CNPA 137    Page 1 of 57 pages  
  Technical Specification  for Type A pproval 
of Diaphragm Gas Meters  S/N CNPA  137 
Rev. 1 
1. This Technical Specification is enacted pursuant to Paragraph 3, Articles 25 of the Weights 
and Measures Act.  
2. The date of promulgation, document  number, date of enforcement and content of the 
amendment are listed as follows:  
Rev. Date of  
Promulgation  Document  No. 
(Ching -Piao-Szu-Tsu ) Date of Enforcement  Content of Amendment  
1 2003 -11-19 
(CNPA 31)  No. 09240008950  2004 -01-01 
 
2 2016 -09-05 
(CNPA 31)  No. 1054001 6080  2019 -09-05 Referring to  OIML R 137 -1&2: 
2012, adding the provisions on the 
maximum working pressure and other 
features to meet the metrological 
requirements.  
Adding the testing on pressure 
features for gas meters with working 
pressure over 10 kPa. 
Corresponding to the testing capacity 
of the constant temperature, revi sing 
the applicable maximum measurable 
range for temperature.  
3 2017 -10-27 
(CNPA 31)  No. 10640006480  2018 -01-01 Adding the manufacturing year on the 
name plate.  
1 2023-02-06 
(CNPA 137)  No. 11 24000 0520 2023 -07-01 Referring to  OIML R 137 -1 & 2: 
2012, amending the existing CNPA 
31. 
Changing the document  number and 
the revision of this specification from 
CNPA 31 , rev.3 to CNPA 137 , rev.1 . 
3. This specification  is formulated with reference to the following s tandard s: 
OIML R 137-1&2 Gas meters  (2012 ) 
OIML R31  Diaphragm gas meters  (1995 ) 
CNS 14741  Diaphragm gas meter with micro computer for nature gas  (2007) 
   
   
 
Date of Promulgation  
2023-2-6  Bureau of Standards, Metrolo gy and Inspection, 
Ministry of Economic Affairs  Date of Enforcement  
2023 -07-01  
NO GUARANTEE ON THE TRANSLATION  
In case of discrepancies  between the English translation and Chinese text, the Chinese text shall govern.  CNPA 137    Page 2 of 57 pages  
 CONTENTS  
1. Scope   3 
2. Definition   3 
3. Metrological requirements   8 
4. Technical requirements  12 
5. Inscriptions  18 
6. Operating instructions   19 
7. Sealing  20 
8. Metrological controls  21 
9. Type a pproval  22   
10. Date of Enforcement  28 
Annex A. Environmental tests for electronic instruments or devices (mandatory)  29 
Annex B. Type - evaluation tests of safety performance and electromagnetic compatibility 
performance for d iaphragm gas meter with micro co mputer  39 
Annex C. The requirements of a dditional test s for diaphragm  gas meters with maximum 
working pressure more than 10 kPa   54 
Annex D. Type evaluation of a family of gas meters (Mandatory)  56 
 CNPA 137    Page 3 of 57 pages  
 1. Scope  
This t echnical specification  applies to diaphr agm gas meters  for metering natural gas and 
liquidfied petroleum gas . These gas meters  are gas volume meters in which the gas flow is 
measured by means of measuring chambers with deformable films , including any other 
(electronic) devices that may be attach ed to the gas meter s and have potential impact to 
their metrological performance.  
2. Definition  
2.1 Gas meter and constituents  
2.1.1 Gas meters  
Instrument intended to measure, memorize and display the quantity of gas passing 
the flow sensor . 
2.1.2 Measuran d 
Quantity intended to be measured . 
2.1.3 Sensor  
Element of a measuring system that is directly affected by a phenomenon, body, 
or substance carrying a quantity to be measured . 
2.1.4 Measuring transducer  
Device, used in measurement, that provides an output  quantity having a specified 
relation to the input quantity . 
2.1.5 Calculator  
Part of the gas meter which receives the output signals from the measuring 
transducer(s) and, possibly, associated measuring instruments, transforms them 
and, if appropriate, sto res the results in memory until they are used. In addition, 
the calculator may be capable of communicating both ways with ancillary 
devices . 
2.1.6 Indicating or displaying device  
Part of the gas meter which displays the measurement results, either continuo usly 
or on demand . 
2.1.7 Ancillary device  
Device intended to perform a particular function, directly involved in elaborating, 
transmitting or displaying measurement results . The main ancillary devices  
include repeating indicating device , printing device,  memory device, and  
communication device . An ancillary device is not necessarily subject to 
metrological control  and may be integrated in the gas meter.  
2.1.8 Equipment under test (EUT)  
(part of the) Gas meter and/or associated devices which is exposed to on e of the 
tests. 
2.1.9 Family of gas meters  CNPA 137    Page 4 of 57 pages  
 Group of gas meters of different sizes and/or different flow rates, in which all the 
meters shall have the following characteristics:  
- the same manufacturer,  
- geometric similarity of the measuring part,  
- the sa me metering principle,  
- roughly the same ratios Qmax/Qmin and Qmax/Qt, 
- the same accuracy class,  
- the same temperature range , 
- the same electronic device for each meter size , 
- a similar standard of design and component assembly , 
- using the same metro logical software routines (if applicable) and the same 
materials for those components that are critical to the performance of the meter . 
2.1.10 Diaphragm gas meter  with micro computer  
A diaphragm gas meter consists of metrological unit and safety reference  
detection control unit, the former being composed of metrology related 
components and the latter being composed of flow sensor, shut -off valve, 
pressure sensor, earthquake sensor, mother board for identification of abnormal 
conditions and lithium battery.  
2.2 Metrological characteristics  
2.2.1 Q uantity of gas  
Total quantity of gas obtained by integrating the flow passed through the gas 
meter over time, which is expressed as volume V, disregarding the time taken. 
The quantity of gas is the measurand concern ed. 
2.2.2 Indicated value (of a quantity)  
Value of a quantity, as indicated by the meter . 
2.2.3 Cyclic volume  
Volume of gas corresponding to one full revolution of the moving part(s) inside 
the meter . 
2.2.4 Error  
Measurand quantity value minus a reference quantity value  (relative error) . 
2.2.5 W eighted Mean Error ( WME ) 
The weighted mean error ( WME ) within the scope of The Specification  is defined 
as: 

n
iin
iii
kEk
WME
11
  
with 
maxQQki
i  for 
max7.0Q Qi  CNPA 137    Page 5 of 57 pages  
 
max4.1QQki
i for 
max max7.0 Q Q Qi  
where:  
ki = weighting factor at the flow rate Qi; 
Ei = the error at the flow rate Qi.      
2.2.6 I ntrinsic error  
Error determined under reference conditions . 
2.2.7 Fault 
Difference between the error of indication and the intrinsic erro r of a measuring 
instrument . In practice fault is the difference between the error of the meter 
observed during or after a test, and the error of the meter prior to this test, 
performed under reference conditions.  
2.2.8 Maximum Permissible Error (MPE)  
Extreme value of measurement error, with respect to a known reference quantity 
value, permitted by specifications or regulations for a measuring instrument . 
2.2.9  Accuracy class  
Class of gas meters  that meet s tated metrological requirements  to keep 
measurement  errors within specified limits under specified operating conditions . 
2.2.10  Durability  
Ability of a gas meter  to maintain its performance characteristics over a period 
of use . 
2.2.11  Measurement precision  
Closeness of agreement between indications or meas ured quantity values 
obtained by replicate measurements on the same or similar objects under 
specified conditions . 
2.2.12  Repeatability  
Measurement precision under a set of repeatability conditions of measurement . 
2.2.13  Repeatability of error  
Repeatabilit y under reference conditions and not changing the flow rate between 
the measurements . 
2.2.14  Reproducibility  
Measurement precision under reproducibility condition of measurement . 
2.2.15  Reproducibility of error  
Reproducibility under reference conditions an d changing the flow rate between 
the measurements . 
2.2.16  Operating conditions  
Conditions of the gas (temperature, pressure , flow rate  and composition) at 
which the quantity of gas is measured . CNPA 137    Page 6 of 57 pages  
 2.2.17  Rated operating conditions  
Operating  conditions of use giving the range of values of the measurand and the 
influence quantities, for which the errors of the gas meter are required to be 
within the limits of the maximum permissible error . 
2.2.18  Reference conditions  
Set of reference values, or reference ranges of influence quantities, prescribed 
for testing the performance of a gas meter, or for the intercomparsion of the 
results of measurements . 
2.2.19  Test element  
Device to enable precise reading of the measured gas quantity . 
2.2.20  Resolution  
Smallest differe nce between displayed indications that can be meaningfully 
distinguished . For a digital device, this is the change in the indication when the 
least significant digit changes by one step. For an analogue device, this is half 
the difference between subsequen t scale marks.  
2.2.21  Drift  
Continuous or incremental change over time in indication, due to changes in the 
metrological properties of a measuring instrument . 
2.3 Operating conditions  
2.3.1  Flow rate, Q 
Quotient of the actual quantity of gas passing throug h the gas meter and the time 
taken for this quantity to pass through the gas meter . 
2.3.2  Maximum flow rate, Qmax 
Highest flow rate at which a gas meter is required to operate within the limits of 
its maximum permissible error, whilst operated within its r ated operating 
conditions . 
2.3.3  Minimum flow rate, Qmin 
Lowest flow rate at which a gas meter is required to operate within the limits of 
its maximum permissible error, whilst operated within its rated operating 
conditions . 
2.3.4  Transitional flow rate, Qt 
Flow rate which occurs between the maximum flow rate Qmax and the minimum 
flow rate Qmin that divides the flow rate range into two zones, the "upper zone" 
and the "lower zone", each characterized by its own maximum permissible error . 
2.3.5  Working temper ature  
Temperature of the gas to be measured at the gas meter . 
2.3.6  Minimum and maximum working temperature, tmin and tmax 
Minimum and maximum gas temperature that a gas meter can withstand, within CNPA 137    Page 7 of 57 pages  
 its rated operating conditions, without unacceptable deter ioration of its 
metrological performance . 
2.3.7  Working pressure  
Pressure of the gas to be measured at the gas meter . 
2.3.8  Minimum and maximum working pressure, Pmin and Pmax 
Minimum and maximum internal pressure that a gas meter can withstand, within 
its rated operating conditions, without deterioration of its metrological 
performance . 
2.3.9  Static pressure loss or pressure differential, ∆ P 
Mean difference between the pressures at the inlet and outlet of the gas meter 
while the gas is flowing . 
2.3.10  Working density, ρw 
Density of the gas flowing through the gas meter, corresponding to working 
pressure  and working temperature . 
2.3.11  Pressure absorption  
With a flow of air of density 1.2 kg/m3 as a medium, at a flow  rate equal to  Q max, 
the pressure loss averaged over a measuring cycle of a gas meter as the total 
pressure absorption.  
2.4 Test con ditions  
2.4.1  Influence quantity  
Quantity that, in a direct measurement, does not affect the quantity that is actually 
measured, but that affects the relation between the indication and the 
measurement result . 
2.4.2 D isturbance  
Influence quantity having a value within the limits specified in This Specification , 
but outside the specified rated operating conditions of the gas meter . 
2.4.3 Overload conditions  
Conditions outside the rated operating conditions (including flow rate, 
temperature, pressure, humidit y and electromagnetic interference) that a gas 
meter is required to withstand without deterioration . 
2.4.4  Test 
Series of operations intended to verify the compliance of the equipment under test 
(EUT) with certain requirements . 
2.4.5  Test procedure  
Detaile d description of the test operations . 
2.4.6  Test program  
Description of a series of tests for a certain type of equipment . CNPA 137    Page 8 of 57 pages  
 2.4.7  Performance test  
Test intended to verify whether the equipment under test (EUT) is capable of 
accomplishing its intended functi ons. 
2.5 Electronic equipment  
2.5.1  Electronic gas meter  
Gas meter equipped with electronic devices . Ancillary equipment, as far as it is 
subject to metrological control, is considered part of the gas meter, unless the 
ancillary equipment is approved and v erified separately.  
2.5.2  Electronic device  
Device performing a specific function. Electronic devices are usually 
manufactured as separate units and are capable of being tested independently . 
2.5.3  Electronic component  
Smallest physical entity in an electr onic device used to affect electrons and/or 
their associated fields in their movement through a medium or vacuum . 
3. Metrological requirements  
3.1 Rated operating conditions  
Rated operating conditions for a gas meter  
(1) Ambient temperature  -5 ℃ to  +55 ℃ 
(2) Ambient relative humidity  at least up to 93 %  
(3) Vibration less than  10 Hz  - 150 Hz, 1.6  ms-2, 0.05 m2s-3, -3 dB/octave  
(4) DC mains voltage , if applicable  as specified by the manufacturer  
(5) AC mains voltage , if applicable  Unom－15 % t o Unom＋10 %  
(6) AC mains frequency , if applicable  fnom－2 % to fnom＋2 % 
(7) Flow rate range  Qmin to Qmax inclusive  
(8) Working pressure range  Pmin to Pmax inclusive  
3.2 Values of Qmax, Qt and Qmin 
The flow rate characteristics of a gas meter shall be de fined by the values of Qmax, Qt 
and Qmin. Their ratios and relations shall be within the ranges as stated in table 1.  
Table 1  
Qmax  
m3/h Upper limit of  Qt 
m3/h Upper limit of  Qmin 
m3/h 
1 
1.6 
2.5 
4 
6 
10 
16 
25 
40 0.10 
0.16 
0.25 
0.40 
0.60 
1.0 
1.6 
2.5 
4.0 0.016  
0.016  
0.016  
0.025  
0.040  
0.060  
0.100  
0.160  
0.250  CNPA 137    Page 9 of 57 pages  
 65 
100 
160 
250 
400 
650 
1000  6.5 
10 
16 
25 
40 
65 
100 0.400  
0.650  
1.000  
1.600  
2.500  
4.000  
6.500  
3.3 Accuracy classes and maximum permissible errors  
3.3.1 General  
A gas meter shall be designed and manufacture d such that its errors do not exceed 
the applicable MPE under rated operating conditions.  
3.3.2 Accuracy classes  
Gas meters may be divided in two accuracy classes , 1.0 and 1.5. The value of the 
MPE is dependent on the applicable accuracy class as listed in  Table 2 below.  
3.3.3  Maximum permissible errors (MPE)  
Use air of ambient temperature and ambient pressure  as the test medium . The 
maximum permissible errors are given in Table 2. 
Table 2  
Flow rate  During type evaluation and verification  
 (During in-servic e) 
Accuracy class  
1.0 1.5 
Qmin ≤ Q < Qt ± 2 %  
(± 4 %)  ± 3 %  
(± 6 %)  
Qt ≤ Q ≤ Qmax ± 1 %  
(± 2 %)   ± 1.5 %  
(± 3 %)  
3.3.4  Calculation  of error  
The instrument error of measuring shall  be expressed by percentage to the relative 
value; i.e., the ratio of deviation between the indicated value of gas meter and 
standard value made from standard element, then divided by the standard value 
made from standard element:    
Error (%) = 
  value) (standard value) standard -  value (Indicated x 100%  
 
