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ARS Home » Plains Area » Manhattan, Kansas » Center for Grain and Animal Health Research » Stored Product Insect and Engineering Research » Research » Publications at this Location » Publication #336831

Research Project: Impacting Quality through Preservation, Enhancement, and Measurement of Grain and Plant Traits

Location: Stored Product Insect and Engineering Research

Title: Development and evaluation of a low-cost probe-type instrument to measure the equilibrium moisture content of grain

Author
item Armstrong, Paul
item Mcneil, Samuel - University Of Kentucky
item Manu, Naomi - Kwame Nkrumah University Of Science And Technology
item Bosomtwe, Augustine - Kwame Nkrumah University Of Science And Technology
item Danso, James - Kwame Nkrumah University Of Science And Technology
item Osekre, Enoch - Kwame Nkrumah University Of Science And Technology
item Opit, George - Oklahoma State University

Submitted to: Applied Engineering in Agriculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/22/2017
Publication Date: 10/1/2017
Citation: Armstrong, P.R., McNeil, S., Manu, N., Bosomtwe, A., Danso, J.K., Osekre, E., Opit, G. 2017. Development and evaluation of a low-cost probe-type instrument to measure the equilibrium moisture content of grain. Applied Engineering in Agriculture. 33(5):619-629. https://doi.org/10.1303/aea.12266.
DOI: https://doi.org/10.1303/aea.12266

Interpretive Summary: Drying grain to the proper moisture content (MC) before storage and maintaining proper MC during storage is critical for maintaining grain quality, but in developing countries devices to measure MC are typically to expensive to be widely available. Storage of grain in bags is common in developing countries around the world, so a grain probing method is well-suited for MC measurement. A low cost meter was developed as part of a USAID project to reduce the post-harvest loss (PHL). The meter measures the MC of maize and other grains based on relative humidity (RH) and temperature (T) measurements obtained by a small digital sensor located in the tip of a tubular probe that can be inserted into bags of grain or other bulk grains. These readings are then used to predict moisture content using equilibrium moisture (EMC) equations programmed into the moisture meter. A handheld reader connected to the probe provides a user interface. The PHL moisture meter was evaluated based on laboratory studies in the U.S. and field studies in Ghana and the meter accuracy was compared to a John Deere Chek-Plus-SW08120 grain moisture tester and a DICKEY-john GAC®2100 Agri meter. The accuracy of the PHL moisture meter was comparable to the GAC2100 moisture meter for maize below 15%wb MC with readings averaging 0.45% higher for the PHL meter. Laboratory studies showed the PHL moisture meter requires approximately six minutes to take a measurement due to the time required by the probe tip and sensor to equilibrate to the grain. Methods were developed to reduce the measurement time by calculating how fast MC was changing with respect to time. This will be programmed into the reader and used to shorten test times for many measurement conditions. The PHL meter provided an effective tool for probing bulk grain and bags and providing MC measurements that can help improve grain storage in developing countries.

Technical Abstract: Storage bags are common in Africa, Asia and many other less developed countries therefore a grain probing method is well-suited for moisture content (MC) measurement. A low cost meter was developed as part of a USAID project to reduce the post-harvest loss (PHL). The meter measures the MC of maize and other grains based on relative humidity (RH) and temperature (T) measurements obtained by a small digital sensor located in the tip of a tubular probe that can be inserted into bags of grain or other bulk grains. Measurements are used by equilibrium moisture content (EMC) equations programmed into the meter to predict MC. A handheld reader connected to the probe provides a user interface. The PHL moisture meter was evaluated based on laboratory studies in the U.S. and field studies in Ghana. Meter accuracy was compared to two commercial meters, a John Deere Chek- Plus-SW08120 grain moisture tester and a DICKEY-john GAC®2100 Agri meter. The John Deere SW08120 portable moisture meter is a low cost meter by developed country standards (~US$250, 2016 price); the GAC2100 benchtop moisture meter is a GIPSA-approved moisture tester and has been a highly regarded and used electronic meter. Laboratory studies indicated that the PHL moisture meter requires approximately six minutes to take a measurement due to the time required by the probe tip and sensor to equilibrate to the grain. Methods to reduce the measurement time by measuring temporal equilibration rates were developed. These can be programmed into the reader to shorten measurement time for many conditions. The accuracy of the PHL moisture meter was comparable to the GAC2100 moisture meter for maize below 15%wb MC. Average differences showed a positive offset of 0.45% for the PHL meter relative to the GAC2100. The PHL meter provided an effective tool probing bulk grain and bags.