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United States Department of Agriculture

Agricultural Research Service

Title: Variable-Rate, Digitally-Controlled Metering Device

Authors
item Camp Jr, Carl
item Sadler, Edward
item Evans, Dean
item Usrey, L - STORK GAMCO, GAINESVILLE

Submitted to: Applied Engineering in Agriculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 25, 1999
Publication Date: N/A

Interpretive Summary: The site-specific application of irrigation water and fertilizer should offer opportunities to conserve water, to reduce drought or flooding stress, and to reduce loss of fertilizer or pesticides from farm fields. Although site-specific irrigation machines have been developed, a major barrier to their broad use is the lack of a variable-rate sprinkler or metering valve. Limitations of current variable-rate devices restrict thei application. A variable-rate metering device was developed to provide a wide range of flow rates with a wide range of liquids. The device consists of a reservoir that is alternately filled and emptied at a rate determined by an electrical pulse, which is generated by a digital controller. Reservoirs of different sizes can also be used to change the flow rate. A second liquid or gas is needed to operate the metering device. The primary use described here is the use of compressed air to control water flow rates sfor irrigation. Sprinklers or nozzles used with the metering device will not affect flow rate as long as they are not restrictive. Reproducible flow rates were measured with working models of the device for a range of operating pressures and cycle times. A patent application has been filed by ARS.

Technical Abstract: A variable-rate, digitally-controlled metering device was developed to permit variable flow or injection of a fluid into either another fluid or the atmosphere. The device consists of a reservoir that is alternately filled and emptied at a rate determined by a digital pulse from an external source. The flow rate can be altered by changing the frequency of discharge within the total duty cycle, by altering the charge and discharg durations when the reservoir is not allowed to completely fill and/or empty, or by exchanging the reservoir with one of a different volume. The metering device can be used in a wide variety of applications with a variety of fluids. The primary use described here is for variable-rate irrigation applications using water and air. Flow rate of the device is not affected by a sprinkler or nozzle provided it does not restrict flow. Tests with prototypes operating either as a single unit or three devices operating on a manifold indicate reproducible flow rates for a range of operating pressures and discharge cycle durations. Because of its intermittent operation, water supply and delivery components have to be about 1.4X normal size to achieve the same maximum flow rate possible without the metering device. A patent application has been filed by ARS.

Last Modified: 10/1/2014
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