Czech Metrology Institute  
Okružní 31, 638 00 Brno  
 
CZECH 
METROLOGY 
INSTITUTE  
1. ------IND- 2018 0308 CZ - EN- ------ 20180712 --- --- PROJET 
Executive summary for the EC (not part of this legislation)  
Flow -through vibrational relative density transducers are placed on the market and put into use in the 
Czech Republic as legally controlled measuring instruments following type approval and initial 
verification pursuant to Act No  505/1990 on metrology, as amended.This notified legislation 
concerns national metrol ogy regulation through type approval and verification of measuring 
instruments used as components of instruments and systems for measuring the flow volume of liquids.  
(End of executive summary.)  
 
Contact person:  Mgr.  Tomáš 
Hendrych  
Phone:545  555 414 
 
 
P U B L I C  D E C R E E  
 
As the authority with substantive and territorial jurisdiction in the matter of laying down metrological 
and technical requirements for legally controlled measuring instruments and stipulating the testing 
methods for type approval and verifi cation of legally controlled measuring instruments pursuant to 
§ 14(1) of Act No  505/1990 on metrology, as amended (hereinafter referred to as the ‘Metrology Act’), 
and in accordance with the provisions of §  172 et seq. of Act No  500/2004, the Administrati ve Procedure 
Code (hereinafter referred to as the ‘APC’), the Czech Metrology Institute (hereinafter referred to as the 
‘CMI’) commenced ex officio proceedings on 2 February 2017 pursuant to §  46 APC, and, on the basis 
of supporting documents, issues the f ollowing:  
 
I. 
D R A F T  G E N E R A L  M E A S U R E 
number:0111 -OOP -C068 -17 
laying down the metrological and technical requirements for legally controlled measuring 
instruments, including testing methods for type approval and verification of the following legally 
controlled measuring instruments:  
‘flow -through vibrational relative gas density transducers’  
 
This legislation stipulates metrological and technical requirements for flow -through vibrational relative 
gas density transducers with an analogue and/or digital  output signal used as elements of instruments 
and systems for measuring liquid flow quantity.  General Measure No  0111 -OOP -C068 -17 
2 
 1 Definitions  
For the purposes of this general measure, terms and definitions pursuant to VIM and VIML as well as 
the terms and definitions stated below shall appl y. 
1.2  
relative gas density, density  
the proportion of gas density to dry air density under the same temperature and pressure  
1.1  
flow-through vibrational relative gas density transducer; measuring relative density 
transducer; transducer; density meter, hydrometer  
an element of a measuring instrument or measuring system that converts an input signal concerning 
measured relative gas density from a relative density sensor to an output signal that has a stipulated 
relationship to the value of the measured relative density  
For the purposes of this legislation, a flow -through vibrational relative gas density transducer is 
considered to be a flow -through vibrational density meter as an element of measuring instruments or 
measuring systems for liquid flow quant ities.  
2 Metrological requirements  
Metrological requirements applicable to the placement of relative density transducers on the market are 
applied during verification.  
2.1 Reference conditions  
Ambient reference conditions are defined relative to the intended use  of the relative density transducers.  
2.2 Rated operating conditions  
Operating conditions are specified by the manufacturer relative to the intended use of the relative density 
transducers.  
The measuring range of a relative density transducer must correspond t o the requirements of its intended 
measuring application.  
All relevant usability conditions for the relative density transducer in relation to the type of application 
must be met.  
2.3 Maximum permissible error  
The maximum permissible error for a relative densi ty transducer is stipulated by the manufacturer 
according to its expected use.At each test point, the following condition must be met:  
dov
 (1) 
where: ............  is the determined measurement error;  
dov ...... is the maximum permissible error of the relative density transducer.  
                                                      
