FINAL DRAFT  UGANDA 
STANDARD  
  FDUS 1025  
First Edition  
2013 -mm-dd 
 
 
 Reference number  
FDUS 1025 : 2013 
© UNBS 2013   
  
Moisture meters for cereal grain and oilseeds — Specification 
 FDUS 1025: 2013  
ii © UNBS 2013 – All rights reserved  
 Compliance with this standard does not, of itself confer immunity from legal obligations  
A Uganda Standard does not purport to include all necessary provisions of a contract. Users are 
responsible for its correct application  
© UNBS 2013  
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilised in any 
form or by any means, electronic or mechanical, including photocopying and microfilm, without prior written 
permission from UNBS. 
Requests for permission to reproduce this document should be addressed to 
The Executive Director 
Uganda National Bureau of Standards 
P.O. Box 6329 
Kampala 
Uganda 
Tel: 256 414 505 995 
Fax: 256 414 286 123 
E-mail: unbs@infocom.co.ug  
Web: www.unbs.go.ug  FDUS 1025: 2013  
© UNBS 2013  – All rights reserved  iii 
 Contents Page 
Foreword .............................................................................................................................................................  v 
1 Scope  ................................ ................................ ................................ ................................ ...................... 1 
2 Principle of measurement  ................................ ................................ ................................ .................... 1 
3 General  ................................ ................................ ................................ ................................ ................... 1 
4 Requirements  ................................................................ ................................ ................................ ......... 2 
4.1 General  ................................ ................................ ................................ ................................ ................... 2 
4.1.1  Construction  ................................................................ ................................ ................................ .......... 2 
4.1.2  Direct and indirect indication of moisture content  ................................ ................................ ............ 2 
4.1.3  Conversion and correction tables  ................................ ................................ ................................ ....... 3 
4.1.4  Indicating device  ................................ ................................................................ ................................ ... 3 
4.1.5  Security  ................................ ................................ ................................ ................................ .................. 4 
4.1.6  Additional requirements relating to moisture meters using the principle of drying by heat  ........ 4 
4.2 Specific requirements  ................................ ................................ ...........................................................  4 
4.2.1  Moisture meters of category A  ................................ ................................ ................................ ............. 4 
4.2.2  Moisture meters of category B  ................................ ................................ ................................ ............. 5 
4.2.3  Seals for protection and guarantee and table certification marks  ................................ ................... 5 
5 Marking  ................................ ................................ ................................ ................................ ................... 6 
5.1 General  ................................ ................................ ................................ ................................ ................... 6 
5.2 Identification  ................................................................ ................................ ................................ .......... 6 
5.3 Supervision  ................................................................ ................................ ................................ ............ 6 
5.4 Sanction of the controls (stamping)  ................................................................ ................................ .... 7 
6 Maximum permissible errors  ................................ ................................ ................................ ............... 7 
6.1 General  ................................ ................................ ................................ ................................ ................... 7 
6.2 Maximum permissible errors during pattern approval testing  ................................ ......................... 7 
6.3 Maximum permissible errors during pattern approval testing, including influen ce 
quantities, and on initial verification  ................................................................ ................................ ... 7 
6.4 Maximum permissible errors in service  ................................ ..............................................................  7 
7 Provisions to assure fairness of the measurement operations  ................................ ....................... 8 
7.1 General  ................................ ................................ ................................ ................................ ................... 8 
7.2 Minimum guarantees offered by the sellers of moisture meters  ................................ ..................... 8 
7.3 Conditions of installation  ................................ ................................ ................................ ..................... 8 
7.3.1  Place of installation and environment  ................................................................ ................................ . 8 
7.3.2  Visibility of the moisture meter and of the measurement operations  ................................ ............. 8 
7.3.3  Displaying the descriptive notice  ................................ ................................ ................................ ........ 8 
7.3.4  Accessibility of the instrument for the legal metrological controls  ................................ ................. 8 
7.4 Choice and preparation of the sample for measurement ................................ ................................ .. 9 
7.4.1  Sampling  ................................ ................................ ................................ ................................ ................ 9 
7.4.2  Cleanness and sanitary state of the sample  ................................ ................................ ...................... 9 
7.4.3  Temperature stabilization of the sample ................................ .............................................................  9 
7.5 Conditions of use  ................................ ................................................................ ................................ .. 9 
7.5.1  General conditions  ................................ ................................ ................................................................  9 
7.5.2  Measurement  ................................................................ ................................ ................................ ......... 9 
7.5.3  Choice of printing paper  ................................ ................................ ................................ ....................... 9 
7.5.4  Special precautions for moisture meters requiring manual operations  ................................ .......... 9 
Annex A (normative)  Practical reference methods for the verification of moisture meters used for 
the determination of moisture content of cereal grains .................................................................. 10 
A.1 Scope ................................ ................................ ................................ ................................ .................... 10 
A.2 Reference methods  ................................ ................................ .............................................................  10 FDUS 1025: 2013  
iv © UNBS 2013 – All rights reserved  
 3 Adaptation of the ISO Standards to this Recommendation  ................................ ...........................  10 
Annex B (normative)  Routine reference method for the verification of moisture meters used for 
the determination of moisture and volatile matter content of oilseeds ........................................ 11 
B.1 Scope  ................................ ................................ ................................................................ ...................  11 
B.2 Reference method ................................ ................................ ................................ ...............................  11 
Annex C (normative)  Metrological controls  ................................ ................................ ................................ . 12 
C.1 Pattern approval ................................ ................................ ................................ ................................ .. 12 
C.1.1  General  ................................ ................................ ................................ .................................................  12 
C.1.2  Preparation of samples  ................................ ................................................................ ......................  12 
C.1.3  Test procedure  ................................ ................................ ................................ ................................ .... 13 
C.1.4  Tests including the various influence quantities  ................................ ............................................  13 
C.1.5  Additional tests  ................................ ................................ ................................ ................................ ... 14 
C.1.5  Pattern approval ................................ ................................ ................................ ................................ .. 14 
C.2 Initial verification  ................................ ................................ ................................ ................................  14 
C.3 Periodic verification  ................................................................ ................................ ...........................  14 
Bibliography .....................................................................................................................................................  15 
 
. FDUS 1025: 2013  
© UNBS 2013  – All rights reserved  v 
 Foreword 
Uganda National Bureau of Standards (UNBS) is a parastatal under the Ministry of Tourism, Trade and 
Industry established under Cap 327, of the Laws of Uganda.  UNBS is mandated to co-ordinate the 
elaboration of standards and is  
(a) a member of International Organisation for Standardisation (ISO) and  
(b) a contact point for the WHO/FAO Codex Alimentarius Commission on Food Standards, and  
(c) the National Enquiry Point on TBT/SPS Agreements of the World Trade Organisation (WTO). 
