A redesigned DFA moisture meter
2012
Haff, R. P. | Young, R.
The DFA moisture meter has been internationally recognized as the standard for determining moisture content of dried fruit in general and is the AOAC Official Method 972.2 for measuring moisture in prunes and raisins since 1972. The device has remained virtually unchanged since its inception, with its operation based on conductance of a sample across an electrode pair that forms one branch of a Wheatstone bridge. In recent times, obtaining appropriate parts for the device has become problematic, as maintaining the original Wheatstone bridge design requires a precision potentiometer with nearly identical non-linear characteristics to the original. The design of the moisture meter has now been updated to use modern electronic components to, among other things, mimic the original potentiometer so that calibration charts, as well as AOAC certification, remain valid. The redesigned meter was compared to the original in moisture readings of raisins, prunes, and apricots. Scatter plot regression resulted in R(2) of 0.9999 and slope of 0.9902, indicating high correlation and identity between the original and modified meters. The updated device automates the time-consuming and error-prone steps currently performed manually and determines moisture content in 7 s.
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