3.4 Weighted mean error  (WME)  
The weighted mean er ror shall only be applicable during type evaluation and shall be 
within the ranges  given in table 3.  
Table 3  
Accuracy class  1.0 1.5 
WME  ± 0.4 %  ± 0.6 %  CNPA 137    Page 10 of 57 pages  
 3.5 Reproducibility  
For flow rates equal to or greater than Qt the reproducibility of error at the spe cific 
flow rate shall be less than or equal to one third of the maximum permissible error.  
3.6 Repeatability  
The repeatability of error of three consecutive measurements at the specific flow rate 
shall be less than or equal to one third of the maximum perm issible error.  
3.7 Working pressure  
The requirements of accuracy class and weighted mean error  for the gas meter shall be 
fulfilled within the rated working pressure range.  
3.8 Working temperature  
The requirements of accuracy class and weighted mean error  for the gas meter shall be 
fulfilled within the rated working temperature  range , where the ambient temperature 
equals the gas temperature within 5 ℃. 
3.9 Pressure absorption  
The total pressure absorption of a gas meter, averaged over a measuring cycle, wit h a 
flow of air of density 1.2 kg/m3, at a flow  rate equal to Qmax , shall not exceed the 
values given in Table 4.  
Table 4  
Flow rate  Maximum permissible values for average total pressure 
absorption (equipped with safety reference  detection control unit ) 
Pa 
  1 to 10 inclusive  
 16 to 65 inclusive  
100 to 1000inclusive  200 (242)  
300 (330)  
400 (440)  
3.10 Durability  test 
A gas meter shall meet the following requirements after being subjected to a flow with 
rate between 0.8  Qmax and Qmax comprising a quantity t hat is equivalent to a flow at 
Qmax during a period of 2000 hours  (The test may be discontinuous but shall be 
completed within 100 days) : 
- the maximum permissible errors as specified in Table 2 for in-service , and  
- for flow rates from Qt up to Qmax a fau lt of less than or equal to:  
1.0 times the maximum permissible error applicable for class 1.5 , or 0.5 times the 
maximum permissible error applicable for class  1.0. 
3.11 Overload flow  
A gas meter shall meet the following requirements, after being exposed to  an overload 
of 1.2 Qmax for a period of 1 hour : 
- the maximum permissible errors as mentioned in Table 2 for  verification , CNPA 137    Page 11 of 57 pages  
 - and a fault of less than or equal to one third of the maximum permissible error.  
3.12 Vibrations and shocks  
The fault after the ga s meter being exposed to the following vibrations and shocks 
shall be less than or equal to 0.5 times the maximum permissible error  for verification . 
3.12.1 Vibrations  
total frequency range:   10 Hz – 150 Hz  
total RMS level:    7 ms-2 
ASD level 10 Hz – 20 Hz:  1 m2s-3 
ASD level 20 Hz – 150 Hz:   –3 dB/octave   
3.12.2 Shocks  
Height of fall:  50 mm  
3.13 Metrological requirements specific to certain types of gas meters  
3.13.1 Electronics  
If a gas meter includes electronic components, the requirements as presented  in 
Table 5 and Table 6 apply.  The test methods are given in Annex A: 
Environmental tests for electronic instruments or devices (mandatory) . 
3.13.2 Influences from ancillary devices  
Gas meters provided with ancillary devices shall be designed such that all  
functions of the ancillary devices (e.g. provisions for communication purposes) 
do not affect the metrological behavior.  
Table 5 Requirements for gas meters containing electronic components  
No Influence factor  Range  Error limit  
1 Dry heat  upper temperatu re specified  MPE  
2 Cold  lower temperature specified  MPE  
3 Damp heat, steady state 
(non-condensing)  upper temperature specified,  
93 % relative humidity  MPE  
4 DC mains voltage variation , if 
applicable  as specified by the manufacturer  MPE  
5 AC mains volta ge variation , if 
applicable  85 % & 110 % of the rated voltage  MPE  
6 Low voltage of internal battery , if 
applicable  as specified by the manufacturer  MPE  
Table 6 Immunity requirements for gas meters containing electronic components  
No. Disturbance  Required  immunity  Fault limit / test 
condition (1) 
1 Damp heat, cyclic  
(condensing)  upper temperature specified  
93 % relative humidity  1/2 MPE /  NSFa  
2 Vibrations (random)   
 Total frequency range:10 Hz ~ 150 Hz  
Total RMS level:   7 ms-2 1/2 MPE /  NSFa  CNPA 137    Page 12 of 57 pages  
 ASD lev el 10 Hz~20 Hz:  1 m2s-3 
ASD level 20 Hz~150 Hz:  -3 dB/octave  
3 Mechanical shock  50 mm  1/2 MPE /  NSFa  
4 Radiated, RF, 
electromagnetic fields  10 V/m, up to 3 GHz  MPE /  NSFd  
5 Conducted (common 
mode) currents generated 
by RF EM fields  10 V ( e.m.f), up to 80 MHz  MPE /  NSFd  
6 Electrostatic discharges  6 kV contact discharge  
8 kV air discharge  1/2 MPE /  NSFa+d  
7 Bursts (transients) on 
signal, data and control 
lines  Amplitude 1 kV  
Repetition rate 5 kHz  1/2 MPE /  NSFd  
8 Surges on signal, data 
and control lines  
 unsymmetrical lines:  
 line to line 0.5 kV  
 line to ground 1.0 kV  
symmetrical lines:  
 line to line NA  
 line to ground 1.0 kV  
shielded I/O and communication lines:  
 line to line NA  
 line to ground 0.5 kV  1/2 MPE /  NSFd  
9 AC mains voltage di ps 
and short interruptions , if 
applicable  1/2 cycle   0 % 
1 cycle   0 % 
12 cycles   40 %  
30 cycles   70 %  
300 cycles      80 %  1/2 MPE /  NSFd  
10 DC mains voltage dips 
and short interruptions, if 
applicable  40 % and 70 % of the rated voltage 
during 0.1 s and 0 % of rated voltage 
during 0.01 s  1/2 MPE /  NSFd  
11 Bursts (transients) on AC 
and DC mains  Amplitude 2 kV  
Repetition rate 5 kHz  1/2 MPE /  NSFd  
12 Surges on AC and DC 
mains  line to line 1.0 kV  
line to ground 2.0 kV  1/2 MPE /  NSFa+d  
13 Ripple on DC mains 
power, if applicable  2 % of nominal DC voltage  1/2 MPE /  NSFd  
(1) NSFa: No significant fault shall occur after the disturbance.  
NSFd:  No significant fault shall occur during the disturbance.    
4. Technical requirements  
4.1 Construction  
4.1.1  Material  
The mate rials of outer shell and internal components of the gas meter in direct 
contact with the gas shall be corrosion -resistant or subjected to surface 
anti-corrosive treatment, and comply with the requirements given in 4.1.3.  CNPA 137    Page 13 of 57 pages  
 4.1.2  Impact resistance  
Material co nnecting to the fuel -gas-supplying  portion should be able to withstand 
the external impact under normal operation , and shall comply with the 
requirements given in Section 4.1.4. 
4.1.3  Material test  
4.1.3.1 Metallic material test (corrosion resistance test)  
The test apparatus is set up according to the requirements in CNS 8886 
“Methods of salt spray testing ”. After the metallic components being 
continuously sprayed with neutral salt solution for 24 hours under the 
required condition for salt spray chamber prescribed in CNS 8886 , their 
corrosion area ratio  shall be within the range between rating number 9.8 to 9 
listed in the same standard.  
4.1.3.2 Non-Metallic material test  
Three samples of same parts are taken and weighted individually, then 
immersed into n -pentane for 72 hours within the temperature range between 
5 ℃ and 25 ℃. After that, the samples are taken out and placed under 
atmosphere for 24 hours, then weighted individually. The mass change rate 
for individual part shall be less than 20% calculated according to the 
following formula, and no occurrence  of degr adation or deformation shall be 
conformed.  
Mass change rate = mass  after  test  g –mass  before  test  g  
mass  before  test  g  × 100 % 
 
4.1.4  Impact resistance test  
The gas meter is connect ed to the gas pipe joint, and screw ed in with half of the 
corresponding torque according to the nominal diameter shown in Table 7. An 
impact torque correspond ing to the nominal diameter shown in Table 8  is applied 
to the center of the joint connecting the gas meter and the gas pipe , as shown in 
Figure 1. There sh all be no cracks, damage or significant deformation  via visual 
inspection . For diaphragm gas meter w ith micro computer,  the shut -off test in 
Section B.6.18.4  is performed subsequently,  then the restoration action and 
restoration confirmation test in Section B.6.19 is performed afterwards to confirm 
that the shut -off and alarm functions are correct . When the impact force is applied 
from the front direction, the steel plate with a thickness of 5 mm should be fixed at 
the position of the gas meter's measuring window, and then the surface of the steel 
plate should be impacted.  
Table 7  
Nominal diameter  Joint s crew -in torque  
1/2 inch (15A)  70 N．m 
3/4 inch (20A)  100 N．m 
1 inch (25A)  120 N．m CNPA 137    Page 14 of 57 pages  
 1 1/4 inch (32A)  160 N．m 
1 1/2 inch (40A)  180 N．m 
Table 8 
Nominal diameter  Impact torque  
1/2 inch (15A)  8 N．m 
3/4 inch (20A)  10 N．m 
1 inch (25A)  13 N．m 
1 1/4 inch (3 2A) 16 N．m 
1 1/2 inch (40A)  18 N．m 
 
 
 
 
 
 
 
 
 