The work of preparing Uganda Standards is carried out through Technical Committees. A Technical 
Committee is established to deliberate on standards in a given field or area and consists of representatives of 
consumers, traders, academicians, manufacturers, government and other stakeholders. 
Draft Uganda Standards adopted by the Technical Committee are widely circulated to stakeholders and the 
general public for comments. The committee reviews the comments before recommending the draft standards 
for approval and declaration as Uganda Standards by the National Standards Council. 
This Final Draft Uganda Standard is based on OIML R 59 Moisture meters for cereal grain and oilseeds . 
Committee membership 
The following organizations were represented on the Metrology standards Technical Committee (UNBS/TC 9), 
during the development of this standard:  
 Civil Aviation Authority (CAA) 
 Kampala City Traders Association (KACITA) 
 Kyambogo University Kampala 
 Makerere University Kampala 
 Ministry of Defence 
 Ministry of Energy 
 Ministry of Internal Affairs 
 Ministry of Works and Transport 
 National Environmental Management Authority (NEMA) 
 Uganda National Bureau of Standards 
 UMEME  
 
.FINAL DRAFT UGANDA STANDARD  FDUS 1025 : 2013  
 
© UNBS 2013 – All rights reserved  1 
 Moisture meters for cereal grain and oilseeds — Specification 
1 Scope 
This Final Draft Uganda Standard specifies requirements moisture meters for cereal grains and oilseeds, that 
is to say instruments measuring and indicating, either directly or by means of conversion tables and (or) 
correction tables, the moisture content of cereal grains and the moisture and volatile matter content of 
oilseeds. 
This standard applies only to moisture meters used for measurements on statical samples. The moisture 
meters are subdivided in the following two categories for which the different technical specificati ons differ: 
a) Category A: automatic moisture meters which are provided with printing devices for the results of the 
measurements and with various securities (see Clause 5); and 
b) Category B: moisture meters which do not comply with the requirements relating to moisture meters of 
category A, but are provided with minimum securities (see Clause 6). 
2 Principle of measurement  
The principle of measurement of moisture meters may be based on any physical or physicochemical method 
which enables an indication of the moisture content of a sample of whole grains or seeds to be obtained 
directly or indirectly . When the principle of measurement of a moisture meter requires the use of a grinding 
mill, the mill shall be considered as part of the moisture meter. Its design, method of use and integration with 
the measuring device shall be such that any uncontrolled change in moisture content because of its use is 
avoided. 
3 General   
For the purposes of this standard, the following terms and definitions shall apply  
3.1 
moisture content of a sample of cereal grains 
loss in mass expressed as a percentage of the mass of a sample, % mass, of a product under test conditions 
specified in Annex A 
3.2 
moisture and volatile matter content of a sample of oilseeds  
loss in mass expressed as a percentage of the mass of a sample, % mass, of a product under test conditions 
specified in Annex B 
3.3  
conversion tables 
any system namely table, graph, abacus or slide rule, used for the determination of the moisture content from 
the value indicated by the moisture meter, when the latter is not fitted with a device for selecting the species 
and the relationship between the indications of the moisture meter and the moisture content differs according 
to the species of grains or seeds on which the measurement is carried out FDUS 1025: 2013  
2 © UN BS 2013 – All rights reserved  
 3.4 
conventional scale 
indicating scale of the moisture meter which uses conversion tables to obtain the moisture content. The values 
indicated on this scale are dimensionless. 
NOTE The principle of measurement of a moisture meter may be such that the indicated values have a dimension 
corresponding to a quantity actually measured (mass, electrical capacity, etc.). However, in order to avoid any confusion 
between such a moisture meter and a balance or a capacitance meter, the scale should remain dimensionless and 
consequently be graduated in pure numbers. 
