Storage of grain in bags is common in Africa, Asia, and many other less developed countries making a bag probing method well-suited for moisture content (MC) measurement. A low-cost meter was developed under a USAID project to reduce post-harvest loss (PHL). The meter, referred to as the PHL 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 grain bulks. 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 United States and field studies in Ghana. Meter readings from field studies were 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 portable moisture meter is a low-cost meter by developed country standards (~US$250, 2016 price); the GAC 2100 bench-top moisture meter is an approved moisturetester by the Grain Inspection, Packers and Stockyards Administration (GIPSA) and has been a highly regarded and used electronic meter. Laboratory studies indicated that the PHL meter may require up to 6 min to take a measurement because of the time required by the probe tip and sensor to equilibrate to grain conditions. 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 GAC 2100 moisture meter for maize below 15% MCwb. Average differences showed a positive offset of 0.45% for the PHL meter relative to the GAC 2100. The PHL meter provided an effective tool to probe bulk grain and bags.

Document Type


Publication Date


Notes/Citation Information

Published in Applied Engineering in Agriculture, v. 33, issue 5, p. 619-627.

The copyright holder has granted the permission for posting the article here.

Digital Object Identifier (DOI)


Funding Information

This research was funded by the United States Agency for International Development as part of the Feed the Future Innovation Lab for the Reduction of Post-Harvest Loss.