Czech Metrology Institute  
Okružní 31, 638 00  Brno  
 
 
1. ------IND- 2018 0593 CZ - EN- ------ 20181217 --- --- PROJET 
Executive summary for the EC (not part of this legislation)  
'Rotary -piston and velocity gas flow meters ' may be placed on the market and put into use in the Czech 
Republic pursuant to Directive  2014/32/EU (MID) or for non -MID areas pursuant to Act  No 505/1990 
on metrology, as amended.Pursuant to this act, the specified measuring instruments are measuring 
instruments in the List of Specified Measuring Device Types (Decree  No 345/2002) and specifi ed (by 
the manufacturer/importer) for measurement with relevance in the protection of public interests in the 
following areas: consumer protection; contractual relations; stipulation of sanctions, fees, tariffs and 
duties; health protection; environmental protection; occupational safety or protection of other public 
interests protected by special legislation .This therefore refers to a purpose similar to that used to 
identify stipulated products — non-automatic measuring and weighing instruments pursuant to 
Directives  2014/31/EU and 2014/32/EU.The requirements of this legislation do not apply to 
measuring instruments not placed on the market in the Czech Republic for the above purposes, 
identified by Act  No 505/1990 on metrology.  
The purpose of this notified regulation is to stipulate:  
1) metrological and technical requirements for specified measuring instruments and tests for 
purposes of type approval, if these measuring instruments are not being placed on the market 
with conformity assessment pursuant to MID; a nd 
2) tests for purposes of verification of specified measuring instruments (once they have been 
placed on the market), regardless of whether they are being placed on the market pursuant to 
Act No 505/1990 on metrology, or pursuant to MID with conformity asse ssment.  
(End of executive summary)  
 
Author:Mgr.Tomáš Hendrych  
Telephone:+420 545 555 414  
 
 
As the authority with substantive and territorial jurisdiction in the matter of laying down metrological 
and technical requirements for legally controlled measuring instruments and stipulating the testing 
methods for type approval and verification of legally controlled measuring instruments pursuant to 
§ 14(1) of Act  No 505/1990, on metrology, as amended (hereinafter the ‘Metrology Act ’), and in 
accordance with the pr ovisions of §  172 et seq. of Act  No 500/2004, the Code of Administrative 
Procedure (hereinafter the ‘CAP ’), the Czech Metrology Institute (hereinafter the ‘CMI ’) commenced 
ex officio proceedings on 12  March  2017 pursuant to §  46 of the CAP, and, based on s upporting 
documents, issues the following:  
 
I. 
DRAFT MEASURE OF A G ENERAL NATURE  
number:0111 -OOP -C031 -18 
laying down metrological and technical requirements for legally controlled measuring 
instruments, including the testing methods for the type approval a nd verification of legally 
controlled measuring instruments:  General Measure No 0111 -OOP -C031 -18 
 
2/10 'rotary -piston and velocity gas flow meters'  
 
