You are here

Calibration made easier

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.


“It’s a huge time-saving device,” says John Lipscomb, an application business development specialist with AGCO Corporation, who is based in Alabama. So much so that Lipscomb has urged AGCO dealerships to include the calibrators as part of their inventory. If a nozzle test can be completed in 10 seconds as opposed to one minute, that’s a big help.

Once a nozzle has more than 10% wear, it needs to be replaced, according to most manufacturers. The SpotOn is a tool that can help make that determination more quickly. The danger isn’t so much that wear will cause application rates to increase so much that plants can be hurt, according to Lipscomb. Flow meters or electronic flow control devices on board tractors or spray rigs generally prevent overapplication of product, says Lipscomb.


“What happens when the nozzle wears is that the spray isn’t nice and uniform,” says Lipscomb. “You get a distorted pattern.”

“A rate controller won’t pick up differences between nozzles if the flow is bad,” says ISU’s Hanna. “If some are giving more and some are going less, overall spray rates may be accurate, but differences can occur between nozzles.”

The availability of a device that quickly and easily checks the calibration of sprayer nozzles just might get producers to evaluate their equipment more often. 

“My guess is that most operators don’t calibrate as often as they should,” says Wolf. “They should do it at least once a year, or calibrate when changing to a different nozzle type.”

“For someone spraying 1,500 to 2,000 acres or more annually, checking nozzles at midseason or a couple times each year is a good idea,” says ISU’s Hanna.

In addition to nozzles, Hanna recommends checking spray system plumbing for leaks, hose condition, filters, and screens. Pressure gauges and the rate controller should also be checked.

How it Started

Innoquest was founded in 1993 by Bill Hughes, an ag engineer by training. The company primarily designs and manufactures electronic handheld devices for other businesses in agriculture and elsewhere. One of its first products was an electronic rain gauge. Innoquest has designed products as diverse as a soil compaction meter, an electronic golf putter, and a water-dispensing comb.

The firm began working on its own brand-name products, such as SpotOn, five years ago. Exposure to the sprayer industry on behalf of a potential client prompted Hughes to consider making a simple handheld device that “would be a step up from using a jug-and-stopwatch method” to test nozzles. 

Hughes estimates that under most conditions, the polycarbonate and stainless steel SpotOn has at least a 10-year life.

Learn more

Read more about