1TNI 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 accessible at www.unmz.cz  General Measure No  0111 -OOP -C068 -17 
3 
 2.3.1 Maximum permissible error under reference conditions  
The maximum permissible error of indication for a relative density transducer is the absolute value of 
the error  expressed as a percentage of the output signal range or as a percentage of the measured 
quantity.It is expressed as the relative density transducer’s accuracy class, which, for type approval and 
verification purposes, is one of the following accuracy clas ses: 
0.1; 0.2; 0.5.  
A different form of accuracy specification for the relative density transducer can be chosen on the basis 
of the type approval decision.  
2.3.2 Maximum permissible error under operating conditions  
The maximum permissible error for a relative d ensity transducer under operating conditions is stipulated 
by the manufacturer according to its expected use.The figure used is double the maximum permissible 
error of the density transducer under reference conditions.  
2.3.3 Maximum permissible error during use  
Unless otherwise specified by binding legislation, the figure used is double the maximum permissible 
error under reference conditions according to the measuring instrument type approval certificate.  
3 Technical requirements  
Technical requirements applicable to placing relative density transducers on the market are applied 
during verification.  
3.1 Measuring instrument design  
In general, a relative density transducer is a functional unit comprising a relative density sensor and a 
module that modifies and amplifies the output signal.This module may also include a means of setting 
the output signal’s zero value and measurement range.The sensor and this module are built into the 
casing of the relative density transducer.The transducer includes a pressure connector or c onnectors for 
connection to the pressure system, and an electrical connector or connectors.  
The design of the relative density transducer must take into account the operating conditions for its 
expected applications.  
3.2 Protection from unauthorised tampering  
3.2.1 Protection of adjustment elements  
The design and implementation of the relative density transducer must make it possible to protect 
adjustment elements from unauthorised tampering.  
3.2.2 External system interface  
In the case of relative density transducers equip ped with an external system interface that permits 
parallel or serial communication with an external data collection system, control system or manual 
terminal, it must be possible to protect transducer parameter changes from unauthorised tampering using 
this communication.  
The method of protection from unauthorised tampering and placement of official marks shall be 
specified in the measuring instrument’s type approval certificate.  General Measure No  0111 -OOP -C068 -17 
4 
 3.2.3 Electromagnetic compatibility  
Relative density transducers must not be affect ed by electrical or electromagnetic interference, or must 
react to it in a defined manner (for example by reporting an error, blocking measurements, etc.).In 
addition, they must not emit unwanted electromagnetic fields.  
During electromagnetic compatibility  tests, the measuring instrument must exhibit normal functionality 
within the maximum permissible error range pursuant to Article 2.3, or react in a defined manner  if this 
is exceeded.  
4 Instrument markings  
4.1 In general  
All inscriptions and markings must be easily visible, legible and indelible under ordinary conditions and 
must be a source of the information needed for the proper application of the relative density tra nsducer 
within the measurement system in relation to other system components.  
The use of internationally recognised markings and abbreviations is permitted.  
4.2 Mandatory labelling  
Relative density transducers must be labelled with the following:  
a) the manufacturer’s name or mark;  
b) the relative density transducer type;  
c) its serial number;  
d) the set measuring range;  
e) the output electrical signal (including units of measurement) and/or type of communication 
protocol (relevant information applicable to measuring instrument verification);  
f) power voltage;  
g) type approval mark;  
h) accuracy class;  
i) the relationship and parameters of dependence of the measured relative density on the output 
signal value.  
If a relative density transducer makes it possi ble to use various types of output signals, the transducer 
casing must clearly indicate which output signal is used in the application or which output signal was 
subject to verification.If a measuring instrument is not labelled in this manner, any of the l isted output 
signals may be used; all listed signals are subject to verification pursuant to this document.  
4.3 Marking with official marks  
Suitable areas for placement of the type approval mark and official mark(s) must be provided.  
For measuring instruments with built -in adjustment elements or means of changing metrological 
parameters, the access to these elements must be protected in an effective manner.  
It must be possible to secure the relative density transducer against unauthorised disassembly or 
substit ution.  
5 Type approval of measuring instruments  