This legislation stipulates metrological and technical requirements for type approval and initial 
verification of rotary -piston and velocity gas flow  meters used expressly in areas of use other than 
those defined by Government Regulation  No 120/2016, on assessment of conformity of measuring 
instruments when they are placed on the market, as amended (hereinafter 'Government 
Regulation  No 120/2016').  
This legislation also stipulates metrological and technical requirements for subsequent verification of 
rotary -piston and velocity gas flow meters.  
1   Basic definitions  
For the purposes of this general measure, terms and definitions pursuant to VIM and VIML1) and the 
following apply:  
1.1 
gas meter with rotary pistons (hereinafter a 'rotary gas meter')  
a volumetric gas meter in which a fixed measuring chamber is formed between the walls of a 
stationary chamber and a rotary element; each rotation cycle of the e lement(s) moves a defined volume 
of gas, which is comprehensively recorded and indicated on a display device.  
1.2 
turbine gas meter  
a velocity gas flow meter in which the dynamic forces of the flowing gas cause the turbine wheel to 
rotate at a velocity whi ch is the function of the volumetric flow; the number of rotations of the turbine 
wheel form the basis for indicating the volume which flowed through the turbine gas meter  
1.3 
ultrasonic gas meter  
a velocity gas flow meter in which the measurement principl e is to measure the velocity of the gas 
flowing in a pipe. This measurement principle is based on determining the time it takes for ultrasonic 
signals to pass through the flowing gas between the units for transmitting and receiving the ultrasonic 
signals.u ltrasonic gas meters can be classified as classical multi -path meters, which contain several 
ultrasonic measurement paths (usually three or more), and are manufactured with nominal dimensions 
from DN80 and higher, and belong to an accuracy class  1.0.ultras onic gas meters for the home 
(hereinafter 'household ultrasonic gas meters') have a maximum flow rate of 10  m3/h, usually contain 
one measurement path, are shaped like a household membrane gas meter, are used at pressures up to 
0.5 bar, are battery -powered , and belong to accuracy class  1.5. 
1.4 
vortex gas flow meter  
A velocity gas flow meter which is based on an effect in which vortices are alternately separated on 
both sides of a non -aerodynamically shaped obstacle around which gas flows on both sides. The  
vortices are generated at a frequency which is proportionate to the velocity of the gas flow, and thus 
the size of the flow as well. A suitable sensor picks up the frequency of the vortices which are 
generated this way and converts them into the value of the volumetric flow in the required 
measurement units.  
                                                      
1) International Vocabulary of Metrology – Basic and General Concepts and Associated Terms (VIM) and 
International Vocabulary of Terms in Legal Metrology (VIML) are part of the technical h armonisation 
compendium 'Terminology in the Area of Metrology', which is publicly accessible at www.unmz.cz.  General Measure No 0111 -OOP -C031 -18 
 
3/10 1.5 
pressure drop  
the difference between the pressure recorded at the intake and outlet of the gas meter if it is in 
operation  
1.6 
error  
a percentage value that expresses the ratio of the difference be tween the volume indicated by the gas 
meter and the volume that actually flowed through the gas meter, to the actual flow volume.  
1.7 
maximum flow Q max 
the maximum flow for which the gas meter provides readings that comply with requirements for 
maximum per missible error (MPE).  
1.8 
minimum flow Q min 
the minimum flow for which the gas meter provides readings that comply with requirements for 
maximum permissible error (MPE).  
1.9 
transitional flow Q t 
a value between the maximum and minimum flow that splits the flow range into two bands: the 'upper 
band' and the 'lower band'.A specific maximum permissible error (MPE) applies to each band.  
2   Metrological requirements  
Metrological requirements are based on the requirements of relevant harmonised European standard s 
and norms. Gas  meters must have the required metrological characteristics over the entire range of 
conditions for which they have been approved and the required repeatability and reproducibility.  
Measuring instruments that are type approved pursuant to t he Metrology Act or pursuant to European 
directives2) are subject to the metrological requirements applicable at the time they were put into 
circulation.  
2.1   Stipulated operating conditions  
2.1.1    Flow range  
The gas flow range must meet requirements for  relative proportions of maximum flow  Qmax, minimum 
flow Qmin, transitional flow Qt and overload flow  Qr: 
a) Qmax/Qmin  20 
b) Qmax/Qt   5 
c) Qr/Qmax  = 1.2  
The following relative proportions of maximum flow  Qmax, minimum flow  Qmin, transitional flow Qt 
and overlo ad flow  Qr apply only to household ultrasonic gas meters:  
a) Qmax/Qmin  150 
                                                      
2) Directive  2004/22/EC of the European Parliament and of the Council of 31  March  2004 on measuring 
instruments and Directive  2014/32/EU of the Eur opean Parliament and of the Council of 26  February  2014 on 
the harmonisation of the laws of the Member States relating to the making available on the market of measuring 
instruments.  General Measure No 0111 -OOP -C031 -18 
 
