C z e c h  M e t r o l o g y  I n s t i t u t e  
Okružní 31,  638 00  
Brno  
 
1. ------IND- 2012 0301 CZ - EN- ------ 20120119 --- --- PROJET 
 
The Czech Metrology Institute  (CMI), being the competent authority  for laying down metrological and 
technical requirements for legal measuring instrument s and laying down testing methods for t he type 
approval and verification of legal measuring instrument s pursuant to Section 14(1) of Act No 
505/1990  Coll. on metrology, as amended, and pursuant to the provisions of Section 172 et seq. of Act 
No 500/2004  Coll., the Administrative Code, as amende d, initiated  ex officio  administrative 
proceedings on 10 February 2012 pursuant to Section 46 of the Administrative  Code and, on the basis 
of supporting documentation, hereby issues this : 
 
 
I 
G E N E R A L  M E A S U R E  
Number : 0111 -OOP -C027-12 
Ref. No:  0313/ 002/12/Pos., 
 
 
establishing the metrological and technical requirements for legal measuring instruments, 
including testing methods for the type approval and verification of the legal measuring 
instruments : 
‘electronic thermometers for checking ambient and hot utili ty water temperatures with intervals 
of 0.1°C and smaller that are used by state inspection bodies’  
 
1   Basic definitions  
For the purposes of this General Measure, the terms and definitions according to the VIM1) and the 
following terms and definitions sh all apply : 
electronic thermometers for checking ambient and hot utility water temperatures that are used 
by state inspection bodies (hereinafter referred to as ‘thermometers’) : thermometers used to 
check the fulfilment of requirements for heating and hot w ater supply  for the purposes of a separate 
legal regulation2) 
                                                      