The type approval process for a relative density transducer includes the following tests and activities:  
a) an external inspection;  General Measure No  0111 -OOP -C068 -17 
5 
 b) a basic functional test;  
 a measurement accuracy and repeatability test;  
c) tests of resistance to interference affecting measured quantities;  
 a test of resistance to ambient temperature limits;  
 a test of the effect of ambient humidity;  
 a vibration resistance test;  
 an installation position influence test;  
 a measuring instrument stability test;  
d) supplementary tests for electrically powered measuring instruments:  
 a test of immunity to changes in supply voltage and frequency;  
 an electromagnetic compatibility (EMC) test.  
Taking into account the intended use of the rela tive density transducer, tests other than those listed above 
may also be performed or, conversely, in justified cases, certain tests may be reduced or omitted entirely.  
5.1 External inspection  
The following is assessed during an external inspection:  
 that the  requisite technical documentation pursuant to §  6(2) of the Metrology Act is complete;  
 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 
Articles  2 and 3;  
 the completeness and condition of the density transducer according to the prescribed technical 
documentation.  
5.2 Test conditions during type approval  
5.2.1 Ambient conditions  
During type approval, ambient conditions must be maintained within the following limits depending on 
the intended use of the measuring instrument:  
 ambient temperature;(20  ± 3) °C; 
 ambient relative humidity:(60  ± 15) %; 
 atmospheric pressure:(86 to 106)  kPa, if the effect of atmospheric press ure is relevant.  
In justified cases, other ambient reference conditions may also be chosen.  
The tests shall be performed under ambient conditions specified for individual tests.  
The maximum ambient temperature rate of change during any test may be up to 1  °C every 10 minutes, 
but no more than 3  °C per hour (or the actual temperature must not change during the test by more than 
±1 °C).During the test, the ambient relative humidity must not change by more than 10  %. 
5.2.2 Electrical power supply specifications  
The reference values of the measuring instrument’s electrical power supply are stipulated by the 
manufacturer.The normal supply voltage for relative density transducers is 24 VDC.  
5.2.3 Load conditions  
The relative density transducer being tested must be connected t o a load in a manner specified by the 
manufacturer.The load value usually used for electrically powered measuring transducers is 250  Ω. General Measure No  0111 -OOP -C068 -17 
6 
 5.2.4 Installation position  
The relative density transducer must be installed according to the manufacturer’s instructions in only 
one of the stipulated normal operating positions with a tolerance of ±3° or less.  
During testing, the relative density transducer must have all of its covers installed.  
5.2.5 External vibrations  
The installation of a relative density transducer must rule ou t the effects of ambient vibrations on the 
transducer.  
5.2.6 External physical stress  
Aside from manufacturer -recommended installation tools, no external physical stress is permitted.  
5.2.7 Test equipment requirements  
Suitable equipment that meets the test requirements must be used for the individual type -approval tests 
of the relative density transducer.  
The following equipment is used to test metrological properties:  
 a reference gas source with a given purity grade (for methane at least 4.5; for nitrogen  or argon at 
least 5.0, other gases and mixtures with a relative density uncertainty equal to at most ½ the 
maximum permissible error of the tested measuring instrument under reference conditions);  
 devices and/or communications equipment for measurement and indication of the output signal 
of the tested relative density transducer;  
 devices for monitoring measurement conditions: thermometer, hygrometer, etc.;  
 auxiliary measuring devices: air pumps, regulators, flow meters, filters, etc.;  
 absolute pres sure references with measurement uncertainty of at most 0.01 % of the measured 
value;  
 a thermometer for measuring the temperature of the reference gas with a measurement uncertainty 
of at most 0.1 °C;  
 software or calculation procedures to stipulate the  density of the reference gas based on its 
composition, temperature and absolute pressure with a relative density equal to at most ½ the 
maximum permissible error of the tested measuring instrument under reference conditions.  
References used during the tes t must have valid metrological traceability.  
Software and calculation procedures must be validated with regard to their intended application.  
5.3 Basic functional tests  
5.3.1 Accuracy and repeatability test  
The test is performed at a minimum of two test points at a constant temperature using direct comparison 
with the reference measurement system.The test is performed in at least three repeated cycles involving 
ascending and descending loading directions.  
If it is possible to switch between ranges or change the relat ive density transducer’s settings, tests of 
parameters relating to accuracy will be performed with the range set to the maximum and minimum 
values declared by the manufacturer and at one intermediate position.  