4/10 b) Qmax/Qt   10 
c) Qr/Qmax  = 1.2  
2.1.2    Maximum load  
After being subjected for one hour to an overload flow of Qr, the gas meter must be within the limits of 
maximum permissible error w ithin its measurement range.  
2.1.3    Maximum operating pressure  
The gas meter's maximum operating pressure must be marked on its label.  
2.1.4    Temperature range  
All gas meters must be capable of meeting the requirements for the minimum ambient temperature  
range –10 °C to +40  °C. 
The minimum gas temperature range is 40  °C. 
2.1.5 Stability  
Gas meters must meet metrological requirements for their stipulated period of use, which is 
demonstrated through a long -term stability test.  
2.2   Maximum permissible erro r 
2.2.1    Maximum permissible error during verification  
The maximum permissible errors for rotary and velocity gas meters are generally specified in Table  1. 
Table  1 – Maximum permissible errors  
Flow  
(m3/h) Maximum permissible errors  
During verification  During use  
QminQQt ± 2.0 % ± 4 % 
QtQQmax ± 1.0 % ± 2 % 
 
Rotary and velocity gas meters are in accuracy class  1.0. 
Maximum permissible errors for household ultrasonic gas meters are specified in Table  2. 
Table  2 – Maximum permissible errors for house hold ultrasonic gas meters  
Flow  
(m3/h) Maximum permissible errors  
During verification  During use  
QminQQt ± 3.0 % ± 6 % 
QtQQmax ± 1.5 % ± 3 % 
 
Household ultrasonic gas meters have an accuracy class of 1.5.  
With certain types of gas meters to which the national technical standards were applied during 
approval, the maximum permissible error valid at the time of approval may differ from the maximum 
permissible error specified above; in such case, the maximum permissible error specified in the type -
approval certificate will take precedence.  General Measure No 0111 -OOP -C031 -18 
 
5/10 2.3   Pressure drop  
The manufacturer must declare the maximum pressure drop at Qmax. 
The mean pressure drop for a gas meter at maximum flow Qmax with an air density of 1.2  kg/m3 must 
not exceed the manufacturer ’s spec ified values or the values in the type -approval certificate, if 
specified.  
3   Technical requirements  
Technical requirements are based on requirements of relevant harmonised European standards or 
OIML standardisation documents.  
3.1   Construction of the me asuring instrument  
Rotary and velocity gas flow meters have two connection points for flanged or threaded measuring 
instrument connections, or one coaxial connection.  
3.2   Counter  
The gas meter must be equipped with a metrologically inspected counter (dis play).  
The counter must function properly under normal conditions of use throughout the typical service life 
of the gas meter being tested.  
The counter can be a mechanical device comprising cylinders that cannot be zeroed, minimally for a 
volume correspond ing to the volume recorded after 8  000 h at flow Qmax.The counter's cylinders past 
the decimal point must be framed or have a different colour than the cylinders before the decimal 
point.  
The counter's digits must indicate cubic metres or decimal multiples  or fractions of a cubic metre.The 
mark m3 must be situated on the counter's label near the digit cylinders or on the counter's display.  
For a mechanical counter, the rotation of the cylinder during the final tenth of its course, i.e. from 9 to 
0, must cau se the cylinder of the next higher digit to move by one unit.  
For electronic counters, the number of the next higher digit level must increase by one when any digit 
changes from 9 to 0.  
It must be possible to read the counter clearly and correctly at an an gle of 15° from the perpendicular 
to the window over a temperature range of –10 °C to 40  °C or greater if specified by the manufacturer.  
3.3   Materials  
The components of the gas meter in the gas flow must be resistant to the effects of the constituents of  
the gas medium in which they operate, and they must be resistant to ageing and corrosion over the 
standard life of the gas meter.The housing and all other parts of the gas meter must be made of 
materials or surfaces capable of withstanding pressure and th e environment for which they are 
intended.  
3.4   Resistance to improper handling  
The gas meter must be designed so that any kind of mechanical action that is capable of affecting 
measurement accuracy will visibly and permanently damage the meter or the off icial or security 
marks.  
3.5   Storage and transport  
Wherever possible, the connections of the gas meter must be equipped with suitable unsealed caps or 
covers which prevent foreign matter from getting into the meter during transport and storage.  General Measure No 0111 -OOP -C031 -18 
 
