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Cotton bale being tested with a new moisture sensing system. Link to photo information
ARS has developed a new system for more accurately measuring moisture in cotton bales, an important measure of quality. Click the image for more information about it.

Graph of moisture found in a cotton bale by a new microwave sensing system. Link to photo information.
The pencil beam microwave imaging system can clearly show the level of moisture throughout a cotton bale from very wet (blue) to very dry (dark red).

For further reading

CAT-scanning Cotton Bales for Moisture

By Don Comis
November 7, 2008

A new system for more accurately measuring moisture in cotton bales has been developed by an Agricultural Research Service (ARS) scientist.

Measuring moisture in cotton bales is important, because high moisture levels can ruin cotton bales while they are being stored. Changes in cotton ginning technology are creating wetter bales, with moisture distributed less uniformly within the bales.

To deal with this problem, agricultural engineer Mathew Pelletier at the ARS Cotton Production and Processing Unit in Lubbock, Tex. has developed a CAT scan—three-dimensional imaging technology—to measure moisture in cotton bales.

In recent years, there have been a growing number of incidents in which large numbers of cotton bales—up to an entire season's worth from all the farmers who used a particular cotton gin—were ruined. Intensive analysis of these bales revealed moisture levels ranging from below 7 percent to well above 13 percent.

A 7.5 percent moisture level is the maximum safe storage level for cotton bales. It doesn't take moisture levels much higher than that to quickly cause color deterioration, fiber damage and mold.

Previous microwave sensors developed by Pelletier used wide microwave beams to scan bales for average moisture readings. The systems worked well with uniformly moist bales. But since more and more bales now vary in moisture, equipment needs to be capable of detecting the highest moisture point, as well as average bale moisture.

The new prototype system developed by Pelletier sends multiple pencil-thin microwave beams through each bale to sensors on opposite sides, giving a 3-D image of the water distribution throughout the entire bale. It can detect high moisture layers as well as determine overall average bale moisture.

Read more about this research in the November-December 2008 issue of Agricultural Research magazine.

ARS is a scientific research agency of the U.S. Department of Agriculture.