Figure 1 Impact test  
Note: impact torque is calculated as follows  
F=W‧L‧G(1 －cosθ)  
Where F:  impact torque  (N‧m)  
W: mass of hammer (kg) 
L: distance from the center line of the return a xis of the hammer to 
the center of gravity  
4.1.5  Indicating device  
The indicating device can be connected to the meter body physically or remotely. 
In the latter case the data to be displayed shall be stored in the gas meter.  
4.1.6  Safety device  
The gas me ter may be equipped with safety device that shuts off the gas flow in the 
event of calamities, such as an earthquake or a fire. For gas m eters equipped with  
safety reference  detection control unit , the requirements of Annex B “Type - 
evaluation test s of saf ety performance and electromagnetic compatibility 
performance for gas meters  with micro computer ” shall be fulfilled in addition to 
metrological requirements . The safety device may be connected to the gas meter, 
provided that it does not influence the metr ological integrity of the meter. A 
mechanical gas meter equipped with an earthquake sensor plus an electrical 
CNPA 137    Page 15 of 57 pages  
 powered valve is not considered to be an electronic gas meter.  
4.1.7  Connections between electronic parts  
Connections between electronic parts sha ll be reliable and durable.  
4.2 Flow direction  
4.2.1 Direction of the gas flow  
The flow direction of gas meter shall be indicated by a method which is clearly 
understood . 
4.2.2  Indicating device  
A gas meter shall be provided with a device to prevent the in dicating device from 
functioning whenever gas is flowing in an unauthorized direction.  
4.3 Indicating device  
4.3.1 General provisions  
The indicating device associated with the gas meter shall indicate the quantity of 
gas measured in volume  and its  reading shall be clear and unambiguous.  
The indicating device may include : 
(1) a mechanical indicating device . 
(2) an electromechanical or electronic indicating device . 
(3) a combination of (1) and (2). 
Indicating devices shall be non -resettable (i.e. they shall b e able to show the last 
stored indication after the device has recovered from an intervening power failure). 
Where the indicating device shows decimal submultiples of the quantity measured, 
this fraction shall be separated from the integer value by a clear  decimal sign.  
It may be possible to use one display for other indications as well, as long as it is 
clear which quantity is being displayed.  
4.3.2  Indicating range  
The indicating device shall be able to record and display the indicated quantity of 
gas cor responding to at least 1000 hours of operation at the maximum flow rate 
Qmax, without returning to the original reading.  
4.3.3  Resolution  
The quantity corresponding to the least significant digit shall not exceed the 
quantity of gas passed during one hour at Qmin. 
If the least significant digit shows a decimal multiple of the quantity measured, the 
faceplate or electronic display shall bear:  
(1) either one (or two, or three, etc.) fixed zero(s) after the last drum or digit; or  
(2) the marking: "× 10" (or "×  100", or "× 1 000", etc.),   
so that the reading is indicated in SI units or other units permitted by the competent 
metrology authority . CNPA 137    Page 16 of 57 pages  
 4.3.4  Mechanical indicating device  
The minimum height of the numerals shall be 4.0 mm and their minimum width 
shall be 2.4 mm.  
The last element (i.e. the decade with the least significant scale interval) of a 
mechanical indicating device may deviate in manner of display from the other 
decades.  
In the case of drum indicating devices the advance by one unit of a figure of an y 
order shall take place completely while the figure of an order which is immediately 
below passes through the last tenth of its course.  
4.3.5  Electromechanical or electronic indicating device  
The continuous display of the quantity of gas during the period  of measurement is 
not mandatory. The electronic indicating device shall be provided with a display 
test. 
4.3.6  Remote indicating device  
If an indicating device is used remotely, the associated gas meter shall be clearly 
identified by their serial number s. The integrity of the communication between the 
instrument and the indicating device shall be checked.  
4.4 Test element of indicating device  
4.4.1 General  
A gas meter shall be designed and constructed incorporating:  
(1) an integral test element, or  
(2) a pulse generator, or  
(3) arrangements permitting the connection of a portable test unit.  
4.4.2 Integral test element  
The integral test element may consist of the last element of the mechanical 
indicating device in one of the following forms:  
(1) a continuous ly moving drum bearing a scale, where each subdivision on the 
drum is regarded as an increment of the test element;  
(2) a pointer moving over a fixed dial with a scale, or a disk with a scale moving 
past a fixed reference mark, where each subdivision on th e dial or disk is 
regarded as an increment of the test element.  
4.4.2.1  On the numbered scale of a test element the value of one complete revolution 
of the pointer shall be indicated in the form: "1 rev = … m3 (or dm3)". The 
beginning of the scale shall be  indicated by the figure zero.  
4.4.2.2  The scale spacing shall not be less than 1 mm and shall be constant  
throughout the whole scale.  
4.4.2.3  The scale interval shall be in the form 1 × 10n, 2 × 10n, or 5 × 10n m3 (n 
being a positive or negative whole num ber or zero).  CNPA 137    Page 17 of 57 pages  
 4.4.2.4  The scale marks shall be fine and uniformly drawn.  
4.4.2.5  The test element may be provided with a scale mark which stands out in 
contrast to the scale and is of sufficient size to allow automatic photoelectric 
scanning. The scale mar k shall not obscure the graduation. If proper, the 
index mark can replace “zero” value. And its presence shall not be 
detrimental to the accuracy of reading.  
4.4.2.6 For electronic indicating device the last digit is used as the integral test 
element.  Thro ugh either physical or electronic means a specific test mode 
may be entered in which the number of digits can be increased or some 
alternative method can be applied for gaining resolution.  
4.4.3 Pulse generator  
A pulse generator may be used as a test eleme nt if the value of one pulse, 
expressed in units of volume, is marked on the gas meter.  
The gas meter shall be constructed in such a way that the pulse value can be 
checked experimentally. The difference between the measured value of the pulse 
value and it s value indicated on the gas meter, shall not exceed 0.05 % of the latter.  
4.4.4  Attachable test device  
An indicating device may include provisions for testing by inclusion of 
complementary elements (e.g. star wheels or discs), which provide signals for an  
attachable test device.  The attachable test device may be used as a test element if 
the value of one pulse, expressed in units of volume, is marked on the gas meter.  
4.4.5  Increment of test element or pulse  
The increment of the test element or pulse shall  occur at least every 60 seconds at 
Qmin. 
4.5 Ancillary device  
The gas meter may include ancillary devices, which may be permanently incorporated or 
added temporarily.  Ancillary devices shall not affect the correct operation of the 
instrument. If an ancill ary device is not subject to legal metrology control it shall be 
clearly indicated.  
4.6 Power sources  
4.6.1  Types of power sources  
Gas meters may be powered by  mains power sources,  non-replaceable power 
sources, or  replaceable power sources.  These three ty pes of power source may be 
used alone or in combination.  
The rechargeable power sources are considered replaceable.  
4.6.2  Mains power  source  
An electronic gas meter shall be designed such that in the event of a mains power 
failure (AC or DC), the meter ind ication of the quantity of gas just before failure is 
not lost, and remains accessible for reading after failure without any difficulty.  Any CNPA 137    Page 18 of 57 pages  
 other properties or parameters of the meter shall not be affected by an interruption 
of the electrical supply.  
The connection to the mains power source shall be capable of being secured from 
tampering.  
4.6.3  Non-replaceable power source  
The manufacturer shall ensure that the indicated lifetime of the power source 
guarantees that the meter functions correctly for at lea st as long as the valid ity 
period  of verification  of the meter . The remaining battery capacity in units of time 
can be presented on the electronic indicating device.  
4.6.4  Replaceable power source  
If the gas meter  is powered by a replaceable power source, the manufacturer shall 
give detailed specifications for the replacement thereof.  The date by which the 
power source is to be replaced shall be indicated on the meter. Alternatively, the 
estimated remaining life of the power source shall be displayed or a w arning shall 
be given when the estimated remaining life of the power source is at or below 10 
%. 
The properties and parameters of the meter shall not be affected during 
replacement of the power source. It shall be possible to replace the power source 
witho ut breaking the metrological seal. The compartment of the power source shall 
be capable of being secured from tampering.  
5. Inscriptions  
5.1 Markings and inscriptions  
All markings shall be easily legible and indelible under normal  conditions of use.  
Any ma rking other than those prescribed in the type approval document shall not lead to 
confusion.  
The information given in Section  5.1.1 shall be marked on the casing or on an 
identification plate.  
5.1.1  General applicable markings for gas meters  include:  
(1) type approval number;  
(2) name of the manufacturer;  
(3) type number and serial number;  
(4) metrological gas name;  
(5) accuracy class  (other than class 1.5 ) ; 
(6) maximum flow rate : expressed  as Qmax = …m3 / h; 
(7) minimum flow rate : expressed  as Qmin = …m3 / h; 
(8) transition al flow rate : expressed  as Qt = …m3 / h, other than being  equal to 0.1 
Qmax; CNPA 137    Page 19 of 57 pages  
 (9) working temperature range : expressed  as tmin – tmax = … - …℃ or tm = … 
- …℃ ; 
(10) working pressure range: expressed  as Pmin – Pmax = … - …kPa or Pm = … 
- …kPa; 
(11) pulse values of HF and LF outputs : expressed  as L / pulse  (dm3 / pulse or  m3 / 
pulse) or pulse / L (pulse / dm3, or pulse / m3). The pulse value is gi ven to at 
least 4 significant figures, unless it is equal to an integer multiple or decimal 
fraction of the used unit.  
(12) indication of the flow direction : expressed  by an arrow  symbol.  
(13) year of manufacture: expressed by 4 digits of the year of C.E. , or year of the 
Republic Era;  
(14) the normal value of the cyclic volume: expressed as V = …dm3 (or m3); 
(15) the maximum permissible pressure deviation between meter inlet and outlet: 
expresses as Pmax = …Pa (or kPa);  
(16) the nominal diameter (inside di ameter of inlet and outlet): expressed by mm.  
5.1.2  Additional markings for gas meters with electronic indicating devices  
(1) for an external power supply: the nominal voltage and nominal frequency;  
(2) for a non -replaceable power source: the operational l ifetime of the measuring 
device or, alternatively, the remaining battery capacity in units of time can be 
presented on the electronic indicating device;  
(3) for a replaceable battery: the latest date by which the battery is to be replaced or, 
alternatively , the remaining battery capacity can be presented on the electronic 
indicating device  (In case an automatic alarm indicates when the battery life is 
below 10 %, the above markings are not required ); 
(4) software identification of the firmware.  
6. Operating  instructions  
6.1 Instruction manual  
Each individual gas meter  shall be accompanied by an instruction manual in traditional 
Chinese for the user.  
The instruction manual shall  include:  
(1) operating instructions ; 
(2) m aximum and minimum storage temperatures ; 
(3) rated operating conditions ; 
(4) all relevant mechanical and electromagnetic environmental conditions ; 
(5) any specific installation conditions, for instance a limitation of the length of signal, 
data, and control lines ; 
(6) the specifications of the battery , if applicable ; 
(7) instructions for installation, maintenance, repair, storage, transport and permissible CNPA 137    Page 20 of 57 pages  
 adjustments , if applicable ; 
(8) conditions for compatibility with interfaces, sub -assemblies (modules) or other 
measuring instruments.  
6.2 Installation conditions  
The manufacturer shall specify the installation conditions (as applicable) with respect to:  
(1) the position to measure the working temperature of the gas ; 
(2) leveling and orientation ; 
(3) pulsed interference ; 
(4) rapid pressure chan ges; 
(5) mounting instructions ; 
(6) other relevant installation conditions.  
7. Sealing  
7.1 Verification marks and protection devices  
7.1.1  General provision  
Protection of the metrological properties of the meter is accomplished via hardware 
(mechanical) se aling or via electronic sealing.  Memorized quantities of gas volume  
measured shall be sealed to prevent unauthorized access.  
7.1.2  Verification marks  
Verification marks indicate that the gas meter has passed the verification.  
7.1.3  Hardware sealing (if app licable)  
In case of hardware sealing, the location of the marks shall be chosen in such a way 
that the dismantling of the part sealed by one of these marks results in permanently 
visible damage to this seal.   
Seals shall be able to withstand outdoor condit ions without any embrittlement. The 
embossing text should be easily identifiable . 
7.1.4  Electronic sealing (if applicable)  
7.1.4.1 When the access to parameters that contribute in the determination of 
results of measurements needs to be protected, and elec tronic sealing is 
permitted by competent metrology authorit y, the protection shall fulfill the 
following provisions:  
(1) Only authorized people are allowed to enter the configuration mode to 
modify these parameters using securing means such as a code 
(pass word) or special device (hard key) . 
- For access prior to changing the parameters, after which the 
instrument may be put into use “in sealed condition” again without 
any restriction, or  
- for confirmation after the parameters have been changed, in order to  
bring the instrument back into service being the “in sealed CNPA 137    Page 21 of 57 pages  
 condition” (similar to classical sealing).  
(2) The code (password) shall be alterable.  
(3) The device shall either clearly indicate when it is in the configuration 
mode (not under legal metrologi cal control), or it shall not operate 
while in this mode. This status shall remain until the instrument has 
been put into use “in sealed condition” in accordance with clause ( 1). 
(4) Identification data concerning the most recent intervention shall be 
recorded in an event logger. The record shall include at least:  
- an identification of the authorized person that implemented the 
intervention, and  
- an event counter or date and time of the intervention as generated by 
the internal clock.  
In addition to the a bove -mentioned data the following data is to be 
stored:  
- the old value of the changed parameter, and  
- the totals of the registers.  
The traceability of the most recent intervention shall be assured. If it is 
possible to store the records of more than one intervention, and if deletion 
of a previous intervention must occur to permit a new record, the oldest 
record shall be deleted.  
7.1.4.2  For gas meters of which parts may be disconnected, the following 
provisions shall be fulfilled:  
(1) Access to the parame ters that contribute to the determination of results 
of measurements shall not be possible via a disconnected port unless 
the provisions in Section  7.1.4 are fulfilled.  
(2) Interposing any device which may influence the accuracy shall be 
prevented by means  of electronic and data processing securities or, if 
not possible, by mechanical means.  
(3) Moreover, these gas meters shall be equipped with provisions which do 
not allow the meter to operate if the various parts are not configured 
according to the manufa cturer’s specifications.  
8. Metrological controls  
8.1 General procedures  
8.1.1 Test method  
All tests shall be carried out under the installation conditions stipulated by the 
supplier of the type of meter to be tested.  
All equipment used and incorporated as  part of the execution of the test procedure 
shall be suitable for the testing of the meter(s) under test. The working range of all 
equipment and reference standards shall equal or exceed that of the meter(s) under 
test. All reference standards used shall be traceable to national or international CNPA 137    Page 22 of 57 pages  
 standards of measurement.  
If meters are to be tested in series, there should be no significant interaction 
between the meters. This condition may be verified by testing every meter of the 
series once at each positi on in the line.  
During the tests corrections shall be made for temperature and pressure differences 
between the meter(s) under test and the reference standard; otherwise these 
differences have to be taken into account in the uncertainty calculations.  
The t emperature and pressure measurements have to be performed at a 
representative position on the meter(s) under test and on the reference standard.  
8.1.2 Uncertainty  
When a test is conducted for type evaluation, the expanded uncertainty (U) of the 
determinati on of errors of the measured gas quantity shall be less than one -fifth of 
the applicable MPE . However, if the above -mentioned criteria cannot be met, the 
test results can be approved alternatively by reducing the applied maximum 
permissible errors with the  excess of the uncertainties. For type evaluation the 
acceptance criteria ± (6/5 ⋅MPE −U) shall be used . 
The estimation of the expanded uncertainty U is made according to OIML G 1 -100: 
2008  Guide to the expression of uncertainty in measurement  (GUM) with a  level of 
confidence of 95 %.  
9. Type evaluation  
9.1 General  provision  
A submitted type of gas meter is subject to the type evaluation procedure.  
A type approval certificate is issued only for the complete gas meter.  
9.2 Documentation  
Applications for type  evaluation of a gas meter shall be accompanied by the following 
documentation:  
(1) Identification of the type, including:  
- name of the manufacturer and type designation;  
- version(s) of hardware and software , if applicable ; 
- drawing of name plate  with d escription or sample image.  
(2) Metrological characteristics of the meter, including:  
- description of the principle(s) of measurement;  
- metrological specifications such as accuracy class and rated operating conditions  
(ambient temperature , ambient relati ve humidity , vibration, DC mains voltage , flow 
rate and working pressure, etc ); 
- any steps which should be performed prior to testing the meter.  
(3) The technical specification for the meter, including:  
- a structural dimension  drawing , including dimensio n drawing of gas meters and their CNPA 137    Page 23 of 57 pages  
 critical components;  
- a list of parts with description of constituent materials  and quantities  of such parts ; 
- a perspective drawing of the meter, including identification of the listed parts ; 
- a drawing of indicating d evice , including  its adjustment mechanism ; 
- a drawing of the attachable  devices, if applicable;  
- a table setting out the characteristics of the drive shafts , if applicable ; 
- a list of electronic components with their essential characteristics , if applic able;  
- a description of electronic devices, including appearance, operating diagrams, 
software structure and brief explaination of their practice , if applicable;  
- a description of the type and location for verification marks and seals or other 
protective  methods;  
- a documentation related to durability characteristics  (optional) ; 
- any document or other evidence that supports the assumption that the design and 
construction of the meter complies with the requirements of This Specification . 
(4) User manual . 
(5) Installation manual . 
9.3 Design inspection  
Each type of gas meter submitted shall be inspected externally to ensure that it complies 
with the provisions of the relevant preceding clauses of these requirements ( Section  3, 4,  
5, 6 and 7). 
9.4 Number of  specimens  
The applicant shall deliver the requested number of specimens of gas meters at the 
disposal of the authority responsible for type evaluation.  
If so requested by the authority responsible for the type evaluation, these meters shall 
include more t han one size if simultaneous approval of a family of gas meters is 
requested.  
Depending on the demand  for tests, the authority responsible for the type evaluation may 
request further specimens.  
In order to accelerate the test procedure, the testing laborat ory may carry out different 
tests simultaneously on different units. In this case, the testing laboratory shall ensure 
that all submitted instruments are of the same type.  
In general all accuracy and influence tests shall be performed on the same unit, but  
disturbance tests may be carried out on additional instruments. In this case, the testing 
laboratory decides which test(s) to be carried out on which unit.  
If a specimen does not pass a specific test and as a result needs to be modified or repaired, 
the a pplicant shall apply this modification to all the specimens submitted for the test.  
These modified specimen(s) shall again be subjected to this particular test.  
If the testing laboratory has well -founded reasons to believe that the modification could CNPA 137    Page 24 of 57 pages  
 have a negative impact on the result of another test or tests already performed, these tests 
shall be repeated as well.  
9.5 Type evaluation procedure  
9.5.1 Hardware evaluation  
9.5.1.1 Reference conditions  
All influence quantities, except for the influence quant ity being tested, shall 
be kept to the following values during type evaluation tests on a gas meter  
(but high pressure tests may be performed at conditions other than reference 
conditions ): 
Working (gas/air) temperature  20.0 ℃ ± 5.0 ℃  
Ambient temperature  20.0 ℃ ± 5.0 ℃  
Ambient atmospheric pressure  86 kPa – 106 kPa  
Ambient relative humidity  60 % ± 25 %  
Power voltage (AC/DC mains)  If one nominal voltage is specified, it is the 
specified nominal voltage ( Unom). 
If a vo ltage range is specified, it is a typical 
voltage within this range, to be negotiated 
between the manufacturer and the test laboratory  
Power voltage (battery)  The nominal voltage of a new or fully charged 
battery (not under charge)  
Power frequency (AC ma ins) The nominal frequency ( fnom) 
9.5.1.2 Flow rates  
The flow rates at which the errors of the gas meters need to be determined 
shall be distributed over the measuring range at regular intervals and 
include Qmin and Qmax and preferably Qt. 
The minimum num ber ( N) of test points can be calculated according to:  
 
