
13.4 Electromagnetic induction (power frequency) . 66
13.5 Electromagnetic induction (pulsed field) . 66
13.6 Radio interference suppression . 66
14 Instructions . 67
15 Meters supplied for testing . 67
16 Production requirements . 70
Annex A (informative) Key physical property of gases for meter performance testing . 71
Annex B (normative) Gases for meter performance testing . 73
Annex C (informative) Meters without temperature or pressure conversion . 75
Annex D (normative) Production requirements for gas meters. 76
Annex ZA (informative) Relationship between this European Standard and the Essential
Requirements of EU Directive 2014/32/EU Measuring Instruments Directive aimed
to be covered . 78
Bibliography . 83
European foreword
This document (EN 17526:2021+A1:2025) has been prepared by Technical Committee CEN/TC 237 “Gas
meters”, the secretariat of which is held by BSI.
This European Standard shall be given the status of a national standard, either by publication of an
identical text or by endorsement, at the latest by October 2025, and conflicting national standards shall
be withdrawn at the latest by October 2025.
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 includes Amendment 1 approved by CEN on 15 December 2024.
This document supersedes EN 17526:2021.
The start and finish of text introduced or altered by amendment is indicated in the text by tags !".
This document has been prepared under a standardization request addressed to CEN by the European
Commission. The Standing Committee of the EFTA States subsequently approves these requests for its
Member States.
For the relationship with EU Legislation, see informative Annex ZA, which is an integral part of this
document.
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 implement this European Standard: 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, Türkiye and the United
Kingdom.
1 Scope
This document specifies requirements and tests for the construction, performance, safety and production
of battery powered class 1,5 Capillary Thermal-Mass Flow sensor gas meters (hereinafter referred to as
meter(s)). This applies to meters having co-axial single pipe, or two pipe connections, which are used to
measure volumes of fuel gases of the 2nd and/or 3rd family, as given in EN 437:2018.
In general, the term “thermal mass flow meters” applies to a flow-measuring device using heat transfer
to measure and indicate gas flowrate, as defined in ISO 14511.
NOTE 1 Although the word “mass” is present in the definition of the measurement principle, gas meters covered
by this document provide measurement of gas at base conditions of temperature and pressure.
These meters have a maximum working pressure not exceeding 0,5 bar and a maximum flowrate not
exceeding 160 m /h over a minimum ambient temperature range of −10 °C to +40 °C and a gas
temperature range as specified by the manufacturer with a minimum range of 40 °C.
This document applies to meters indicating volume at base conditions, which are installed in locations
with vibration and shocks of low significance. It applies to meters in:
— closed locations (indoor or outdoor with protection, as specified by the manufacturer) with
condensing humidity or with non-condensing humidity;
or, if specified by the manufacturer:
— open locations (outdoor without any covering) both with condensing humidity or with non-
condensing humidity;
and in locations with electromagnetic disturbances likely to be found in residential, commercial and light
industrial use.
For meters which indicate unconverted volume, reference can be made to Annex C.
Unless otherwise stated, all pressures given in this document are gauge pressures.
Requirements for electronic indexes, valves and additional requirements for batteries incorporated in
the meter and any other additional functionalities are given in EN 16314:2013.
Unless otherwise stated in a particular test, the tests are carried out on meters that include additional
functionality devices intended by the manufacturer.
Clauses 1 to 13 are for design and type testing only.
