CZECH METROLOGY 
INSTITUTE  Okružní  31, 638 00 Brno  
legmet@cmi.cz  
+420 545 555 414 
 
1. ------IND-  2019 0491 CZ-  EN- ------ 20191021 --- --- PROJET 
 
Executive summary for the EC (not part of this legislation)  
'Transfer medium flow sensors with a multi -hole orifice plate' may be placed on the market and put 
into use in the Czech Republic as legally controlled measuring instruments  pursuant to 
Act No 505/1990 on metrology, as amended.Pursuant to the Act, legally controlled measuring 
instruments are instruments that are included in the list of the types of legally controlled measuring 
instruments (Implementing Decree No  345/2002) and, at the same time, intended (by the 
manufacturer/importer) for measurements of rel evance to the protection of public interests in areas 
of consumer protection, contractual relations, imposition of sanctions, fees, tariffs and taxes, health 
protection, environmental protection, occupational safety, or the protection of other public inter ests 
protected by special legislation. This is therefore a similar purpose as that which is used to identify 
stipulated products -  non-automatic measuring and weighing instruments pursuant to Directives 
2014/31/EU and 2014/32/EU.The requirements of this leg islation do not apply to measuring 
instruments not placed on the market in the Czech Republic for the above purposes, identified by Act 
No 505/1990 on metrology.  
The purpose of this notified legislation is to lay down metrological and technical requirement s for 
these legally controlled measuring instruments.This legislation also stipulates tests for type approval 
and verification of legally controlled measuring instruments of this type.  
(End of executive summary)  
 
 
 
PUBLIC DECREE  
 
As the authority with substantive and territorial jurisdiction for stipulating metrological and technical 
requirements for legally controlled measuring instruments and stipulating test methods for type approval 
and verification of legally specified instruments pursuant to § 14(1) of Act No  505/1990, on metrology, 
as amended (hereinafter the ‘Metrology Act’), and in accordance with the provisions of § 172 et seq. of 
Act No  500/2004, the Code of Administrative Procedure (hereinafter the ‘CAP’), the Czech Metrology 
Institute (herei nafter the ‘CMI’) commenced ex officio proceedings on 154.2016 pursuant to § 46 of the 
AC, and based on the supporting documents, hereby issues the following:  
 
 Measure of a General Nature No 0111 -OOP -C095- 18 
2 I. 
MEASURE OF A GENERAL  NATURE  
number:0111- OOP -C095 -18 
 
laying down metrological and technical requirements for legally controlled measuring 
instruments, including the testing methods for type approval and verification of legally 
controlled measuring instruments:  
'transfer medium flow sensors with a multi -hole orifice plate'  
The specified metrological requirements are on a level comparable with the relevant requirements of the 
European standards and apply to the basic design of transfer medium flow sensors with a multi -hole 
orifice plate.  
 
1 Basic definitions  
For the purposes of this general measure, terms and definitions pursuant to VIM and VIML1 as well as 
the terms and definitions stated below shall apply.  
1.1 
transfer medium  
a liquid used for heat transfer; for the purposes of this measure of a general nature, water vapour is 
consi dered, i.e. the gaseous phase of water and/or condensate  
1.2 
measurement system for measuring the flow quantity of the transfer medium  
a set of one or more measuring instruments (components of measuring instruments) and, often, other 
equipment arranged and  adapted to provide information about the qualitative and quantitative 
characteristics of the transmission medium  
1.3 
transfer medium flow sensor with a multi -hole orifice plate 
a transfer medium flow sensor based on the principle of measuring differential  pressure upstream and 
downstream of a multi -hole orifice plate, inserted in a defined manner into pipes with specified 
geometric parameters  
1.4 multi -hole orifice plate  
a thin plate with circular openings -  an orifice plate  
                                                      
1 TNI 01 0115 International Vocabulary of Metrology –  Basic and General Concepts and Associated Terms 
(VIM) and International Vocabulary of Legal Metrology (VIML) are part of the technical harmonisation 
compendium ‘Terminology in the field of metrology’, which is publicly available at www.unmz.cz.  Measure of a General Nature No 0111 -OOP -C095- 18 
3 1.4.1 
front side A  
the side of the multi -hole orifice plate that is installed facing the influx of transfer medium, with higher 
quality requirements  
1.4.2 back side B  
the side of the multi -hole orifice plate that is installed facing the outflow of the transfer medium, with 
lower quality  requirements and with a space for markings  
1.5 pressure tap (in wall)  
an annular or circular cavity drilled in the wall of a pipe using such a method that the edge of the cavity 
fits with the interior surface of the pipe.  