3.5  
correction tables 
any system namely  table, graph, abacus or slide rule , used  for the determination of the moisture content from 
the value indicated by the moisture meter, when  this i ndicated value is altered by an influence quantity which 
is not automatically taken into account  by the moisture meter (for example, temperature of the sample)  
3.6  
zero value  
mechanical or electrical indication according to the principle of measurement of the instrument. For moisture 
meters with direct indication of the moisture content, that is to say not requiring the use of conversion tables; 
zero may represent the result of a measurement when the measuring cell is empty or the indication of the 
instrument when the measuring operations have not yet been initiated. For moisture meters provided with 
conversion tables, zero may also represent the indication appearing on the conventional scale when the value 
of the measured quantity is zero. 
NOTE 1 The valu e 0 % mass can, in practice, never be reached by the quantity which represents the moisture content 
of a sample of grains or seeds.  
NOTE 2 The measured quantity may be a quantity or a function of various quantities : mass, volume, temperature, 
electrical r esistance or capacity.  
3.7 
test value  
obtained by one or more indications of the indicating device which are the result of a measurement simulation. 
This simulation corresponds to the operation of those elements which determine the parameters having a 
critical effect on the measurement. A device enabling the determination of a test value is a device aiming at 
verifying the smooth running of the measuring part. It should be possible to use the device without the 
operator having at his disposal a sample of grains.  
4 Requirements 
4.1 General  
4.1.1  Construction 
4.1.1 .1 Moisture meters shall be strong and well built. Their main parts shall be made of materials 
assuring adequate strength and stability. 
4.1.1.2 The housing of moisture meters shall be strongly built and so constructed that the main 
components of the instrument are out of reach and protected from dust and moisture . 
4.1.2 Direct and indirect indication of moisture content 
4.1.2.1 Moisture meters with direct indication of moisture content  
When the moisture meters indicate the moisture content directly, without the use of conversion tables for the 
different species, and are fitted with a device allowing the selection of the species of grain or seeds on which FDUS 1025: 2013 
© UNBS 2013 – All rights reserved  3 
 the measurement is being carried out, this device shall be built to make its operation clearly visible to all 
parties present and to indicate clearly the name of the selected species. 
4.1.2.2 Moisture meters with indirect indication of moisture content  
When the moisture meters do not indicate the moisture content directly, they shall be provided with conversion 
table(s) necessary to obtain the moisture content for each species. The requirements concerning the scale 
interval (see 4 .1.4.1) and the maximum permissible errors (see Clause 6) apply to the results of the moisture 
content read in the conversion tables and expressed as a percentage (% mass) and not to the results given by 
the conventional scale of the moisture meter. 
4.1.3 Conversion and correction tables 
4.1.3.1 When a moisture meter requir es the use of conversion or correction tables, the following  
requirements apply:  
a) these tables shall be approved by the competent National Metrology Service; 
b) the manufacturer shall provide on a visible part of the moisture meter, next to the indicating device, a 
written instruction indicating the necessity of the use of this (these) table(s); 
c) when these tables are not made, by the manufacturer, integral with the moisture meter, they shall 
bear the general inscriptions shown on the moisture meter, the list of which is given in 5 .1; and 
d) the moisture meter shall be provided with clear and detailed operating instructions. 
4.1.3.2 When a moisture meter requires the use of correction tables, any conversion tables excluded, its 
scale of indication shall be graduated in percent (% mass). 
4.1.4 Indicating device 
4.1.4.1 The scale interval shall be chosen from the following values : 0.1 % mass, 0.2 % mass or 0.5 % 
mass, so that, whatever the value of the moisture content indicated directly or indirectly by the moisture meter, 
this number remains smaller than or equal to half the maximum permissible error prescribed on pattern 
approval for class I moisture meters. 
4.1.4.2 Moisture meters of which the principle of measurement is not that of drying by heat shall be fitted 
with a device allowing the determination of a test value. 
4.1.4.3 Zero setting 
4.1.4.4 Analogue indicating devices shall include a dial provided with a scale and an index.  The scale 
spacing shall be at least equal to 1.25 mm for scales graduated in percent (% mass) as  well as for 
conventional scales. The scale marks shall be thin and of equal thickness. The index shall  be clearly visible 
and its thickness shall be at most equal to 1/4 of the scale spacing. Its end shall  cover at least 1/3 of the 
length of th e shortest scale marks. It shall be possible to adjust the test value  and possibly zero to within half 
of the scale spacing. In addition to these requirements, other different  requirements shall be added depending 
whether the scale is graduated directly in  per cent (% mass)  or is conventional . 
For direct indication of moisture content , the scale shall be numbered at each whole value of the moisture 
content expressed in percent mass (% mass). The scale marks which correspond to whole values of the 
moisture content shall be longer. When the movement of the index is continuous, the zero indication shall be 
marked by a line and the displacement of the index below zero shall correspond to at least 0.2 % mass. 
For indirect indication of moisture content , the scale interval of the conventional scale value converted into 
units of moisture content shall be less than or equal to the scale interval defined in 4.1.4.1. whatever the 
species chosen. The scale marks which are numbered shall be longer. All the numbers shown on the 
conventional scale shall also be shown in the conversion tables in the entry  column. FDUS 1025: 2013  
4 © UN BS 2013 – All rights reserved  
 4.1.4.5 On a discontinuous digital indicating device, with aligned figures, the figures shall have a height of 
at least 10 mm, the indication of the moisture content being either direct or indirect. In the case of a 
conventional scale, all the numbers likely to appear on the digital indicating device shall be shown in the 
conversion tables in the entry column. 