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 437:2018, Test gases — Test pressures — Appliance categories
EN 549:2019, Rubber materials for seals and diaphragms for gas appliances and gas equipment
EN 1092-1:2018, Flanges and their joints — Circular flanges for pipes, valves, fittings and accessories, PN
designated — Part 1: Steel flanges
EN 16314:2013, Gas meters — Additional functionalities
EN ISO 228-1:2003, Pipe threads where pressure-tight joints are not made on the threads — Part 1:
Dimensions, tolerances and designation (ISO 228-1:2000)
EN ISO 1518-1:2019, Paints and varnishes — Determination of scratch resistance — Part 1: Constant-
loading method (ISO 1518-1:2019)
EN ISO 2409:2020, Paints and varnishes — Cross-cut test (ISO 2409:2020)
EN ISO 2812-1:2017, Paints and varnishes — Determination of resistance to liquids — Part 1: Immersion
in liquids other than water (ISO 2812-1:2017)
EN ISO 4628-2:2016, Paints and varnishes — Evaluation of degradation of coatings — Designation of
quantity and size of defects, and of intensity of uniform changes in appearance — Part 2: Assessment of
degree of blistering (ISO 4628-2:2016)
EN ISO 4628-3:2016, Paints and varnishes — Evaluation of degradation of coatings — Designation of
quantity and size of defects, and of intensity of uniform changes in appearance — Part 3: Assessment of
degree of rusting (ISO 4628-3:2016)
EN ISO 4892-3:2016, Plastics — Methods of exposure to laboratory light sources — Part 3: Fluorescent UV
lamps (ISO 4892-3:2016)
EN ISO 6270-1:2018, Paints and varnishes — Determination of resistance to humidity — Part 1:
Condensation (single-sided exposure) (ISO 6270-1:2017)
EN ISO 6272-1:2011, Paints and varnishes — Rapid-deformation (impact resistance) tests — Part 1:
Falling-weight test, large-area indenter (ISO 6272-1:2011)
EN ISO 9227:2017, Corrosion tests in artificial atmospheres — Salt spray tests (ISO 9227:2017)
EN ISO/CIE 11664-4:2019, Colorimetry — Part 4: CIE 1976 L*a*b* colour space (ISO/CIE 11664-4:2019)
EN 50561-1:2013, Power line communication apparatus used in low-voltage installations — Radio
disturbance characteristics - Limits and methods of measurement — Part 1: Apparatus for in-home use
EN 55032:2015, Electromagnetic compatibility of multimedia equipment — Emission Requirements
EN IEC 60079-0:2018 , Explosive atmospheres — Part 0: Equipment — General requirements
(IEC 60079-0:2017)
EN 60079-10-1:2015, Explosive atmospheres — Part 10-1: Classification of areas — Explosive gas
atmospheres (IEC 60079-10-1:2015)
EN 60079-11:2012, Explosive atmospheres — Part 11: Equipment protection by intrinsic safety “i”
(IEC 60079-11:2011)
EN IEC 60079-15:2019, Explosive atmospheres — Part 15: Equipment protection by type of protection “n”
(IEC 60079-15:2017)
As impacted by EN IEC 60079-0:2018/AC:2020-02.
EN 60529:1991 , Degrees of protection provided by enclosures (IP Code) (IEC 60529:1989)
EN 60695-11-5:2017, Fire hazard testing — Part 11-5: Test flames — Needle-flame test method -
Apparatus, confirmatory test arrangement and guidance (IEC 60695-11-5:2016)
EN 60695-11-10:2013 , Fire hazard testing — Part 11-10: Test flames — 50 W horizontal and vertical
flame test methods (IEC 60695-11-10:2013)
EN 60730-1:2016 , Automatic electrical controls — Part 1: General requirements (IEC 60730-1:2013 ,
modified + COR1:2014)
EN 61000-4-2:2009, Electromagnetic compatibility (EMC) — Part 4-2: Testing and measurement
techniques — Electrostatic discharge immunity test (IEC 61000-4-2:2008)
EN 61000-4-3:20061 , Electromagnetic compatibility (EMC) — Part 4-3: Testing and measurement
techniques — Radiated, radio-frequency, electromagnetic field immunity test (IEC 61000-4-3:2006)
EN 61000-4-8:2010, Electromagnetic compatibility (EMC) — Part 4-8: Testing and measurement
techniques — Power frequency magnetic field immunity test (IEC 61000-4-8:2009)
EN 61000-6-1:2007, Electromagnetic compatibility (EMC) — Part 6-1: Generic standards — Immunity for
residential, commercial and light-industrial environments (IEC 61000-6-1:2005)
EN 61000-4-9:2016, Electromagnetic compatibility (EMC) — Part 4-9: Testing and measurement
techniques — Impulse magnetic field immunity test (IEC 61000-4-9:2016)
EN IEC 61000-6-2:2019, Electromagnetic compatibility (EMC) — Part 6-2: Generic standards — Immunity
standard for industrial environments
EN 62056-21:2002, Electricity metering — Data exchange for meter reading, tariff and load control — Part
21: Direct local data exchange (IEC 62056-21:2002)
ISO 834-1:1999, Fire resistance tests — Elements of building construction — Part 1: General requirements
ISO 12213-2:2006, Natural gas — Calculation of compression factor — Part 2: Calculation using molar-
composition analysis
ASTM D 1003-13, Standard Test Method for Haze and Luminous Transmittance of transparent plastics

As impacted by EN 60529:1991/AC:2006-12, EN 60529:1991/A1:2000, EN 60529:1991/A2:2013 and
EN 60529:1991/A2:2013/AC:2019-02.