1.6 
static pressure of the transf er medium flowing through the pipe:  
pressure that can be measured by connecting a pressure gauge to the pressure tap in the wall  
1.7 differential pressure 
the difference between (static) pressures measured in pressure taps in the wall, one being upstream o f 
and one being downstream of the multi -hole orifice plate inserted in a straight pipe through which the 
transfer medium flows, taking into account all differences in tap height in front of and past the multi -
hole orifice plate  
1.8 
ratio of diameters β  
the ratio of the diameter of the orifices in the multi -hole orifice plate to the internal diameter of the pipe 
upstream of the multi -hole orifice plate  
1.9 pipe Reynolds number Re
D 
a dimensionless parameter expressing the ratio between the inertial forces and  the frictional forces in 
the pipe upstream of the multi -hole orifice plate  
1.10 flow coefficient C  
a coefficient defined for a flow of incompressible liquid; it indicates the ratio of the actual flow through 
the multi -hole orifice plate to the theoretical  flow 
1.11 
expansion coefficient  
a coefficient characterising the degree of compressibility of the liquid in question  
2 Metrological requirements  
The specified metrological requirements are comparable with the relevant requirements of European 
standards and apply to the basic design of the transfer medium flow sensor with a multi -hole orifice 
plate.  Measure of a General Nature No 0111 -OOP -C095- 18 
4 During verification, transfer medium flow sensors with a multi -hole orifice plate are subject to the 
metrological requirements that applied to their being pla ced into circulation.  
2.1 Operating conditions  
The operating conditions are specified by the manufacturer in consideration of the range of anticipated 
ambient temperatures during operation and in consideration of range of temperatures of the transfer 
medium being measured.If there are significant temperature differences between the ambient 
temperature and the temperature of the flowing transmission medium, the transmission medium flow 
sensor shall be thermally insulated by suitable means.  
The following  conditions apply to transfer medium flow sensors with a multi -hole orifice plate when 
using individual types of pressure taps:  
 with corner pressure taps:  for 0.40  ≤ β ≤ 0.56:  
for β > 0.56:  ReD ≥ 5,000  
ReD ≥ 16,000 β2 
  with flange pressure taps:  ReD ≥ 5,000 and ReD ≥ 170 β2D, where D is in millimetres  
 with taps at distances of D and D/2: for 0.40  ≤ β ≤ 0.56:  
for β > 0.56:  ReD ≥ 5,000  
ReD ≥ 16,000 β2 
 
2.2 Limits of use  
Transfer medium flow sensors with a multi -hole orifice plate may only be used for: 
  internal pipe diameter D: 25 mm to 1000  mm 
  minimum orifice plate hole diameter di: 6.25 mm  
  minimum characteristic dimension of the multi -hole orifice plate d: 12.5 mm  
  ratio of diameters β (d/D): 0.4 to 0.65 
2.3 Relative uncertainty of the multi -hole orifice plate flow coefficient  
The following relative uncertainties of flow coefficient C  apply to a multi -hole orifice plate in 
compliance with all technical requirements and installation requirements within the limits of undesired 
increases in the relative uncertainty of the flow coefficient by additional uncertainty: 0.75 % for 
0.40 ≤  β ≤ 0.65.  
If D < 71.12 mm, then the relative uncertainty 0,9(0,75−𝛽𝛽)�2,8−𝐷𝐷
25,4�%, in which D  is in 
millimetres, must be added to the above -mentioned relative uncertainty values of the flow coefficient.  
If β > 0.5 and Re D < 10,000, then the relative uncertainty 0.5 % must be added to the above -mentioned 
relative uncertainty values of the flow coefficient.  