The differences between the output signal valu es obtained at various test points with the relative density 
of the reference gas increasing and decreasing and the corresponding ideal values are recorded as output 
errors.  General Measure No  0111 -OOP -C068 -17 
7 
 Repeatability is determined using the measured and calculated values as the maximu m difference 
between all output values corresponding to any individual input value; this is carried out separately for 
ascending and descending loading directions.  
The condition stipulated in Article  2.3.1  for ambient reference conditions must be met at all test points.  
The repeatability value must not exceed one -half of the maximum permissible error under reference 
conditions specified in Article  2.3.1 . 
5.4 Tests of resistance to interference affecting measured quantities  
5.4.1 Test of resistance to ambient temperature limits  
The effect of ambient temperature must be  measured within the temperature range stipulated by the 
manufacturer or within limits suitable for temperatures corresponding to the operating location of the 
measuring instruments.  
The same properties are always to be tested at each of the selected ambie nt test temperatures, starting 
with the reference temperature (20  °C).Test temperatures are generally chosen in 20  °C increments until 
the relevant stipulated temperature limits are reached.The recommended test temperature tolerance is 
±2 °C and the rate o f ambient temperature change should be less than 1  °C per minute.Two or three 
temperature cycles shall be performed.A test pursuant to Article 5.3.1  is performed at  each test 
temperature.  
The condition stipulated in Article  2.3.2 for ambient operating conditions must be met for at least 90  % 
of test points.  
5.4.2 Test of the effect of ambient humidity  
The effect of ambient humidity is determined in a test chamber where the  relative humidity is maintained 
between -3 % to +2  % of the stipulated relative humidity values.  
The measuring instrument must be conditioned at reference humidity <  60 % and temperature 40  °C 
±2 °C, and subsequently undergo the test pursuant to Article 5.3.1 . 
The relative humidity is then increased to 93  % over a period of more than 3  hours and maintained at 
this value for at least 48  hours.The measuring instrument  need not be supplied with power during this 
time.A test pursuant to Article 5.3.1  is then performed.  
With the measuring instrument still in operation, the relative  humidity must be reduced over a period of 
more than 3  hours to the original reference value of <  60 %.After at least 12 hours of acclimatisation, 
the measurement must be repeated.  
After the test, a visual inspection of the measuring instrument is performe d for any signs of damage to 
individual parts or of moisture ingress into sealed covers.  
The condition stipulated in Article  2.3.2  for ambient operating conditions must be met at all test points.  
5.4.3 Vibration resistance test  
The test conditions will either be specified by the measuring instrument manufacturer or set with re gard 
to the expected operating environment.Measurement is performed under reference conditions before and 
after the measuring instrument is subjected to vibrations.  
The condition stipulated in Article  2.3.1  must be met at all test points for ambient reference conditions.  
5.4.4 Drop and tipping test  
Measurements under reference condition are performed before and after the tests.Inputs and power need 
not be connected during the test.  General Measure No  0111 -OOP -C068 -17 
8 
 The measurement transducer, placed in the normal position on a smooth, hard and rigid concrete or steel 
surface, shall be tilted around one of its bottom edges so that the opposite edge is 50 mm or 100 mm 
above the test surface or so that the ang le between the bottom surface and the test surface is 30° 
(whichever is more stringent).The measuring instrument shall then be allowed to fall freely onto the test 
surface.  
The transducer shall be subjected to one fall on each of its four lower edges.  
The condition stipulated in Article  2.3.2  must be met at all test points before and after the test.  
5.4.5 Installation position influence test  
If the transducer is position -sensitive, the change to the lower range and span limit caused by a tilt of 
10° from the position(s) specified by the manufacturer must be measured and recorded.  
Four measurements shall be performed with the transducer tilted in two mutually perpendicular planes.  
In cases where, due to the measuring instrument's design, a tilt of 10° is too large, the maximum tilt 
specified by the manufacturer must be used.If position -dependent measurement error correction cannot 
be performed for the measuring instrument, t he condition stipulated in Article  2.3.1  must be met.  
5.4.6  Measuring instrument stability test  
The purpose of this test is to simulate measuring instrument ageing and confirm that it meets the given 
specifications.  
First, a test pursuant to Article 5.3.1  is performed. The  measuring instrument is then exposed to ambient 
temperature changes that cycle between the minimum and maximum operating temperature.The 
measuring instrument is alternately exposed to the maximum operating temperature for one week and 