As impacted by EN 60695-11-10:2013/AC:2014.
As impacted by EN 60730-1:2016/A1:2019.
As impacted by EN 61000-4-3:2006/A1:2008, EN 61000-4-3:2006/A2:2010 and EN 61000-4-3:2006/IS1:2009.
3 Terms, definitions and symbols
For the purposes of this document, the following terms, definitions and symbols apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— IEC Electropedia: available at https://www.electropedia.org/
— ISO Online browsing platform: available at https://www.iso.org/obp
3.1 Terms and definitions
3.1.1
actual flow rate
flow rate at the gas pressure and gas temperature conditions prevailing in the gas distribution line in
which the meter is fitted, at the meter inlet
3.1.2
additional functionality
functions over and above that within the meter, which can be integral to the meter, or included within a
connected device
3.1.3
additional functionality device
device that carries out additional functionalities
3.1.4
base conditions
fixed conditions to which a volume of gas is converted (e.g.  base  gas temperature 273,15 K plus 15 K
at base gas pressure of 1 013,25 mbar)
3.1.5
class 1,5 meter
accuracy achieved by a meter, which has an error of indication between −3 % and +3 % for flow rates Q,
where Q ≤ Q < Q , and an error of indication between −1,5 % and +1,5 % for flow rates Q, where
min t
Q ≤ Q ≤ Q , where Q to Q > 150 and Q to Q ≥ 10 and Q to Q is 1,2
t max max min max t r max
3.1.6
contaminants
gas borne dust, vapour and other substances that could affect the operation of the meter
3.1.7
display
device which shows information from the meter (e.g. liquid crystal that displays registers, volume or
flags)
3.1.8
distributed gas
locally available gas
3.1.9
disturbance
influence quantity having a value within the limits specified but outside the specified rated operating
conditions of the measuring instrument
Note 1 to entry: An influence quantity is a disturbance if the rated operating conditions for that influence quantity
are not specified.
3.1.10
durability
ability of an instrument to maintain its performance characteristics over a specified period of use
3.1.11
error of indication
value which shows the relationship in percentage terms of the difference between the volume indicated
by the meter and the volume which has actually flowed through the meter, to the latter value:
Note 1 to entry:
VV−
ic
ε= 100
V
c
where
V is the indicated volume;
i
V is the volume which has actually flowed through the meter.
c
3.1.12
event
condition requiring action or to log an action
3.1.13
external leak tightness
leak tightness of the gas carrying components of the gas meter with respect to the atmosphere
3.1.14
galvanic connection/interface
hard wired serial connection or pulse output from the meter
3.1.15
gas meter
instrument designed to measure, memorize and display the volume of fuel gas that has passed through it
3.1.16
gauge pressure
absolute pressure minus atmospheric pressure
3.1.17
index
current reading of the total volume passed through the meter
3.1.18
maximum operating pressure
maximum pressure at which a system can be operated continuously under normal conditions
Note 1 to entry: Normal conditions are no fault in any device or stream.