4.1.4.6 The indication of the result of the measurement shall never be ambiguous. 
4.1.5 Security 
4.1.5.1  Adjusting devices, the operation of which may alter the results of the measurement shall be designed 
to make any accidental or fraudulent intervention difficult and, in any case, easily visible to all parties present. 
4.1.5.2 Protection against the various influence quantities shall include the following: 
a) moisture meters shall be insensitive to variations from - 15 % to + 10 % of the nominal voltage of the 
electric power supply and, if necessary, to variations from - 2 % to + 2 % of its nominal frequency. 
Moisture meters supplied by a battery shall be fitted with a device indicating clearly the threshold 
condition below which the results of the measurement may be altered and the battery shall be 
recharged or replaced; and 
b) the manufacturer shall specify, in the descriptive notice, the range of the operating temperature of the 
moisture meter. He shall also specify, if appropriate, the limits which the other parameters, likely to 
influence the results of the measurement, shall not exceed (hygrometry, electromagnetic 
interference). 
4.1.6 Additional requirements relating to moisture meters using the principle of drying by heat  
Moisture meters with a drying device and a weighing device shall comply with the following additional 
requirements: 
a) the mass of the sample intended for the measurement of the moisture content shall not be less than 5 
g; 
b) the accuracy of the balance and of the weights shall correspond to the accuracy proposed for the 
moisture meter by the manufacturer; 
c) the dishes for drying and the balance pans shall be made of non-corrodible material which does not 
absorb moisture; 
d) the maximum differences of temperature allowed inside the oven shall be specified by the  
manufacturer in the descriptive notice. The y shall not affect the result of the measurement ; and  
e) when the measurement process is not automatic, the end of drying shall be indicated without  
ambiguity, by a visual or audible signal . 
4.2 Specific requirements 
4.2.1  Moisture meters of category A 
4.2.1.1  In addition to the requirements stated in 4 .1, which shall be met by all moisture meters, the  
moisture meters of category A are subject to requirements  in 4.2.1.2 –  4.2.1.4 . 
4.2.1.2  The moisture meters of category A shall be entirely automatic;  they shal l be designed as one  
integral instrument and all the parts used either to treat the sample (grinding, heating, etc.) or to  measure the 
physical or chemical parameters involved in the calculation of the final result of the  moisture content (weighing 
device,  temperature sensor, etc.) shall be incorporated in the same  instrument. If sorting and cleaning devices 
are used, they may be separate from the moisture meter  itself.  FDUS 1025: 2013 
© UNBS 2013 – All rights reserved  5 
 4.2.1.3  The moisture meters shall be fitted with a printing device which  shall either be  integral with the 
moisture meter or be located next to it (see 7.3.2.). The result of measurement shall be  printed in aligned 
figures and rounded to the nearest scale interval. The printout shall be a replica of  the indication, if the latter is 
digital. T he designation of the grains or seeds shall be specified on the  printed ticket if the moisture meter is 
provided with a device for the selection of the species.  
4.2.1.4  Various security devices are mandatory.  
4.2.1.4.1  To ensure security of printing: 
a) printing of the result shall not be possible before the end of the measurement when the indicator is 
analogue; and 
b) indication and printing of the result shall not be possible before the end of the measurement when the 
indicator is digital. 
4.2.1.4.2  It shall no t be possible to print the result outside the authorized measuring range (fixed in the  
pattern approval notice, if provided).  In addition, a continuous device, on the indicating device or next to it, 
shall reveal incorrect use , for example, a warning light  for a digital indicating device, red colour of the area 
outside the  authorized measuring range for an analogue indicating device . 
4.2.1.4 .3 When zero adjustment is provided it shall not facilitate fraud . 
4.2.1.4 .4 The moisture meter shall be designed so t hat it is not possible to carry out a new measurement  
before the measuring cell is completely empty.  
4.2.1.4.5  In case of moisture meters using drying by heat, a device (visual or audible indicator) shall  
indicate that measurement is prohibited until the c onditions, specified in the descriptive notice (in  particular the 
temperature at the beginning of drying), have been reached and it shall not be possible  for the indicating 
device to provide a result of measurement before the drying period has ended . 
4.2.2  Moisture meters of category B 
4.2.2.1  Moisture meters which do not comply with the requirements in 4.2.1.2 – 4.2.1.4 belong to 
Category B provided they meet the following requirements in addition to the general requirements in 4 .1. They 
may be automatic, semi-automatic or manual, and may include several separate devices with manual 
operation. 
4.2.2.2  When the principle of measurement of the moisture meter requires the introduction of a sample of  
grains or seeds of fixed mass into the measuring cell, the we ighing device used shall be strongly  built and 
shall allow the determination of the mass of the sample with an accuracy which will be  fixed during pattern 
approval with reference to the proposal of the manufacturer . 
4.2.2.3  When the principle of measuremen t of the moisture meter requires the taking of temperature of  
the measured sample, this temperature measuring device shall be strongly built and be integral with  the whole 
measuring unit. The accuracy for the determination of the temperature will be fixed,  during pattern approval, 
with reference to the proposal of the manufacturer . 
4.2.2.4  When the moisture meter is provided with a zero adjusting device, this device may be accessible 
to the user but designed so that its operation is clearly visible to all parties present. 
4.2.3  Seals for protection and guarantee and table certification marks 
4.2.3.1 The housing containing the mechanical, electrical and electronic parts of moisture meters shall be 
constructed to enable sealing by means of lead seals or protec tion and guarantee marks. If necessary 
however, it shall be possible to recharge or to replace the battery without destroying or damaging the seals.  
4.2.3.2 Any mandatory data plates and stamping plates shall be fixed to the housing and be protected by 
guarantee marks. FDUS 1025: 2013  
6 © UN BS 2013 – All rights reserved  
 4.2.3.3  National requirements shall specify, possibly in the pattern approval notices: 
a) the location of the seals, 
b) the nature and form of the guarantee marks. 
4.2.3 .4 The conversion and correction tables which are provided with the moisture me ters shall bear the 
certification marks proving that they were checked by the competent National Metrology Service . 
5 Marking 
5.1 General 
Each moisture meter shall bear the following markings: 
a) identification or trade-mark of the manufacturer; 
b) designation of its pattern, given by the manufacturer and serial number ; and  
c) pattern approval sign, if approval is mandatory. 
5.2 Identification 
A fixed data plate shall show: 
a) the category in which the pattern was classified by the National Metrology Service. For example, two 
zero adjusting devices which make fraud difficult: 
i. adjusting knob accessible to the user, designed and located in such a way that its operation can 
be easily noticed and can affect the result indicated by the moisture meter only if the measuring 
cell is empty or if the measurement has not yet been initiated; and 
ii. adjusting device the operation of which is made possible only by using a tool, the tool being kept 
separate from the moisture meter during normal use of the meter; 
b) the accuracy class of the instrument; 
c) either the species of grains and seeds for which the moisture meter was calibrated and for each of 
them the measuring range, if this is not shown clearly on the indicating device, or when there are too 
many of these markings, to be shown clearly on the data plate, the following inscription : ―The species 
and the measuring ranges for which this moisture meter was approved are shown in the descriptive 
notice‖;  
d) the nominal value(s) of the test value(s) and possibly the upper and lower permissible limits for this 
(these) value(s) ; and  
e) the temperature range for which the moisture meter was built. 
5.3 Supervision 
Each moisture meter shall have a place for the application of the initial and periodic verification marks when 
required by national regulations. FDUS 1025: 2013 
© UNBS 2013 – All rights reserved  7 
 5.4 Sanction of the controls (stamping) 
The results of the controls shall be sanctioned by applying one or more verification marks on the moisture 
meters which comply with the statutory requirements. These marks and the additional markings shall be 
applied in conformity with national regulations, for example, on a special plate . 
6 Maximum permissible errors 
6.1 General 
The absolute error of a moisture meter for a given sample of grains or seeds is the algebraic difference 
between the result of a measurement and a conventionally true value of the moisture content obtained using 
the reference methods described in Annex A and Annex B. Moisture meters, either of category A or of 
category B, belong to one of the accuracy classes, class I or class II, for which the values of the maximum 
permissible error are given below. 
6.2 Maximum permissible errors during pattern approval testing  
The reference conditions are specified in Annex C. The absolute maximum permissible error, plus or minus, 
on the moisture content shall be equal to: 
a) Class I: 
i. cereal grains other than maize, rice and sorghum and oilseeds other than sunflower :0.3 % mass 
if the moisture content is less than or equal to 10 % mass, 3/100 of the moisture content if the 
latter is more than 10 % mass ; and  
ii. maize, rice, sorghum, sunflower : 0.4 % mass if the moisture content is less than or equal to 10 
% mass, 4/100 of the moisture content if the latter is more than 10 % mass; 
b) Class II: 
i. cereal grains other than maize, rice and sorghum and oilseeds other than sunflower : 0.4 % 
mass if the moisture content is less than or equal to 10 % mass, 4/100 of the moisture content if 
the latter is more than 10 % mass, 
ii. maize, rice, sorghum, sunflower : 0.5 % mass if the moisture content is less than or equal to 10 
% mass, 5/100 of the moisture content if the latter is more than 10 % mass. 
6.3 Maximum permissible errors during pattern approval testing, including influence 
quantities, and on initial verification  
The absolute maximum permissible error, plus or minus, on the moisture content shall be equal to the error 
stated in 6.2, increased by 0.2 % mass. 
6.4 Maximum permissible errors in service  
The absolute maximum permissible error, plus or minus, on the moisture content shall be equal to the error 
stated in 6.2, increased by 0.4 % mass.  FDUS 1025: 2013  
8 © UN BS 2013 – All rights reserved  
 7 Provisions to assure fairness of the measurement operations 
7.1 General 
The requirements which follow apply to moisture meters used in the grain trade. Moisture meters which have 
not received approval of the National Metrology Service may not be used for commercial transactions and 
shall bear on the front face a clearly visible small plate with an inscription stating that their use for commercial 
transactions in grain is prohibited . 
