Czech Metrology Institute  
Okružní 31, 638 00 Brno  
 
1. ------IND- 2018 0329 CZ - EN- ------ 20180803 --- --- PROJET 
Executive summary for the EC (not part of this legislation)  
Hygrometers for cereals and oilseeds are placed on the market and put into use in the Czech Republic 
as specified measuring instrumen ts following type approval and initial verification pursuant to Act 
No 505/1990 on metrology, as amended. This legislation contains national metrological regulation of 
type approval and verification of these measuring instruments.  
(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 specified measuring instruments and stipulat ing test methods for type 
approval and verification of specified measuring 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  500/200 4, the Code of Administrative Procedure (hereinafter the CAP), the 
Czech Metrology Institute (CMI) commenced ex officio proceedings on 26. 2. 2016 pursuant to §  46 
of the CAP and, based on supporting documents, issues the following:  
 
 
I. 
D R A F T  G E N E R A L  M E A S U R E  
number: 0111 -OOP -C071 -18 
 
establishing metrological and technical requirements for specified measuring instruments, 
including testing methods for the type approval and verification of the specified measuring 
instruments:  
hygrometers for cereals and oil seeds  
 General Measure No  0111 -OOP -C071 -18 
2 1 Basic definitions  
The terms and definitions pursuant to the VIM and VIML1 as well as the following terms and 
definitions shall apply for the purposes of this general measure:  
1.1 
hygrometer for cereals  
measuring instrument intended to measure the moisture of cereals within defined error limits The 
moisture is displayed directly on the basis of the measurement and conversion of certain physical 
parameters of the cereals, such as electrical or optical.  
1.2 
cereal  
For the purposes of this document, th is includes the seeds of cereals, oilseeds and legumes  and 
potentially the seeds of other plants as well.  
1.3 
water content (moisture)  
The proportion of loss in weight from the total weight of the sample expressed in % (m·m-1) 
established under the stipula ted conditions using the applicable reference methods.  
1.4 
calibration curve (calibration)  
Expression of conformity between the content of water (and liquid substances) and the dielectric 
values or other physical parameters of the measured sample recorded by the hygrometer; it is 
characterised by the calibration constants, designation and version number of calibration.  
1.5 
calibration network of hygrometers  
a set of hygrometers of the same type with known identity of function and positioning  
1.6 
master cali bration network  
a standard gauge for hygrometers of the same type with known functionality  
2 Metrological requirements  
The metrological requirements are based on the requirements under Recommendation OIML  R 592 
and ISO  7700 – Parts  1 and 23. 
                                                      