3.1.19
maximum error shift
maximum mean error shift at any of the tested flow rates
3.1.20
maximum flow rate
highest flow rate at which the gas meter provides indications that satisfy the requirements regarding
maximum permissible error (MPE)
3.1.21
maximum permissible error
extreme value of measurement error, with respect to a known reference quantity value, permitted by
specifications for a given measurement, measuring instrument, or measuring system
3.1.22
maximum working pressure
upper limit of the working pressure for which the meter has been designed, as declared by the
manufacturer and marked on the index or the data plate
3.1.23
mean error
arithmetic mean of consecutive errors of indication at a flow rate
3.1.24
memory
element which stores digital information
3.1.25
meter case
pressure containing structure of the meter
3.1.26
meter class
class to which a meter belongs, according to the metrological requirements of this document, i.e. class 1,5
3.1.27
meter error curve
plot of average error of indication against actual flow rate
3.1.28
minimum flow rate
lowest flowrate at which the gas meter provides indications that satisfy the requirements regarding MPE
3.1.29
normal conditions of use
conditions referring to the meter operating:
— at a pressure up to the maximum working pressure (with or without a flow of gas);
— within the range of flow rates;
— within the ambient and gas temperature range;
— with the distributed gas
3.1.30
pressure absorption
difference between the pressure measured at the inlet and outlet connections of the meter whilst the
meter is operating
3.1.31
pressure measuring point
permanent fitting on the meter outlet enabling a direct measurement of the outlet pressure to be obtained
3.1.32
operating mode
method (sample frequency and timing) of obtaining volume flow measurements
3.1.33
optical port
serial data port using an infra-red transmitter and receiver
3.1.34
overload flow rate
highest flow rate at which the meter operates for a short period of time without deteriorating
3.1.35
reference conditions
condition of use prescribed for testing the performance of a measuring instrument or for inter-
comparison of results of measurements
3.1.36
register
electronic device comprising both memory and display, which stores and displays information
3.1.37
sensor
element of a measuring instrument or measuring chain that is directly affected by the measurand
3.1.38
software identifier
sequence of characters, that identifies the software; the identifier is logically considered a part of the
software
3.1.39
starting flow rate
lowest flow rate at which the meter is able to indicate a volume of gas passed
3.1.40
storage temperature range
range of temperatures at which the meter can be stored without being adversely affected
3.1.41
thermal mass flow-meter
TMF meter
flow-measuring device which uses heat transfer to measure and indicate mass flowrate
Note 1 to entry: The term thermal mass flowmeter also applies to the measuring portion of a thermal mass flow
controller and not the control function.
[SOURCE: ISO 14511:2019, 3.2.3)
3.1.42
transitional flow rate
flow rate occurring between the maximum and minimum flow rates at which the flow rate range is
divided into two zones, the upper zone and the lower zone, each zone having a characteristic MPE
3.1.43
volume
volume without specifying whether it is a corrected volume at measurement conditions or an
uncorrected volume at measurement conditions
3.1.44
working pressure
difference between the pressure of the gas at the inlet of the meter and the atmospheric pressure
3.2 Symbols
outside diameter of the pipe in millimetres (mm)
D
−2
g acceleration due to gravity, in metres per square second (m · s )
H lower calorific value
i
H upper calorific value
s
MPE maximum permissible error, in percent (%)
p base pressure to which the indicated volume is referred
b
p maximum operating pressure
max
Q maximum flow rate
max
Q minimum flow rate
min
Q overload flow rate
r
Q starting flow rate
start
Q transitional flow rate
t
Q distributed air or gas flow, referred to the base conditions of the meter, with x = min, max, t, r;
x
as described below
t base reference temperature to which the indicated volume is referred
b
t gas temperature
g
t ambient temperature
m
t maximum operating temperature
max
t minimum operating temperature
min
t specified centre temperature for a temperature converted meter
sp
V volume read by the meter, at base conditions
b
W lower Wobbe index
i
W upper Wobbe index
s
ε error of indication
4 Working conditions
4.1 General
If no specific requirements are given, the test equipment shall be traceable to a national or international
reference standard error of and the uncertainty shall be equal or better than:
a) for type evaluation: 1/5 of the maximum permissible error (MPE);
b) for verifications: 1/3 of the maximum permissible error (MPE).
4.2 Base conditions
Base conditions of temperature (t ) and pressure (p ) shall be specified by the manufacturer and marked
b b
on the data plate of the meter.