If a straight length of pipe with additional uncertainty is used, then this uncertainty must be added to the 
uncertainty of the flow coefficient.The use of a stra ight length of pipe load weighted with additional 
uncertainty is limited to either only the section upstream of the orifice plate, or only the section 
downstream of the orifice plate.  
Compliance with technical requirements is determined during the verifica tion of the individual parts of 
the transfer medium sensor, and compliance with installation requirements is determined within the 
scope of verification of the evaluation unit for the measurement of transfer medium flow quantity. Measure of a General Nature No 0111 -OOP -C095- 18 
5 2.4 Relative uncertainty o f the expansion coefficient  
In compliance with all of the established technical requirements, it holds true that the relative uncertainty 
of the expansion coefficient ε is 5Δ𝑝𝑝
𝜅𝜅𝑝𝑝1 %, in which κ is the isentropic exponent, Δ p is the differential 
pressure and p1 is the absolute static pressure of the transfer medium upstream of the orifice plate.  
Compliance with technical requirements is ascertained during the verification of the individual parts of 
the transfer medium flow sensor.  
3 Technical requirements  
The specified metrological requirements are on the level of the relevant requirements of the European 
standards and apply to the basic design of the transfer medium flow sensor with a multi -hole orifice 
plate.  
During verification, transfer medium flow sens ors with a multi- hole orifice plate are subject to the 
technical requirements that applied to their being placed into circulation.  
3.1 Design  
The basic design of a transfer medium flow sensor with a multi -hole orifice plate includes the following 
parts:  
  orifice plate;  
  pressure taps;  
  a stabilising straight length of pipe upstream of the orifice plate with total minimum length of 10 D, 
or a shorter length if specified in the type approval certificate;  
  a stabilising straight length of pipe past the orifice plate with total minimum length of 2 D, or a shorter 
length if specified in the type approval certificate;  
The design and installation of the multi -hole orifice plate must ensure that it is not subject to plastic or 
elastic deformation during operation under the pressure of the flowing transfer medium, or that said 
deformation is within specified limits.  
3.2 Orifice plate  
The part of the orifice plate with diameter D  that is located inside the pipe after installation must be 
circular and concen tric with the pipe axis.The front and back side of the orifice plate must be parallel.  
Unless specified otherwise, all requirements placed on the design of the orifice plate only apply to the 
parts that are located in the pipe.  
3.2.1 Front side A  
3.2.1.1 Flatness  
The maximum deviation between the linear straight edge of length D , positioned in a discretionary 
direction above diameter D  on the orifice plate, and the plane of the front side of orifice plate A must be 
less than 0.005 D  – d)/2, i.e. the inclin ation of the surface must be less than 0.5 %.  
3.2.1.2 Surface roughness  
Inside a circle of diameter D, concentric with the axis of the pipe in which the orifice plate is installed, 
the orifice plate must have a roughness parameter of Ra  < 10-4d. Measure of a General Nature No 0111 -OOP -C095- 18 
6 3.2.2 Back  side B  
The back side of the orifice plate must be flat and parallel with the front side.The roughness of the 
surface on the back side of the orifice plate need not achieve the quality required on the front side of the 
orifice plate.  
3.2.3 The thickness e of the holes in the orifice plate and orifice plate thickness E  
The thickness e of the holes in the orifice plate must be between 0.005D  and 0.02D .The difference 
between the values of e  measured at an arbitrary point of the orifice plate holes may not be g reater than 
0.001D . 
The thickness of the orifice plate E  must be between e and 0.05D .In the case of 50 mm ≤ D ≤ 64 mm, E 
can be up to 3.2 mm.  
For orifice plates with D  < 200 mm, the difference between the values of E  measured at an arbitrary 
point must not be greater than 0.001D .For orifice plates with D  < 200 mm, the difference between the 
values of E  measured at an arbitrary point must not be greater than 0.2 mm.  
3.2.4 Chamfer angle α 
If the thickness E of the orifi ce plate is greater than the thickness of the orifice plate holes e, then the 
orifice plate holes on the back side of the orifice plate must be chamfered; the chamfer angle α must be 
45° ± 15°.The chamfered surface must be finished smoothly. 