 
 




minmaxlog31QQN  
Where N ≥ 6, and rounded to the nearest integer.  
Each individual test point can be calculated according to:  
 
 
m ax13
i 10 Q Qi
 
Where i = 1 to i = N-1, and QN = Qmin 
9.5.1.3 Test gases  
All the tests listed in Secti on 9.6 are performed with air under the rated 
operating conditions stated in Section  3.1. For the temperature tests in 
Section  9.6.5 the gas must be dry.  
9.6 Type evaluation tests  CNPA 137    Page 25 of 57 pages  
 During the type evaluation gas meters are tested while applying the requirem ents as 
stated in Section  3. 
9.6.1  Error  
The error of the gas meter shall be determined, while using the flow rates 
according to the prescriptions stated in Section  9.5.1.2. The error curve as well as 
the WME shall be within the requirements as specified i n Section  3.3 and Section  
3.4 respectively.  
During the accuracy test applied on the gas meter, the following quantities shall be 
determined:  
- The pulse value  of the gas meter (if applicable ): the gas meter shall be 
constructed in such a way that the puls e value can be checked experimentally. 
The difference between the measured value of the pulse value and its value 
indicated on the gas meter, shall not exceed 0.05 % of the latter.  
9.6.2  Reproducibility  
The tests are conducted at flow rates prescribed in S ection 9.5.1.2. The 
reproducibility of error at flow rate s equal to or greater than Qt shall be less than or 
equal to one third of the maximum permissible error.  
For each of these flow rates, the errors shall normally be determined six times 
independently,  while varying the flow rate betwe en each consecutive measurement . 
The reproducibility of error  is calculated as the difference between the maximum 
and the minimum measured  error for each flow rate .  
In case the reproducibility of error of the first three measurements is less than or 
equal to one sixth  of the MPE the requirement is deemed to be met.  
9.6.3  Repeatability  
The repeatability of error is determined at the flow rates Qmin, Qt, and Qmax. At each 
of these flow rates, the errors are determined three times without changing the flow 
rate and the difference between the minimum and maximum measured error is 
calculated  as the repeatability of error  which shall be less than or equal to one third 
of the maximum permissible error.  
9.6.4  Working pressure  
The a ccuracy measurements  under different  working pressure are evaluated with 
the requirements as laid down in Section 3.7  and Annex C “The requirements of 
additional tests for diaphragm gas meters with maximum working pressure more 
than 10 kPa ”. The requiremen ts shall be fulfilled for the operating pressure range 
without intermediate adjustments . 
9.6.5  Temperature  
The temperature dependency of the gas meter shall be evaluated within the 
temperature range specified by the manufacturer. Flow tests at different 
temperatures are performed with a gas temperature equal to the ambient 
temperature as specified in Section 9.6.5.1.  
9.6.5.1 Flow tests with equal gas and ambient temperatures  CNPA 137    Page 26 of 57 pages  
 The flow tests as determined in Section 9.5.1.2 are performed, in the range 
Qt up to Qmax, with the gas temperature equal to the ambient temperature 
(within 5 ℃), sequentially at:  
- reference temperature;  
- maximum ambient temperature;  
- minimum ambient temperature;  
- reference temperature.  
The test results shall comply with the corresponding requirements of error 
for the accuracy class of the gas meter . 
9.6.6  Durability  
All gas meters with internal moving parts are submitted to the durability test  which 
comprises exposure to a continuous flow during the required period of time, while 
using gases for which the meters are intended to be used.  
In case the manufactu rer has demonstrated that the material composition of the gas 
meter is sufficiently insensitive to the gas composition, the authority responsible 
for the type evaluation may decide to perform the durability test with air or another 
suitable type of gas. Th e applied flow rate is at least 0.8  Qmax. This test shall be 
performed at the working pressure  prescribed in relevant sections of This 
Specification, besides the same reference equipment shall be used  before and after 
the test.  
The authority responsible fo r the type evaluation shall choose the number of meters 
of the same type to be submitted for the durability test from the options given in 
Table 9 in consultation with the applicant  (option 1) . If different sizes are included, 
the total number of meters to  be submitted shall be as stated in option 2.  
In case the application for evaluation concerns a family of meters according to the 
criteria stated in Annex D (D .2) the selection of meters is to be performed 
according to D .3. 
Table 9 Number of meters to be t ested  
Maximum volume flow 
rate [m3/h] Number of meters to be tested  
Option 1  Option 2  
Qmax ≤ 25 3 6 
25 < Qmax ≤ 100 2 4 
Qmax > 100  1 3 
After the durability test the gas meters are tested for errors at flow rates as 
determined in Section 9.5.1.2. The measured errors  shall comply with the 
requirements laid down in Section 3.10 (with the excepti on of one of them if the 
durability test has been carried out on a number of gas meters according to option 
2). 
9.6.7  Overload flow  
Gas meters with internal moving parts are submitted to the overload flow. Before CNPA 137    Page 27 of 57 pages  
 and after the overload the error of the gas  meter is determined for its whole flow 
rate range according to Section 9.5.1.2. The requirements as laid down in Section 
3.11 are applicable.  
9.6.8  Vibration and shocks  
Gas meters having a maximum mass of 10 kg are submitted to vibrations and 
shocks. For gas meters exceeding this weight only the electronic part of the meter 
is to be tested. Before and after these tests the intrinsic error of the gas meter is 
determined according to Section 9.5.1.2 over the whole flow rate range.  The 
requirements as laid do wn in Section 3.12 are applicable.  
9.6.9  Gas meters containing electronic components  
For gas meters containing electronic components, additionally the requirements as 
described in Section 3.13.1 are applicable. Performance tests shall be executed 
using the  test methods described in Section 8  “Metrological controls ” and Section 
9 “Type evaluation ”. An overview of the requirements is shown in Table 5 and 
Table 6. After each test it shall be verified that no loss of data has occurred.  
If the electronic devices  of a gas meter are located in a separate housing, their 
electronic functions may be tested independently of the measuring transducer of 
the gas meter by simulated signals representing the rated operating conditions of 
the meter. In this case the electroni c devices shall be tested in their final housing.   
In all cases, ancillary equipment may be tested separately.  
The tests as indicated in Table 5 and Table 6 are to be performed with t he meter 
under test being  powered up  and t he dependency of the gas meter’ s performance 
shall be evaluated  during actual flow . 
9.6.10  Influences from ancillary devices  
The effect of all functions of ancillary devices is determined by performing an 
accuracy test at Qmin, with and without applying the specific function. The effect  
shall be negligible if the test result is less than or equal to  0.1 MPE.  
9.7 Type approval certficate  
The following information and data shall appear on the type approval certificate:  
- name and address of the  applicant;  
- name and address of the manufact urer;  
- type of the gas meter and/or trade mark ; 
- principal metrological and technical characteristics, including  accuracy class, values of 
Qmax, Qmin and Qt, the rated operating conditions ( Section 3.1), nominal internal 
diameter of the connecting pieces  and the nominal value of the cyclic volume , etc; 
- type approval mark;  
- period of validity of the type approval;  
- information on the location of the marks and inscriptions required in Section 5.1, initial 
verification marks and seals (where applicable, in the form of photographs or 
drawings);  CNPA 137    Page 28 of 57 pages  
 - list of the documents accompanying the type approval certificate;  
- any special comments.  
10. Implementation date  
This Specification will be implemented from July 1, 2023 , and for diaphragm gas  meters 
containing e lectronic components  from January 1, 2026 ; the correction period ends on 
December 31, 2027 . 
 CNPA 137    Page 29 of 57 pages  
 Annex A  
Environmental tests for electronic instruments or devices (mandatory)  
A.1 General  
This annex defines the program of performance tests intended to verify t hat gas meters 
containing electronics and their ancillary devices may perform and function as intended 
in a specified environment and under specified conditions. Each test indicates, where 
appropriate, the reference conditions for determining the error.  
These tests supplement any other prescribed tests.  When the effect of one influence 
quantity is being evaluated, all other influence quantities are to be kept within the limits 
of the reference conditions.  
A.2 Test conditions  
For each performance test, typic al test conditions are indicated. These correspond to the 
climatic and mechanical environment conditions to which instruments are usually 
exposed. The competent metrolog y authority carries out performance tests at the test 
levels corresponding to these env ironmental conditions.  
A.3 Reference conditions  
Conditions described in  Section 9.5.1.1.  
A.4 Performance tests (climatic)  
A.4.1 Static temperatures  
A.4.1.1 Dry heat (non condensing): influence test  
Applicable standards  IEC 60068 -2-2 (2007 -07) 
Object of t he test  
 Verification of compliance under conditions of high environmental 
temperature.  
Test procedure in 
brief  
 The test comprises exposure to the specified high temperature under 
atmospheric air for the time specified (the time specified is the time 
after the EUT has reached temperature stability).  
The change of temperature shall not exceed 1  ℃/min during heating 
up and cooling down.  
The absolute humidity of the test atmosphere shall not exceed 20 
g/m3.  
When testing is performed at temperatures lower th an 35 ℃, the 
relative humidity shall not exceed 50 %.  
Temperature  upper temperature specified  ℃ 
Duration  2 h 
 
A.4.1.2 Cold: influence test  
Applicable standards  IEC 60068 -2-1 (2007 -03) 
Object of the test   Verification of compliance under conditions of low environmental 
temperature.  
Test procedure in 
brief  The test comprises exposure to the specified low temperature under 
atmospheric  air for the time specified (the time specified is the time CNPA 137    Page 30 of 57 pages  
 after the EUT has reached temperature stability).   
The change  of temperature shall not exceed 1 ℃/min during heating 
up and cooling down.   
The power to the EUT shall be switched off before the temperature is 
raised.  
Temperature  lower temperature specified  ℃ 
Duration  2 h 
A.4.2 Damp heat  
A.4.2.1 Damp heat, steady -state (non condensing): influence te st 
Applicable standards  IEC 60068 -2-78 (2001 -08) 
Object of the test  Verification of compliance under conditions of high environmental 
humidity and constant temperature .  
Test procedure in 
brief  The test comprises exposure to the specified temperature  and the 
specified constant relative humidity for a certain fixed period of time. 
The EUT shall be handled such that no condensation of water occurs 
on it.  
The gas meter shall be subjected 3 times to an accuracy test:  
- at reference conditions, before the  increase of temperature;  
- at the end of the upper temperature phase;  
- at reference conditions, 24 hours after the decrease of temperature.  
Temperature  Upper temperature specified   ℃ 
Relative humidity 
(RH)  93 % 
Duration  4 Days  
 