7.2 Minimum guarantees offered by the sellers of moisture meters  
New commercial moisture meters shall be provided with the following elements : 
a) all the accessories mentioned in the pattern approval notice and in the descriptive notice, and 
necessary for the correct performance of the measurement operations; 
b) any conversion and correction tables which may be required, bearing the statutory inscriptions; and 
c) a detailed descriptive notice describing clearly the conditions of installation and use of the moisture 
meter and its accessories ; this notice shall have received prior approval of the National Metrology 
Service on all points relating to the metrological qualities of the instrument. 
7.3 Conditions of installation 
7.3.1 Place of installation and environment   
The moisture meter shall be installed in conformity with the requirements given in the descriptive notice 
provided by the manufacturer. Among these requirements, which differ according to the principle of 
measurement of the moisture meter, the following ones are most frequently retained:  
a) the support of the moisture meter shall be flat, strong and stable; it shall be protected especially 
against vibrations when the moisture meter is either equipped or used with a balance, 
b) the moisture meter shall be installed as far as possible from any powerful source of magnetic field (for 
example, heavy current electric cables) and of electro-magnetic radiation; it shall be protected against 
air currents and be located in premises where it does not risk being subjected to appreciable or 
sudden variations in temperature. 
7.3.2 Visibility of the moisture meter and of the measurement operations  
Moisture meters in service shall be so placed that all parties present have the possibility of seeing 
simultaneously all the measurement operations. When the measuring chain (some moisture meters of 
category B) is too extended for the measurement operations and the indicating or printing device to be seen at 
the same time, the necessary steps shall be taken to remedy this and to avoid, in any case, every possibility 
of error or fraud. 
7.3.3 Displaying the descriptive notice 
The descriptive notice showing the conditions of installation and the exact operating method of the moisture 
meter shall be displayed in the premises in which the moisture meter is installed. It shall be easily visible to all 
parties present at the time of the measurement. The conversion and correction tables which may be required 
shall be attached to it . 
7.3.4 Accessibility of the instrument for the legal metrological controls 
The moisture meter shall be placed and arranged so that, on the one hand, the conformity of the official 
verification marks on the stamping plate and on the lead seals may easily be verified and, on the other hand, FDUS 1025: 2013 
© UNBS 2013 – All rights reserved  9 
 the metrological controls may be carried out under optimum conditions when requested by the officers of the 
National Metrology Service. In case of difficulties of access to the moisture meter during the control operations 
or for the means necessary for this control, the owner should make the necessary arrangements for the 
control to be possible on request of these officers. 
7.4 Choice and preparation of the sample for measurement 
7.4.1 Sampling 
For the result of measurement of moisture content to be significant, the user of the moisture meter shall 
arrange for the measured sample to be representative of the load of grains which is the object of the 
commercial transaction. Therefore, the use of an adequate sampling device is necessary when there is a risk 
that the humidity of the load of grains is heterogeneous. 
7.4.2 Cleanness and sanitary state of the sample  
Samples used for the calibration of moisture meters by the manufacturer, or for the statutory metrological 
controls, shall be free from impurities and broken grains, and in an adequate sanitary state (see C.1.2.2 ). For 
usual measurement, given that the sensitivity of moisture meters to impurities contained in the grains and to 
the sanitary state of the grains may vary from one pattern to another (see test specified in C.1.4.3), the user 
shall follow any cleaning procedures included in the descriptive notice by the manufacturer. When the 
cleaning device for the measured sample is separate from the moisture meter, it shall allow rapid cleaning, 
avoiding to the utmost the hygrometric exchanges between the ambient air and the sample. 
7.4.3 Temperature stabilization of the sample 
When the measured sample of grains is at a temperature very much lower than that of the premises in which 
the moisture meter is installed, there is risk of water condensation on the grains. To avoid the detrimental 
effect of this phenomenon on the measurement, it is necessary to keep the sample in a closed vessel until its 
temperature is close to that of the ambient air. The same rule shall be applied when the temperature of the 
grains is outside the permissible limits specified in the descriptive notice. 
NOTE For species such as maize, harvested at a rather cold time of the year, it is advisable to install the moisture 
meter in cool premises in order to avoid condensation on the grain.  
7.5 Conditions of use 
7.5.1 General conditions 
Any owner of a moisture meter is bound to ensure the accuracy, good maintenance, correct operation and 
statutory use of his instrument. 
7.5.2 Measurement 
The moisture meter shall be used, in conformity with the specifications indicated in the descriptive notice 
provided by the manufacturer. 
7.5.3 Choice of printing paper 
In the case of moisture meters of category A, the printed tickets which are used shall be free from any 
previous indications relating to the result of a measurement of the moisture content or to the selected species. 
7.5.4 Special precautions for moisture meters requiring manual operations 
When the measurement requires a certain number of manual operations (it is mainly the case of moisture 
meters of category B) the descriptive notice shall be scrupulously followed in order to avoid any risk of 
uncontrolled variation of the moisture content of the sample . FDUS 1025: 2013  
10 © UN BS 2013 – All rights reserved  
 Annex A 
(normative) 
 
Practical reference methods for the verification of moisture meters used 
for the determination of moisture content of cereal grains  
A.1 Scope 
Moisture meters are verified by comparing the results they provide with those obtained by the methods 
described below using grains from the same batch. 
A.2 Reference methods 
ISO 712, Cereals and cereal products — Determination of moisture content (Routine method)   
ISO 6540, Maize — Determination of moisture content (on milled grains and on whole grains)   
NOTE ISO 712 is applicable to cereals with small grains for example, durum and soft common wheat, rice (paddy or 
dehul led), barley, winter barley, sorghum, rye and oat. 
3 Adaptation of the ISO Standards to this standard 
To be adapted for use within the framework of this standard, the standards mentioned in A.2 shall be modified 
as follows: 
 ISO 712 shall be modified so that pre-drying is made mandatory when the moisture content is greater 
than or equal to 15 % mass, 
« Expression of the results »  and « Method of calculation and formula » : « Validity of the conditioning carried 
out In the case of preliminary conditioning, check that the moisture content of the sample is between 9 
and 15 % mass, after conditioning, or :  
 
 
 
 Where mo  mass of the sample before drying, m1 mass of sample after predrying.  
If not, repeat the procedure »  
. 
(1) First edition, 1 September 1979.  
(2) First edition, 1 November 1980.  
(3) It is also used at present for sorghum, while awaiting the official standardization of a method concerning this  
species.  FDUS 1025: 2013 
© UNBS 2013 – All rights reserved  11 
 Annex B 
(normative)  
 
Routine reference method for the verification of moisture meters used 
for the determination of moisture and volatile matter content of oilseeds  
B.1 Scope 
Moisture meters are verified by comparing the results they provide to those obtained by the method described 
below using grains from the same batch. 
B.2 Reference method 
ISO 665, Oilseeds — Determination of moisture and volatile matter content  FDUS 1025: 2013  
12 © UN BS 2013 – All rights reserved  
 Annex C 
(normative)  
 
Metrological controls 
C.1 Pattern approval 
C.1.1 General 
Pattern approval consists of a comprehensive examination of several prototypes of the same pattern of 
moisture meter in order to approve or not the manufacture of this pattern of meter in series. The tests to be 
carried out are as follows: 
a) tests of conformity with the requirements prescribed in Clause 4 (according to the category of the 
moisture meter). 
b) accuracy tests under reference condition where, one verifies that under reference conditions (of 
temperature, voltage, ambient humidity, sanitary state of samples, etc.) the errors of the results 
obtained with the prototypes do not exceed those which are shown in 6.2. 
C.1.2 Preparation of samples 
C.1.2 .1 Choice of species and varieties  
Tests shall be carried out on each species of grains or seeds for which the manufacturer of the pattern 
requires approval. The choice of varieties or blend of varieties on which the tests are carried out is defined by 
the National Metrology Service. 
For moisture meters with indirect principle of measurement the test samples shall be constituted of varieties of 
grain most common in a given country and in proportions corresponding to the tonnages collected at national 
level; this in order to use, for testing, samples which are representative of the national average.  
C.1.2 .2 Sanitary state of the sample  
For cereal grains, the test sample shall not have too many impurities, broken, sprouted or heated grains. For 
oilseeds, in addition to the above-mentioned conditions, the acidity index shall be less than 2. 
NOTE The acidity index is the number of milligrams of potassium hydroxide n ecessary to neutralize the free 
acidity of  one gram of fat su bstance.  
C.1.2 .3 Choice of the moisture content of samples  
For each species of grains ten samples with a different moisture content are prepared. 
NOTE To prepare the most humid samples, it may be necessary to re -humidif y the grain. In such cases, 
one shou ld refer  to ISO 7700 -1 and ISO 7700 -2. 
                                                      
 This anne x is given as an example since the procedure conce rning metrological controls may vary from one country to 
another. A detailed description of a calibra tion method can be found in ISO 7700 -1, Check of the calibration of moisture 
meters — Part 1: Moisture meters for cereals  and ISO 7700 -2, Check of the calibration of moisture meters — Part 2: 
Moisture meters for oil seeds  (under development ). FDUS 1025: 2013 
© UNBS 2013 – All rights reserved  13 
 C.1.3 Test procedure 
Pattern approval tests shall be carried out on three prototypes. Four successive measurements shall be 
carried out on each sample, the used test portions being replaced in the overall sample, after each 
measurement, if the measurement is nondestructive. 
At the beginning and at the end of each set of four measurements, the moisture content shall be determined 
by means of the routine reference methods indicated in Annex A and Annex B. The arithmetic mean of the two 
values determined by the reference methods mentioned above is considered as the true value of the moisture 
content. 
NOTE Provided however that these two values do not vary by more than 0.2 % mass if the moisture content of the 
sample is lower than 20 % mass, or more than 0.3 % mass if the moisture content of the sample is higher than 20 % 
mass. If not, the test cannot be taken into consideration and shall be carried out again. 
This procedure shall be repeated after an interval of twenty four hours on a series of samples of which the 
moisture content is close to that of the samples in the preceding test. 
C.1.4 Tests including the various influence quantities  
C.1.4.1 General 
For each influence quantity mentioned above, taken separately or as a whole, the tested prototypes shall give 
results with errors not exceeding those indicated in 6.3. 
C.1.4.2 Influence of temperature variations  
These tests shall be carried out by bringing the prototypes to be tested as well as the batches of grains or 
seeds in a closed vessel, to the two extreme temperatures for which the manufacturer has requested pattern 
approval. The batches of grains or seeds chosen for this test shall have, at the reference temperature of the 
instrument, a moisture content close to 15 % mass for the cereal grains and 10 % mass for the oilseeds. In 
the two extreme cases, the result of the measurement shall be in conformity with the limits indicated 6.3. 
C.1.4.3 Influence of impurities  
This test is intended to provide the users of moisture meters based on the indirect principle of measurement 
with information on the large errors which may result when measurements are carried out on samples 
containing impurities. It concerns part or all of the following impurities : broken grains, germinating grains, 
frozen grains, overheated grains, stalks and cobs, grains of different species. The results of the tests shall be 
recorded in the pattern approval notice to show when the maximum permissible errors may be exceeded 
owing to impurities (if, at present, such cases may occur at the collection centers in a given country). Each 
test result shall be associated with the following data: nature of impurities, ratio of impurities, difference 
between the moisture content of the impurities and that of the samples. 
To the tests in C.1.4.2 and C.1.4.3 which are specific to moisture meters, other tests shall be added, usually 
carried out on the measuring instruments containing electrical or electronic parts, to determine the effects of 
the characteristic variations of electric power supply (voltage and possibly frequency) and if possible, of the 
variations of the humidity of ambient air. 
C.1.4.4 Influence of external disturbances  
Additional tests are carried out on moisture meters containing electrical and electronic parts, to evaluate the 
disturbances caused by the external magnetic fields, electro-magnetic radiations, electrostatic discharges, 
failures of the electric power supply (interruptions of short duration, transient over-voltages, etc.). FDUS 1025: 2013  
14 © UN BS 2013 – All rights reserved  
 C.1.5 Additional tests 
The prototypes which have undergone the laboratory tests mentioned above shall then be tested under 
normal conditions of use. For this, they shall be installed during the harvest time following the laboratory tests, 
in collection centers where they are tested by the officers of the National Metrology Service.  
The following tests shall be carried out: 
a) influence of various varieties of the same species on the results; 
b) influence of the climatological conditions (temperature, humidity); 
c) influence of the various methods of harvesting the grains or seeds; and 
d) endurance tests on mechanical, electrical and electronic components under normal conditions of use 
of the moisture meters. 
After this test campaign in the field, the prototypes shall again be tested in the laboratory according to the 
same criteria as before. The pattern approval depends on the good working of each prototype throughout the 
tests. 
C.1.5 Pattern approval 
The pattern approval tests shall be endorsed by the pattern approval notice describing certain qualities of the 
moisture meters which vary according to the principle of operation or manufacture of the instruments and 
depending on them being automatic or semi-automatic. 
Pattern approval notices shall fix, in particular: 
a) the measuring range according to the species of grains or seeds; 
b) the range of zero adjustment; 
c) the mass of grains or seeds to be introduced into the measuring cell when this mass influences the 
result of the measurement as well as the minimum accuracy of the weighing device; and 
d) for moisture meters using drying by heat, the drying conditions predetermined for each species of 
grains or seeds as well as the accuracy in obtaining the predetermined temperatures or in 
programming the temperatures, if these must vary with time, in a controlled way. 
C.2 Initial verification 
Each new moisture meter corresponding to an approved pattern, shall be submitted to initial verification tests. 
These tests shall ensure that the instruments comply with the prescribed accuracy and the requirements 
concerning manufacture, laid down in this standard. The accuracy tests shall be carried out in a room with a 
temperature between the limiting values for which the pattern was approved and with a relative humidity of air 
between 40 % and 75 %. The samples used (two or three for each species or for the most important species) 
shall have a moisture content within the range for which the pattern was approved. 
C.3 Periodic verification 
Moisture meters in service shall be submitted to periodic verification. The tests to be carried out shall include 
all or part of the initial verification tests. The national regulations shall determine the periodicity of this 
verification, as well as the tests to be carried out and the methods and means to be used. FDUS 1025: 2013 
© UNBS 2013 – All rights reserved  15 
 Bibliography 
[1] OIML R 59, Moisture meters for cereal grain and oilseeds , Edition 1984 (E) 
[2] ISO International Standard 665 :1977,  Oilseeds — Determination of moisture and volatile matter 
content   
. FDUS 1025: 2013  
© UNBS 2013 – All rights reserved  17 
 Certification marking 
Products that conform to Uganda standards may be marked with Uganda National Bureau of Standards 
(UNBS) Certification Mark shown in the figure below.  
The use of the UNBS Certification Mark is governed by the Standards Act, and the Regulations made 
thereunder. This mark can be used only by those licensed under the certification mark scheme operated by 
the Uganda National Bureau of Standards and in conjunction with the relevant Uganda Standard. The 
presence of this mark on a product or in relation to a product is an assurance that the goods comply with the 
requirements of that standard under a system of supervision, control and testing in accordance with the 
certification mark scheme of the Uganda National Bureau of Standards. UNBS marked products are 
continually checked by UNBS for conformity to that standard.  
Further particulars of the terms and conditions of licensing may be obtained from the Director, Uganda 
National Bureau of Standards.  
 
 FDUS 1025 : 2013   
 
ICS nn.nnn.nn 
Price based on nn pages 
© UNBS 2013 – All rights reserved