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Calibration made easier

05/10/2012 @ 10:04am

Sprayer operators have tested the calibration of the nozzles on their sprayers for years by using an effective, but distinctly low-tech method. Each nozzle would be used to spray water into an empty jug while producers timed the process for up to a minute per nozzle with a stopwatch.

By timing the spray and with knowledge of the volume of the liquid in the jug, farmers could be reasonably certain their nozzles delivered the product at the desired rate. Though necessary, this process can be time-consuming. A 120-foot boom being used for 20-inch spacing would involve testing 73 nozzles – a process likely to last an hour and a half. 

In the last few years, several products have tried to streamline the process while increasing nozzle-test accuracy. Tests conducted at six universities (and sponsored by Successful Farming magazine) indicate a relatively new, simple device may be up to the task. 

Illinois-based Innoquest designed and manufactures the SpotOn sprayer calibrator, which demonstrated excellent accuracy in tests that only took 10 to 20 seconds per spray nozzle. The tests were conducted during the summer of 2010.

“We did find it to be most convenient,” says Mark Hanna, an Extension agricultural engineer at Iowa State University (ISU) who helped conduct the test. “There have been other devices on the market previous to this that will give a flow reading, but not with as much accuracy as this device.”

On average, the SpotOn gpm readings agreed with actual scale measurements taken of a given nozzle flow. The SpotOn average reading was never more than ¹⁄100 off from the actual measurements. The tests were conducted using nozzles with opening sizes of 11002, 11004, and 11006 at pressures of 15, 30, and 45 psi.

“If there were some gross flaw in the device, we wanted to know that, and we didn’t find any,” says Bob Wolf, retired Kansas State University Extension application specialist who now operates Wolf Consulting and Research, LLC in Illinois.

The SpotOn sprayer calibrator costs about $150 and is a mostly clear tube with a metal frame that can be placed over a sprayer nozzle for a test. A type of diffuser pad is incorporated to reduce splash or turbulence of the spray stream so it doesn’t strike electrodes directly and cause a false read. A digital readout on the side of the SpotOn tube registers flow rate.

A quick, accurate tool of this type is valuable, according to Wolf, who conducts calibration workshops as part of his business. The readout on the device replaces the need for testers to do the conversion math themselves after measuring the actual liquid in the containers used during traditional calibration tests.

Most producers should check calibrations when they change to a different nozzle type, and this tool “would make that a lot simpler,” says Wolf.

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