3.2.5 Edges of  the orifice plate holes  
The front edge of the orifice plate holes must not have any burrs or other damage.The edges must be 
sharp and right -angled.The radius of curvature of the front edge of the orifice plate holes must not be 
greater than 0.0004d.  
The a ngle between individual orifice plate holes and the front edge of the orifice plate must be 
90° ± 0.3°. 
The back edge(s) of the orifice plate holes need not meet the qualitative requirements for the front edges 
of the orifice plate holes.  
3.2.6 Orifice plate hole diameters d i 
The diameters of the orifice plate holes d i must meet the requirements specified in Article 2.2.  
Orifice plate hole diameter d i is the mean value of the measurement of at least four diameters at 
approximately the same angles to each other.  
3.2.7 Cylindricity of the orifice plate holes  
The orifice plate holes must be cylindrical, and no diameter measured in the cylindrical part of the orifice 
plate holes may differ by more than 0.05 % of the mean of diameters d i. 
3.2.8 Surface roughness of the orifice plate holes  
The surface roughness of the cylindrical part of the orifice plate holes must not influence the measurement of the sharpness of the edge.  
3.2.9 Orifice plate material  
The orifice plate may be made of any kind of material with a known longitudinal expansion coefficient, 
on condition that it will continuously meet all of the relevant requirements of this regulation under  
operating conditions.  Measure of a General Nature No 0111 -OOP -C095- 18 
7 3.2.10 Design execution of the orifice plate for flow in both directions  
With orifice plates intended for measuring transfer medium flow in both directions, the technical and 
metrological requirements for the front side A of the orif ice plate must be applied on both sides of the 
orifice plate (edges).The orifice plate holes must not be chamfered.  
3.3 Differential pressure taps  
Flange pressure taps, corner pressure taps or pressure taps at distances D  and D/2 may be used for 
differenti al pressure taps.  
In the case of a bi -directional version of a transfer medium flow sensor with a centric orifice and pressure 
taps at distances D  and D/2, two pairs of said taps must be used upstream and downstream of the orifice, 
depending on the directi on of flow.  
3.4 Straight lengths of pipe upstream and downstream of the orifice plate  
3.4.1 Design  
The minimum straight length of pipe upstream of the orifice plate which must be complied with in the 
specific application shall be determined based on the ra tio of diameters β and according to the type and 
mutual arrangement of at least two adapters placed upstream of the orifice plate.  
The straight length of pipe between the first adapter in front of the orifice plate and the orifice plate 
itself can consist of one or more pieces, but the part of the pipe up to a length of 2 D in front of the orifice 
plate must always consist of one single piece.  
The design and execution of the straight lengths of pipe must facilitate the performance of the tests defined in Art icle 5.2.4 or Article  6.2.4.  
3.4.2 Pipe straightness  
The straightness of the stabilising minimum straight lengths of pipe is to be deemed adequate if the 
surface deviation of the pipe from a straight line running parallel to the axis of the pipe does not exceed 
0.4 % of its length upstream and downstream of the orifice plate.  
3.4.3 Mean value of the inner diameter of the pipe  
The internal diameter D of the pipe is the arithmetic mean of at least twelve measured diameter values, 
i.e. four diameters lying at  approximately the same angles to one another at each of at least three cross 
sections evenly distributed at a length of 0.5 D upstream of the orifice plate.Two of these cross -sections 
must lie on the plane of the front pressure tap and at a distance of 0.5D  from the front pressure tap.If a 
welded joint is located at a length of 0.5D  upstream of the front pressure tap, then the third cross section 
must be placed precisely into said joint.  
3.4.4 Circularity and cylindricity of pipe  
The internal shape of the p ipe must be circular along the entire minimum straight length of pipe.  
No inner pipe diameter may differ from the mean value of inner diameter D  by more than 0.3 % in any 
plane in the part of the straight length of pipe up to a distance of 2D  upstream of t he orifice plate.  
