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United States Department of Agriculture

Agricultural Research Service

Microwave Scale Takes a “Hands-off” Approach

By Jill Lee
August 18, 1997

Need to know the mass of an object that is literally too hot to handle? A new device originally designed to measure corn kernel moisture could prove useful in manufacturing because it can measure the mass of objects dangerous to touch, such as molten ceramics or glass.

Developed by engineers Andrzej Kraszewski and Stuart Nelson with USDA’s Agricultural Research Service, the instrument uses microwaves to accurately measure grain’s moisture content without harming the seeds. The device also works on peanuts and soybeans.

The seed moisture measurements are part of a larger effort to protect food quality. Moisture gives a foothold to the fungus Aspergillus flavus, which produces aflatoxin, a dangerous food contaminant. Keeping seed moisture low during storage reduces the risk of A. flavus contamination.

Kraszewski and Nelson’s invention is based on something called a microwave resonant cavity. The microwave resonant cavity measures the disturbance an object creates as it moves through a microwave field. Based on these measurements, the researchers’ new device calculates mass and moisture content and reveals defects without harming the measured object.

The scale is fast, taking a measurement in as little as 20 milliseconds. Best of all, it can be manufactured with readily obtained components, researchers said. They received a patent (# 555-4935) on the technology and it is available for license.

Scientific contact: Stuart O. Nelson, USDA, ARS, Russell Research Center, Athens, Ga. Phone: (706) 546-3101; fax (706) 546-3607, e-mail:

Last Modified: 8/22/2017
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