Performance of Farm-Type Moisture Meters

Abstract

<p>Three farm-type moisture meters (Dickey-john DJMC, Dole 400-B, and Electrex DMT-2)* were compared to USDA-approved oven methods on 225 corn samples (10.4% - 33.8% moisturet) and 96 soybean samples (8.0% - 16.6% moisture) from the 1984 crop. In corn, the DJMC read ±0.5 percentage point of the oven up to 27% moisture. The 400-B read ±0.5 percentage point of the oven up to 28% moisture. The DMT-2 read equivalent to the oven at 11% moisture, but read progressively lower than the oven as moisture increased. At 25% corn moisture, DMT-2 read 4.4 percentage points less than the oven. In soybeans, DJMC tested a relatively constant 0.52 percentage points higher than the oven, 400-B read ±0.25 points, and DMT-2 varied linearly from 1.2 points high at 10% moisture to 1.5 point low at 17% moisture. Calibration correction equations are given for all three meters. Variability (with respect to the oven) of the farm-type meters increased as corn moisture increased, with an average coefficient of variation (CV) of 4.2%. Three trade-type meters, included for reference purposes, had an average CV of 2.4% on the same samples. In soybeans, variability was not a function of moisture content; the farm and trade meters had standard deviations relative to the oven of 0.37 and 0.26 points respectively. The major share of variability originated from sample-to-sample variations in electrical properties, followed by differences among individual units of the same brand then variations among replicate meter tests and oven tests on a sample.</p>