The difference between inner pipe diameters of two arbitrary sections of pipe may not exceed 0.3 % of 
the mean value of inner diameter D  along the straight section of pipe between 2D  and 10D  upstream of 
the orifice plate.At the same time,  the overlap of the inner diameters of parts of the pipe connected to 
one another, caused by a deviation and/or change in diameter D , may not exceed 0.3 % of the mean 
value of the internal diameter D at any point along the inner circumference of the pipe.  Measure of a General Nature No 0111 -OOP -C095- 18 
8 No internal diameter of a straight length of pipe behind the orifice plate may differ from the mean 
internal diameter D  of the pipe upstream of the orifice plate by more than 3 %, at least over a length of 
2D from the front side of the orifice plate.  
3.4.5 Quality of the internal surface of the pipe  
The internal surface of the pipe must be clean and free of any visible defects.  
The internal pipe surface must meet specified requirements for surface roughness Ra  in front of the 
orifice plate over the stipulated minimum straight length of the basic version of the sensor.The value of 
the mean arithmetic deviation (roughness) of the profile Ra  must be such that 104Ra/D is less than the 
maximum permissible value given in Table 1 and greater than the minimum permissible value given in Table 2.  
Table 1 – Maximum permissible value 10
4Ra/D 
β ReD 
≤ 104 3 × 104 105 3 × 105 106 3 × 106 107 3 × 107 108 
≤ 0.20 15 15 15 15 15 15 15 15 15 
0.30 15 15 15 15 15 15 15 14 13 
0.40 15 15 10 7.2 5.2 4.1 3.5 3.1 2.7 
0.50 11 7.7 4.9 3.3 2.2 1.6 1.3 1.1 0.9 
0.60 5.6 4.0 2.5 1.6 1.0 0.7 0.6 0.5 0.4 
≥ 0.65 4.2 3.0 1.9 1.2 0.8 0.6 0.4 0.3 0.3 
Table 2 – Minimum permissible value 104Ra/D 
β ReD 
≤ 3 × 106 107 3 × 107 108 
≤ 0.50 0.0 0.0 0.0 0.0 
0.60 0.0 0.0 0.003  0.004  
≥ 0.65 0.0 0.013  0.016  0.012  
 
3.5 Installation requirements  
The installation position of the orifice plate must be clearly defined by its design, or it must be schematically marked directly on the orifice plate.  
4 Measuring instrument markings  
4.1 General  
All inscriptions and markings must be easily visible, legible, and indelible and must be a source of the 
information needed for the trouble -free implementation of the transfer medium flow sensor with a multi -
hole orifice plate into the transfer medium flow mea surement system in relation to its other components.  
4.2 Markings  
4.2.1 Markings on the orifice plate  
The following information must be on the orifice plate:  
a) serial number;  Measure of a General Nature No 0111 -OOP -C095- 18 
9 b)  the value of the characteristic dimension of the multi -hole orifice plate d20 in relation to a reference 
temperature of 20  °C; 
c)  type approval mark;  
d)  suitable marking for type identification and placement of the differential pressure taps, if the pressure 
taps are a fixed component of the design execution of the orifice plat e. 
In cases in which the above -mentioned information is not visible once the multi- hole orifices have been 
installed into the pipe, the orifice plate must also be equipped with a separate additional nameplate with 
the information in question, which will he lp safeguard the orifice plate against removal or replacement.  
In cases in which the orifice plate could be improperly installed relative to the direction of transfer medium flow, the direction of flow must be indicated on the orifice plate in a way that r ules out error.  
4.2.2 Markings on transfer medium flow sensors with a multi -hole orifice plate  
The following information must be on transfer medium flow sensors with a multi -hole orifice plate  
a)  the name of the manufacturer and type (design variant);  
b)  serial number and year of production;  
c)  the value of the internal diameter D
20 of the pipe in relation to a reference temperature of 20  °C; 
d)  type approval mark;  
e)  nominal size DN/nominal pressure PN;  
f)  indication of the direction of flow;  
g)  suitable marking for type identification and placement of differential pressure taps, if pressure taps 
are a permanent part of the design of straight lengths of pipe;  
h)  the measured flow range or the maximum flow value.  