6/10 3.6   Gas meter operating position  
The operating position in which the gas meter is to be used must be indicated on the label of the gas 
meter, or it must be specified on the type -approval certificate.  
3.7   Rectifier tubes  
A gas meter with which the metrological p roperties depend on the length of the rectifier tube 
connected to the gas meter must be validated and used with the rectifier tube specified by the 
manufacturer or on the type -approval certificate.  
3.8   Software  
If the evaluation or indication unit contai ns software which is essential to the metrological properties, 
it must be identified and secured.The gas meter must enable the software to be identified by simple 
means.  
3.9   Electronics  
If the gas meter contains electronic components, they must comply wi th relevant EMC requirements.  
4   Measuring instrument markings  
Requirements for marking measuring instruments pursuant to this chapter concern measuring 
instruments that are approved pursuant to the Metrology Act.They do not apply to measuring 
instruments  placed on the market with type approval pursuant to Government Regulation  120/2016.  
4.1   Every gas meter must be marked with at least the following information on the counter or on a 
separate label:  
a) the identification mark or name of the manufacturer;  
b) the serial number and year of production;  
c) maximum flow Qmax (m3/h); 
d) minimum flow Qmin (m3/h); 
e) maximum operating pressure pmax; 
f) for rotary gas meters, the rated cyclic volume value V (dm3); 
g) the impulse number value, which corresponds to the specified recorded  flow volume at the 
place where the impulse transmitter is to be used;  
h) transitional flow Qt, only for gas meters approved pursuant to this legislation;  
i) a type -approval mark.  
Connectors for sampling pressure and temperature from the gas meter must be proper ly marked with 
the appropriate labels.  
The markings must be at a clearly visible location and must be permanent under normal conditions of 
gas meter use.  
With certain gas meters whose type was approved in accordance with the national technical standards, 
the requirement for the measuring instrument ’s markings which were valid at the time the measuring 
instrument received its type approval may differ from the above -mentioned official requirement. In 
such case, the requirements specified on the type -approval certificate will be decisive.  General Measure No 0111 -OOP -C031 -18 
 
7/10 4.2   Gas meter with two connectors  
Gas meters with two connectors must have the gas flow direction clearly and permanently marked by 
an arrow between these two connection points.  
5   Type approval of measuring instruments  
Type approval of measuring instruments that are not covered by Government Regulation  No 120/2016 
and are subject to type approval pursuant to the Metrology Act, as amended, are subject to 
requirements that are identical to those of Government Regulation  No 120/2016.  
6   Initial verification  
Initial verification applies to measuring instruments that at the given time have a valid type -approval 
certificate.A procedure identical to that used for subsequent verification referred to in Chapter  7 is 
applied in the i nitial verification.  
7   Subsequent verification  
7.1   General  
The following tests are performed during initial verification of a gas meter:  
a) a visual inspection;  
b) accuracy test;  
c) a pressure loss test, but only in cases where this is specified on the type -approval certificate.  
7.2   Visual inspection  
The visual inspection checks whether the gas meter submitted for verification is in conformity with the 
approved type or with the measuring instrument design for which conformity was declared during 
placement on t he market, and special attention must be paid in checking that markings are correct 
pursuant to Article  4.1 or the relevant certificate.  
The durability and legibility of the markings is also checked.  
Gas meters that have been mechanically damaged and those  that do not conform with the approved 
type or measuring instrument design for which conformity was declared during placement on the 
market will not be tested further.  
7.3   Functional tests  
Compliance with relevant metrological and technical requirements pursuant to Chapters  2, 3 and 4 is 
monitored over the course of functional tests and evaluation thereof.  
7.3.1    Test equipment requirements  
Test equipment must be equipped with reference standards that are suitable for testing the relevant gas 
meters and have up -to-date metrological traceability.  
Pressure gauges, thermometers and reference calibrating devices for volume flow must have up -to-
date metrological traceability and must state the uncertainty of calibration.  
The total extended uncertainty when tes ting and determining the error of the gas meter must be at least 
three times less than the value of the maximum permissible error specified for the measuring 
instrument undergoing testing at the given flow.  General Measure No 0111 -OOP -C031 -18 
 
8/10 7.3.2    Accuracy test  
Prior to the accuracy test it is necessary to ensure that the gas meter has been tempered sufficiently, 
perform a leak test on the gas meter's connection to the test station, and operate the gas meter for a 
sufficient amount of time at approximately 0.6Q max.If the gas meter is not b eing tested at a high -
pressure test lab, the tests must take place at ambient temperature (18 – 25 °C) and at relative humidity 
less than or equal to 80  %. 
Gas meters are preferentially tested at the flows specified in the Table  3 below.  
Table  3 — Test flo ws for verification of gas meters  
Gas meter measurement range Qmax:Qmin Test flows  
20:1 Qmax; 0.7Qmax; 0.4Qmax; 0.25 Qmax; 0.1Qmax; 0.05 Qmax 
Over 20:1 up to 30:1  Qmax; 0.7Qmax; 0,4Qmax; 0.25 Qmax; 0.1Qmax; 0.05 Qmax; Qmin 
Over 30:1 up to 50:1 and higher  Qmax; 0.7Qmax; 0.4Qmax; 0.25 Qmax; 0.15 Qmax; 0.05 Qmax; Qmin 
 
Household ultrasonic gas meters are tested with the following flows: Qmax; 0.2Qmax; Qmin. 
Measuring instruments to which the requirements of national technical standards were applied during 
their a pproval are tested at the flow rates specified in the type -approval certificate.Tests are always 
performed from the highest flow to the lowest.  
In the case of velocity gas meters that will be used at the installation location under static pressure 
greater than 4  bar and if simultaneously the user intends to use gas meter error correction in a 
connected gas volume converter, it is necessary to perform verification using natural gas at static 
pressure corresponding to the gas pressure at the installation loca tion.In this case, after verification, the 
gas meter can be used over a pressure range of 0.5 Ptest to 2Ptest, where Ptest is the static gas pressure at 
which the given velocity gas meter was tested during verification.  
If the type -approval certificate for multi -path ultrasonic gas meters specifies that they must be verified 
under increased static pressure, then accuracy tests for verification of these gas meters must be 
performed using natural gas at a high -pressure test lab.In this case the gas mater can b e used following 
verification over a pressure range of 0.5 Ptest to 2Ptest, where Ptest is the static pressure of gas used to test 
the given multi -path gas meter during verification.  
The calculated indication error for individual test flow rates must meet t he requirements for the 
maximum permissible error during verification specified in Table  1 or 2 or in the type -approval 
certificate.  
If specified on type -approval certificates, it is necessary to meet gas meter installation requirements 
such as the length of the calming tube before and after the gas meter and the position of the gas meter 
(vertical, horizontal) during testing.  
During the accuracy test all apparatus in the gas meter capable of generating an electronic signal or 
pulses proportional to the amo unt of gas that has flowed through the meter are checked at least at flow 
Qmax. 
Vortex gas flow meters are tested using a different method pursuant to a special technical regulation.  
7.3.3    Loss of pressure test  
The loss of pressure test is conducted in c ases in which its value was specified by the manufacturer or 
is specified on the type -approval certificate.Gas meters are tested using air with a density of 1.2  kg/m3 
at a maximum flow of Qmax and the differential pressure is measured between the gas meter 's inlet and 
outlet.  General Measure No 0111 -OOP -C031 -18 
 
9/10 The mean pressure drop, calculated as the mean of the measured maximum and minimum differential 
pressure, may not exceed the maximum pressure drop specified by the manufacturer or on the type -
approval certificate.  
7.3.4    Official mark  placement  
Gas meters that have complied with verification requirements stipulated by this legislation and their 
type-approval certificate are sealed using official marks in places specified in the type -approval 
certificate.  
7.3.5    Other  
A type -approval c ertificate can stipulate other requirements that need to be fulfilled when verifying a 
gas meter.  
8   Measuring instrument examination by request of a concerned party  
Examination of a measuring instruments pursuant to §  11a of the Metrology Act at the requ est of a 
person who may be affected by incorrect measurement takes place pursuant to Chapter  7, except for 
the last sentence of Article  7.2.The test is always performed if it is technically possible.The 'maximum 
permissible errors during use' specified in Table  1 or Table  2, as applicable, will be used as maximum 
permissible errors.  
In the case of measuring instruments in use up to now to which requirements of national technical 
standards were applied during their approval, the maximum permissible error wil l be double the 
maximum permissible error specified in the type -approval certificate.  
9   Notified standards  
For the purposes of specifying the metrological and technical requirements for measuring instruments 
and specifying the testing methods for their t ype approval and verification arising from this general 
measure, the CMI will notify Czech technical standards, other technical standards or technical 
documents of international or foreign organisations, or other technical documents containing more 
detaile d technical requirements (hereinafter referred to as ‘notified standards ’).The CMI will publish a 
list of these notified standards attached to the relevant measures, together with the general measure, in 
a manner accessible to the public www.cmi.cz ). 
Compliance with notified standards or parts thereof is considered, to the extent and under the 
conditions laid down in the general measure, as compliance with those requirements laid down in this 
measure to which these standard s or parts thereof apply.  
Compliance with notified standards is one way of demonstrating compliance with the 
requirements.These requirements may also be met by using another technical solution guaranteeing an 
equivalent or higher level of protection of leg itimate interests.  
II. 
G R O U N D S 
Pursuant to §  14(1)(j) of the Metrology Act, the CMI has issued this Measure of a General Nature 
toward the implementation of §  6(2), §  9(1) and (9), and  § 11a(3) of the Metrology Act, laying down 
metrological and techn ical requirements for specified measuring instruments and tests for type 
approval and verification of specified measuring instruments — rotary -piston and velocity gas flow 
meters.  
Decree  No 345/2002 stipulating measuring instruments for mandatory verificat ion and measuring 
instruments subject to type approval, as amended, classifies this type of measuring instrument as a General Measure No 0111 -OOP -C031 -18 
 
10/10 measuring instrument subject to verification under item  1.3.10(b) in the Annex 'List of Specified 
Measuring Device Types'.  
This legislatio n (Measure of a General Nature) will be notified in accordance with 
Directive  (EU)  2015/1535 of the European Parliament and of the Council of 9  September  2015 laying 
down a procedure for the provision of information in the field of technical regulations an d of rules on 
Information Society services.  
III. 
I N S T R U C T I O N S 
In accordance with §  172(l) APC in conjunction with §  39(l) APC, the CMI has stipulated a time limit 
for comments of 30  days as of the date of posting the draft on the official notice  board. Comments  
submitted after this time limit will not be considered.  
The persons concerned are hereby invited to comment on this general draft measure. With  regard to 
the provisions of § 172(4) APC, comments are to be submitted in writing.  
Pursuant to the provisions of § 174(1) APC, in conjunction with the provisions of § 37(1) APC, it must 
be clearly stated who is submitting the comments, which general measure the comments concern, how 
the draft contradicts legislation or how the general measure is ina ccurate. The comments must also 
contain the signature of the person making the comments.  
The supporting documents for this draft general measure may be consulted at the Czech Metrology 
Institute, Legal Metrology Department, Okružní 31, 638 00 Brno, after m aking arrangements by 
telephone.  
This draft general measure shall be posted for 15  days.  
 
 
 
 
RNDr.Pavel Klenovský  
Director -General  
Person responsible for accuracy:  Mgr.  Tomáš Hendrych  
Posted on:  
Signature of the authorised person confirming posting:  
 
Removed on:  
Signature of the authorised person confirming removal: