C z e c h  M e t r o l o g y  I n s t i t u t e  
Okružní 31, 638 00  
Brno  
 
1. ------IND- 2014 0021 CZ - EN- ------ 20140128 --- --- PROJET 
Executive summary for the E uropean Commission  (not part of this legislation)  
Placement  on the market and the making operational  of gas-volume conversion devices intended for 
use in residential,  commercial and light -industrial environments  in the Czech Republic  is governed by 
Directive 2004/22/EC (MID). Once the se have been made operational , they become subject to 
national metrological regulation – verification (at specifi c intervals). The legisl ation to which this 
notification relates  only applies to the verification of measuring instruments that have already been 
made operational . It does not concern their plac ement  on the market or making operational  (with the 
exception of cases referred to in Article 23 of the MID).  
The requirements incumbent  upon measuring instruments in use are fully compatible with the MID 
and originate in  EN 12405 -1, the harmonised standard concerning the MID.  
Some of the parameters specified in this document are properties  of measuring instruments in new 
condition and are only noted here as the preservation of these properties during use is only subject to 
visual or other inspection within the scope of verification.  
(End of executive summary.)  
 
 
 
 
 
 
 
As the authority with substantive and territorial jurisdiction in the matter of laying down the 
metrological and technical requirements for specified measuring instruments and laying down the 
testing methods for type approval and verification of specified measuring instruments  under §  14(1) of 
Act No 505/1990  on metrology, as amended (hereinafter referred to as the “Metrology Act”), and in 
accordance with the provisions of §  172 et seq. of Act No 500/2004 , the Administrative Procedure 
Code (hereinafter referred to as the “APC ”), the Czech Metrology Institute (hereinafter referred to as 
the “CMI”) commenced ex officio proceedings on 4 September 2013 under § 46 of the APC and, 
based on the supporting documents, issues the following:  
 
 
I. 
G E N E R A L   M E A S U R E  
number: 011 1-OOP -C032 -13 
ref. no. 0313/005/13/Pos.,  
 
laying down metrological and technical requirements for specified measuring 
instruments, including the testing methods for verification of the following specified 
instruments:  General Measure  No. 0111 -OOP -C032-13 
2 “gas-volume conversion devices intende d for use in residential, commercial and light -
industrial environments”  
 
This general measure  lays down the metrological and technical requirements for gas -volume 
conversion devices intended for use in residential, commercial and light -industrial environme nts to be 
applied after they have been placed on the market or made operational during verification . The 
requirements under this general measure  conform to  the requirements under Government Order No 
464/2005  laying down the technical requirements for meas uring instruments, as amended (hereinafter 
referred to as the “Government Order on Measuring Instruments”)1, and apply the relevant 
requirements under the harmonised standards.  
The verification of gas -volume conversion devices type approved under the Metro logy Act effective 
until 30 October 2006, i.e. prior to the transposition of Directive 2004/22/EC of the European 
Parliament and of the Council, as amended, into Czech law, shall be subject to metrological 
requirements applicable at the time the latter  were published . 
Only three types of conversion are treated in this regulation:  
 conversion as a function of temperature only (T conversion);  
 conversion as a function of pressure and temperature , with a constant compression factor (PT 
conversion);  
 conversio n as a function of the pressure and  temperature , and taking into account the compression 
factor (PTZ conversion).  
1   Basic definitions   
For the purposes of this general measure , the terms and definitions according to VIM and VIML2 and 
the definitions below sh all apply:  
1.1 
gas-volume conversion device   
a device fitted to a gas meter that automatically converts the quantity measured by the gas meter at 
measurement conditions into a quantity at base conditions using as inputs the volume at measurement 
conditions  as measured by the gas meter and other parameters, such as gas temperature and gas 
pressure, or gas specifications  
NOTE  1 The conversion device may also compensate for the error curve of the gas meter.  
NOTE  2 The deviation from the ideal gas law may be compensated for by the compression factor.  
1.1.1  
compact gas -volume conversion device   
a conversion device with specific types of transducer for pressure and temperature or for temperature 
only that cannot be separated from the calculator unit  
1.1.2  
combin ed gas -volume conversion device   
a conversion device with external separate transducers for pressure and temperature or for temperature 
only and with a separate calculator unit  
                                                   
1)   This Government Order transposed Directive 2004/22/EC of the European Parliament and of the Council of 
31 March 2004 on measuring instruments, as amended, into Czech legislation.  
2)   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 harmonisation 
compendium “Terminology in the Area of Metrology”, which is publicly accessible at www.unmz.cz  General Measure No 0111 -OOP -C032 -13 
3 1.2 
specified field of measurement of the gas -volume conversion device   
a set o f values at measurement conditions for which the errors of the conversion device are within 
specified limits  
NOTE  1 A conversion device has a measurement range for every quantity that it processes, i.e. gas pressure 
and gas temperature.  
NOTE  2 The specifie d field of measurement applies to the characteristic quantities of the gas that are used to 
determine the conversion factor.  
1.3 
base conditions   
the specified conditions under  which the measured quantity of gas is converted  
1.4 
conversion factor C  
a fact or representing the relationship between volume at measurement conditions as indicated by the 
gas meter and volume at base conditions subsequently indicated by the gas -volume conversion device; 
the following relationship holds:  
 
zz
TT
pp
VVCb b
b mb
 (1) 
1.5 
conventional value of the conversion factor CCV  
a value of the conversion factor C representing the relationship between volume at measurement 
conditions as indicated by the gas meter and volume at base conditions, with values indicated by the 
measurem ent standards for temperature Te and pressure pe and compression factor values z and zb as 
calculated by the calculator unit; the following relationship holds:  
 
zz
TT
pp
VVCCVb
eb
be
mb
 (2) 
1.6 
simulated conversion factor Cs  
the conversion factor in a dynami c test simulating the unconverted volume Vm from the gas meter at 
measurement conditions; the following relationship holds for the conversion factor Cs indicated by the 
measuring instrument under test:  
 
1m 2m1b 2b
mb
V VV V
VVC
s (3) 
1.7 
compression factor z  
the ratio of the actual volume of any mass of gas at a specified pressure and specified temperature to 
the volume of the same gas at the same conditions calculated using the ideal gas law  
In terms of accuracy of the known methods for the calculation of com pression factors of natural gas, it 
is recommended that the methods below be used in the order listed:  
– AGA8 -DC92,  
– SGERG -88, 
– AGA8 Gross Characterisation Method 1,  General Measure  No. 0111 -OOP -C032-13 
4 – AGA8 Gross Characterisation Method 2,  
– AGA NX19 mod.,  
– AGA NX19.  General Measure No 0111 -OOP -C032 -13 
5 1.8   SYMBOLS AND UNITS OF MEAS UREMENT  
Symbols  Represented quantity  Measurement units  
Vm, Vm1, Vm2 volume at measurement conditions, “1” – initial, “2“” - final m3 
Vb, Vb1, Vb2 volume at base conditions, “1” – initial, “2“” - final m3 
p, p min, pmax absolute pressure at measurement co nditions, minimum, maximum  bar, kPa, MPa  
pb absolute pressure at base conditions  bar, kPa, MPa  
T, T min, Tmax absolute temperature at measurement conditions, minimum, maximum  K 
Tb absolute temperature at base conditions  K 
z compression factor of the gas  at measurement conditions  – 
zb compression factor of the gas at base conditions  – 
2   Metrological requirements  
The metrological requirements are based on the requirements under the Government Order on 
Measuring Instruments, applying the relevant requir ements in line with  harmonised standards.  
The verification of measuring instruments shall be subject to metrological requirements governing 
placement  on the market.  
2.1   Rated operating conditions  
Gas-volume conversion devices must be able to meet the re quirements for the minimum ambient 
temperature range of –10 °C to 40 °C.  
The manufacturer shall specify the base conditions for converted quantities.  
2.2   Range of gas pressure transducer   
A transducer of absolute gas pressure must be used for absolute pr essures of less than 21  bar. For 
absolute pressures equal to or greater than 21  bar, a gauge pressure transducer may be used, while the 
average value of barometric pressure at the site of installation shall be entered into the calculator unit.  
2.3   Range  of gas temperature sensor/transducer  
The minimum gas temperature range shall be 40°C.  
2.4   Maximum permissible error  
2.4.1    Maximum permissible error during verification  
Maximum permissible errors shall be set separately for reference conditions and the  range of specified 
operating conditions.  
The reference conditions shall be: ambient temperature (20  
3) °C, relative air humidity (60  
15) % 
and the nominal values of power supply.  General Measure  No. 0111 -OOP -C032-13 
6 Table 1  – Maximum permissible errors  
Indication or element  Reference 
condi tions  Rated operating  
 conditions  
total main indication  ec for gas -volume conversion devices 
with a pressure transducer (PT and PTZ)  
0.5%  
 1.0%  
total main indication  ec for gas -volume conversion devices 
with a temperature transducer (T) without a press ure 
transducer  
0.5%  
 0.7%  
separate calculator unit ej 
 0.2%  
 0.3%  
separate temperature transducer eT a) 
0.1%  
 0.2%  
separate pressure transducer ep b) 
0.2%  
 0.5%  
compression degree  
 0.2%   
a) Refers to thermodynamic temperature expressed in degrees Kel vin. 
b) Refers to the absolute pressure value measured.  
 
Measuring instruments shall not exploit the maximum permissible error or systematically favour any 
of the parties.  
2.4.2    Maximum permissible errors in use  
When testing gas -volume conversion devices w ithin the period of validity of verification, whe re 
incorrect measurement could harm significantly the interests of one of the parties, the maximum 
permissible errors for reference conditions shall be used in testing  to be performed under  reference 
conditi ons. 
2.4.3    Maximum permissible error in shorter  tests  
When conducting shorter  tests at the site of installation, the maximum permissible errors for the 
specified operating conditions apply.  
3   Technical requirements  
The technical requirements are based on the requirements under the Government Order on Measuring 
Instruments, while applying the relevant requirements under harmonised standards.  
The verification of measuring instruments shall be subject to the metrological requirements governing 
placement  on the market.  
3.1   Construction  
A gas -volume conversion device connected to a gas meter constitutes a separate sub -assembly 
consisting of a calculator unit, as well as temperature and pressure transducers.  
All parts of a gas -volume conversion device shall  be designed in such a way that they do  not degrade 
the accuracy of the measurement of the gas meter with which it is associated. A gas -volume 
conversion device must be able to withstand the external environment for which it is intended.  
3.2   Indicating device  
The device indicating the volume at base conditions must be equipped with the means for checking 
whether  the display is operating correctly. The counter must be clearly and accurately readable within 
an angle of 15° from normal to the window. When not all  the digits of the indicating device are used 
for indicating  the volume, every unused digit to the left of the significant digit must be zero.  General Measure No 0111 -OOP -C032 -13 
7 3.3   Indications   
The gas -volume conversion device must be able to indicate the following data:  
– the increm ental  volume at base conditions Vb; 
– the incremental  volume at measurement conditions Vm; 
– the incremental  corrected volume Vc (if applicable);  
– alarm indications;  
– conversion factor C; 
– the compression factors z, zb, or the ratio between them
bzzK
 , if applicable;  
– the current parameter values measured by the transducers (e.g. pressure p and temperature T at 
measurement conditions);  
– the entered data which affect the metrological result, such as the base conditions pb, and Tb, 
correction functions o r the coefficient used for gas meter error correction;  
– gas properties used in the computation of compression factors, if applicable;  
– the reference to the method by which the compression factor is calculated or the constant, if 
applicable;  
– the lower and upp er limits of the specified measurement range of the temperature transducer 
in K or °C and the lower and upper limits of the absolute pressure of the pressure transducer;  
– the value of one volumetric pulse at measurement conditions in the form:  
– 1 imp = ... m3 (or dm3); or 
– 1 m3 (or dm3) = ... imp;  
– end of battery life (if battery is used);  
– the software version.  
3.4   Security indications and alarms  
The gas -volume conversion device must be able to detect  whether : 
– any of the measured or calculated values are outside the specified measurement ranges,  
– the instrument operates outside the limits of validity of the computing algorithm;  
– any of the electrical signals are outside of the range of the input(s) of the calculator unit;  
– a battery  has expired . 
With the excepti on of an expiring battery, as long as such a defective operation is detected by the 
conversion device, any further increase in the volume at base conditions Vb shall not be permitted. The 
recording of volume Vm at measurement conditions and, if applicable,  the volume Vc corrected for gas 
meter error must continue to operate.  
The resetting of a triggered alarm shall be possible only if the cause for  alarm has been rectified . The 
reset device may be  sealed.  
3.5   Gas meter error correction  
The gas -volume conv ersion device may be equipped with a gas meter error correction  device . In such 
cases, it must be ensured that the error curve of the gas meter to be corrected corresponds to the 
operating conditions at the site of installation of the gas meter. The gas me ter must be verified under  
the measurement conditions in which it is used at the site of installation and with the gas used at the 
site of installation. The resulting error curve of the gas meter shall be used for correction in the gas -General Measure  No. 0111 -OOP -C032-13 
8 volume conversion de vice whe re a high -frequency pulse transmitter is used or the conversion device 
and the gas meter communicate digitally.  
3.6   Inputs from the gas meter   
The gas -volume conversion device must have an input that process es a signal from the associated gas 
meter.  
Pulse inputs  must respond to every pulse in such a manner that no pulses are gained or lost when 
operating  the conversion device. The manufacturer must specify the pulse input characteristic of the 
gas-volume conversion device and the maximum frequenc y. If the gas meter and conversion device 
communicate digitally, the manufacturer of both the gas meter and the conversion device must specify 
the precise compatibility requirements.  
3.7   Methods for compression factor calculation  
The manufacturer must pr opose a method for calculating the  compression factors of natural gas and 
the relevant software for doing this . 
Compression factors , or their ratio K, or their constant values must be used in the gas -volume 
conversion device whenever the upper limit of the  pressure transducer is equal to or greater th an 4 bars 
of absolute pressure.  
3.8   Software  
Software relating to  metrological characteristics must be validated, be readily identifiable and secured. 
Evidence must be available of any changes made to  the sof tware.  
Access shall only be obtained by using a password or a code that may be updated , or by using a 
specific device.  
3.9   Resistance to unauthorised tampering  
The gas -volume conversion device must be constructed in such a way that any intervention whic h may  
influence the results of measurement shall cause permanently visible damage to the measuring 
instrument or its official or protective MARKS, or trigger an alarm so that proof of unauthorised 
intervention is available and stored in a memory.  
Where ele ctronic seals are used for setting of the conversion device  in an authorised or approved 
manner , the seals must comply with the following requirements:  
– at least the last intervention, but preferably the past 100 interventions , shall be registered in 
the me mory, including the date and time of intervention and a specific identification of the 
intervention , 
– it shall be possible to have access to the intervention(s) registered in the memory and it shall 
not be possible to erase or overwrite this memory without breaking the official mark.  
For gas -volume conversion devices where the given transducers or calculator unit may be dismantled 
or replaced, all connections and interfaces between the calculator unit and transducers or the 
measuring instrument must be prote cted by separate seals. Access to parameters which help determine 
the measured results or access to the measured results themselves must not be possible  by 
disconnecting the elements.  
4   Measuring instrument markings  
4.1   Each gas -volume conversion devic e must bear, at least, the following markings on the counter or 
a separate label:  
a) identification mark or name of the manufacturer,  General Measure No 0111 -OOP -C032 -13 
9 b) type designation,  
c) serial number and year of manufacture,  
d) specified measurement range (temperature, pressure, if applicable),  
e) limit temperatures of the environment class in the form  of: 
– tamb, max  = ... °C, 
– tamb, min  = ... °C, 
f) class of explosion hazard area for the pressure transducer, if necessary,  
g) any other markings def ined in a binding manner, e.g. the type number or test certificate 
number, conformity marking, additional metrological markings, etc.  
The markings must be attached in a clearly visible place and be durable under normal conditions of 
use or be displayed on the electronic counter.  
For certain gas -volume conversion devices  type approved in accordance with requirements under 
national technical standards, the requirements for measuring instrument markings applicable at the 
time of type approval of the measuring instrument may differ from the above official requirements; in 
such case s, the requirements specified in the type approval certificate shall be decisive.  
4.2   Placement of the official mark  
The placement of marks  is laid down in the type approval certific ate or the EC certificate of type 
examination or other document applied within the context of conformity assessment when placing the 
device on the market and putting into use in accordance with the Government Order on Measuring 
Instruments.  
5   Type approv al of measuring instruments  
Gas-volume conversion devices intended for use in residential, commercial and light -industrial 
environments are placed on the market and put into use after their conformity has been assessed in 
accordance with the Government Ord er on Measuring Instruments;  therefore, they are not subject to 
type approval.  
6   Initial verification  
Initial verification shall only apply to measuring instruments which have, at the given time, a valid 
type approval certificate applying the transition al provisions under § 9 of the Government Order on 
Measuring Instruments and to the verification of measuring instruments following repairs.  
Initial verification shall follow a procedure identical to that for subsequent verification as referred to in 
Artic les 7.1 to 7.3.  
7   Subsequent verification  
7.1   General   
The tests below shall be performed when subsequently verifying gas-volume conversion devices, i.e. 
during  verification of t he measuring instrument : 
– visual inspection,  
– test of accuracy of the gas -volume conversion device,  
– test of accuracy of quantity conversion by the calculator unit.  General Measure  No. 0111 -OOP -C032-13 
10 7.2   Visual inspection   
The purpose of visual inspection shall be to check that the gas -volume conversion device submitted 
for verification conforms to the approved ty pe or design of the measuring instrument for which 
conformity was declared when it was placed on the market, while paying special attention to verifying 
the correctness of markings as defined in  Article 4.1.  
The durability and legibility of the markings sh all also be inspected.  
Testing shall not take place  if the gas -volume conversion device has been mechanically damaged or it 
does not comply with the approved type or design of the measuring instrument for which conformity 
was declared when it was placed on  the market.  
7.3   Functional tests  
Compliance with the relevant metrological requirements referred to in Chapter 2 and technical 
requirements referred to in Chapter 3 shall be continuously monitored during the functional  tests and 
evaluations thereof.  
7.3.1   Requirements for test equipment  
The test equipment must include  measurement standards for pressure and temperature and pulse 
generators, all of which must have valid metrological traceability.  
The homogeneity and temperature -field stability of the th ermostatic bath used for temperature 
simulation must be guaranteed.  
The software for determining  conventional values of compression factors must be validated.  
A stable pressure source and the means of connection must allow for connecting the pressure 
measu rement standard and pressure transducer of the gas -volume conversion device into a single 
circuit.  
A stable source of unified signals with valid metrological traceability or a stable source of signals 
connected to a signal measuring instrument with valid m etrological traceability shall be used for 
testing calculator units of combined gas -volume conversion devices.  
The test equipment error must be less than 1/4 of the maximum permissible error under the reference 
conditions given in Table 1.  
7.3.2    Accurac y test  
7.3.2.1    Compact gas -volume conversion devices  
7.3.2.1.1    Static test   
Compact gas -volume conversion devices shall be tested by means of comparison with the 
measurement standard for temperature at ambient temperature:  
– t1 within interval tmin ≤ t1 ≤ (tmin + 5) 
– t2 = 0°C  
– t3 within interval ( tmax – 5) ≤ t ≤ tmax 
At each temperature, the pressure transducer and the measurement standard for pressure shall be tested 
at five pressure levels:  
min max min p pd p pi i
 
where di = 0.00, 0.25, 0.50, 0.75 and 1.00; both increasing and decreasing pressure conditions shall be 
used, i.e. there will 30 test points in total.  General Measure No 0111 -OOP -C032 -13 
11 For gas -volume conversion devices equipped only with a temperature transducer, only the maximum 
pressure pmax and minimum pressure pmin values shall be used, i.e. there will be 6 testing points in total.  
The conventional conversion factor value CCV calculated according to relationship (2) under Article 
1.5 and the indicated conversion factor values C shall be used to determine the indication error in 
percent according to the relationship:  
1001
CVc
CCe
 
The indication error ec determined at the individual test points must comply with the maximum 
permissible error requirements under the reference conditions given in Table 1.  
If it is not possible t o read the value of the conversion factor C from the gas -volume conversion 
device, tests for all test points shall be performed in the form of a dynamic test.  
7.3.2.1.2   Dynamic test   
The test shall be performed at no less than three points - t1/pmax, t2/pmax and t3/pmax - by simulating 
pulses from the gas meter using a pulse generator or another method of simulation of unconverted 
volume 
 Vm from the gas meter at measurement conditions. Then, relationship (3) under Article 1.6 
holds for conversion factor Cs indicated by the compact gas -volume conversion device being tested.  
The minimum test volume 
 Vm used as the simulated quantity that has passed through the meter must 
provide a readout of the volume Vb at base conditions with increased  uncertainty of ±0. 02%.  
The conventional conversion factor value CCV calculated according to relationship (2) under Article 
1.5 and the indicated conversion factor values Cs shall be used to determine the indication error in 
percent according to the relationship:  
1001
CV
CCecs
 
The indication error ec determined at the individual test points must comply with the maximum 
permissible error requirement under the reference conditions given in Table 1.  
7.3.2.2    Combined gas -volume conversion devices  
The components of combin ed gas -volume conversion devices shall be tested separately by means of 
comparison with the values measured by the measurement standards for the relevant quantities being 
measured.  
7.3.2.2.1    Temperature transducer   
Temperature transducers shall be tested  in a thermostatic bath at three ambient temperatures - tmin, 0°C 
and tmax.  
The temperature transducer error eT determined at individual test points must comply with the 
maximum permissible error requirement under the reference conditions given in Table 1 . 
7.3.2.2.2    Pressure transducer  
The pressure transducers shall be tested at 8 evenly distributed pressure points - from pmin to pmax, 
under both increasing and decreasing pressure conditions. For pressure transducers measuring 
pressure, the relative erro r needs to be determined from absolute pressures.  
The pressure transducer error ep determined at the individual test points must comply with the 
maximum permissible error requirement under the reference conditions outlined  in Table 1.  General Measure  No. 0111 -OOP -C032-13 
12 7.3.2.2.3    Calculato r unit  
7.3.2.2.3.1    Static test  
The calculator unit shall be tested using a static test at Qmax at no fewer  than five test points: Tmin/pmin, 
Tmin/pmax, Tmax/pmin, Tmax/pmax and one further point in the middle of the temperature and pressure range. 
The in put signals (temperature, pressure) shall be simulated using suitable devices sending accurate 
signals.  
The conventional conversion factor value CCV calculated according to relationship (3) under Article 
1.5 and the indicated conversion factor values C shall be used to determine the indication error in 
percent according to the relationship:  
1001
CVCCej
 
The indication error of the calculator unit ej determined at the individual test points must comply with 
the maximum permissible error requirement under the reference conditions outlined  in Table 1.  
If it is not possible to read the value of the conversion factor C from the calculator unit, tests for all 
test points shall be performed in the form of a dynamic test.  
7.3.2.2.3.2   Dynamic test  
The test of the calculator unit shall be performed at least for the combination of simulated values 
Tmax/pmin/Qmax. The input signals (temperature, pressure and volume that has passed through the meter) 
shall be simulated using suitable devices sending accurate sig nals and by simulating pulses from the 
gas meter using a pulse generator or another method of simulation of the unconverted volume from the 
gas meter at measurement conditions. Then, relationship (3) under Article 1.6 holds for conversion 
factor Cs indicat ed by the calculator unit.  
The minimum test volume 
 Vm used as the simulated quantity that has passed through the meter must 
provide readout of the volume Vb at base conditions with an uncertainty of ±0.02%.  
The conventional conversion factor value CCV calculated according to relationship (2) under Article 
1.5 and the indicated conversion factor values C shall be used to determine the indication error ej in 
percent according to the relationship:  
1001
CVs
jCCe
 