This information must be placed on  a part of the transfer medium flow sensor that is inseparably joined 
to a straight pipe section 0.5 D in front of the orifice plate (installation chamber, connector flange in front 
of the orifice plate, a straight length of pipe at most 2 D in front of the orifice plate).  
The following information must be specified on the connection flange or other location of the straight 
length of pipe past the orifice plate (at a maximum length of 2D  past the orifice plate).  
i)  the manufacturer's name;  
j)  serial number and year of production;  
k)  type approval mark;  
l)  an indication of the direction of flow (if reverse installation is possible).  
If, in the basic configuration of the transfer medium flow sensor, the straight length of pipe upstream of the orifice plate i s made up of multiple parts of pipe, then all of these parts must bear a type approval 
mark.In general, all major separate parts of transfer medium flow sensors with a multi -hole orifice plate 
must bear a type approval mark.  
4.3 Marking with official marks  
Suitable areas for placement of the type approval mark and official mark(s) must be provided.  
It must be possible to safeguard the orifice plate against unauthorised removal or replacement.  Measure of a General Nature No 0111 -OOP -C095- 18 
10 5 Type approval of the measuring instrument  
The type approval pro cess for a transfer medium flow sensor with a multi -hole orifice plate includes the 
following tests and activities:  
a)  an external inspection;  
b)  a check of geometric parameters.  
5.1 External inspection  
The following are checked during the external inspe ction: 
  completeness of the required technical documentation;  
  the conformity of the metrological and technical characteristics specified by the manufacturer in the 
documentation with this regulation's technical and metrological requirements specified in Chapters  2 
and 3;  
  the orifice plate, pressure taps and straight lengths of pipe in terms of potential mechanical damage 
or potential traces of corrosion which would preclude further testing; and  
  places for indicating the basic geometric parameters of the transfer medium flow sensor with a multi -
hole orifice plate and places for placing official marks are determined.  
5.2 Check of geometric parameters  
5.2.1 Test equipment  
Suitable equipment with valid metrological traceability must be used during the  check of geometric 
parameters.  
5.2.2 Reference ambient temperature for tests  
5.2.2.1 Orifice plate  
During the test, the ambient temperature must be between 18 and 22 °C and must not change by more 
than 2 °C.  
5.2.2.2 Straight lengths of pipe  
Pipe ≤ DN  300:  During the test, the ambient temperature must be between 15 and 25 °C and must 
not change by more than 2 °C. 
Pipe > DN 300:  During the test, the ambient temperature must be between 10 and 30 °C and must 
not change by more than 5 °C. 
5.2.3 Check of the geo metric parameters of the orifice plate  
The internal diameters di of the orifice plate holes must be established in accordance with the 
requirement of Article 3.2.6 and must relate to a reference temperature 20  °C. 
The following geometric parameters of the orifice plate are also checked:  
  flatness of the front side (see Article 3.2.1.1);  
 surface roughness of the front side (see Article 3.2.1.2);  
  thickness of the orifice plate holes and thickness of the orifice plate (see Article 3.2.3);  
  chamfer ang le (see Article 3.2.4);  
  the edges of the orifice plate holes (see Article 3.2.5);  
  cylindricity of the orifice plate holes (see Article 3.2.7);  
  surface roughness of the orifice plate holes (see Article 3.2.8).  Measure of a General Nature No 0111 -OOP -C095- 18 
11 In the case of an orifice plate intended for measuring transfer medium flow in both directions, all of the 
tests specified in Article 5.2.3 must be carried out for both sides of the orifice plate.  
5.2.4 Check of the geometric parameters of straight lengths of pipe  
The mean internal diameter value D20 of the pipe must be established in accordance with the requirement 
of Article  3.4.3 and must relate to a reference temperature of 20  °C. 
The following geometric parameters are checked for straight lengths of pipe:  
  the straightness of the p ipe (see Article 3.4.2);  
  the circularity and cylindricity of the pipe (see Article 3.4.4);  
  the roughness of the pipe's internal surface (see Article 3.4.5).  