A.4.2.2 Damp heat, cy clic (condensing): disturbance test  
Applicable standards  IEC 60068 -2-30 (2005 -08) 
Object of the test   Verification of compliance under conditions of high environmental 
humidity combined with cyclic temperature changes . 
Test procedure in 
brief  
 The tes t comprises exposure to cyclic temperature variation between 
25 ℃ and the appropriate upper temperature while maintaining the 
relative humidity above 95 % during the temperature change and low 
temperature phases, and at or above 93 % at the upper temperature 
phases.   
Condensation is expected to occur on the EUT during the temperature 
rise.  
The 24 hours cycle consists of:   
- Temperature rise during 3 hours.   
- Temperature maintained at upper temperature level until 12 hours 
from the start of the cycle.   
- Temperature lowered to the lower temperature level within a perio d 
of 3 to 6 hours, the rate of fall during the first hour and a half being 
such that the lower temperature level would be reached in 3 hours.   
- Temperature maintained at lower temperature level until the 24 CNPA 137    Page 31 of 57 pages  
 hours cycle is completed.  
The stabilizing period  before and recovery period after the cyclic 
exposure shall be such that the temperature of all parts of the EUT is 
within 3 ℃ of its final value.   
During the test the instrument is switched on; gas flow is not required.   
The gas meter shall be subjected t o an accuracy test both:   
- at reference conditions, before the increase of temperature and  
- at reference conditions, at least 4 hours after the last cycle.  
Temperature   upper temperature specified   ℃ 
Duration   2 cycles   
A.5 Performance tests (mechanic al) 
A.5.1 Vibration (random): disturbance test  
Applicable standards  IEC 60068 -2-47(2005 -04), IEC 60068 -2-64 (2008 -04) 
Object of the test  Verification of compliance under conditions of random vibration  
Test procedure in 
brief  The test comprises exposu re to the level of vibration for the time 
specified. The EUT shall, subsequently, be tested in three, mutually 
perpendicular axes mounted on a rigid fixture by its normal mounting 
means.   
The EUT shall normally be mounted in such a way that the gravity 
vector points in the same direction as it would do in normal use.   
Where, based on the metering principle the effect of gravitational 
force can be assumed negligible the EUT may be mounted in any 
position.   
During the test the instrument is not required to be  powered up 
(switched on).  
Total frequency 
range   10 Hz – 150 Hz  
Total RMS level  7 m· s-2 
ASD level   
10 Hz－20 Hz  1 m2·s-3 
ASD level  
20 Hz－150 Hz  -3 dB  / octave  
Number of axes  3 
Duration per axis   2 minutes   
 
A.5.2 Mechanical shock: disturbance test  
Applicable standards  IEC 60068 -2-31 (2008 -05) 
Object of the test  Verification of compliance under cond itions of mechanical shocks  
Test procedure in 
brief  The EUT, placed in its normal position of use on a rigid surface, is 
tilted towards one bottom edge and is then allowed to fall freely onto 
the test surface.  
The height of fall is the distance between the opposite edge and the 
test surface.  
However, the angle made by the bottom and the test surface shall not CNPA 137    Page 32 of 57 pages  
 exceed 30°.   
During the test the instrument is not powered up.  
Height of fall  50 mm  
Number of falls ( on 
each bottom edge)  1 
A.6 Performance  tests (electrical, general)  
A.6.1 Radio frequency immunity tests  
A.6.1.1 Radiated, RF, electromagnetic fields: disturbance test  
Applicable standards  IEC 61000 -4-3 (2010 -04) 
Object of the test  Verification of compliance of the EUT while being exposed to RF 
electromagnetic fields.   
Test procedure in 
brief  The EUT is exposed to electromagnetic fields having the required 
field strength level specified and the field uniformity as defined in the 
referred standard.   
The EUT shall be exposed to the modulate d wave field. The 
frequency sweep shall be performed only pausing to adjust the RF 
signal level or to switch RF -generators, amplifiers and antennas if 
necessary.   
Where the frequency range is swept incrementally, the step size shall 
not exceed 1 % of the p receding frequency value.   
The dwell time of the amplitude modulated carrier at each frequency 
shall not be less than the time necessary for the EUT to be exercised 
and to respond, but shall in no case be less than 0.5 s.  
The expected most critical frequen cies (e.g. clock frequencies) shall 
be analyzed separately.  
Frequency range  80 MHz – 3 GHz  
Field strength  10 V/m  
Modulation  80 % AM, 1 kHz, sine wave  
 
A.6.1.2 Conducted radio -frequency fields: disturbance  test 
Applicable standards   IEC 61000 -4-6 (2008-10) 
Object of the test   Verification of compliance of the EUT while being exposed to RF 
electromagnetic fields  
Test procedure in 
brief  Radio frequency EM current, simulating the influence of EM fields 
shall be coupled or injected into the power ports  and I/O ports of the 
EUT using coupling/decoupling devices as defined in the referred 
standard.   
The performance of the test equipment consisting of an RF generator, 
(de-)coupling devices, attenuators, etc. shall be verified.   
RF amplitude (50 Ω)  10 V (e .m.f)  
Frequency range   0.15 MHz  – 80 MHz  
Modulation   80 % AM, 1 kHz , sine wave   
 CNPA 137    Page 33 of 57 pages  
 A.6.2 Electrostatic discharge: disturbance test  
Applicable standards  IEC 61000 -4-2 (2008 -12) 
Object of the test  Verification of compliance in case of direct exposure to  discharging 
of electrostatic charged objects or persons on the EUT of such 
discharges in the neighborhood of the EUT . 
Test procedure in 
brief  An ESD generator as defined in the referred standard shall be used 
and the test setup shall comply with the dim ensions, materials used 
and conditions as specified in this standard.   
Before starting the tests, the performance of the generator shall be 
verified.  
At each pre -selected discharge location on the EUT at least 10 
discharges shall be applied. The time inte rval between successive 
discharges shall be at least 1 second. For EUTs not equipped with a 
ground terminal, the EUT shall be fully discharged between the 
discharges applied using the ESD generator.   
Contact discharge is the preferred test method. Air disc harges are less 
reproducible and therefore shall be used only where contact discharge 
cannot be applied.   
Direct application:   
In the contact discharge mode to be carried out on conductive 
surfaces, the electrode shall be in contact with the EUT.   
In the a ir discharge mode on insulated surfaces, the electrode is 
approached to the EUT and the discharge occurs by spark.   
Indirect application:   
The discharges are applied in the contact mode to coupling planes 
mounted in the vicinity of the EUT.   
Test voltage   Contact discharge   6 kV  
Air di scharge   8 kV  
 
A.6.3 Burst (transients) on signal , data and control lines: disturbance test   
Applicable standards  IEC 61000 -4-4 (2012 -04) 
Object of the test  Verification of compliance of the EUT to conditions where el ectrical 
bursts are superimposed on I  / O and communication ports . 
Test procedure in 
brief  A burst generator as defined in the referred standard shall be used.  
The characteristics of the generator shall be verified before 
connecting the EUT.  
The test com prises the exposure to bursts of voltage spikes for which 
the repetition frequency of the impulses and peak values of the output 
voltage on 50 Ω and 1000 Ω load are defined in the referred standard.   
The characteristics of the generator shall be verified b efore 
connecting the EUT.   
Both positive and negative polarity of the bursts shall be applied.   
The duration of the test shall not be less than 1 min for each 
amplitude and polarity.  
For the coupling of the bursts into the I  / O and communication lines, CNPA 137    Page 34 of 57 pages  
 a capacitive coupling clamp as defined in the standard shall be used.   
The test pulses shall be continuously applied during the measuring 
time.   
Test voltage   Amplitude (peak value)   1 kV  
Repetition rate   5 kHz  
 
A.6.4 Surges on signal, data and control l ines: disturbance test   
Applicable standards   IEC 61000 -4-5 (2005 -11) 
Object of the test   Verification of compliance during conditions where electrical surges 
are superimposed on I/O and communication ports . 
Test procedure in 
brief  A surge generator as  defined  in the referred standard shall be used.  
The characteristics of the generator shall be verified before 
connecting the EUT.  
The test comprises exposure to surges for which the rise time, pulse 
width, peak values of the output voltage/current on high /low 
impedance load and minimum time interval between two successive 
pulses are defined in the referred standard.   
At least 3 positive and 3 negative surges shall be applied.  
The applicable injection network depends on the kind of wiring the 
surge is coupl ed into and is defined in the referred standard.   
The test pulses shall be continuously applied during the measuring 
time.   
Test voltage   Unsymmetrical 
lines  Line to line: 0.5 kV  Line to ground: 1.0 kV  
Symmetrical 
lines  Line to line: N/A  Line to ground : 1.0 kV  
Shielded I/O and 
communication 
lines  Line to line: N/A   Line to ground: 0.5 kV  
A.7 Performance tests (electrical, mains power)  
A.7.1 DC mains voltage variation: influence test  
Applicable standards  IEC 60654 -2 (1979 -01) 
Object of the test  Verification of compliance during conditions of DC mains network 
changes between upper and lower limit.  
Test procedure in 
brief  The test comprises exposure to the specified power supply condition 
for a period sufficient for achieving temperature stabilit y and 
subsequently performing the required measurements.   
Test severity  The upper limit is the DC level at which the EUT is claimed and 
proven to have been manufactured to automatically detect high -level 
conditions.   
The lower limit is the DC level at wh ich the EUT is claimed and 
proven to have been manufactured to automatically detect low -level 
conditions.   
The instrument shall comply with the specified maximum permissible CNPA 137    Page 35 of 57 pages  
 error at supply voltage levels between the two levels.   
 
A.7.2 AC mains voltage v ariation: influence test  
Applicable standards  IEC/TR 61000 -2-1 (1990 -05) 
Object of the test  Verification of compliance during conditions of AC mains network 
voltage changes between upper and lower limit.  
Test procedure in 
brief  The test comprises ex posure to the specified power condition for a 
period sufficient for achieving temperature stability and for 
performing the required measurements.   
Mains voltage (1), (2)  upper limit   Unom + 10 %  
lower limit   Unom - 15 %  
Notes   (1) In the case of three -phase power supply, the voltage variation shall 
apply for each phase successively.   
(2) The values of U are those marked on the measuring instrument.  
In case a range is specified, the “ -” relates to the lowest value and 
the “+” to the highest value of the  range.   
 
A.7.3 AC mains voltage dips and short interruptions: disturbance test   
Applicable standards   IEC 61000 -4-11 (2004 -03), IEC 61000 -6-1 (2005 -03), IEC 
61000 -6-2 (2005 -01) 
Object of the test   Verification of compliance during conditions of short t ime mains 
voltage reductions . 
Test procedure in 
brief  A test generator is to be used which is suitable to reduce the 
amplitude of the AC mains voltage for the required period of time.   
The performance of the test generator shall be verified before 
connec ting the EUT.   
The mains voltage reduction tests shall be repeated 10 times with 
intervals of at least 10 seconds between the tests.   
The test pulses shall be continuously applied during the measuring 
time.   
Test severity   test a  test b  test c  test d  test e Unit 
V oltage reduction   Reduction to   0 0 40 70 80 % 
Duration   0.5 1 12(1) 30(1) 300(1) cycle  
Notes   (1) These values are for 60 Hz.   
(2) All 5 tests (a, b, c, d and e) are applicable; it is possible that any of 
the tests fail while the other tests pass.   
 
A.7.4 V oltage dips, short interruptions and voltage variations on DC mains power: 
disturbance test   
Applicable standards   IEC 61000 -4-29 (2000 -08) 
Object of the test   Verification of compliance during conditions of DC mains 
voltage dips, variati ons and short time reductions . 
Test procedure in brief   A test generator as defined in the referred standard shall be 
used.   CNPA 137    Page 36 of 57 pages  
 Before starting the tests, the performance characteristics of 
the generator shall be verified.   
The EUT shall be exposed to voltag e dips and short 
interruptions for each of the selected combinations of 
amplitude and duration, using a sequence of three 
dips/interruptions and intervals of at least 10 seconds 
between each test event.   
The most common operating modes of the EUT shall be 
tested three times at 10 second intervals for each of the 
specified voltage variations.   
If the EUT is an integrating instrument, the test pulses shall 
be continuously applied during the measuring time.   
Test severity level  The following levels shall be 
applied:   Unit  
V oltage dips  Amplitude  40 and 70  % of the rated voltage  
Duration(1) 10; 30; 100  ms 
Short 
interruptions(1)  Test 
condition   High impedance and/or low 
impedance    
Amplitude   0 % of the rated voltage   
Duration(1)  1; 3; 10  ms 
V oltage 
variations  Amplitude  85 and 120  % of the rated voltage  
Duration(1)  0.1; 0.3; 1; 3; 10  s 
Notes   (1) all intervals are to be tested . 
 