then to the minimum temperature for one week.The entire duration of the test shall be 4 weeks.Changes 
between minimum and maximum temperatures shall take place in steps of 10 °C·h-1.After stabil isation 
under reference conditions for 24  hours, the test pursuant to Article 5.3.1  must be repeated.  
At all test points, the absolute value of the error differenc e before and after the stability test must not 
exceed the maximum permissible error under reference conditions pursuant to Article 2.3.1 . 
5.5 Supplementary tests for electrically powered relative density transducers  
5.5.1 Tests of immunity to changes in supply voltage and frequency  
Tests are performed at a constant output signal value.The condition stipulated in Article  2.3.1  for 
ambient reference conditions must be met at all test points.  
5.5.1.1 Test of immunity to AC supply voltage limit values  
Immunity to AC supply voltage limit values shall be tested with the transducer switched o n at the lowest 
specified voltage, at nominal voltage and at the highest specified voltage at nominal frequency.  
5.5.1.2 Test of immunity to changes in AC supply voltage frequency  
Immunity to changes in AC supply voltage frequency shall be tested with the transducer switched on at 
the lowest specified frequency, at nominal frequency and at the highest specified frequency at nominal 
supply voltage.  
5.5.1.3  Test of immunity to DC supply voltage limit values  
Immunity to DC supply voltage limit values shall be tested with the transducer switched on at limit 
voltage values of Umin and Umax, where Umin and Umax are DC supply voltage limit values specified by 
the manufacturer of the measuring instrument.  General Measure No  0111 -OOP -C068 -17 
9 
 5.5.2 Electromagnetic compatibility tests  
During testing, the transducer’s output signal is monitored.The condition stipulated in Article 2.3.1  for 
reference ambient conditions must be met prior to each el ectromagnetic compatibility test.The 
difference between the errors recorded before and during electromagnetic compatibility tests must not 
exceed the maximum permissible error under reference or operating conditions, or the relative density 
transducer must  react in a defined manner.  
5.5.2.1 Resistance to supply voltage dips and short interruptions  
The transducer's resistance to supply voltage dips is tested at nominal supply voltage.  
The supply voltage is reduced to 75  % of the nominal supply voltage for 5  seconds.In order to rule out 
transients, the ramp -up period should not be shorter than 100  ms. 
For DC -powered devices, the interruptions must last 5  ms, 20  ms, 100  ms and 500  ms. 
For AC -powered devices, dips always begin when the voltage passes through its  zero point, sequentially 
before both the positive and negative cycle.The interruption must last for 1, 5, 10, and 25  AC voltage 
cycles.  
5.5.2.2  Resistance to asymmetric interference caused by power lines in the 0 to 150 kHz frequency 
range  
The following is applied to transducers with input/output terminals isolated from the ground potential:  
 250 Vef AC at mains frequency consistently on insulated input/output terminals;  
 50 VDC consistently on insulated input/output terminals.  
After the test, the trans ducer must function normally and all measured errors must be within the range 
of the relative density transducer’s permissible errors stipulated in Article  2.3.1 . 
5.5.2.3 Resistance to symmetric interference  
1 Vef AC is applied to the transducer's output terminals at constant output signal voltage.  
5.5.2.4 Resistance to bursts (transients)  
The relative density transducer’s immunity to electrical fast transient/burst  disturbances is tested with 
the transducer switched on using the following voltages:  
±2 kV on the AC supply voltage terminals;  
±2 kV on the DC supply voltage terminals;  
±1 kV on terminals for signal, data, and control lines longer than 3  m; 
±2 kV on termi nals for signal, data, and control lines that can be connected directly to power grids.  
The pulse repetition frequency is 5  kHz, the interval of repetition of groups of pulses is 300  ms and the 
total duration of the test for each of the inputs and one puls e polarity is at least 1  minute.  
During testing, the transducer’s output signal shall be monitored.  
5.5.2.5 Resistance to surges  
The relative density transducer's resistance to surges is tested when it is switched on with a surge of tr/th 
= 1.2/50 (8/20) µ s with the following voltage:  
±2 kV asymmetric and ±1  kV symmetric on AC or DC power inputs;  
±1 kV  asymmetric on signal, data and control lines longer than 30 m not directly connected to the 
power grid;  
±2 kV asymmetric and ±1  kV symmetric on signal, data and control lines.  
During testing, the transducer’s output signal is monitored.  General Measure No  0111 -OOP -C068 -17 
10 
 5.5.2.6 Resistance to a slow, damped oscillatory wave  
The relative density transducer’s immunity to a slow damped oscillatory wave is tested with the 
transducer switched on using a slow 1  MHz and 0.1  MHz oscillatory wave, where the voltage of the first 
peak on the test waveform is 1.0  kV for asymmetric mode and 0.5  kV for symmetric mode.  
5.5.2.7 Resistance to conducted disturbances induced by radio frequency fields  
