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Humidity and Thermal State Behaviour

Working Group 3.41

Grain Moisture

In order to determine the moisture in different types of grain, oilseeds and corn, defined reference procedures are performed in accordance with ISO standards. These reference procedures consist in the drying of grain in an oven at defined temperatures and at defined drying times. The weight lost during the drying process is, per definition, the moisture content.



For moisture meters for cereal grain and oilseeds, conformity assessments of the meters are carried out in accordance with Module B of the Measures and Verification Ordinance (MessEV) on behalf of the customer. To this effect, the correctness of the measurements  is checked in relation to the reference procedures.

Furthermore, metrological traceability of the verification standards used by the verification authorities is established for the different measuring principles of the grain moisture meters that are present in the market.

Opens external link in new windowCalibration and measurement capabilities

Information on grain probers (to determine the bulk density)

Information on the testing and conformity assessment of meters for the bulk density of grain, called "mass per hectolitre" as well as on the so-called "Amtliche Tafeln" edition 1938 (official correction tables) are available here Opens external link in new windowAG 1.81 "Darstellung der Masse".


Collaboration with DLG within the scope of the conformity assessment of moisture meters for cereal grain and oilseeds

The tests required for conformity assessments according to Module B of the Measures and Verification Ordinance (MessEV) encompass not only purely physical, technical aspects of moisture meters for cereal grain and oilseeds, but also checking the calibrations carried out for the different types of crops.

The testing of the calibrations is carried out as a comparison to the routine reference procedure according to the respective ISO standards and GMP 9.1 "Legal Metrology – Testing Instructions – Humidity Meters for Grain Cereals and Oilseeds".

In 2004, a collaboration agreement was concluded between PTB and DLG (German Agricultural Society). It lays down the details of the cooperation in the testing of calibrations of moisture meters for cereal grain and oilseeds.

DLG, as a free and independent specialist organization of agriculture and agronomy, has many years of experience and thus has the expertise and logistics required to carry out such tests on behalf of PTB and according to its specifications. Interlaboratory comparisons taking place at regular intervals with PTB and BFEL (Federal Research Center for Nutrition and Food of Germany) contribute to monitoring compliance with the quality requirements of EN ISO 17025.

Details about the collaboration on type examinations of moisture meters for cereal grain and oilseeds can be found Opens internal link in current windowhere.

International and national regulatory documents

  • OIML R 59 (Edition 2016): Moisture meters for cereal grains and oilseeds, 2016
  • OIML R 59 (Edition 1984): Moisture Meters for Cereal Grain and Oilseeds, 1984
  • DIN EN ISO 712 Cereals and cereal products – Determination of moisture content – Reference method (ISO 712:2009)
  • DIN EN ISO 6540Maize; Determination of moisture content (on milled grains and on whole grains = ISO 6540:1980)
  • DIN EN ISO 665 Oilseeds – Determination of moisture and volatile matter content = (ISO 665:2000)
  • WELMEC 7.2 (2015) Software Guide (European Measuring Instruments Directive 2014/32/EU)


  • OIML TC 17/ SC 1: Humidity; participating member
  • OIML TC 17/ SC 8: Instruments for quality analysis of agricultural products; participating member


  • Klüß, R.; Breier, A.; Heine, N.; Kramp, T.; May, K.; Östreich-Schmidt, S.: Vergleichsmessungen – ein wirksames Instrument zur Dokumentation der eigenen Leistungsfähigkeit; PTB-Mitteilungen, 124. Jahrgang, Heft 2, Juni 2011