1) International  Vocabulary of Metrology —Basic and General Concepts and Associated Terms  (VIM)  
2) Regulation No 194/2007 Coll. of the Ministry of Industry and Trade establishing rules for heating and hot 
water supply, indicators for heat consumption for heating and hot wa ter preparation, and requirements for the 
installation of devices for internal heating equipment  General Measure No 0111 -OOP -C027-12 
2 2   Metrological requirements  
2.1   Specified working conditions  
The correct functioning of a thermometer must be guaranteed under the following working conditions:  
– ambient temperature in the range  (–10 to 50)°C 
– relative humidity in the range  (10 to 95)  %. 
2.2   Measurement interval  
The measurement interval of a thermometer for checking the ambient temperature must be at least 
from –10.0°C to +50.0°C. 
The measurement interval of a thermometer f or checking the temperature of hot water must be at least 
from  0.0°C to 100 .0°C. 
2.3   Maximum permissible error  
The maximum permissible error of a thermometer as a unit for checking the ambient temperature or 
checking the temperature of hot water shall b e ±0.4°C. 
2.4   Response time  
The response time of a thermometer for checking the temperature of hot water  must be ≤ 60 s. 
The response time of a thermometer for checking the ambient temperature must be  ≤ 180 s. 
2.5   Maximum permissible error in recording time  
If a thermometer for checking the ambient temperature is fitted with a recording device for registering 
meas ured values over a time interval, the maximum permissible error in the recording time shall be 
±0.2% of the recording time . 
3   Technical requirements  
3.1   General  
Thermometers must be designed to  measure air temperature, water temperature or both variabl es. 
Thermometers may be compact or have structurally separate parts. The design of a thermometer must 
permit its verification as a unit.  
The structural component materials must be resistant to the various forms of corrosion and wear that 
occur under normal  operating conditions.  
3.2   Temperature sensor  
Resistive temperature sensors shall be used in these thermometers.  The temperature sensor may be 
internal (built into the body  of the device) or external . General Measure No 0111 -OOP -C027-12 
3 An external temperature sensor may form a single uni t together with the thermometer or it may be 
detachable, e.g. using a connector. A detachable temperature sensor must be permanently identifiable 
so as to avoid the possibility of confusion . 
If the connecting wir ing length  might have a significant effect o n the metrological properties of the 
measuring instrument or the external temperature sensor is difficult to identify, the external 
temperature sensor must be permanently connected to the evaluation unit and no access to the 
connecting terminals m ust be po ssible without breaking the official mark s. 
The design of the temperature sensor must be such that it cannot be damaged and its metrological 
properties (especially its water  tightness and chemical and mechanical resistance) cannot be affected 
by normal use  or cleaning . 
In the case of thermometers that have a protective casing comprising electrically conductive parts 
where the insulation resistance value (the resistance between the internal wiring and the sensor casing ) 
might affect the metrological properti es of the thermometer, the insulation resistance value must be 
greater than 100 M
  at a test voltage of up to 100 V and an ambient temperature of (15 to 25) °C. 
A temperature sensor must be designed so as to permit its immersion in hot water or the working fluid 
of a thermostatic bath (alcohol, water, oil) during use or verification wit hout damaging it or affecting 
its properties.  
3.3   Indication devices  
An analogue indication device  of a thermometer must have a scale interval of  ≤ 0.1°C.  
A digital indication device  of a thermometer must have a resolution of 0. 1°C or smaller .  
The heig ht of the digits on indication devices  (displays) must be at least 4 mm . 
The measurement units shall be  °C.  
If a measuring instrument is not equipped with a display, measured indications may be displayed via a 
communications interface that permits the con nection of peripherals (PC, printer). This interface must 
not affect its metrological properties.   
The design of the measuring instrument must ensure that recorded indications cannot be altered or 
deleted using  ordinary  computer technologies at the user le vel. 
3.4   Peripherals  
A thermometer may be fitted with a  recording device for monitoring temperature behaviour at set 
intervals and recording the temperature behaviour in the internal memory of the measuring instrument.   
A thermometer for checking the amb ient tem perature and a thermometer for checking the temperature 
of hot water may be combined as a single unit with other measuring instruments, for example a 
hygrometer or a barometer; their operation must not, however, affect or disable the temperature 
measurement functions or the accuracy of the measurement of temperature.  
3.5   Software  
For electronic thermometers, device -identifiable software must be used (except where only measured 
values are display ed, without other functions). Software must be secure d against accidental or General Measure No 0111 -OOP -C027-12 
4 intentional effects and damage, and must comply with the technical standards document WELMEC 
7.23). 
3.6   Power supply  
Thermometers may be powered from a mains supply via an adapter or from an independent battery 
source . 
It must be possible to connect a thermometer with an external power supply to a supply of rated  value  
12 V or 24 V (alternating and direct current ).  
Thermometers connected to the mains must be supplied with alternating current  UN in the range UN – 15 % 
and UN + 10 %, where UN is the rated  voltage specified by the manufacturer of the measuring instrument, 
with a frequency fN 
 2 %. 
For reference purposes, a voltage UN ± 2 % and frequency fN 
 0.4 % are used .  
An independent power source must be defined in the manufact urer’s specifications and the 
thermometer must indicate the need to recharge or replace the power source , and block itself or switch 
itself off if the source voltage drops below the limit specified by the manufacturer.  
3.7   Resistance to external influenc es 
3.7.1   Mechanic al resistance   
The design of the thermometer and materials used must guarantee sufficient strength, stability and 
resistance to mechanical shock and free fall .  
3.7.2   Resistance to climatic conditions   
3.7.2.1   Limiting conditions for  storage and transportation  
During storage, a thermometer and its constituent parts must withstand  temperature limits  of 
30°C to 
+70°C without damage or deterioration of its metrological properties.   
3.7.2.2   Degree of protection provided by enclosures , electromagnetic compatibility  
The degree of protection provided by enclosures must be : 
– IP 65 for immersion temperature sensors ; 
– IP 55 for indication devices  and portable compact thermometers.  
3.8   Electromagnetic compatibility  
Thermometers that contain el ectronic components must not be affected by electrical or 
electromagnetic interference, or they must respond to such interference in a defined way (for example, 
by reporting an error, blocking measurement, etc.). They must furthermore not emit unwanted  
electromagnetic fields . 
For thermometers containing electronic components, an E1 electromagnetic environment is defined 
(i.e. residential and commercial premises or light industrial environments) . 
                                                      
3) WELMEC 7.2 Software Guide; publicly accessible at www.welmec.org  General Measure No 0111 -OOP -C027-12 
5 3.9   Resistance to  unauthorised manipulation  
Thermometers mus t have no properties that might facilitate fraudulent use, and the possibility of their 
unintentional misuse must be minimal. Components that must not be dismantled or adjusted by the 
user must be secured against such actions . 
The adjustment devices of a t hermometer must be secured so that settings cannot be changed during 
normal handling without breaking the official marks . 
4   Marking of a measuring instrument  
4.1   Markings on a measuring instrument  
Measuring instruments must be clearly and visibly mar ked with the following information:   
– the name or mark of the manufacturer;  
– the type of measuring instrument;  
– the serial number and year of manufacture of the measuring instrument;  
– the type approval mark of the measuring instrument ; 
– the range of working tem peratures;  
– the measurement unit (°C) must be stated on the scale or indication device . 
In the case of a temperature sensor t hat can be detached from its indication device , the sensor label 
must , at a minimum , state the unambiguous assignment of the sensor to the indication device (e.g. 
serial number) and a space must be reserved on the body of the sensor for an official mark. All data, 
specifications, information, etc., required under the provisions of this General Measure must be given 
in the operating man ual. 
4.2   Location of the official mark  
A space must be prepared on a measuring instrument for the affixing of official marks. The location of 
official marks on a thermometer shall be  specified in the type approval certificate of the measuring 
instrument.  
5   Type approval of a measuring instrument  
5.1   General  
The type approval process for an electronic thermometer shall comprise the following tests : 
– external inspection ; 
– functional tests : 
– insulation resistance test ; 
– accuracy test ; 
– determination of respon se time ; 
– determination of recording time errors of the recording device ; 
– tests of resistance to external influences:  
– test of ability to withstand the temperature limits for storage and transportation ; 
– test of protection against the ingress of water and for eign particles (degree of protection 
provided by the enclosure ); General Measure No 0111 -OOP -C027-12 
6 – test of resistance to limit ing supply voltage values : 
– test of resistance to  limit ing alternating current values ; 
– test of resistance to  changes in alternating current frequency ; 
– test of resist ance to  limiting direct current supply voltage values ; 
– electromagnetic compatibility tests : 
– test of resistance to  a radiated high -frequency electromagnetic field ; 
– test of resistance to  an electrostatic discharge . 
5.2   External inspection   
In an external inspection of a thermometer, the following shall be assessed : 
– the completeness of the prescribed technical documentation;  
– the conformity of the metrological and technical characteristics specified by the manufacturer 
in the documentation with the requireme nts of this regulation pursuant to sections 2, 3 and 4 ; 
– the completeness and condition of the thermometer according to the prescribed technical 
documentation ; 
– the compatibility of the thermometer software with the version specified by the manufacturer, 
where relevant  (see section 3.5). 
If any serious deficiencies are found, the measuring instrument shall not be tested further . 
5.3   Functional tests  
5.3.1   Testing equipment  
The following equipment shall be used in the tests : 
a) a standard thermometer with a p latinum resistive temperature sensor with a minimum 
measurement interval of (–20 to +120)°C and a combined measurement uncertainty smaller 
than 
0.03°C; 
b) fluid thermostatic baths with a minimum temperature range of (–20 to +120)°C enabling the 
testing of te mperature sensors with a minimum immersion of 200 mm and a combined 
standard measurement uncertainty caused by the effects of  temperature field homogeneity and 
stability smaller than  
 0.03°C; 
c) a climatic chamber for testing thermometers with an internal t emperature sensor ; 
d) a device for measuring resistance (DC or AC) with a range according to the type of standard 
resistive thermometer;  
e) a stopwatch or other time measurement device with a minimum measurement interval of 10 h 
and a permissible error smaller t han 0.02% of the recording time ; 
f) an insulation resistance measuring instrument —direct current up to 100 V, range up to at least 
100 M
. 
All measuring instruments must have a valid connection, and the thermostat must have an established 
and measured homogen eity and stability . General Measure No 0111 -OOP -C027-12 
7 5.3.2    Insulation resistance test  
Insulation resistance shall be  measured in thermometers supplied with power from the mains at the 
ambient temperature between the conductors of the internal wiring of the sensor and the electrically 
conductive casing of the sensor. The test shall only be carried out if the internal wiring conductors are 
accessible. The test shall be carried out with a direct current test voltage of up to 100 V at both polarities 
of the test voltage; the result of the te st shall be the lower of the two measured values of insulation 
resistance.   
The measured value must meet the requirements for insulation resistance according to section  3.2. 
5.3.3   Accuracy test  
A thermometer for checking the temperature of hot water and a thermometer for checking the ambient 
temperature shall be tested at five points evenly distributed across the whole measurement interval. 
The first and last points must be close to the measurement interval limit . 
In the test, the actual steady temperatur e of the bath as determined by a standard thermometer shall be  
compared with the indications of the test thermometer. A series of at least four readings of the 
standard thermometer and the test thermometer shall be made at each test temperature.  
Measuremen t errors at the individual points must not exceed the maximum permissible errors given in 
section 2.3. 
5.3.4   Determination of response time  
The response time shall be determined in a thermostatic bath that is set at a temperature of 20°C higher 
or lower than the initial temperature (e.g. ambient temperature). The thermometer shall be allowed to 
stabilise at the initial temperature, and the temperature sensor shall then be immersed in the 
thermostatic bath as quickly as possible. The time from the instant of immersion of the temperature 
sensor until an indication of 90% of the actual temperature change is reached shall be measured.  
The observed response time must not exceed the response time specified in section 2.4.  
5.3.5   Determination of recording time errors of a recording device  
In this test, the error in the recording time specified in the technical requirements for recording devices 
shall be  checked. The check may be carried out either by evaluating a test record or by another 
procedure if one is recommended by the manufacturer and can be used for this purpose.  
The recording time error must be less than or equal to the maximum permissible error specified in 
section 2.4 . 
5.4   Tests of resistance to external influences  
5.4.1    Test of ability to withst and temperature limits for storage and transportation  
A whole thermometer that is not in operation must be placed in a climatic chamber for a period of 
three hours at both temperature limit s of –30°C and +70°C and at a rate of temperature change of 
1°C/min during the transition from one temperature limit  to the other. This shall be carried out over 
five cycles . 
Immediately after the end of the test, the measuring instrument shall be checked for any change in 
appearance. It must not have changed in appearanc e, and the material and surface must not be cracked, 
blistered or discoloured.   General Measure No 0111 -OOP -C027-12 
8 After two hours have passed from  the end of the test, the thermometer at the reference temperature 
must meet the requirements set out in section 2.3. 
5.4.2    Test of protection  against the ingress of water and foreign particles (degree of protection 
provided by the enclosure)  
This test shall verif y whether the measuring instrument conforms to the specified degree of protection 
pursuant to section  3.7.2.2. 
NOTE    ‘Enclosure’ shall mean the casing of the instrument in the working position, i.e. including connectors 
(with possible closing devices), seals and other fittings.  
5.5   Tests of resistance to limiting supply voltage values  
5.5.1    Test of resistance to  limiting alternating  current values  
Resistance to  limiting alternating current values shall be tested on a thermometer that is switched on at 
the limiting voltage values UN – 15% a nd UN + 10%, where UN is the rated  supply voltage specified by 
the manufacturer of the measuring  instrument. If the supply voltage is determined within a range of 
rated  voltage values, the test shall be carried out at the lowest and highest voltages  in the range .  
Measurement errors at the limiting supply voltage values must not exceed the maximum pe rmissible 
errors pursuant to section  2.3. 
5.5.2    Test of resistance to  changes in alternating current frequency  
Resistance to  changes in supply voltage frequency shall be tested on a thermometer that is switched on 
at the limiting frequencies of fN ±2% , where fN is the rated  frequency of the supply voltage.  
Measurement errors at the limiting supply voltage frequency values must not exceed the maximum 
permissible errors pursuant to section  2.3. 
5.5.3    Test of resistance to  limiting direct current supply vo ltage values  
Resistance to  limiting direct current supply voltage values shall be tested on a thermometer that is 
switched on at the limiting voltage values of Umin and Umax, where  Umin and Umax are the limiting 
supply voltage values specifi ed by the manuf acturer of the measuring instrument.  
Measurement errors at the limiting supply voltage frequency values must not exceed the maximum 
permissible errors pursuant to  section  2.3. 
5.6  Electromagnetic compatibility (EMC) tests  
5.6.1    Test of resistance to  an electrostatic  discharge  
Resistance to  an electrostatic  discharge shall be tested on a thermometer that is switched on , preferably 
at a voltage of ±6 kV for a contact discharge, or ±8 kV for an air discharge if a contact discharge 
cannot be used. Discharges  shall be applied to the enclosure of the thermometer and to coupling plates 
close to the thermometer.  
In this test, the thermometer must function normally  within the limits of the maximum permissible 
error pursuant to section  2.3, or it must identify a se rious error and react to it in a defined way . 
5.6.2   Test of resistance to a radiated high -frequency electromagnetic field   
Resistance to  a radiated high -frequency electromagnetic field shall be tested on a measuring 
instrument that is switched on , in the  frequency band : General Measure No 0111 -OOP -C027-12 
9 – frequency 80 MHz  to 800 MHz, inten sity 3 V/m;  
– frequency 800 MHz  to 960 MHz, intensity 10 V/m;  
– frequency 960 MHz  to 1 400 MHz, intensity 3 V/m;  
– frequency 1 400 MHz  to 2 000 MHz, intensity 10 V/m.  
The intensity amplitude values of the test f ield are given for measurements without modulation. The 
test field shall be amplitude modulated with a depth of 80%, and the modulation signal shall be 
sinusoidal with a modulation frequency of 1 kHz. The frequency step in a frequency scan of the test 
field shall be not more than 1%. The dwell time at each frequency must be less than the time required 
to test the thermometer, including its ability to respond to disturbances. Under no circumstances, 
however, may it be less than 0.5 s. The test field shall be  applied to all sides of the thermometer 
enclosure . 
In this test, the thermometer must function normally within the limits of the maximum permissible 
error pursuant to section 2.3, or it must identify a serious error and react to it in a defined way . 
6   Initial verification  
New electronic thermometers and post -repair electronic thermometers shall undergo initial 
verification.  
6.1   General  
The initial verification process for a thermometer for checking the ambient  temperature or the 
temperature of hot uti lity water shall comprise the following tests : 
– visual inspection ; 
– functional tests : 
– insulation resistance test ; 
– accuracy test . 
6.2   Visual inspection   
In this visual inspection of a thermometer, the following shall be assessed:  
a) whether the measuring instr ument submitted for verification and its components conform to 
the approved type ; 
b) whether the thermometer and its components, including connecting cables, are mechanically 
damaged or show signs of corrosion ; 
c) whether marking s and notices and their design co rrespond to the data and requirements set out 
in the type approval certificate for the measuring instrument.  
If the measuring instrument does not meet the visual inspection requirements, it shall not be tested 
further . 
6.3   Functional tests  
6.3.1   Testin g equipment  
The appropriate equipment shall be used in tests pursuant to section  5.3.1. General Measure No 0111 -OOP -C027-12 
10 6.3.2    Insulation resistance test  
An i nsulation resistance test  of a thermometer shall be carried out on new and repaired measuring 
instruments pursuant to section  5.3.2. 
If a measured value does not meet the insulation resistance value requirements  pursuant to section  3.2, 
the thermometer shall not be tested further . 
6.3.3   Accuracy test  
An accuracy test  of a thermometer shall be carried out pursuant to section  5.3.3. 
The measurement error must not be greater than the values specified in section  2.3. 
6.3.4   Determination of recording time error   
Determination of the recording time error of a recording device of a thermometer shall be carried out 
pursuant to section  5.3.5. 
The recording time error must be less than or equal to the maximum permissible error specified in  
section  2.5. 
7   Subsequent verification  
7.1   General  
The subsequent verification process for an electronic thermometer for checking the ambient  
tempera ture or the temperature of hot utility water shall comprise the following tests:  
– visual inspection ; 
– functional tests —accuracy test . 
7.2   Visual inspection   
The v isual inspection  of a thermometer in a subsequent verification shall be carried out pursuant t o 
section  6.2. 
7.3   Functional tests  
7.3.1   Testing equipment  
The appropriate equipment shall be used in tests pursuant to section 5.3.1. 
7.3.2   Accuracy test   
An a ccuracy test  of a thermometer in a subsequent verification shall be carried out pursuant to section  
5.3.3. 
8   Notified standards  
For the purposes of specifying the metrological and technical requirements for measuring instruments 
and of specifying the testing methods during their type approval and verification stemming from this 
General Measu re, the CMI shall provide notification of Czech technical standards, other technical 
standards and technical documents issued by international or foreign organisations, and other technical 
documents containing detailed technical requirements (hereinafter r eferred to as ‘notified standards’). General Measure No 0111 -OOP -C027-12 
11 The CMI shall p ublish a list of such notified standards and their assignation to the relevant measures, 
together with the General Measure, in a publicly accessible m anner  (on the website www.cmi.cz ). 
Compliance with t he notified standards or parts thereof shall, within the scope and under the 
conditions specified by a general measure, be considered to be compliance with the requirements 
specified in th e general measure to which the stand ards or parts thereof apply . 
 
 
II 
S U B S T A N T I A T I O N   
The CMI issues , for the implementation of Section 24c of Act No 505/1990 Coll. on metrology, as 
amended , this General Measure establishing the metrological and technical requirements for legal 
measuring ins truments and the testing methods for the type approval and verification of such legal 
measuring instruments.  
Regulation No 345/2002  Coll. establishing measuring instruments for mandatory verification and 
measuring instruments subject to type approval, as a mended, classifies electronic thermometers for 
checking ambient and hot utility water temperatures with intervals of 0.1°C and smaller that are used by 
state inspection bodies and that are subject to type approval and verification  under item 3.1.4 b) of th e 
annex ‘List of Legal Measuring Instrument  Type s’. 
The CMI therefore issues , for the implementation of Section 24c of Act No 505/1990 Coll. on 
metrology, as amended,  this General Measure in respect of th e specific type of measuring instrument, 
‘electronic  thermometers for checking ambient and hot utility water temperatures with intervals of 0.1°C 
and smaller that are used by state inspection bodies’, which establishes the metrological and technical 
requirements for electronic thermometers for checking ambi ent and hot utility water temperatures with 
intervals of 0.1°C and smaller that are used by state inspection bodies and the testing methods of the type 
approval and verification of such legal measuring instruments.  
This regulation (General Measure) has bee n notified pursuant to Directive 98/34/EC of the European 
Parliament and of the Council of 22 June 1998 laying down a procedure for the provision of 
information in the field of technical standards and regulations and of rules on Information Society 
service s, as amended 98/48/E C. 
 
 
III 
N O T I C E  
No remedy may be sought against this General Measure (Section 173(2) of Act No 500/2004  Coll., the 
Administrative Code, as amended ). 
Pursuant to the provisions of Section 172(5) of the Administrative Code, no appeal may  be filed 
against a decision on objections.  
The conformity of this General Measure with legal regulations may be assessed in review proceedings 
pursuant to the provisions of Sections 94 to 96 of the Administrative Code. A party may submit a 
proposal for th e holding of review proceedings to the administrative body that issued this General 
Measure. If the administrative body finds no reason to initiate review proceedings, it shall inform the 
proposer of this fact, stating reasons, within 30 days. A resolution  to initiate  review proceedings may  be General Measure No 0111 -OOP -C027-12 
12 issued up to three years from the entry into effect of the General Measure , pursuant to the provisions of 
Section 174(2) of the Administrative Code.  
 
 
IV 
E F F E C T I V E N E S S  
This General Measure shall enter into effect on t he 15th day after the date of its publication  (Section 
24d of Act No 505/1990  Coll. on metrology, as amended ). 
 
 
 
 ...…………………………..............  
 RNDr Pavel Klenovský  
 General Director  
 
Responsible for accuracy : Ing. Miroslav Pospíšil  
 
Posted on :  
Signature of authorised person in confirmation of posting : ....................................................  
 
Removed on:  
Signature of authorised person in confirmation of removal:  ....................................................