Ounces Equal Gallons: Sprayer Calibration

Roberto N. Barbosa, Koske, Thomas J., Parish, Richard L.  |  4/18/2005 11:37:02 PM

spray

A simple but accurate way of checking the output of your sprayer is the H 128 method of sprayer calibration. When properly set up and executed, each ounce of output caught will translate into 1 gallon per acre sprayer output.

THEORY: DIVIDE ONE ACRE INTO 128 EQUAL PARTS. (Note: There are 128 ounces per gallon. One ounce on each of the 128 parts is 1 gallon per acre (GPA).

1/128 Acre = 43,560 ft2 divided by 128 = 340 square feet
One ounce/340 ft2 = 1 GPA

COLUMN 1

COLUMN 2

COLUMN 3

Nozzle spacing or swath width "W" Inches

Length "L" per 340 ft2
at "W" Swath

Seconds to Travel Length
in Column 2

30

136'

 

28

146'

 

26

157'

 

24

170'

 

22

185'

 

20

204'

 

18

227'

 

16

255'

 

14

291'

 

12

340'

 

10

408'

 

Doubling "W" gives half of "L" ; or doubling "L" gives half of "W" .

To calibrate your sprayer:

Step 1: Lay out required distance in column 2. Write the distance down on the tank and wall of the barn

Step 2: Measure seconds to travel this distance. Use known constant speed. Note throttle setting and RPM .   Write the seconds to travel this distance, speed, throttle setting, pressure and rpm on the tank and on the wall of the barn.

Step 3: With sprayer stopped and throttle set at same RPM or pressure, catch the spray from all nozzle(s) within "W". Swath, nozzles at 20 inches apart, collect one for 20 inches or two for 40 inches. Measure it in ounces .
* To Improve accuracy, average over all nozzles.

Step 4: Each ounce collected equals 1 gallon/acre. Ounces equals  GPA.

Step 5.  To check the calibration of the sprayer in the future, collect from a nozzle for the seconds to travel at the same rpm and pressure as the original collection.

Examples:

1.) 40-inch rows, two nozzles/row; "L" is 102 feet distance17 seconds to travel 102 feet; Collect 14 ounces/17 seconds from both nozzles equals 14 gallons/acre (band or broadcast).

2.) 32-inch rows, three nozzles/row; 127 feet distance;23 seconds to travel 127 feet; Collect 18 ounces in 23 seconds per 3 nozzles equals 18 gallons/acre (band or broadcast).

3.) Boom, 20-inch spacing; "L" is 204 feet; column 3 is 35 seconds; 35 seconds of spray gives 25 ounces, thus 25 GPA.

4.) Boom, 18-inch spacing; the L is 227 ft.; travel time for L is 39 seconds; 39 seconds of spray gives 26 ounces, thus 26 GPA.

Note: to cut back on long runs of L, use half of L, but calculate with double the amount of output you catch.

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