A.7.5 Burst (transients) on AC and DC mains: disturbance test  
Applicable standards  IEC 61000 -4-4 (2012 -04) 
Object of  the test  Verification of compliance during conditions where electrical bursts 
are superimposed on the mains voltage.  
Test procedure in 
brief  A burst generator as defined in the referred standard shall be used.   
The characteristics of the generator shal l be verified before 
connecting the EUT.   
The test comprises exposure to bursts of voltage spikes for which the 
repetition frequency of the impulses and peak values of the output 
voltage on 50 Ω and 1000 Ω loads are defined in the referred 
standard.   
Both positive and negative polarity of the bursts shall be applied.   
The duration of the test shall not be less than 1 min for each 
amplitude and polarity.   
The injection network on the mains shall contain blocking filters to 
prevent the burst energy from being  dissipated in the mains.   
The test pulses shall be continuously applied during the measuring 
time.   
Amplitude  
(peak value)  2 kV  
Repetition rate  5 kHz  CNPA 137    Page 37 of 57 pages  
  
A.7.6 Surges on AC and DC mains: disturbance test  
Applicable standards  IEC 61000 -4-5 (2005 -11) 
Object of the test  Verification of compliance during conditions where electrical surges 
are superimposed on the mains voltage.  
Test procedure in 
brief  A surge generator as defined in the referred standard shall be used.   
The characteristics of the gene rator shall be verified before 
connecting the EUT.   
The test comprises exposure to electrical surges for which the rise 
time, pulse width, peak values of the output voltage/current on 
high/low impedance load and the minimum time interval between 
two succes sive pulses are defined in the referred standard.   
At least 3 positive and 3 negative surges shall be applied.   
On AC mains supply lines, surges shall be synchronous with the AC 
supply frequency and shall be repeated such that injection of surges 
on all th e 4 phase shifts with 0°, 90° , 180° and 270° with the mains 
frequency is covered.   
The injection network circuitry depends on the applicable conductors 
the surge is coupled into and is defined in the referred standard.   
The test pulses shall be continuousl y applied during the measuring 
time.   
Test voltage   Line to line: 1.0 kV   Line to ground: 2.0 kV   
 
A.7.7 Ripple on DC mains power : disturbance test  
Applicable standards   IEC 61000 -4-17 (2009 -01) 
Object of the test   Verification of compliance during co nditions where electrical surges 
are superimposed on the mains voltage . 
Test procedure in 
brief  A test generator as defined in the referred standard shall be used.  
Before starting the tests, the performance of the generator shall be 
verified.   
The test c omprises subjecting the EUT to ripple voltages such as 
those generated by traditional rectifier systems and/or auxiliary 
service battery chargers overlaying on DC power supply sources.  
The frequency of the ripple voltage is the applicable power frequency 
or its multiple (2, 3 or 6), dependent on the rectifier system used for 
the mains. The waveform of the ripple, at the output of the test 
generator, has a sinusoid linear character.   
The test shall be applied for at least 10 min or for the time period 
necess ary to allow a complete verification of the EUT’s operating 
performance.   
Percentage of the 
nominal DC 
voltage(1) 2 
Notes   (1) The test levels are a peak -to-peak voltage expressed as a 
percentage of the nominal DC voltage.   CNPA 137    Page 38 of 57 pages  
 (2) This test does not apply t o instruments connected to battery 
charger systems incorporating switch mode converters.   
A.8 Performance test (battery powered instrument)  
A.8.1 Low voltage of internal battery (not connected to the mains power): influence test  
Applicable standards  There is no reference to standards for this test.  
Object of the test  Verification of compliance during low battery voltage conditions.  
Test procedure in 
brief  The test comprises exposure of the EUT to the specific low battery 
level condition during a peri od sufficient for achieving temperature 
stability and for performing the required measurements.  
The maximum internal impedance of the battery and the minimum 
battery supply voltage level ( Ubmin) are to be specified by the 
manufacturer of the instrument.   
In case of simulating the battery by using an alternative power supply 
source such as in bench testing, the internal impedance of the 
specified type of battery shall also be simulated.   
The alternative power supply shall be capable of delivering sufficient 
current at the applicable supply voltage.   
The test sequence is as follows:   
- Let the power supply stabilize at a voltage as defined within the 
rated operating conditions and apply the measurement and/or 
loading condition.   
- Record:   
(a) the data definin g the actual measurement conditions including 
date, ti me and environmental conditions ;  
(b) the actual power supply voltage.   
- Perform measurements and record the error(s) and other relevant 
performance parameters.   
- Verify compliance with the requiremen ts. 
- Repeat the above procedure with actual supply voltage at Ubmin and 
again at 0.9 Ubmin. 
- Verify compliance with the requirements.   
The maximum internal impedance of the battery is to be specified by 
the manufacturer of the instrument.   
Lower limit o f the 
voltage   The lowest voltage at which the instrument functions properly 
according to the specifications.   
Number of cycles   At least one test cycle for each functional mode.   
 
 
 
 
 
 CNPA 137    Page 39 of 57 pages  
 Annex B  
Type - evaluation tests of safety performance and electromag netic compatibility performance 
for diaphragm gas meter with micro computer  
B.1 G eneral  
This annex  specifies the construction, safety performance and electromagnetic 
compatibility performance requirements and test methods for diaphragm gas meters  with 
micro computer . 
B.2 Construction  
A diaphragm gas meter with micro  computer is composed of a measur ement  unit and a 
safety reference detection control unit. The safety reference detection control unit is 
composed of a flow sensor, a shut -off valve, a pressure s ensor, an seismic sensor, a micro  
computer motherboard for the abnormal state judgment reference, and a lithium battery.  
The gas meter is connected to two external circuits . One of which can be connected to a 
gas leakage alarm  device , an incomplete combust ion alarm  device , etc. ; the other can be 
connected to a communication interface.  
The gas meter housing is equipp ed with a restoration  device or an alarm display  device . 
Its structural diagram is shown in Figure B.1.  
 
 
 
 
 
 
 
 
 
Figure B.1 Structural diagram of a diaphragm gas meter with micro  computer  
B.3 Function  
B.3.1 General function  
(1)When the flow rate exceeding 2 times of the maximum flow rate is detected, the 
gas supply will be cut off immediately.  
(2)When there is gas flowing in the gas meter and the  gas pressure is continuously 
detected to be lower than 0.2 kPa, the gas supply will be cut off immediately.  
(3)When there is gas flowing in the gas meter and a n earthquake  of 250 gal is 
detected at the installation site of the gas meter, the gas supply wi ll be cut off 
immediately.  
(4)When the gas meter detects leakage from the pipelines, valves or appliances 
CNPA 137    Page 40 of 57 pages  
 connected to the outlet, it can display a leakage alarm.  
B.3.2 Safety function: when the measurement unit of the diaphragm gas meter  with micro  
comput er is running, it can continuously monitor the gas usage status. If there is an 
abnormal state, the safety function can be activated, and the gas supply will be 
automatically cut off and the display will give an alarm. These abnormal states 
include:  
(1)Exc essive gas flow.  
(2)Use gas for too long.  
(3)Seismic  sensor actuation.  
(4)Gas pressure is too low.  
(5)A linking -up of the connected gas leakage alarm  device , etc.  
(6)A gas leakage stat us of the  downstream piping system of the gas meter is 
automatically det ected during a restoration  operation.  
It can continuously and automatically detect whether there is gas leakage in the 
downstream piping system of the gas meter, and when it is determined that there is a 
gas leakage, the display will continue to give alarm s until there is no gas leakage.  
B.3.3 Communication function: when the communication interface of the diaphragm  gas 
meter with micro  computer is connected to an external communication circuit of the 
gas meter, it has the following functions:  
(1)Two -way co mmunication  of meter reading.  
(2)One -way communication of automatic notification and alarm.  
(3)Notify the gas usage status.  
(4)Cent ral remote control.  
B.4 Performance  
B.4.1 Watertight resistance  performance : the gas meter housing shall be made of metal or 
non-metal such as synthetic resin, and can prevent the infiltration of water.  
B.4.2 Performance of marking/warning light: the marking/warning light shall be displayed 
in an unambiguous way, and the reason for its action shall be clearly displayed.  
B.4.3 Di splay performance of shut -off valve action status  
B.4.3.1 Be ing able to confirm and display the open and closed status: the gas meter 
should have a marking device to display the open or closed status of the shut -off 
valve. However, this does not apply when  the shut -off valve is closed due to a  
battery voltage  drop. 
B.4.4 Joint performance: the joint of the screw thread with the gas pipeline shall meet the 
requirements of Section B. 6.4. 
B.4.5 Vibration resistance  performance : a final product sh all be able to  withstand the 
vibration during transportation.  
B.4.6 Pressure resistance  performance : for gas meters with a maximum working pressure CNPA 137    Page 41 of 57 pages  
 of less than 10 kPa, the gas passing part sh all be able to withstand a pressure of 15 
kPa; gas meter s with a maximum worki ng pressure of more than 10 kPa sh all be able 
to withstand 1.5 times maximum working pressure.  
B.4.7 Airtight resistance  performance  
B.4.7.1 External airtight  resistance  performance: the gas flowing part shall be airtight, 
and its leakage rate shall be  equal to or  less than 0.07 L/h when subjected to the 
specified pressure.  
B.4.7.2 Internal airtight  resistance  performance: the shut -off valve shall be airtight, and 
its leakage rate shall be  equal to or  less than 0.55 L/h when subjected to the 
specified press ure. 
B.4.8 Durability  
B.4.8.1 Gas meter: the gas meter shall have a service life that can withstand normal use  
circumstance s. 
B.4.8.2 Shut -off valve: under the pressure of 1.5 kPa, the shut -off valve shall be able to 
withstand repeated operations for 500 t imes and still function as well as 
original ly. 
B.4.9 Explosion  resistance  performance : the live part in contact with the gas sh all be 
explosion -proof.  
B.4.10 Magnetic field s resistance  performance : under normal use  circumstance s, the flow 
detection functio n shall not be affected by magnetic fields.  
B.4.11 M ains voltage dips: no obstacle to use due to mains voltage dips . 
B.4.12 Leakage detection performance  
B.4.12.1 Leakage detection capability: a leakage at the connection part of the gas outlet 
of the gas m eter shall be detected while leakage rate equal to or more than 0.003 
m3/h. 
B.4.12.2 Leakage detection activation capability: when the leakage rate at the connection 
part of the gas outlet of the gas meter exceeds 0.003 m3/h and continues to leak 
within 30  days, it sh all be able to automatically display a n alarm  signal . 
B.4.12.3 Leakage alarm display and restoration capability: it shall have the inner pipe 
leak alarm  and restoration function. The alarm  can only be eliminated and 
restored through special too ls or operative setting. F or those with automatic 
restoration function s, they  shall not automatically restore if small leakge s are 
being detected continually . 
B.4.13 Resistance to temperature change s: tha gas meter  shall not be affected by the 
temperature change s under  normal use environment.  
B.4.14 Resistance to humidity change s: the gas meter  shall not be affected by  the humidity  
changes under  normal use environment.  
B.4.15 Abnormal flow  rate shut-off performance  
B.4.15.1 Shut -off of abnormally large flow  rate: under normal use circumstance s, when 
the combined gas flow  rate of gas appliance s is twice  as the maximum flow  CNPA 137    Page 42 of 57 pages  
 rate(abnormally large flow  rate), the gas meter shall be shut off within 2 minutes 
and an alarm shall  be displayed.  
B.4.15.2 Shut -off of individual maximum flow  rate: under normal use circumstance s, 
when the individual gas flow rate of gas appliances is greater than the maximum 
flow rate of the gas meter, the gas meter shall be shut off within 2 minutes and 
an alarm shall  be displayed.  
B.4.15.3 Shut -off of overtime use: under normal use circumstance s, when the continuous 
use time (distinguished by different gas appliances and amount of gas 
consumption) reaches the limited time, the gas meter shall be shut off and an 
alarm shall be displayed.  
B.4.16 Shut -off performance  
B.4.16.1 Earthquake sensing shut -off performance: under normal use circumstance s, 
when an earthquake occurs near the gas meter, the gas  meter  shall be shut off 
and a n alarm  shall be displayed before the earthquake intensity rea ches 250 gal.  
B.4.16.2 Shut -off performance of gas pressure drop: under normal use circumstance s, 
when the gas pressure drops to 0.2 kPa, the gas meter shall  be shut off and a n 
alarm  shall be displayed . 
B.4.16.3 Linking -up shut -off performance of  a gas leakage  alarm  device, etc. : under 
normal use circumstance s, when the gas meter is connected to a gas  leakage  
alarm device or other devices, the device  can be linked up to the gas meter to 
shut off the gas supply and display an alarm.  
B.4.16.4 Shut-off testing  performance: shut -off testing can be performed using special 
tools.  
B.4.17 Restoration action and restoration confirmation performance: the gas meter  shall 
have the function of confirming restoration and be able to restore reliably.  
B.4.18 Burst s resistan ce performance: the gas meter  shall not be affected by voltages of 
burst s generated under normal use circumstance s. 
B.4.19 Electrostatic discharge s resistance performance : the gas meter  shall not be affected 
by voltages of  electrostatic discharge s generate d under normal use circumstance s. 
B.4.20 Electromagnetic fields  resistance performance: the gas meter  shall not be affected 
by electromagnetic fields  generated under normal use circumstance s. 
B.4.21 Connection s ignal performance: the signal connection line  shall have sufficient 
strength and polarity identification; no abnormality shalll occur after being 
short -circuited and then reconnected.  
B.5 Test conditions: if the test method in this annex  does not specify its specific test 
conditions, the following co nditions shall be followed.  
B.5.1 Temperature requirements of t est labratory: during the test, the temperature change s 
shall be  within ±5°C, and the temperature shall be kept within the range of 20°C ±  
15°C.  
B.5.2 Humidity requirement of t est laboratory: t he relative humidity shall be kept within 
the range of 60% ± 25%.  CNPA 137    Page 43 of 57 pages  
 
B.5.3 Normal use circumstance s: when a gas meter is tested, the connecting pipes on the 
inlet side and the outlet side are straight pipes with a length of 8 to 10 times of the 
connecting dia meter  in principle . If the volume of the detected part is easily affected 
by the inner pipe volume, it shall be tested with the maximum inner pipe volume. 
The pressure tapping hole is located at a position  of 2 to 3 times  of the length of the 
inlet/outlet diameter of the gas meter, and the inner surface of the pressure tapping 
hole shall be smooth. The installation position of the standard gas meter shall be at 
upstream or downstream of the straight pipe, depending on the test items. The test 
layout diagram  is shown in Figure B.2.  
 
 
 
 
 
 
Figure B.2 Gas meter test layout diagram  
B.5.4 Test range: the gas meter body and its external circuit s (communication interface  
excluded ) are shown  as the range surrounded by dotted line in Figure B.3.  
 
 
 
 
 
 
 
Figure B.3  
Note(1)  CNS 14273 “Meter interface units for communications in automatic meter 
reading systems”  
Note (2) CNS 14274 “Meter interface unit for automatic meter reading system via 
wireless communication network”  
B.6 Test  
B.6.1 Watertight resistance test: the enclosure  structure shall be free from obvious defects 
by visual inspection, and shall comply with the provisions in Section 14.2.4 IPX4 of 
CNS 14165 “Degrees of protection provided by enclosures (IP code)”.  
B.6.2 Marking/warning light performance test  
B.6.2.1  For light-emitting diodes (LED) display : the indicated state can be clearly 
identified visually at a position of 3 m in front of the main body of the 
marking/warning light  in a room with an illuminance of 300 lx.  CNPA 137    Page 44 of 57 pages  
 
If reasons for marking/warning actions are  provid ed, confirm them according to 
the specified methods described in the manufacturer's specification.  
B.6.2.2 For liquid crystal (LCD) display: measure the size of the displayed text s or 
numbers with a vernier caliper, etc., and  these texts or numbers  shall have a 
height of equal to or more than 4 mm.  
If reasons for marking/warning  actions are provid ed, confirm them according to 
the specified methods described in the manufacturer's specification.  
B.6.3 T est for c onfirmation of the operating st atus of th e shut -off valve: after operating the 
opening and closing of the shut -off valve, visually check the open and clos ed status 
of the shut -off valve. If only one status can be displayed, the closed status shall be 
displayed.  
However, this does not apply when t he shut -off valve is closed due to battery voltage  
dips. 
B.6.4 Performance test of connection with pipe 
B.6.4.1 Screw thread joints: check with CNS 12753 “Gauges for Taper Pipe Threads”, 
and the screw thread shall meet the requirements of CNS 495 “Taper Pi pe 
Threads”.  
B.6.5 Vibration resistance performance test: fix the gas meter  on the vibration testing 
machine in the shipping package sta tus, and perform vibration of 600 times per 
minute  and full amplitude  of 5 mm for 20 minutes in each of the up and down,  front 
and rear, and left and right directions . And then perform Section B.6.7 Airtight test 
and Section B.6.19 Restoration action and restoration confirmation test to confirm 
that there is no abnormality . 
B.6.6 Pressure resistance test: close the outlet s ide, and continuously introduce air with 1.5 
times the maximum working pressure from the inlet side for 1 minute (if the 
maximum working pressure is below 10 kPa, apply 15 kPa pressure) . Then visually 
check that there is no crack, damage , obvious deformati on, or other abnormalities.  
B.6.7 Airtight test  
B.6.7.1 External airtight test: close the outlet side, continuously introduce 10 kPa air 
from the inlet side for 1 minute, and the leakage  rate shall be equal to or  less 
than 0.07 L/h.  
B.6.7.2 Internal airtig ht test: with the shut -off valve operating in the “closed” sta tus as 
shown in Figure B.2, introduce  air of 0.5 kPa and 4.2 kPa from the inlet side 
respectively . Then t he leakage  rate(Q) is measured by a flow meter and 
converted to the leakage rate (Q0) of the standard state (0  °C, 101.325 kPa),  and 
confirm that it is equal to or less than  0.55 L/h.  
  
 
 
Where Q 0: leakage rate (L/h) of standard state (0  ℃, 101.325 kPa)  CNPA 137    Page 45 of 57 pages  
 t: Test lab room temperature ( ℃) 
B: Atmospheric pressure in the laboratory (kPa)  
P: Applied meter pressure (kPa)  
B.6.8 Service  life performance test  
B.6.8.1 Durability  test using the maximum flow rate:  run at the maximum flow rate of 
the ga s meter by gas or air, and accumulate the volume corresponding to 2000 
hours in a continuous or intermittent way within 100 days. After completion, 
perform the leak age detection performance test in Section B.6.14 to confirm 
compliance with the requirements . 
B.6.8.2 Durability  test of electrical components: use the temperature and humidity test 
device to perform 10 temperature and humidity cycles , where each cycle is  24 
hours . After that  place it in the atmosphere for 2 hours, and then perform the 
shut-off t est in Section B.6.18.4 and restoration action and restoration 
confirmation test in Section B.6.19 to confirm that each function is normal.  
 Any 5 cycles among the 1st to 9th cycles shall include low temperature (i.e. a 
cycle of 24-hour with low temperatur e), and the remaining 4 cycles and the last 
cycle shall not be implemented at low temperature (i.e. a cycle of 24-hour 
without low temperature).  
B.6.8.2.1 24 -hour cycle with low temperature (refer to Figure B.4.1)  
(1)Set the temperature of the test device to 25 ℃ ± 2 ℃, and set the relative 
humidity to 93% ± 3%. 
(2)Continuously increase the temperature of the test device to 50 °C ± 2 °C 
within 1.5 to 2.5 hours while maintaining the relative humidity at 93% ± 
3%. 
(3)Maintain the temperature at 50 °C ± 2 °C a nd the relative humidity at 93% 
± 3% until 5.5 hours since  the cycle starts.  
(4)Decrease  the temperature to 25 °C ± 2 °C within 1.5 to 2.5 hours while 
maintaining the relative humidity at 80% to 96%.  
(5)8 hours after the cycle start s, continuously increase  the temperature to  
make it reach  50 °C ± 2 °C within 1.5 to 2.5 hours and stabilize  it while 
maintaining  the relative humidity  at 93% ± 3%.  
(6)Maintain the temperature at 50 °C ± 2 °C and the relative humidity at 93% 
± 3% until 13.5 hours since  the cycle starts.  
(7)Decrease  the temperature to 25 °C ± 2 °C within 1.5 to 2.5 hours while 
maintaining the relative humidity at 80% to 96%.  
(8)Maintain the temperature at 25 °C ± 2 °C and the relative humidity at 93% 
± 3% for 1.5 to 2.5 hours.  
(9)Decrease  the tempe rature after 17.5 hours from the start of the cycle, and 
make  the temperature to -5 °C ± 2  °C before 18 hours from the start of the 
cycle.  CNPA 137    Page 46 of 57 pages  
 (10)After 18 hours from the start of the cycle, maintain the temperature at -5 
°C ± 2 °C for 3 hours  while  the relati ve humidity is not controlled.  
(11)Increase the temperature after 21 hours from the start of the cycle, and 
make the temperature  to 25  °C ± 2  °C before 22.5 hours from the start of 
the cycle.  
(12)Maintain t he temperature at 25 °C ± 2 °C until the end of th e 24-hour 
cycle  while  maintaining the relative humidity at 93% ± 3%.  
B.6.8.2.2 24 -hour cycle without low temperature (refer to Figure B.4.2)  
(1)Set the temperature of the test device to 25 ℃ ± 2 ℃, and set the relative 
humidity to 93% ± 3%. 
(2)Continuously increase the temperature of the test device to 50 °C ± 2 °C 
within 1.5 to 2.5 hours while maintaining the relative humidity at 93% ± 
3%. 
(3)Maintain the temperature at 50 °C ± 2 °C and the  relative humidity at 93% 
± 3% until 5.5 hours since  the cycle starts.  
(4)Decrease  the temperature to 25 °C ± 2 °C within 1.5 to 2.5 hours while 
maintaining the relative humidity at 80% to 96%.  
(5)8 hours after the cycle  starts, continuously increase the t emperature to  
make it reach  50 °C ± 2 °C within 1.5 to 2.5 hours and stabilize  it while  
maintaining the relative humidity at 93% ± 3%.  
(6)Maintain the temperature at 50 °C ± 2 °C and the relative humidity at 93% 
± 3% until 13.5 hours after the cycle starts . 
(7)Decrease  the temperature to 25 °C ± 2 °C within 1.5 to 2.5 hours while 
maintaining the relative humidity at 80% to 96%.  
(8)Maintain t he temperature at 25 °C ± 2 °C until the end of the 24 -hour 
cycle  while maintaining the relative humidity at 93% ± 3%.  CNPA 137    Page 47 of 57 pages  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
*: Indicates that the permissi ble error at this point is ±5 minutes  
Figure B.4.1 24 -hour cycle with low temperature  
 
 
 
 
 
 
 
 
 
 
 
 
 
*: Indicates that the permissible error at this point is ±5 minutes  
Figure B.4.2 24 -hour cycle without low tem perature  
B.6.9 Durability test  of repetitive  operation  
B.6.9.1 Structure without connecting lines of gas alarm  devices , etc.:  introduce 1.5 kPa 
air from the inlet side as shown in Figure B.2, and perform the  shut-off test in 
Section B.6.18.4 for 500 times.  Then confirm the shut -off valve does have the 
function of shut -off and restoration.  CNPA 137    Page 48 of 57 pages  
 B.6.9.2 Structure with connecting lines of gas alarm  devices , etc.: introduce 1.5 kPa air 
from the inlet side as shown in Figure B.2,  and perform the linking -up shut -off 
test with gas alarm devices , etc. in Section B.6.18.3 and  shut-off test  in Section 
B.6.18.4  for 500 times (at least one of them, the shut -off and restoration safety 
confirmation action is carried out in the way of linking -up shut -off with gas 
alarm  devices , etc., to confirm its connection function. The restoration operation 
shall be carried out under the condition of differential pressure) . Then confirm 
that the shut -off valve does have the function of shut -off and restoration.  
B.6.10 E xplosion  resistance te st: place the gas meter in the explosion proof  tester, and 
inject a mixed gas with a hydrogen concentration between 19% and 23% . Keep the 
gas meter in the energized  operation  status for 1 hour, then implement  linking -up 
shut-off test with gas alarm  device s, etc.  in Section B.6.18.3 or implement shut -off 
test in Section B.6.18.4 to confirm that there is no detonation.  
B.6.11 Electromagnetic susceptibility  and electromagnetic interference test: 
Electromagnetic susceptibility  test shall be in accordance with C NS 14675 
"Information technology equipment - Immunity characteristics - Limits and methods 
of measurement", and the test results shall conform to the requirements stipulated in 
the Judgment Criterion A of the standard. And the electromagnetic interference test 
is in accordance with the provisions of CNS 13438 " Information technology 
equipment - Radio disturbance characteristics - Limits and methods of 
measurement".  
B.6.12 Magnetic field s resistance test of the flow detection unit: use a permanent magnet 
with a surface magnetic density of 0.3  T (Tesla) as close as to the position of the 
upper cover of the magnetic induction lead -switch sensor, etc of the flow detection 
unit, and confirm that the contact points of the magnetic induction lead -switch 
sensor, et c. are not closed.  
B.6.13 Mains  voltage d ips test: perform  and pass  the electromagnetic susceptibility  test in 
Section B.6.11 first. Then perform the shut -off test in Section B.6.18.4 and the 
restoration action and restoration confirmation test in Section B.6.19. After 
confirming that the aforementioned functions are normal, decrease  the specified 
voltage and confirm that there is a display corresponding to the action or a shut -off 
action . 
B.6.14 Leakage detection performance test  
B.6.14.1 Leakage detection  capability (start -up flow) test: maintain  the pressure on the 
outlet side of the gas meter at 1.5 kPa  as shown in Figure B.2, and slowly 
increase the gas flow  rate from "0" to 0.003 m3/h. Gas leakage can be detected 
by output  of pulse signals or mechanica l actions.  
B.6.14.2 Leakage detection actuation test: maintain  the pressure on the  outlet side of the 
gas meter at 1.5 kPa  as shown in Figure B.2 . When the gas continues to flow 
through the gas meter at a flow rate of 0.003 m3/h or more , confirm  an alarm  
signal  can be automatically displayed after  passing  the time limit set by the 
manufacturer (the longest is 30 days) . 
If the gas meter is equipped with communication function s, confirm that the CNPA 137    Page 49 of 57 pages  
 display  of the alarm signal  is actually performed on the communi cation.  
B.6.14.3 Leakage alarm  signal restoration test: after implementing the leakage detection 
actuation test in Section B.6.14.2, the alarm  signal can be eliminated by using a 
special tool (provided by the manufacturer of the diaphragm gas meter  with 
micro computer).  
For those with the function of automatically eliminating the alarm  signal , after 
implementing the leakage detection actuation test in Section B.6.14.2, adjust the 
gas flow  rate on the outlet side to the "0" state . The gas meter shall continu e to 
display the alarm  signal within 1 hour and clear the alarm  signal in -between 1 to 
2 hours.  
B.6.15 Ambient temperature test  
B.6.15.1 Low temperature test: place the gas meter in a test device with a temperature of 
-5 °C, and maintain the temperature fo r 1 hour. Under the temperature condition , 
implement the linking -up shut -off test with gas alarm  devices , etc. in Section 
B.6.18.3 or the shut -off test in Section B.6.18.4. Then carry out the restoration 
action and restoration confirmation test in Section B.6.19 to confirm that the 
shut-off and alarm functions are correct . 
Those with communication functions shall  confirm that the ir communication 
operation s are actually executed.  
B.6.15.2 High temperature test: place the gas meter in a test device with a tem perature of 
55 °C and a relative humidity of 40 % ± 10 %, and maintain these conditions for 
1 hour. Under the temperature and humidity conditions, carry out the linking -up 
shut-off test with gas alarm  devices , etc. in Section B.6.18.3 or the shut -off test 
in Section B.6.18.4. Then carry out restoration action and restoration 
confirmation test in Section B.6.19 to confirm that the shut -off and alarm 
functions are correct . 
Those with communication functions shall confirm that their communication 
operations ar e actually executed.  
B.6.16 Humidity test: place the gas meter in a test device with a temperature of 40 °C and a 
relative humidity of over 90%, and maintain these conditions for 1 hour. Under these 
conditions, carry out the linking -up shut -off test with gas alarm  device s, etc. in 
Section B.6.18.3 or the shut -off test in Section B.6.18.4. Then perform the 
restoration action and restoration confirmation test in Section B.6.19 to confirm that 
the shut -off and alarm functions are correct . 
     Those with commu nication functions shall confirm that their communication 
operations are actually executed.  
B.6.17 Abnormal flow  rate shut-off performance test  
B.6.17.1 Shut -off test of abnormally large flow  rate: under normal use circumstance s as 
shown in Figure B.2, if the flow rate reaches 2 times of the maximum flow rate 
of the gas meter ( an abnormally large flow  rate), confirm that the shut -off 
function  will activate  within 2 minutes and  an al arm signal will be  display ed. 
Those with communication functions shall confi rm that their communication CNPA 137    Page 50 of 57 pages  
 