The relati ve density transducer's resistance to conducted disturbances induced by radio frequency fields 
is tested when it is switched on, over a frequency range of 150 kHz to 80 MHz, with an open -circuit test 
voltage of 10 V. The disturbance is applied to:  
 AC or DC power inputs;  
 signal data, and control lines longer than 30  m not directly connected to the power grid;  
 signal, data and control lines directly connected to the power grid.  
During testing, the transducer’s output signal is monitored.  
5.5.2.8 Resista nce to electrostatic discharge  
Immunity to electrostatic discharge is tested with the transducer switched on, using a voltage of ±6 kV 
for contact discharge and ±8 kV for air discharge.The discharges shall be applied to the transducer’s 
enclosure and the coupling plane adjacent to the transducer.  
During testing, the transducer’s output signal is monitored.  
5.5.2.9 Resistance to a power frequency magnetic field  
Long -term immunity to a power frequency magnetic field is tested with the transducer switched on in a 
100 A/m magnetic field.The transducer shall be exposed to the field consecutively along all three basic 
axes.  
Short -term resistance to a power frequency magnetic field is tested with the transducer switched on in a 
400 A/m magnetic field for 1 second. The transducer must be exposed to the field consecutively along 
all three basic axes.  
5.5.2.10 Resistance to a damped oscillatory magnetic field  
Immunity to a damped oscillatory magnetic field is tested with the transducer switched on, in a magnetic 
field with a peak intensity of 30  A/m and at an oscillation frequency of 0.1 MHz and 1.0 MHz.The 
transducer shall be exposed to the field consecutively along all three basic axes.During testing, the 
transducer’s output signal is monitored.  
5.5.2.11 Resistance to  a radiated high -frequency electromagnetic field  
Immunity to a radiated radio -frequency electromagnetic field is tested with the transducer switched on, 
in the frequency range of 80  MHz to 1  GHz at a test field intensity of 10  V/m.The test field shall be 
amplitude -modulated to a depth of 80  %; the modulation signal shall have a sinusoidal waveform with 
a modulation frequency of 1  kHz.The frequency step during the wobble of the test field is at most 1  %, 
the delay for each frequency must not be less than the  time needed to examine the tested measuring 
instrument and/or for any reaction of the tested transducer to interference; in no case may it be shorter 
than 0.5  s.The test field is applied to all sides of the transducer’s cover.  
During testing, the transduc er’s output signal is monitored.  
6 Initial verification  
Initial verification may only be performed if the density transducer meets the technical and metrological 
requirements and labelling requirements stipulated in Articles  2, 3, and 4 of this general measure and if 
it has a valid type -approval certificate.If the manufacturer specifies a functional relationship between 
the input and output, all calibration constants of this relationship must be known.  General Measure No  0111 -OOP -C068 -17 
11 
 The following is performed during i nitial verification of a relative density transducer:  
 a visual inspection, including a labelling check;  
 an accuracy test and a repeatability test.  
6.1 Visual inspection  
The purpose of the visual inspection is to check that:  
 the measuring instrument submitted for verification conforms to the approved type;  
 the measuring instrument is not physically damaged and that none of its parts are loose;  
 the measuring instrument does not show signs of corrosion that would impair its metrological 
characterist ics; 
 the content and implementation of markings and inscriptions correspond to the data and 
requirements specified in the type approval certificate for the measuring instrument.  
If the measuring instrument fails to meet external inspection requirements, no further tests are 
performed.  
6.2 Test conditions during verification  
6.2.1 Test equipment  
The requirements are defined in Article 5.2.7. 
6.2.2 Conditions during tests  
6.2.2.1 Ambient conditions when testing a relative density transducer  
The tests must be performed under the following ambient conditions:  
 temperature:(20  ± 5) °C; 
 relative humidity:(50  ± 30) %; 
 atmospheric pressure:(86 to 106)  kPa, if the effect of atmospheric pressure is relevant.  
The maximum permitted rate of ambient temperature change during the test is 1  °C per 10 minutes, but 
no more than 3  °C per hour.  
6.2.2.2 Power supply specifications  
The requirements are defined in Article 5.2.2 . 
6.2.2.3 Loading specifications  
The requirements are defined in Article 5.2.3 . 
6.2.2.4 Installation position  
Pursuant to Article 5.2.4 , the tested transducer must be installed acco rding to the manufacturer’s 
instructions and in accordance with its type approval certificate in its operating position with a tolerance 
of ±3° or less.  
6.2.2.5 External vibration  
The requirements are defined in Article 5.2.5 . 
6.2.2.6 External physical stress  
The requirements are defined in Article 5.2.6 . General Measure No  0111 -OOP -C068 -17 
12 
 6.3 Accuracy and repeatability test  
The relative density transducer’s temperature must be sufficiently stabilised.The accuracy test is 
