The DFA Moisture Meter: Then, Now, and Next

History of the Moisture Meter

In the January of 1933, Charles D. Fisher applied for a patent for what has come to be known as the DFA Moisture Meter, describing it as an “…apparatus for determining moisture content of various edibles, particularly those handled by the dried fruit industry such as prunes, raisins, apricots, figs, dates, and the like”. The drawings in Fisher’s application show an apparatus much like the ones on display today in the Safe Food Alliance Fresno lab: a wedge shape, familiar to any user of the modern moisture meter, but wooden rather than powder coated metal; almost twice as large: 12 x 15” at the base and 12” high at its back; and with the clamp unit attached to the main body of the tester, rather than a separate piece. There’s a reason the moisture meter hasn’t changed much over the years (even the current, more compact design has been around since the early 70’s); the simplicity and ruggedness of the meter have made it the go to method for determining the moisture content of dried fruit. To this day, it remains the only AOAC validated method for moisture determination that can be completed in minutes, rather than hours.

Digital Meter

While the basic theory of operation for the moisture meter remains unchanged, Safe Food Alliance has exciting plans for the future of the moisture meter. Look for our new digital version of the moisture meter to be released June of 2018. Developed in collaboration with Rich Young and Ronald Haff of the USDA-ARS’s Western Regional Research Center, the digital meter uses a programmable controller with a digital variable resistor in place of the wire-wound potentiometer currently used without altering the underlying principle of operation. Combined with an integrated digital thermometer and other modern electronics, the digital meter will further simplify moisture meter operations (determining the null reading will now happen automatically) and reduce the probability of user error.

Moisture Calculator App and Maintenance Program

Safe Food alliance is working to improve the user experience of the current moisture meter. Our new moisture calculator app is freely available for both android and iOS devices and replaces the old print moisture meter charts. Simply enter commodity, tap setting, temperature and null reading and it will tell you the moisture content of your commodity. To download, please search SFA Moisture Calculator. We are also instituting a yearly preventative maintenance service for all moisture meters, which is designed to prevent instrument downtime and provide audit certification. Send your meter in once a year and our technicians will:

  • Check for signs of user damage, and replace any wires, resistors, leads and other electronic components that show signs of corrosion or wear.
  • Replace the variable resistor, clean and calibrate the meter.
  • Test, and if necessary, replace the validation cylinders.
  • Provide a calibration certificate (meter meets standards of performance described in AOAC method #OMA 972.20)
  • A 10% discount will be applied to the cost of any major components found to be in need of replacement

Interested in using the DFA moisture meter for your commodity? Contact us at to receive a quote to develop a set of moisture charts.