The error of the calculator unit ej determined at the individual test points must comply with the 
maximum permissible error requirement under the reference conditions given in Table 1.  
7.3.3    Test of accuracy of quantity conversion by the calculator unit  
The test shall be performed at no less t han 4 points  - Tmin/pmin, Tmin/pmax, Tmax/pmin and Tmax/pmax - 
during the course of the test of accuracy of the compact gas -volume conversion device under Article 
7.3.2.1 or the calculator unit of a combined gas -volume conversion device under Article 7.3.2 .2.3.  
Some conversion devices display only the compression degree K, on the counter as given by the 
relationship:  
bzzK
 
The conventional value of compression degree Ke shall be calculated using validated software 
according to the calculati on method used in the gas -volume conversion device and the set parameters 
(composition) of the gas. The value of Ke shall  then be compared with the readout of the compression 
degree (or the value of the compression degree K calculated from the indicated co mpression factors of General Measure No 0111 -OOP -C032 -13 
13 the gas -volume conversion device) and the compression calculation error shall be determined in 
percent age terms : 
1001
eKKKe
 
The compression degree error determined at the individual test points must comply with the maximum 
permissible error requirement under the reference conditions given in Table 1.  
7.4   Shorter  test of the gas -volume conversion device   
The shorter  test shall be performed for the gas -volume conversion device at the site of installation and 
use: 
– after each a ssembly of the conversion device as a whole or its parts,  
– one year after the date the preceding shorter  test was conducted, throughout the period of 
validity of verification of the conversion device.  
7.4.1    General   
When performing a shorter  test on the g as-volume conversion device at the site of installation, the 
following tests shall be performed:  
– visual inspection and control of parameters;  
– conversion device accuracy test.  
7.4.2    Visual inspection and control of parameters  
It shall be checked that the device is not damaged, that the period of validity of verification has not 
expired and that the official marks attached to the gas -volume conversion device and the associated 
gas meter are intact, legible and complete. A check of the gas -volume conversion device settings, such 
as gas parameters, the method of gas compression calculation and gas meter pulse number, shall also 
be performed.  
7.4.3    Functional tests  
7.4.3.1    Requirements for test equipment  
The test equipment must be equipped with measurement standards for pressure and temperature and 
pulse generators with valid metrological traceability.  
The test equipment must be portable and usable at the site of installation of the gas -volume conversion 
device. The operating pressure of the gas being measur ed at the site of installation, to which the 
measurement standard can be connected through a three -way valve, is most commonly used as the 
source of pressure. A container with a constant temperature bath, such as a thermos flask with water, 
also needs to b e used.  
The test equipment error for the shorter  test must be less than 1/4 of the maximum permissible error 
under the reference conditions given in Table 1.  
7.4.3.2    Conversion device accuracy test  
7.4.3.2.1    Dynamic test  
The test shall be performed at the site of installation of the gas -volume conversion device at a single 
value of operating pressure in the system and at a single temperature value, which shall be within the 
range of the operating conditions of the gas -volume conversion device.  General Measure  No. 0111 -OOP -C032-13 
14 The test shall be performed by simulating pulses from the gas meter using a pulse generator or another 
method of simulation of unconverted volume 
 Vm at measurement conditions, for example by reading 
the counters of the associated gas meter. Then, relationship (3) under Article 1.6 holds for conversion 
factor C indicated by the gas -volume conversion device being tested.  
The minimum test volume 
 Vm used as the simulated quantity that has passed through the meter must 
provide readout of the volume Vb at base condition s with an uncertainty of ±0.10%.  
The conventional conversion factor value CCV calculated according to relationship (2) under Article 
1.5 and the indicated conversion factor values Cs shall be used to determine the indication error ec dyn 
in percent accordi ng to the relationship:  
1001
CVs
dyn cCCe
 
The indication error ec dyn determined must comply with the maximum permissible error requirement at 
the set operating conditions given in Table 1.  
7.4.3.2.2    Static test   
If the value of the conversion factor C can be read from the counter of the gas -volume conversion 
device, this value of the conversion factor C shall be read during  the dynamic test.  
The conventional conversion factor value CCV calculated according to relationship (2) under Article 
1.5 and the  indicated conversion factor values C shall  be used to determine the indication error ec stat in 
percent age terms  according to the relationship:  
1001
CVsta cCCe
 
The indication error ec stat determined must comply with the maximum permissible error req uirement at 
the set operating conditions given in Table 1.  
7.4.3.2.3    Interpretation of the results of static and dynamic tests   
The absolute value of the differences between indications obtained from the static and dynamic tests 
must be less than or equa l to 0.30 %. Therefore, it must hold that  
ec stat – ec dyn
  
 0.30 %.  
If the value of the conversion factor C cannot be read from the gas -volume conversion device, only the 
shorter  test shall be performed in the form of a dynamic test.  
If the gas -volume conversion device does not comply with the above requirements in the shorter  test, 
the verification shall cease to be valid.  
7.4.3.2.4    Securing the measuring instrument  
The official marks inspected under Article 7.4.2 must not be removed or damaged duri ng the shorter  
test. 
After the shorter  test has been performed, protective marks preventing disassembly of the gas -volume 
conversion device of parts thereof, i.e. the pressure outlet from the gas meter, the three -way valve, 
temperature and pressure transdu cer connection and pulse transmitter, need to  be attached to the 
instrument.  
The inspector shall draw up a report of the results of the shorter  test. General Measure No 0111 -OOP -C032 -13 
15 8   Notified standards  
For the purposes of specifying the metrological and technical requirements for meas uring instruments 
and specifying the testing methods for verification based on this general measure , the CMI shall 
provide notification of the Czech technical standards, other technical standards or technical documents 
of international or foreign organisat ions, or other technical documents containing more detailed 
technical requirements (hereinafter referred to as “notified standards”). The CMI shall publish a list of 
these notified standards attached  to the relevant measures, together with the general meas ure, in a 
manner accessible to the public (on the www.cmi.cz website).  
Notified standards or parts thereof shall be considered complied with within the scope of and under the 
conditions laid down in this general measure , if the requirements laid down by this measure, to which 
these standards or parts thereof apply, are complied with.  
 
 
II. 
G R O U N D S   
The CMI has issued  this general measure  laying down metrological and technical requirements for 
specified measuring instr uments and the testing methods for the verification of these specified 
measuring instruments so as  to implement § 24c of Act No 505/1990  
Under item 1.3.10d) of the Annex “List of the Types of Specified Measuring Instruments” to Decree 
No 345/2002  specify ing the measuring instruments whose verification is mandatory and the 
measuring instruments subject to type approval as amended, gas -volume conversion devices are 
classified as measuring instruments subject to verification.  
As such , the CMI has issued this  general measure laying down metrological and technical 
requirements for gas -volume conversion devices and the testing methods for the verification of these 
specified measuring instruments in order to implement § 24c of Act No 505/ 1990 on  metrology for 
this particular type of measuring instrument - gas-volume conversion devices intended for use in 
residential, commercial and light -industrial environments.  
This regulation ( general measure ) has been notified in accordance with Directive 98/34/EC of the 
Europe an Parliament and of the Council of 22 June 1998 laying down a procedure for the provision of 
information in the field of technical standards and regulations and of rules on Information Society 
services , as amended.  
 
 
III. 
I N S T R U C T I O N S  
In accor dance with  § 173(2) of the APC, no appeals may be made regarding general measures.  
In accordance with the provisions of § 172(5) of the APC, decisions on objections are final  and 
appeals may not be made against them . 
Conformity of a general measure with le gislation may be assessed in review proceedings pursuant to 
§§ 94 to 96 of the APC. A party to the proceedings may initiate review proceedings , to be conducted 
by the administrative authority issuing  the general measure. If the administrative authority fin ds no 
reason to commence the review proceedings, it shall communicate and provide grounds for this within 
thirty days. Pursuant to § 174(2) of the APC, a ruling on the commencement of review proceedings 
may be issued within three years of the entry into fo rce of the general measure.  
 General Measure  No. 0111 -OOP -C032-13 
16  
IV. 
E N T R Y    I N T O    F O R C E  
This general measure  shall enter into force on the fifteenth day of the date of publication (§  24d of the 
Metrology Act).  
 
 
 
...…………………………..............  
RNDr. Pavel Klenovský  
Director General