performed with pure gases or with a gas mixture or mixtures with known relative density.  
The test is performed at  a minimum of two test points at a constant temperature using direct comparison 
with the reference measurement system.The test is performed in at least three repeated cycles involving 
ascending and descending loading directions.  
The difference between the output signal values obtained at various test points at increasing and 
decreasing relative gas densities and their corresponding ideal values are recorded as measurement 
errors.  
Repeatability is determined using the measured and calculated values as the ma ximum difference 
between all output values corresponding to any individual input value; this is carried out separately for 
ascending and descending loading directions.  
The condition stipulated in Article  2.3.1  for reference ambient conditions must be met at all test points, 
as must the condition that the repeatability value at all points equals at most half the maximum 
permissible error for ambient reference conditi ons pursuant to Article 2.3.1 , or the maximum permissible 
repeatability value according to the measuring instrument's type -approval certificate.  
The measuring inst rument must allow for protection against unauthorised tampering in accordance with 
Articles 3.2 and 4.3. 
The official verification mark or marks are affixed to relative density transducers that meet the specified 
requirements in the spaces specified in the type -approval certificate.  
7 Subsequent verification  
The subsequent verification procedure is identical to that for initial verification pursuant to Article 6. 
8 Measuring instrument check  
When checking measuring instruments pursuant to § 11a of the Metrology Act at the request of an entity 
that could be affected by its incorrect measurement, Chapter  7 is followed.The maximum permissible 
error used is double the maximum permissible errors pursuant to Chapter 7.  
9 Notified standards  
For the purposes of specifying the metrological and technical requirements for measuring instruments 
and specifying the tes ting methods for their type approval and verification stemming from this general 
measure, the CMI shall notify Czech technical standards, other technical standards or technical 
documents of international or foreign organisations, or other technical documen ts containing more 
detailed technical requirements (hereinafter referred to as ‘notified standards’).The CMI shall publish a 
list of these notified standards attached to the relevant measures, together with the general 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 a general measure, 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.  General Measure No  0111 -OOP -C068 -17 
13 
 II. 
G R O U N D S  
The CMI issues, pursuant to §  14(1)(j) of the Metrology Act, towards the implementation of § 6(2),  
§ 9(1), §  9(9) and §  11a(3) of the Metrology Act, this general measure, stipulating metrol ogical and 
technical requirements for specified measuring instruments and tests for the type approval and 
verification of specified measuring instruments - 'flow -through vibrational relative gas density 
transducers'.  
Implementing Decree No 345/2002 specify ing measuring instruments for mandatory verification and 
measuring instruments subject to type approval, as amended, classifies the measuring instruments under 
item 1.3.11(g) in the annex entitled ‘List of legally controlled measuring instruments’ as measu ring 
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.  
III. 
I N S T R U C T I O N S  
In accordance with §  172(l), in conjunction with §  39(l) APC, the CMI has stipulated a time limit for 
comments of 30  days as of the date of posting on the official notice board.Comments submitted after 
this time limit will not be considered.  
The persons concerned are hereby invited to comment on this draft general measure.With a view to the 
provisions of §  172(4) APC, the co mments shall be submitted in writing and meet the requirements for 
submissions in accordance with §  37 APC.  
The comments shall include the particulars referred to in §  37(2) APC and clearly state the following: 
who is making the comments; which general mea sure they concern; to what extent the comments 
challenge the measure; how the general measure runs contrary to legislation or how the general measure 
or the procedure that preceded it is inaccurate; which matters the comments concern and what is being 
proposed. Said comments must also identify the administrative authority to which they are addressed 
and be signed by the person making them.  
The supporting documents for this draft general measure may be consulted at the Czech Metrology 
Institute, Legal Metrol ogy Department, Okružní 31, 638 00 Brno, after making arrangements by 
telephone.  
This general measure shall be posted for 15  days.  
 
 
 
 
 
 
 ................................ .............................   
RNDr.  Pavel Klenovský  
Director -General  
 
 General Measure No  0111 -OOP -C068 -17 
14 
 Person responsible for accuracy:  Mgr.  Tomáš Hendrych  
 
Posted on:  12 April  2018  
Signature of the authorised person confirming posting:   ................................ .............   
 
Removed on:  
Signature of the authorised person confirming removal:   ................................ .............