In particular, the following formula applies for the conversion of test volumes to the base conditions of
the meter under test:
tC°+ 273,15
( ) p ()bar
b
a
V =V⋅⋅  where pp=+ p  (1)
t ,p a a amb gauge
bb
tC°+ 273,15 p ()bar
( )
a b
where
p is the absolute inlet pressure of the meter under test, i.e. the sum of two pressure
a
contributes defined as follows:
p : barometric pressure during test;
amb
p : inlet gauge pressure of meter under test;
gauge
t is the steady temperature of the test volume;
a
V is the volume at actual condition.
a
4.3 Flow range
The flow rate range shall be one of those given in Table 1.
Table 1 — Flow rate range
Q Upper limits of Q Upper limit of Q Q
max min t r
3 3 3 3
(m /h) (m /h) (m /h) (m /h)
2,5 0,016 0,25 3,0
4 0,025 0,4 4,8
6 0,040 0,6 7,2
10 0,060 1,0 12,0
16 0,10 1,6 19,2
25 0,16 2,5 30,0
40 0,25 4,0 48,0
65 0,40 6,5 78,0
100 0,65 10,0 120,0
160 1,00 16,0 192,0
A gas meter may have a lower value for the minimum flow rate, Q , than that shown in Table 1, but this
min
lower value shall be equal to one of the values shown in the table or to a decimal submultiple of these
values.
The values given in Table 1 ensure the minimum turndown ratio given in Table 2.
Table 2 — Turndown ratio
Q / Q Q / Q Q / Q
max min max t r max
≥ 150 ≥ 10 ≥ 1,2
4.4 Maximum working pressure
The manufacturer shall declare the maximum working pressure of the meter which shall not exceed
0,5 bar.
4.5 Temperature range
4.5.1 General
Unless otherwise stated, all temperatures given in this document shall be measured to within ± 1 °C.
4.5.2 Ambient temperature range
All meters shall be designed for a minimum ambient temperature range of
−10 °C to + 40 °C. This shall be verified by conforming with the requirements given in Clause 5 and
Clause 6.
The manufacturer can declare a wider design temperature range but shall use the minimum and
maximum temperature limits as specified in Table 3 and Table 4.
Table 3 — Upper temperature limit
Upper temperature limit of t
max
30 °C 40 °C 55 °C 70 °C
Table 4 — Lower temperature limit
Lower temperature limit of t
min
5 °C − 10 °C − 25 °C − 40 °C
4.5.3 Gas temperature range
All meters shall be designed for a gas temperature range equal to, or within, the ambient temperature
range, with a minimum span of 40 °C. Upper and lower limit of gas temperature shall be chosen in
accordance with Table 3 and Table 4. This shall be verified by conforming with the requirements of 5.3.1
and 5.9.
4.5.4 Storage temperature range
All meters shall be designed for a storage temperature range of −20 ° to 60 °C, and in any case shall have
a range equal to or wider than the declared ambient temperature range. This shall be verified by
conforming with the requirement of 6.9.
4.6 Range of gases
The manufacturer shall specify the range of gases for which the meter has been designed, in terms of gas
families, for at least one group in accordance with EN 437:2018.
Additionally, the meter shall also be designed for working on air; therefore fulfilling air-gas relationship
requirements specified in 5.4.
Conformity to gas families, or pertaining groups, for which the meters have been designed, shall be
included in the technical design file of the instrument.
Therefore, the meter shall be tested with:
a) air;
b) test gases representing the variability of distributed gases within the respective groups (see
Annex B).
4.7 Installation orientation
Where more than one installation orientation is specified in the manufacturer’s instruction manual,
meters shall be tested in all these orientations.
5 Metrological performance
5.1 General
Where the manufacturer declares that the meter can be used in two directions (forward and reverse flow)
then all tests shall be performed in both directions.
The flow rate shall be determined using sampling times that are not readily predictable within discrete
time intervals.
These time intervals (T) shall not exceed 2 s, unless the manufacturer can demonstrate that a proposed
longer time interval will not cause the metrological characteristics of the meter to be affected by unsteady
flow conditions.