operations are actually executed.  
B.6.17.2 Shut-off test  of individual maximum flow rate 
(1)Under normal use circumstance s as shown in Figure B.2, set the gas meter 
flow rate as twice as of 5% of the maximum flow rate, and maint ain it for 
more than 2 minutes under the pressure of 2.5 kPa. T hen a  multiple  flow rate 
of the individual maximum flow rate  specified by the  gas meter 
manufacturer's manual  is rapidly increased  and passes through the gas meter , 
confirm that the shut -off va lve is shut off within 2 minutes and  an alarm  
signal will be  display ed. However, after  a 0.9 times  flow rate of  the 
individual maximum flow rate is rapidly increased  and passes through the 
gas meter  under the pressure of 2.5 kPa, the gas meter  shall not be  shut off 
and an alarm signal shall not be displayed within 5 minutes.  
(2)In this test, when the flow rate used for the test exceeds the abnormally large 
flow rate of the gas meter, the 5%  setting  of the test method in the preceding 
paragraph can be change d to 1% and the 2 minutes  setting  can be changed to 
5 minutes.  
B.6.17.3 Shut-off test of overtime use: under normal use circumstance s as shown in 
Figure B.2, the corresponding flow rate s (under 2.5 kPa pressure) are 
distinguished according to the gas consu mption specifi ed in the gas meter 
manufacturer's specification. Select a medium  flow rate  and a large flow  rate 
respectively, continue to flow  through the gas meter , and confirm that the 
shut-off valve is indeed shut off and  an alarm  signal is  display ed within the 
specified shut -off time.  
B.6.18 Shut -off function test  
B.6.18.1 Shut-off test  of earthquake sensing  
(1)Adjust the pressure on the inlet side of the gas meter to 1.5 kPa  under normal 
use circumstance s, and let the gas flow  at a test flow rate speci fied in Table 
B.1. Apply horizontal vibration s to all directions of the gas meter with a 
vibration testing device . The period  of the vibrations  ranges from 0.3 seconds 
to 0.7 seconds, the acceleration is increased from 9 gal at a rate of 11 gal per 
second.  When reaching 250 gal, the seismic detection unit of the gas meter 
shall indeed detect  it and make the shut -off valve shut off , and an alarm 
signal shall be  display ed. 
(2)This test is carried out in the horizontal  direction X and direction Y with 
periods of 0.3 seconds (+), 0.5 seconds and 0.7 seconds (−).  
Table B.1  
 
 
 
 
B.6.18.2 Shut-off test of  gas pressure d rop: adjust the air pressure on the inlet side to 1.5 CNPA 137    Page 51 of 57 pages  
 kPa as shown in Figure B.2  under normal use circumstance s, and let the gas 
flow at  a test flow rate specified in Table B.1. Slowly dec rease  the pressure to 
0.4 kPa ~ 0.2 kPa, the shut -off valve can be shut off and a n alarm  signal shall be  
displayed.  
B.6.18.3 Linking -up shut -off test with gas alarm  devices , etc.: when gas alarm  device s, 
etc. designa ted by the gas -fuel company are connected to the gas meter under 
normal use circumstance s, the shut -off valve can be shut off and an alarm  signal 
can be displayed  within 2 minutes upon  the gas meter receiving the transmission  
of signal from the gas alarm  devices . 
Those with communication functions shall confirm that their communication 
operations are actually executed.  
B.6.18.4 Shut -off test: when a special tool is used to perform a shut -off operation on the 
gas meter  under normal use circumstance s, the shu t-off valve can be reliably 
shut off.  
B.6.19 Restoration action and restoration confirmation test  
B.6.19.1 Restoration action test: introduce 1.5 kPa air into the inlet side of the gas meter  
as shown in Figure B.2, and continue to give air according to the  test flow  rate 
specified in Table B.1. After closing the shut -off valve, carry out the restoration 
operation  and the gas meter shall be shut off within 3 minutes.  
B.6.19.2 Restoration confirmation test: when there is no leakage on the downstream side 
of the shut -off valve as shown in Figure B.2 and the shut -off valve is kept open , 
introduce 1.5 kPa air at the inlet side of the gas meter. Close the shut -off valve  
and the supply source of gas, then carry out the re storation  operation. After the 
gas meter displays  a completion message of  self-checking, introduce 1.5 kPa air 
into the inlet side of the gas meter again, and the shut -off valve should  remain 
open.  
Note : for a gas meter using pressure detection method s, the volume on the outlet 
side of the gas meter under test shall be set to be  equal to or  less than 0.02 m3 
when performing the restoration action test in Section B.6.19.1 and the 
restoration confirmation test in Section B.6.19.2.  
B.6.20 Burst s resistance  test: after passing the test according to  the requirements of  CNS 
14676 -4 "Electromagnetic compatibility(EMC) − Testing and measurement 
techniques − Part 4: Electrical fast transient/burst immunity test", then implement  
the shut -off test  in Section B.6.18.4 and the re storation action and restoration 
confirmation test  in Section B.6.19 to confirm that all operation s are correct  and not 
affected.  
Those with communication functions shall confirm that their communication 
operations are actually executed.  
B.6.21 Electrostat ic discharge s resistance test: after passing the test according to  the 
requirements of  CNS 14676 -2 "Electromagnetic compatibility (EMC) − Testing and 
measurement techniques − Part 2: Electrostatic discharge immunity test",  then 
implement  the shut -off test in Section B.6.18.4 and  the restoration action and CNPA 137    Page 52 of 57 pages  
 restoration confirmation test in se ction B.6.19 to confirm that all operatio s are 
correct . 
Those with communication functions shall confirm that their communication 
operations are actually executed.  
B.6.22 Electromagnetic fields  resistance test  
(1)After passing the test according to  the req uirements of  CNS 14676 -3 
"Electromagnetic compatibility (EMC) − Testing and measurement techniques – 
Part 3: Radiated, radio -frequency, electromagnetic field immunity test", then 
perform the shut -off test in Section B.6.18.4 and  the restoration action and 
restoration confirmation test in Section B.6.19 to confirm that all operation s are 
correct . 
Those with communication functions shall confirm that their communication 
operations are actually executed.  
(2)Test conditions: the communication and external alarm lines are e xtended with a 
length of 3 m, and the distance between  the body of the  gas meter and the 
transmission antenna is 1 m. Confirm that the  strength of the  electric field in front 
of the  body of the  gas meter body is 3 V/m, and use the frequency scan increment 
change method with its increment not exceed ing 1% of the basic frequency 
[referring to the frequency of each stage less than the frequency of the previous 
stage multiplied by 1.01 (with 1 % stage specification)]. In this state, scan from 
26 MHz to 1 GHz to  confirm that the communication or display is correct . Then 
carry out  the shut off test in Section B.6.18.4 and  the restoration action and 
restoration confirmation test  in Section B.6.19 without  the electric field strength 
to confirm that all operations ar e correct . 
B.6.23 Connection signal performance test  
(1)Confirmation of lead wire polarity  
If the lead wire has polarity, its polarity shall be identifiable.  
(2)Confirmation of lead wire strength  
After applying a force of 30 N to the lead wire in the verti cal direction of the 
lead-out surface for 15 seconds, visually inspect it to confirm that there is no 
abnormality. Then implement the shut -off test in Section B.6.18.4 and the 
restoration action and restoration confirmation test in Section B.6.19 to confir m 
that all operations are correct . 
Those with communication functions must confirm that their communication 
operations are actually executed.  
(3)Lead wire short -circuit test  
After the lead wire being  lapped into a short circuit and  then returned to normal,  
carry out the shut -off test in Section B.6.18.4 and the restoration action and 
restoration confirmation test in Section B.6.19 to confirm that all operation s are 
correct . 
Those with communication functions must confirm that their communication CNPA 137    Page 53 of 57 pages  
 operations are actually executed.  CNPA 137    Page 54 of 57 pages  
 Annex C  
The requirements of additional tests for diaphragm gas meters with maximum working 
pressure more than 10 kPa   
 
C.1 General  
In case the nominal maximum working pressure of the gas meter is more than 10 kPa, 
the pressure conce rned performance  tests shall be conducted  in sequence of  initial error  
test under ambient pressure, initial error test under elevated  pressure, durable operation 
under elevated  pressure , the final error test under elevated  pressure  and the final error 
test under ambient pressure.  
C.2 Initial error test under ambient pressure  
The metrological performance of the gas meter is determined at five flow rate s, which 
are Q max, 0.46 Q max, 0.2 Q max, 0.1 Q max and 0.05 Q max, under ambient pressure.  
Each flow  rate shall  be tested at least six times independently to decide the errors  while 
varying the flow rate between each consecutive measurement . The metrological 
performance of each flow rate shall comply with the requirements laid down in Section 
3.3 to Section 3.6 .  
C.3 Initial error test under elevated  pressure  
The metrological performance of the gas meter is determined at five flow rates, which 
are Q max, 0.46 Q max, 0.2 Q max, 0.1 Q max and 0.05 Q max, under nominal maximum working 
pressure.  
Each flow  rate shall be test ed at least six times independently to decide the errors  while 
varying the flow rate between each consecutive measurement . The metrological 
performance of each flow rate shall comply with the requirements laid down in Section 
3.3 to Section 3.6 . 
C.4 D urabl e operation under elevated  pressure  
The gas meter is flowed with air at maximum flow rate under nominal maximum 
working pressure . 
The duration of the operation  is 500 hours. The operation  may be discontinuous but shall 
be completed within 35 days . 
C.5 F inal error test under elevated  pressure  
The metrological performance of the gas meter is determined at five flow rates, which 
are Q max, 0.46 Q max, 0.2 Q max, 0.1 Q max and 0.05 Q max, under nominal maximum working 
pressure.  
Each flow  rate shall be tested at lea st two times independently to decide the errors  while 
varying the flow rate between each consecutive measurement . 
The error curve shall meet the following requirements : 
- the maximum permissible errors as specified in Table 2 for in-service . 
- for flow rat es from Qt up to Qmax a fault of less than or equal to  1.0 times the maximum CNPA 137    Page 55 of 57 pages  
 permissible error applicable for class 1.5 , or 0.5 times the maximum permissible error 
applicable for class  1.0.  
C.6 F inal error test under ambient  pressure  
The metrological per formance of the gas meter is determined at five flow rates, which 
are Q max, 0.46 Q max, 0.2 Q max, 0.1 Q max and 0.05 Q max, under ambient  pressure.  
Each flow  rate shall be tested at least two times independently to decide the errors  while 
varying the flow rat e between each consecutive measurement . 
The error curve shall meet the following requirements : 
- the maximum permissible errors as specified in Table 2 for in-service . 
- for flow rates from Qt up to Qmax a fault of less than or equal to  1.0 times the maxim um 
permissible error applicable for class 1.5 , or 0.5 times the maximum permissible error 
applicable for class  1.0. CNPA 137    Page 56 of 57 pages  
 Annex D  
Type evaluation of a family of gas meters (Mandatory)  
 
D.1 General  
This Annex describes the criteria to be applied by the evaluatin g authority in deciding 
whether a group of gas meters can be considered to be from the same family for type 
evaluation purposes, for which only selected samples of meter sizes are to be tested.  
D.2 Definition  
A family of meters is a group of gas meters of different sizes and/or different flow rates, 
in which all the meters shall have the following characteristics:  
(1) the same manufacturer;  
(2) geometric similarity of the parts in contact with the gas;  
(3) the same metering principle;  
(4) the same accuracy class;  
(5) the same temperature range;  
(6) the same electronic device for each meter size;  
(7) a similar standard of design and component assembly;  
(8) the same metrological software routines (if applicable) and the same materials for 
those components that  are critical to the performance of the meter ; 
(9) the same installation requirements relative to the meter size ; 
(10) roughly the same ratios Qmax/Qmin and Qmax/Qt. 
D.3 Meter selection  
When considering which sizes of a family of gas meters should be teste d, the following 
rules shall be  followed:  
(1) the evaluating authority shall declare the reasons for including and omitting particular 
meter sizes from testing;  
(2) the smallest meter in any family of meters shall always be tested;  
(3) meters which have th e most extreme operating parameters within a family shall be 
considered for testing, e.g. the largest flow rate range, the highest peripheral speed of 
moving parts, etc;  
(4) if practical, the largest meter in any family of meters should always be tested. 
However, if the largest meter is not tested, then any meter having a Qmax > 2 × Qmax 
of the largest meter tested shall not be considered part of the family concerned;  
(5) durability tests shall be applied to meters where the highest wear is expected;  
(6) for meters with no moving parts in the measurement transducer, the smallest size 
shall be selected for durability tests;  
(7) all performance tests relating to influence quantities shall be carried out on one size CNPA 137    Page 57 of 57 pages  
 
from a family of meters;  
(8) the family mem bers underlined in Figure D.1 may be considered as an example for 
testing  (each row represents one family, meter 1 being the smallest ). 
 
 
 
 
 
 
 
 
 
 
Figure D.1: Family of meters pyramid