1 TNI 01 0115 Inte rnational Vocabulary of Metrology – Basic and General Concepts and Associated Terms 
(VIM) and International Vocabulary of Terms in Legal Metrology (VIML) are part of the technical 
harmonisation compendium ‘Terminology in the Area of Metrology ’, which is pu blicly accessible at 
www.unmz.cz.  
2 OIML  R 59 Moisture Meters for Cereal Grains and Oilseeds – available to the public at www.oiml.org  
3 ISO 7700 -1 Food product – Checking the performance of moisture meters in use – Part 1: Moisture meters for 
cereals a IS O 7700 -2 Food product – Checking the performance of mousture meters in use – Part 2: Moisture 
meters for oilseeds  General Measure No  0111 -OOP -C071 -18 
3 2.1 Measuremen t range  
A hygrometer must be equipped with a selection of the cereals which may be measured. The moisture 
measurement range must be at least 6  % and the minimum number of cereals (calibration curves) must 
be three.  
The usual moisture measurement range of h ygrometers for cereals is 5  % to 45  %; the manufacturer 
may also determine others.  
2.2 Rated operating conditions  
Hygrometers for cereals must have an ambient temperature operating range set by the manufacturer of 
at least 20  °C, in which range must be at least 10  °C to 30  °C. 
Hygrometers for cereals must have an temperature operating range for the sample of cereals measured 
set by the manufacturer of at least 2  °C to 40  °C. 
Hygrometers for cereals must have a value of the maximum difference between the amb ient 
temperature and the temperature of the sample of cereals measured set by the manufacturer. The value 
of this difference may not be less than 10  °C. 
If the range of ambient temperature, temperature of the cereal sample and their difference in 
temperatu re is exceeded, the moisture value may not be displayed and printed out.  
If the moisture of the surrounding environment exceeds 85  %, then condensation must not be allowed 
to form.  
The atmospheric pressure range is 86  kPa to 106  kPa. 
The range of supply va lues is −15 % to +10  % nominal values.  
2.3 Reference conditions  
Laboratory tests of the hygrometer shall be conducted at an ambient air temperature of 20  °C to 27  °C 
and a relative air humidity of 30  % to 70  % and an atmospheric pressure of 86  kPa to 106  kPa. 
The measurement conditions may not change by more than ±2  °C or ±10  % air humidity over the 
course of each test.  
The supply values are in nominal or tested values.  
2.4 Maximum permissible errors  
2.4.1  Maximum permissible errors during type approval of a hygrom eter for cereals  
The hygrometer ’s error for the given cereal or seed sample is defined as the difference between the 
average value from repeated measurements of the sample with the hygrometer and conventionally via 
the true value of moisture of the given c ereal or seed sample defined by the reference method.  
Table  1 – Maximum permissible errors (MPE) of hygrometers for cereals during type approval  
(1) (2) (3) (4) (5) 
Type of cereal 
or seed  Maximum 
permissible 
error  
(% moisture 
content wref) Systematic erro r 
(%) Repeatability  
SD 
(%) Reproducibility  
SDD I 
(%)  
Maize, rice, 
sorghum, If 0.025 wref < 
0.4, then MPE = 0.5 × maximum 
permissible error  0.5 × maximum 
permissible error  0.6 × maximum  
permissible err or General Measure No  0111 -OOP -C071 -18 
4 sunflower, 
legumes, oats  0.4 
Otherwise, MPE 
= 0.025 wref 
Other cereals  If 0.02 wref < 
0.35, then MPE 
= 0.35  
Otherwise, MPE 
= 0.02 wref 0.5 × maximum 
permissible error  0.5 × maximum 
permissible error  0.6 × maximum  
permissible error  
NOTE  
wref is the moisture established by the reference gravimetric method  
2.4.2 Maximum permissible error during verification via reference gravimetric method in 
laboratory  
The hygrometer ’s error for the given cereal or seed sample is defined as the difference between each 
value from repeated measurements of the sample with the hy grometer and conventionally via the true 
value of moisture of the given cereal or oilseed sample defined by the reference method.  
Table  2 – Maximum permissible errors of hygrometers for cereals during verification (MPE)  
Type of cereal or seed  Maximum permi ssible error wmax v % 
Cereals and oilseed except for 
* for wref ≤ 10 % for wref ˃ 10 % 
0.7 0.03 wref + 0.4  
*Maize, rice, sorghum, 
sunflower, legumes, oats  for wref ≤ 10 % for wref ˃ 10 % 
0.8 0.04 wref + 0.4  
NOTE  
wref is the moisture established by the reference gravimetric method  
2.4.3  Maximum permissible error  during test via master calibration network method  
Table  3 – Maximum permissible errors of hygrometers for cereals (MPE)  
Type of cereal or seed  Maximum permissible error wmax in %  
Cereals and oilseed except for 
* wm < 22 % wm ≥ 22 % 
0.2 0.3 
* Maize, r ice, sorghum, 
sunflower, legumes, oats  wm < 25 % wm ≥ 25 % 
0.3 0.4 General Measure No  0111 -OOP -C071 -18 
5 NOTE  
wm is the moisture of the cereal sample established by the master calibration network of 
hygrometers  
The error wref of the test samples during measuring with the master may not e xceed 0.5  %. 
3 Technical requirements  
The technical requirements are based on the requirements under Recommendation OIML  R 592. 
3.1 General information  
The measurement principle may be based on any kind of physical method which enables the 
ascertainment of  the moisture content of the cereal and oilseed sample.  
Hygrometers must be durable and sturdy in construction. They must be built as a single inseparable 
device. They must work automatically. The measuring system must be protected from dust and 
vibrations . 
The minimum volume of the measured cereal sample must be 100  g or 400  grains of cereal.  
The measuring system may not allow the operator to influence the precision of measurements of 
volume, weight or temperature of the sample conducted for determining th e precise moisture of the 
cereal sample.  
Milling, weighing and temperature measurement outside the measuring system of the hygrometer is 
not permitted.  
The basic components of the hygrometer are:  
 a measuring chamber with a funnel and measuring system corre sponding to the measurement 
principle;  
 a calculating unit with software for control, calculations, displaying results and saving 
information on the metrological integrity of the hygrometer;  
 potentially an interface for data transmission;  
 a built -in mill in  case the measurement principle is based on measuring milled material;  
 a printer (external or built -in); 
 a classification device, if used (may be external).  
3.1.1  Measuring chamber with funnel and measuring system  
The principle of operation and design of t he measuring chamber depends on the measurement 
principle used.  
The measuring function and measuring algorithms of the hygrometer must be correct.  
The hygrometer must be equipped with a digital indicator; the height of the letters (digits) on the 
display m ay not be less than 10  mm. 
The moisture content results must be displayed immediately and printed out in per  cent of moisture 
content on a wet basis. These units are expressed decadically; the value of the resulting indication 
must be displayed with a reso lution of 0.1  % or, for the purposes of tests for type approval, with a 
resolution of 0.01  %. 
The selection of the calibration curve for measurement according to the quality and type of cereal, 
oilseed and legumes must be clearly visible and unambiguously identifiable. Hygrometers must have 
at a capacity of at least 4  letters on the indication of the cereal type used.  General Measure No  0111 -OOP -C071 -18 
6 The results of the moisture measurement may not b e indicated or registered before the measurement 
cycle has ended.  
The hygrometer may not dis play or register moisture content values if the moisture content of the 
grain sample is outside of its operating range; in that case, there must be a clear error message at the 
displayed and registered moisture value; the same applies in the case of moistu re measurement outside 
the ambient temperature and sample temperature range.  
After being turned on, the hygrometer may not display or print out any moisture value as long as the 
measuring instrument has not reached its fully operational state, i.e. once it  has reached a stable 
operating temperature and ended the initialisation tests, or the hygrometer must give a clear signal that 
it must be turned on for a period of time specified by the manufacturer before use.  
In case of measuring instruments indicating multiple measurement parameters (such as those 
measuring via volume weight, protein content or oils in cereals and oilseeds), the values must be 
allocated to the individual parameters when displayed, registered and saved so that they cannot be 
confused.  
3.1.2 Calculation unit with software  
Software for control, implementing calculations, displaying results and saving information on the 
metrological integrity of the hygrometer must meet the requirements of the document OIML  D 314 for 
level  I and tests via pr ocedure  A. 
It its documentation, the manufacturer must describe the software applied and its relation to the 
hardware equipment of the hygrometer and its securement by means of:  
 describing its legal functions;  
 identifying the software which is allocated to  legal functions;  
 recording and saving information on each intervention into the integrity of the measuring 
instrument.  
The hygrometer must enter the performance of changes which affect the metrological parameters of 
the hygrometer (such as shift and incli nation of calibration curves) into the list of events.  
3.1.3  Data storage  
The data must be saved after the end of measurement. All legally significant information identifying 
and influencing the results of measurement must be saved, and at least the identi fication of the 
measuring instrument, the date of the measurement, the version of the calibration curves, the type of 
cereal, a unique identification of the measurement and sample, the data measured, including the 
identification of the measured parameter a nd the units and an error announcement regarding the 
measurement.  
In the case of external storage, the transmitted data must be protected.  
3.1.4  Printer  
Hygrometers must be equipped with a communication connection enabling connection with a printer 
or reco rding device. The scope of the data transferred must be at least the date, type of grain, result of 
the cereal moisture measurement and identification of the calibration curve. The data transmission 
must be verified.  
                                                      
4 OIML D 31 General requirements for software controlled measuring instruments, Available to the public at www.oiml.org.  General Measure No  0111 -OOP -C071 -18 
7 3.2 Requirements for hygrometer operati on 
3.2.1  Conformity of calibration curves  
During the test, the hygrometer must be able to display all calibration constants, an unambiguous 
identification of the calibration and the calibration version number as proof that their valid version was 
used duri ng the moisture determination.  
If the calibration constants are saved in electronic form, the hygrometer must display an automatic 
control of the error detection of the calibration constant. If the calibration constants are changed, a 
clear error message m ust be displayed.  
The device hardware and software, calibration and communication software must allow the 
development of calibration curves and their transmission to hygrometers of the same type. Hygrometer 
setup procedures must be defined so as to ensure conformity of moisture measurement with 
hygrometers of the same type.  
3.2.2  Measuring instrument positioning and operating position  
If a change in the hygrometer ’s horizontal position by more than 5  causes the maximum permissible 
errors to be exceeded, th e hygrometer must be equipped with a spirit level and elements for setting the 
horizontal position. The spirit level must be positioned to allow reading without removing parts of the 
measuring instruments using a tool.  
The hygrometer must be installed in a ccordance with the manufacturer ’s recommendation in the 
measuring instrument ’s manual in order to make all measuring operations clearly visible.  
3.2.3  Correct hygrometer operation check  
The hygrometer must be equipped with a control function which can be u sed to check the correct 
operations of the hygrometer after turning it on or after selecting an operation.  
3.3 Resistance to environmental influences  
External disruptive influences acting upon the hygrometer may not lead to any measurement errors 
which wou ld exceed the maximum permissible error of the hygrometer for individual tests.  
3.3.1  Electrical supply  
A hygrometer supplied from the mains must be resistant to changes in supply in a supply voltage 
range from ( Unom −15 %) to ( Unom +10 %) during a short i nterruption in supply and within a frequency 
range from 59.5  Hz to 60.5  Hz. 
The measurement error may not exceed the values of the maximum permissible systematic errors 
pursuant to Table  1, Column  3. 
If a battery is used as a source of supply, it must be r eplaceable without violating the official and 
protective marks of the hygrometer.  
Marginal or insufficient supply of a hygrometer via battery may not enable the hygrometer to display, 
record or print measured moisture values outside of the applicable toler ance limits.  
Marginal or insufficient supply of a hygrometer via battery may not enable the hygrometer to display, 
record or print measured moisture values outside of the applicable tolerance limits.  
3.3.2. Influence of climatic conditions  
The hygrometer m ust be resistant within the boundary temperatures of the lower and upper 
temperature range and at reference temperature.  
The hygrometer must be resistant within the boundary temperatures of cereal samples during moisture 
measurement under reference conditi ons at a sample temperature within the reference temperature General Measure No  0111 -OOP -C071 -18 
8 specified by the manufacturer in the measuring instrument ’s manual and at temperatures of +10  °C to 
−10 °C. 
The hygrometer must be resistant to the effects of extreme conditions for the duration of its storage or 
during transport at temperatures from −20 °C to +50  °C. 
3.3.3  Instrument stability  
The hygrometer must be resistant to changes in measurement of the moisture values of the same 
samples in intervals of at least 4  weeks. The measurement sta bility of the hygrometer is tested by 
measuring the moisture of the same cereal samples with the hygrometer before and after the tests for 
type approval.  
3.3.4  Initialisation period  
If the manufacturer has defined the hygrometer ’s initialisation period – the measuring instrument ’s 
run-up to its fully operable state – then the hygrometer must be resistant to changes in the measuring 
of the moisture values of the samples after the end of the initialisation period and for another hour or 
twice the length of th e initialisation period.  
If an initialisation period has not been defined, the hygrometer must be resistant to changes in 
measuring the moisture values of the same samples immediately after turning off the hygrometer and 
repeatedly for one  hour.  
3.3.5  Hori zontal position test  
Hygrometers with and without spirit levels must be resistant to the influence of misalignment of the 
hygrometer from the horizontal position by 5° in all orientations. Resistance is tested by comparing the 
measurement of the samples ’ moisture before misalignment, during misalignment and after restoring 
the hygrometer to the horizontal position in at least two orientations.  
3.4 Resistance to interference  
The hygrometer must be resistant to short -term drops in supply voltage, short interf erence and slow 
changes in voltage, electrical rapid transient phenomena/groups of impulses, radiated electromagnetic 
fields, interference induced by high -frequency fields and electrostatic discharge.  
3.5 Protection from unauthorised tampering  
The hygromet er must allow lead security sealing or other measures to prevent access to the device and 
disruption of its metrological parameters.  
The measuring system and metrological software must be protected from unauthorised interventions 
by means of security measu res. 
The hygrometer must enter the performance of changes which affect the metrological parameters of 
the hygrometer into the list of events. This must contain:  
 serial number;  
 parameter ID;  
 date and time of the change;  
 new parameter value.  
The hygrometer n eed not depict this information, but a printout or electronic file must be available. 
The record of events must have a capacity of records equalling 25 times the number of parameters in 
the device, max. 1  000 records.  
The zero setting, test values and othe r settings of metrological parameters must be fitted with a lead 
seal or other means of security.  General Measure No  0111 -OOP -C071 -18 
9 4 Inscriptions and marks  
4.1 Markings on the measuring instrument  
The hygrometer must bear the following information:  
a) manufacturer identification;  
b) hygrometer type designation;  
c) hygrometer serial number;  
d) type approval mark.  
All inscriptions and marks must be legible, permanent, unambiguous and visible and unremovable by 
ordinary means, including on the external parts of the hygrometer.  
4.2 Information provided by  the manufacturer  
The manufacturer must provide an instruction manual with each measuring instrument which provides 
the operator with all information needed to install the hygrometer and its accessories and maintain and 
measure it in order to minimise the influence of human actions on the precision of measurement.  
The instruction manual must contain at least the following information:  
a) manufacturer ’s name and address;  
b) hygrometer type;  
c) date of manufacture;  
d) types or varieties of cereal for which the hygrometer  is designed;  
e) the hygrometer ’s limits of use – ranges in measured moisture and temperature, maximum 
possible difference between the temperature of the sample and the hygrometer, ranges of 
voltage and supply frequency, EMC compatibility.  
The manual must be provided in Czech.  
5 Type approval of the measuring instrument  
5.1 General information  
The process of type approval of a hygrometer includes the following tests:  
a) external inspection;  
b) hygrometer tests in the laboratory;  
c) tests of the hygrometer ’s resistance to disruptive environmental influences.  
5.2 External inspection  
The following shall be assessed during an external inspection of the hygrometer:  
a) the completeness of the required technical documentation, including operating instructions;  
b) conformity of the m etrological and technical characteristics specified by the manufacturer in 
the documentation with the requirements of this regulation, specified in Chapters 2, 3 and 4;  
c) the completeness and condition of the hygrometer ’s functional units according to the sp ecified 
technical documentation;  
d) conformity of the hygrometer ’s software version with the version specified by the 
manufacturer.  General Measure No  0111 -OOP -C071 -18 
10 5.3 Hygrometer tests in the laboratory  
5.3.1  Test equipment  
The following measuring instruments and equipment are used for labo ratory tests of the hygrometer:  
a secondary reference gauge for the moisture of solid substances:  
 high-precision scales, d = 0.1  mg, maximum measurement error ±0.0005  g; 
 a device for milling, drying and subsequent treatment of the samples according to stan dards for 
reference specification of moisture of cereal, oilseed and legumes;  
 a thermometer with a scale in 0.1  °C increments.  
5.3.2  Precision, repeatability, reproducibility  
5.3.2.1  Test sample selection  
Tests are conducted in at least three intervals of a total scope of the calibration curves of cereal and 
oilseed moisture in which at least 30 samples are examined in each interval. The type and species of 
cereal must factor into the expected measurement volumes, differences in physical structure  and 
impor tance of moisture ranges. The tests must always be conducted at the maximum interval values.  
The sets of samples must be tested for moisture homogeneity by comparing the measurement by the 
tested hygrometer and specifying the moisture with the applicable r eference gravimetric method. The 
standard deviation of differences (SDD) of the measured moisture values in each of the moisture 
intervals may not exceed the maximum permissible error specified in Table  1, Column  2, reduced by 
0.1. 
5.3.2.2  Accuracy test  
The tests of the hygrometer ’s accuracy include:  
determining the error ȳ 

nrx
yn
iii

1
 (1) 
and standard deviation of differences (SDD)  

112



ny y
SDDn
ii
 (2) 
for each of the three test moisture intervals. The reference moisture determination must be determined 
before and after measurement with the test hygrometer . The error and SDD may not exceed the 
maximum permissible error specified in Table  1, Column  2 for each interval of moisture.  
Legend on equations (1) and (2):  
 
y   .........  the average of all measurements with the test hygrometer;  
 
iy   ........  
iirx ; 
 
ix  .........  the average of the measurements of moisture values measured by the test hygrometer 
for sample i (3 repetitions);  
 
ir   .........  moisture sample i determined by the reference method;  
 n  ...........  the number of samples of cereal in each of the three moisture intervals tested ( n = 
30). General Measure No  0111 -OOP -C071 -18 
11 5.3.2.3  Repeatability test  
The repeatability of hygrometers is defined as the standard deviation (SD) of the three repeated 
measurements for each cereal sample and moi sture interval. The repeatability may not exceed the 
maximum permissible repeatability error specified in Table  1, Column  4 for each interval of moisture.  
 

nx x
SDn
i ji ij
213
12


 (3) 
where:  
ijx .........  is the moisture determined by the hygromet er for the sample i and repetition  j; 
 
ix  .........  the average of the three moisture values determined with the hygrometer;  
 n  ...........  the number of samples of cereal in each of the three moisture intervals tested ( n = 
10). 
5.3.2.4  Reproducibility test  
The reproducibility of the moisture measurement is given by calculation as standard deviation of 
differences SDD I. The reproducibility may not exceed the maximum permissible reproducibility error 
specified in Table  1, Column  5 for the entire measurement s cale. 

112



nd d
SDDn
ii
 (4) 
where:  
id= 
)2( )1(
i i x x ; 
 
)1(
ix = average of 3  measurements of sample i with hygrometer  1; 
 
)2(
ix = average of 3  measurements of sample i with hygrometer  2; 
 
d  = Average z 
id ; 
 n = number of samples in all moisture intervals.  
5.3.3  Basic instrument tests  
5.3.3.1  Selection of samples  
Single sample types with a stable moisture which is documented by reference or instrument mo isture 
measurements, preferably of wheat, are selected for the basic instrument tests.  
5.3.3.2  Measuring instrument stability test  
The moisture of a single cereal sample is measured in at least three moisture intervals at the beginning 
and after the end of  testing of the hygrometer, at least after 6  weeks.  
The maximum difference between the averages before and after testing may not exceed the maximum 
permissible systematic error specified in Table  1, Column  3. 
5.3.3.3  Test of measuring instrument ’s warm -up time 
The hygrometer stabilised within reference conditions can be stabilised after being turned on after the 
warm -up time specified by the manufacturer.  General Measure No  0111 -OOP -C071 -18 
12 The moisture of the sample is measured five times after 1 and 2  hours after the warm -up time has 
elapse d. If this time has not been specified by the manufacturer, then the measurement shall be 
conducted after being switched on and after 1  hour.  
The maximum difference between the averages of the moisture measurement may not exceed the 
maximum permissible sys tematic error specified in Table  1, Column  3. 
5.3.3.4  Supply  
5.3.3.4.1  Test of resistance to deviations in supply  
The moisture of the sample is measured 10  times at a supply of −15 % and +10  % from the nominal 
value and at the nominal value. The hygrometer  is left to stabilise for 30  minutes after each change in 
supply.  
The maximum difference between the averages of the moisture measurement at altered and nominal 
supply value may not exceed the maximum permissible systematic error specified in Table  1, 
Colu mn 3. 
The standard deviation of 10 repeated measurements at each supply point may not exceed 0.10  % 
moisture.  
5.3.3.4.2  Test of resistance to low internal battery voltage  
The moisture measurement and recording of the data displayed is conducted at full and  reduced 
battery function. At least one measurement cycle must be conducted at reduced function.  
The maximum difference between the averages of the moisture measurement at altered and nominal 
supply value may not exceed the maximum permissible systematic e rror specified in Table  1, 
Column  3. 
5.3.3.5  Test of resistance to temperature during storage of the hygrometer  
The hygrometer is exposed to a temperature cycle: it is heated up to +50  °C over 1  hour, the 
temperature is maintained for a period of 3  hours, the temperature is reduced to −20 °C over 1  hour, 
then maintained for a period of 3  hours. The average of 10 moisture measurements of the cereal 
sample with the hygrometer is compared before and after the temperature loading cycle.  
The maximum difference b etween the averages of the moisture measurement before and after the 
temperature loading cycle may not exceed the maximum permissible systematic error specified in 
Table  1, Column  3. 
5.3.3.6  Test of resistance to misalignment from the balanced position of the hygrometer  
A moisture measurement of the sample is conducted in horizontal position, a misalignment of 5  % to 
the front and the right and to the left and the right in hygrometers without horizontal position 
indication and in hygrometers with indication  in a balanced position and in the marginal positions in 
both directions.  
The maximum difference between five moisture measurements of the cereal sample in balanced 
position and each of the misaligned positions may not exceed the maximum permissible system atic 
error specified in Table  1, Column  3. 
5.3.3.7  Test of resistance to ambient humidity  
The hygrometer is exposed to a humidity cycle: it is heated up to +50  °C over 1  hour, the temperature 
is maintained for a period of 3  hours, the temperature is reduce d to -20 °C over 1  hour, then 
maintained for a period of 3  hours. The average of 10 moisture measurements of the cereal sample 
with the hygrometer is compared before and after the temperature loading cycle.  General Measure No  0111 -OOP -C071 -18 
13 The maximum difference between the averages of th e moisture measurement before and after the 
temperature loading cycle may not exceed the maximum permissible systematic error specified in 
Table  1, Column  3. 
5.3.3.8  Test of resistance to changes in ambient temperature  
The moisture of a single cereal sampl e is measured at three intervals in an environment with a 
reference temperature and relative humidity of 65  % and in the hygrometer ’s lower and upper 
temperature range. One  third of the cereal sample is used for each temperature point.  
The maximum differen ce between the averages of the moisture at reference temperature and extreme 
ambient temperature may not exceed the maximum permissible systematic error specified in Table  1, 
Column  3. 
5.3.3.9  Test of resistance to changes in sample temperature  
The moistur e of three cereal samples is measured at three moisture intervals in an environment with a 
reference temperature and relative humidity of 65  % and in the lower and upper temperature range of 
the cereal sample specified by the manufacturer. One  third of the  cereal sample is used for each 
temperature point.  
The maximum difference between the averages of the moisture at reference temperature and at 
extreme temperatures may not exceed the maximum permissible systematic error specified in Table  1, 
Column  3. 
5.3.4 Electromagnetic compatibility tests  
5.3.4.1  Selection of samples  
Single sample types with a stable moisture which is documented by reference or instrument moisture 
measurements, preferably of wheat, are selected for the basic instrument tests.  
5.3.4.2  Resistance to mains voltage drops, short interruptions and voltage variations  
The moisture sample is measured 10 times at moderate stable moisture under conditions of reduced 
and interrupted supply to the hygrometer so that at least one drop/interruption has  taken place during 
the course of sample moisture measurement. The moisture measurement, error indication and events 
during measurement are recorded over the course of this.  
 a drop from  Unom to 0 for a time of 0.5  AC voltage period;  
 a drop from  Unom to 0 f or a time of 1  AC voltage period;  
 reduction from  Unom to 70  % for a time of 25/30 (50  Hz/60  Hz) AC period;  
 reduction from  Unom to 0 % for a time of 250/300 (50  Hz/60  Hz) AC period.  
All operations must take place correctly. The moisture measurement error ma y not exceed the 
maximum permissible error specified in Table  1, Column  2 without the hygrometer detecting it and 
reacting to it.  
5.3.4.3  Resistance to electrical rapid transient phenomena/impulse groups  
The moisture sample is measured 10 times at moderate  stable moisture under the conditions of 
application of the disturbance in AC and DC mode so that the disturbance takes place in the course of 
measurement.  
Conditions: amplitude: 1  kV, repetition frequency 5  kHz 
All operations must take place correctly. Th e moisture measurement error may not exceed the 
maximum permissible error specified in Table  1, Column  2 without the hygrometer detecting it and 
reacting to it.  General Measure No  0111 -OOP -C071 -18 
14 5.3.4.4  Resistance to a radiated electromagnetic field  
The moisture of a single sample of moder ate stable moisture is measured 10 times under the 
conditions of application of the disturbances from each side of the cover of the hygrometer in 
frequency bands of 26  MHz to 80  MHz and at 2  GHz at an intensity amplitude of the test field of 
10 V/m and a m odulation amplitude of 80  % AM of the sine wave by a frequency of 1  kHz so that the 
disturbances takes place during the course of measurement.  
All operations must take place correctly. The moisture measurement error may not exceed the 
maximum permissible e rror specified in Table  1, Column  2 without the hygrometer detecting it and 
reacting to it.  
5.3.4.5  Resistance to conducted disturbances induced by high -frequency fields  
The moisture of a single sample with moderate, stable moisture is measured 10 times ag ainst 
conducted disturbances induced by high -frequency fields under the conditions of application of the 
disturbances in a frequency zone of 150  kHz to 80  MHz at a test voltage amplitude of 10  V. 
All operations must take place correctly. The moisture measu rement error may not exceed the 
maximum permissible error specified in Table  1, Column  2 without the hygrometer detecting it and 
reacting to it.  
5.3.4.6  Resistance to electrostatic discharge  
The moisture of a single sample is measured 10 times at moderate,  stable moisture under the 
conditions of application of disturbance via contact discharge 2  V, 4 V and 6  V, or via air discharge 
2 V, 4 V, 6 V and 8  V so that the disturbance takes place in the course of measurement.  
All operations must take place correctl y. The moisture measurement error may not exceed the 
maximum permissible error in Table  1, Column  2 without the hygrometer detecting it and reacting to 
it. 
6 Initial verification  
6.1 General information  
The following is conducted during the initial verific ation of hygrometers for cereals:  
a) visual inspection;  
b) hygrometer tests in the laboratory.  
6.2 Visual inspection  
The following shall be evaluated during the visual inspection of the hygrometer submitted for 
verification:  
a) conformity of the hygrometer with the  approved type;  
b) completeness of the hygrometer according to the specified technical documentation;  
c) whether individual parts of the hygrometer are damaged and whether the hygrometer is 
functional;  
d) conformity of the hygrometer ’s software version with the ver sion approved during the type 
approval of the hygrometer.  
6.3 Tests of hygrometers for cereal  
Measuring instruments pursuant to Article  5.3.1 are used for laboratory tests.  
A master hygrometer of the same type is used for hygrometers verified using the mas ter calibration 
network method.  General Measure No  0111 -OOP -C071 -18 
15 6.3.1  Preparation of cereal samples for testing  
The test cereal samples must be of a single type, without admixtures, impurities, and pests  and must be 
homogenous, of natural moisture and tempered. The accuracy of each calib ration curve is tested with 
the crop in question.  
The moisture is determined from the sample using the associated reference method.  
6.3.2  Accuracy test by comparing with reference method  
Each calibration curve is tested in two to three points of the moistu re range.  
Four repeated measurements of each sample are conducted with the tested hygrometer. The 
hygrometer error is determined as the difference of four measurements via hygrometer and the average 
from two reference moisture determinations.  
The error of each measurement may not exceed the maximum permitted error listed in Table  2. 
6.3.3  Accuracy test via method of comparing with master calibration network  
At least eight test samples are tested at various points of the moisture range of at least two calibr ation 
curves.  
The reference determination is conducted by measuring the moisture on the master calibration 
network.  
The test sample moisture error measured on the master calibration network in relation to the moisture 
determined by the reference method may  not exceed 0.5  %. 
Four repeated measurements of each sample are conducted with the tested hygrometer. The 
hygrometer error is determined as the difference of each moisture measurement of the cereal sample 
with the hygrometer and the average of the four mo isture determinations with the master calibration 
network.  
The error of each measurement may not exceed the maximum permitted error listed in Table  3. 
7 Follow -up verification  
During follow -up verification, tests pursuant to Chapter  6 are conducted, with t he exception of 
accuracy tests via the method of comparison with the master calibration network.  
The measurement may be conducted externally at the hygrometer ’s installation site.  
7.1 Follow -up verification via method of comparing with master calibration n etwork  
At least two samples are tested at various points on the moisture range of the calibration curves which 
are identical to the calibration curves of the master calibration network.  
The reference moisture determination is conducted by measuring the moi sture on the master 
calibration network.  
The test sample moisture error measured on the master calibration network in relation to the moisture 
determined by the reference method may not exceed 0.5  %. 
Four repeated measurements of each sample are conducted with the tested hygrometer. The 
hygrometer error is determined as the difference of each moisture measurement of the cereal sample 
with the hygrometer and the average of the four moisture determinations with the master calibration 
network.  
The error of eac h measurement may not exceed the maximum permitted error listed in Table  3. General Measure No  0111 -OOP -C071 -18 
16 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 an incorrect measur ing instrument, please proceed according to 
Chapter  7. The maximum permitted errors shall be 1.25 times the maximum permitted errors pursuant 
to Chapter  7. 
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 shall provide notification of the Czech technical standards, other technical standards 
or technical documents of in ternational or foreign organisations, or other technical documents 
containing more detailed technical requirements (hereinafter notified standards). The CMI shall 
publish a list of these notified standards attached to the relevant measures, together with t he general 
measure, in a manner accessible to the public (at the website www.cmi.cz ). 
Compliance with notified standards or parts thereof is considered, to the extent and under the 
conditions stipulated by a general measur e, 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 usi ng another technical solution guaranteeing an equivalent or 
higher level of protection of legitimate interests.  
 
II. 
G R O U N D S  
The CMI issues, pursuant to §  14(1)(j) of the Metrology Act, for the implementation §  6(2), §  9(1) and 
(9) as well as §  11a(3) of t he Metrology Act, this measure of a general nature, stipulating metrological 
and technical requirements for specified measuring devices during type approval and test methods for 
verification of these specified measuring devices – hygrometers for cereals an d oilseeds.  
Decree No  345/2002 laying down measurement instruments for mandatory validation and 
measurement instruments subject to type approval, as amended, classifies the measuring instruments 
under Items  7.3.1 in the Annex to the Second List of Specifie d Measurement Instruments of the 
specified type as measurement instruments subject to type approval and mandatory validation.  
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. 
L E G A L  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 invi ted to comment on this draft general measure. With a view to 
the provisions of §  172(4) of the APC, comments shall be submitted in writing and meet the 
requirements for submissions in accordance with §  37 of the APC.  General Measure No  0111 -OOP -C071 -18 
17 The comments shall include the particul ars referred to in §  37(2) APC and clearly state the following: 
who is making the comments; which general measure they concern; to what extent the comments 
challenge the measure; how the general measure runs contrary to legislation or how the general 
measu re 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 suppor ting documents for this draft general measure may be consulted at the Czech Metrology 
Institute, Legal Metrology 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  
Person responsible for accuracy: Mgr. Tomáš Hendrych  
 
Posted on:  22 March 2018  
Signature of the authorised person confirming posting:  ....................................................  
 
Removed on:  
Signature of the authorised person confirming removal:  ....................................................