Irrespective of whether the discrete time intervals are longer than 2 s, the requirements specified in
5.13.2 shall still be applied.
Provision shall be made for synchronizing the start and finish of test periods (with test equipment),
according to manufacturer specification, e.g. via a galvanic connection or optical port.
Any failure in synchronizing test equipment with the meter under test may introduce an error
contribution, calculated as follows:
τ
MAX
ε τ ,t=2⋅⋅100 (2)
( )
%
t
where
τ is the maximum sampling time of the meter under test, in seconds;
t is the test time, in seconds.
Where τ is not specified by manufacturer, τ = 2 s shall be used in the calculation.
The meter shall have a mode, providing volume resolution of at least 0,1 dm .
The meter shall have a fast sampling mode with sampling time not exceeding 0,5 s.
NOTE This mode can be accessible via the display even without any external tools, e.g. by means of a dedicated
display menu. In operative conditions, the meter can be protected by password and not accessible to final user.
All modes other than the normal mode shall only be active for a maximum time of 24 h before reverting
to normal operating mode.
5.2 Test mode comparison
5.2.1 General
When the meter has one or more fast sampling modes in addition to the normal operating mode, then
provided the requirements in 5.2.2 are met, all subsequent tests requiring steady flow profiles in this
document shall be carried out using the same test mode. If the requirements in 5.2.2 are not satisfied,
then all subsequent tests shall be performed in normal operating mode.
Where specific modes of measurement for managing flow outside the controlled range are present in the
normal operating mode, these can be disabled in test mode, unless otherwise specified in this document.
Provision shall be made to ensure that any test gas is properly detected by the meter under test. In
particular, where the meter has a gas detection system that occurs at a fixed time interval, the gas
detection procedure shall also be performed whenever the test mode is activated.
5.2.2 Requirements
The accuracy of the measurements shall not be influenced by different sampling modes.
The difference of the mean errors of the normal operating mode and the test mode shall not exceed the
following limits:
— 0,6 % for any flow rate Q ≤ Q < Q ;
min t
— 0,3 % for any flow rate between Q ≤ Q ≤ Q .
t max
In both modes, the mean error shall be within the maximum permissible errors as specified in Table 5.
5.2.3 Test
Test the meter in the normal operating mode and in the test mode in accordance with 5.3.2, Table 6, Test
a). Calculate the difference in mean error at each flow rate, and ensure that requirements in 5.2.2 are met.
5.2.4 Test mode in flow (optional)
5.2.4.1 General
Where the meter provides instantaneous flow rate readings, these can be used as an alternative to volume
for calculating the error of measurement at steady flow profiles, unless otherwise specified in this
document.
5.2.4.2 Requirements
Select the test mode, and carry out the test in accordance with 5.2.4.3 at a given steady test flow rate. The
difference of the mean errors of the normal operating mode and the test mode shall not exceed the limits
given in 5.2.2, as detailed below:
— 0,6 % for any flow rate Q ≤ Q < Q ;
min t
— 0,3 % for any flow rate between Q ≤ Q ≤ Q .
t max
5.2.4.3 Test
Test the meter in the normal operating mode and in the test mode in flow in accordance with 5.3.2,
Table 6, Test a).
Calculate the difference in mean error at each flow rate, using the following equations, and ensure that
error is within the limits specified in 5.2.4.2.
V − V Q − Q
bc bc
E ⋅ 100 ε ⋅ 100
; (3)
x x
V Q
c c
where
E is the mean error in volume, expressed as a percentage;
x
ε is the mean error in flow, expressed as a percentage;
x
V is the volume read by the meter, at base conditions;
b
V is the volume read by the reference instrument, converted to meter under test base
c
conditions;
Q is the flow rate read by the meter, at base conditions;
b
Qc is the flow rate read by the reference instrument, converted to meter under test base
conditions. Q can be either measured directly or inferred by ratio Q = V / t where t is the
c c c x x
test duration at any given steady test flowrate.

5.3 Permissible errors
5.3.1 Requirements
The meter shall be adjusted as given in Method a) and b).
The manufacturer shall declare which of the following two methods has been adopted:
= =
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