In the case of a transfer medium flow sensor with a multi -hole orifice plate intended for flow in both 
directions, all of the tests specified in Article 5.2.4 must be carried out for the straight lengths of pipe 
positioned upstream and downstream of the orifice plate. 
5.2.5 Check of the geometric parameters of pressure taps  
Compliance with the requirements for differential pressure taps according to the manufacturer’s 
specifications shall be ascertained.  
6 Initial verification  
The following tests and activities are carried out during the initial verification of transfer medium flow 
sensors with a m ulti-hole orifice plate and parts thereof:  
a)  visual inspection;  
b)  test of metrological characteristics;  
c)  marking of the basic geometric parameters on the relevant parts of a transfer medium flow sensor 
with a multi- hole orifice plate.  
6.1 Visual ins pection  
The purpose of a visual inspection is to check that:  
  the execution of the transfer medium flow sensor with a multi -hole orifice plate matches the approved 
type;  
  the orifice plate, pressure taps and straight lengths of pipe are not mechanically damaged and whether 
or not they bear traces of corrosion which would preclude further testing, 
  the content and implementation of markings and inscriptions correspond to the information and requirements specified in the type approval certifi cate for the measuring instrument.  
If the transfer medium flow sensor with a multi -hole orifice plate does not meet the external inspection 
requirements, it will not be tested further.  
6.2 Check of geometric parameters  
6.2.1 Test equipment  
Suitable equipme nt with valid metrological traceability must be used during the check of geometric 
parameters.  
6.2.2 Reference ambient temperature for tests  
The ambient temperature requirements pursuant to Article 5.2.2 apply to the testing.  Measure of a General Nature No 0111 -OOP -C095- 18 
12 6.2.3 Check of the geometric p arameters of the orifice plate  
The internal diameters di of the orifice plate holes must be established in accordance with the 
requirement of Article 3.2.6 and must relate to a reference temperature 20  °C. 
The following geometric parameters are also checked during the initial verification of the orifice plate:  
  flatness of the front side (see Article 3.2.1.1);  
 surface roughness of the front side (see Article 3.2.1.2);  
  thickness of the orifice plate holes and thickness of the orifice plate (see Articl e 3.2.3);  
  chamfer angle (see Article 3.2.4);  
  the edges of the orifice plate holes (see Article 3.2.5);  
  cylindricity of the orifice plate holes (see Article 3.2.7);  
  surface roughness of the orifice plate holes (see Article 3.2.8).  
In the case of  an orifice plate intended for measuring transfer medium flow in both directions, all of the 
tests specified in Article 6.2.3 must be carried out for both sides of the orifice plate.  
6.2.4 Check of the geometric parameters of straight lengths of pipe  
The mean internal diameter value D20 of the pipe must be established in accordance with the requirement 
of Article  3.4.3 and must relate to a reference temperature of 20  °C. 
During initial verification, the following geometric parameters of the straight le ngths of pipe are also 
checked:  
  the straightness of the pipe (see Article 3.4.2);  
  the circularity and cylindricity of the pipe (see Article 3.4.4);  
  the roughness of the internal surface of the pipe (see Article 3.4.5); only the maximum permissible  
value per Table 1 is checked.  
In the case of a transfer medium flow sensor with a multi -hole orifice plate intended for flow in both 
directions, all of the tests specified in Article 6.2.4 must be carried out for the straight lengths of pipe 
positioned up stream and downstream of the orifice plate.  
6.2.5 Check of the geometric parameters of the differential pressure taps  
Compliance with the requirements for differential pressure taps according to the manufacturer’s 
specifications shall be ascertained during  the initial verification.  
6.2.6 Marking of basic geometric parameters on the measuring instrument  
The resultant value of the characteristic dimension d20 of the multi -hole orifice plate calculated from 
internal diameters of orifice plate holes d i determin ed pursuant to Article 6.2.3 must be marked in a 
legible and indelible manner in a suitable location on the orifice plate in accordance with Article 4.2.1.  
The resultant internal diameter value D 20 of the pipe determined pursuant to Article  6.2.4 must be 
marked in a legible and indelible manner in a suitable location on the transfer medium flow sensor in 
accordance with Article  4.2.2. 
7 Subsequent verification  
The procedure for the subsequent verification of the orifice plate is identical to the procedure f or the 
initial verification pursuant to Article 6.2.3.  
Subsequent verification of straight lengths of pipe of transfer medium flow sensors with a multi -hole 
orifice plate is not performed.  Measure of a General Nature No 0111 -OOP -C095- 18 
13 The user of the measuring instrument is responsible for long- term c ompliance with operating conditions, 
including keeping it in proper condition and keeping the inner surface of the pipe clean.For this purpose, 
the user of the measuring instrument performs (or ensures) a visual inspections of the internal surface 
of the pipe at intervals that take into account operating conditions and the type of gas medium being 
measured.This check must also always be performed prior to the installation of the orifice plate.  
The same requirements as for initial verification apply to the t ransfer medium flow sensor during testing 
while verification pursuant to § 11(4) of Act No 505/1990 on metrology, as amended, is valid.  
8 Measuring instrument examination  
When examining measuring instruments pursuant to § 11a of the Metrology Act at the request of a 
person who may be affected by incorrect measurement, the procedure under Chapter  6 shall be followed.  
9 Notified standards  
For the purposes of specifying the metrological and technical requirements for measuring instruments and specifying the testing methods for their type approval and verification arising from this general 
measure, the CMI will notify Czech technical standards, other technical standards or technical 
documents of international or foreign organisations, or other technical docume nts containing more 
detailed technical requirements (hereinafter referred to as ‘notified standards’).The CMI will publish a 
list of these notified standards attached to the relevant measures, together with the general measure, in 
a manner accessible to th e public ( on www.cmi.cz
). 
Compliance with notified standards or parts thereof is considered, to the extent and under the conditions 
stipulated by this measure of a general nature, to be compliance with the requirements stipulated by this 
measure to which these standards or parts thereof apply.  
Compliance with notified standards is one way of demonstrating compliance with the 
requirements.These requirements may also be met by using another technical solution guaranteeing  an 
equivalent or higher level of protection of legitimate interests.  
II. 
GROUNDS  
The CMI has issued this general measure laying down metrological and technical requirements for 
legally controlled measuring instruments and tests for the type approval and v erification of legally 
controlled measuring instruments – ‘transfer medium flow sensors with a multi -hole orifice plate’ – in 
accordance with §  14(1)(j) of the Metrology Act to implement §  6(2), § 9(1) and (9), and § 11a(3) of the 
Metrology Act.  
Decree No 345/2002 stipulating measuring instruments for mandatory verification and measuring instruments subject to type approval, as amended, classifies the measuring instruments under 
item 3.1.2(b) in the annex entitled ‘List of legally controlled measuring instr uments’ as measuring 
instruments subject to type approval and mandatory verification.  
This legislation (General Measure) will be notified in accordance with Directive  (EU) 2015/1535 of the 
European Parliament and of the Council of 9 September  2015 laying down a procedure for the provision 
of information in the field of technical regulations and of rules on Information Society services.  Measure of a General Nature No 0111 -OOP -C095- 18 
14 III. 
INSTRUCTIONS  
In accordance with § 173(2) CAP, no appeals may be made regarding measures of a general nature.  
In accord ance with the provisions of §  172(5) CAP, decisions on objections are final, and appeals may 
not be made against them.  
Compliance with the measure of a general nature with legislation may be subject to a review process 
pursuant to§ 94 to § 96 of the Admini strative Code.A party to the proceedings may initiate review 
proceedings to be conducted by the administrative authority that issued the measure of a general nature.If the administrative authority finds no reason to commence the review proceedings, it shal l communicate 
and provide grounds for this within 30 days.Pursuant to § 174(2) of the Administrative Code,a ruling on 
the commencement of review proceedings can be issued within three years of the effective date of the 
measure of a general nature.  
IV. 
ENTR Y INTO FORCE  
This measure of a general nature comes into effect on the fifteenth day after its date of publication (§  24d 
of the Metrology Act). 
 
Czech Metrology Institute  
Director -General  
Posted on:  
Removed on:  
Effective date: