Sprayer Calibration Explained: How, When and Why to Use the SpotOn SC-2

If you have never measured the flow rate of every nozzle on your sprayer individually, there is a good chance some of them are not working properly. Worn tips, partial blockages and inconsistent wear between nozzles are almost invisible to the eye, yet they are one of the most common causes of uneven crop protection, wasted chemical and, ultimately, lost yield.

At Harvest Agri, we believe you cannot manage what you do not measure. Sprayer calibration is a perfect example. It takes minutes, it costs very little, and it removes guesswork from one of the most expensive jobs on the farm: chemical application.

In this guide we will cover what sprayer calibration actually means, why nozzle wear matters more than most growers realise, and how the SpotOn® Sprayer Calibrator SC-2 makes the job fast, accurate and simple to fit into a normal working week.

What Is Sprayer Calibration, and Why Does It Matter?

Sprayer calibration is the process of checking that every nozzle on your boom is delivering the flow rate it is supposed to, at your working pressure and forward speed. It sounds straightforward, but most sprayers are calibrated once, when new, and then never properly checked again.

The problem is that nozzles wear. Abrasive formulations, general use and age gradually enlarge the orifice in a spray tip, which increases flow rate and distorts the spray pattern. A worn nozzle does not fail all at once, it drifts, and that drift is invisible unless you are actually measuring output.

Poor calibration has real consequences:

• Over-application wastes expensive chemical and increases the risk of crop damage or residue issues.
• Under-application can mean poor pest, weed or disease control, and a wasted spray pass.
• Uneven output across the boom creates striping in the field, visible in yield maps for seasons afterwards.
• Environmental impact increases when product ends up somewhere other than the target.

Industry guidance is consistent on this point: nozzle tips should be replaced once their flow rate exceeds that of a new tip by 10 percent. You cannot apply that rule without a way to measure flow rate accurately, tip by tip.

Why Measure Before You Spray

This is where Harvest Agri's wider approach comes in. Across everything we supply, from soil compaction meters to biological soil amendments, the principle is the same: measure first, understand what the reading means, then act. Guessing whether nozzles need replacing, or assuming your sprayer is “probably fine” because it was calibrated last year, is the agricultural equivalent of applying fertiliser without a soil test.

Sprayer calibration fits the same logic. Measure each nozzle's flow rate. Understand which tips have drifted past the 10 percent threshold. Replace or adjust as needed. Then re-measure to confirm the fix has worked.

Introducing the SpotOn® Sprayer Calibrator SC-2

The SpotOn SC-2 is a handheld digital flow meter built specifically for this job. Rather than timing how long it takes to fill a jug and doing the maths yourself, you hold the calibrator under a running nozzle and it gives you a direct digital reading of flow rate in around ten seconds, with no calculations and no app required.

Key Specifications

Because the SC-2 is built for flow rates below 2.25 GPM (8.52 LPM), it is best suited to herbicide and insecticide application, which is the range most arable and horticultural sprayers in the UK are working within. If you regularly apply liquid fertiliser or run higher output nozzles above that range, the larger-capacity SpotOn SC-5 (available on request) is the better fit, so it is worth checking your typical output before choosing between the two.

How to Use the SpotOn SC-2

One of the main reasons calibration gets skipped is that it feels like a faff. The SC-2 is designed to remove that excuse.

1. Park up and select a nozzle. With the sprayer running at your normal working pressure, choose a nozzle to test.
2. Hold the calibrator under the tip. The SC-2's collection cone captures the output as the nozzle sprays.
3. Read the display. Within about ten seconds, the unit shows the tip's flow rate in your chosen unit (GPM, LPM or oz/min).
4. Check against the new-tip spec. Compare the reading to the manufacturer's rated output for that nozzle type. If it is more than 10 percent above the new-tip figure, the tip is worn and should be replaced.
5. Enter speed and nozzle spacing. The SC-2 will then calculate your actual application rate in GPA or LPH, so you can see exactly what is going down on the ground, not just what the label says should be going down.
6. Repeat across the boom. Because each reading takes seconds, it is realistic to check every nozzle rather than a sample, which is what catches the individual outliers that a quick visual check misses.

When to Calibrate Your Sprayer

Calibration is not a once-a-season job for most operations. It is worth building into your routine at these points:

• Pre-season, before the sprayer comes out of the shed for the first time.
• At the start of each new chemical programme, particularly if you are switching between herbicide, insecticide and liquid fertiliser applications with different pressure and rate requirements.
• Every few weeks during peak spraying periods, since abrasive products and heavy use accelerate tip wear.
• Any time output looks inconsistent, such as visible striping, patchy control, or unexplained differences in crop response across a field.
• Before contract or shared machinery is handed back or handed over, so you have an accurate record of its condition.
• As part of routine maintenance checks, alongside cleaning strainers and checking for blocked filters.

Pair It With the Right Maintenance Tools

Calibration tells you a tip is worn or blocked. Cleaning and maintenance tools are what let you deal with it in the field rather than waiting until you are back at the yard. A SpotOn nozzle cleaner and 4-in-1 tip tool (brush, foldout pick, spanner wrench and utility hook) is a natural companion to the SC-2, letting you clear debris and remove stuck tips on the spot, then re-test with the calibrator to confirm the fix has worked.

The Bottom Line

Sprayer calibration is one of the cheapest forms of insurance available to a farm business. A single worn nozzle, left unchecked, can waste chemical, compromise control, and cost far more over a season than the price of a calibrator. The SpotOn SC-2 turns a job that used to involve stopwatches, jugs and mental arithmetic into a ten-second digital reading, tip by tip, so you know exactly what your sprayer is actually doing rather than what you assume it is doing.

Measure it. Understand it. Fix it. Measure it again.

View the SpotOn® Sprayer Calibrator SC-2 on our website.

Frequently Asked Questions

How often should I calibrate my sprayer nozzles?

As a minimum, calibrate before the season starts and whenever you switch chemical programmes. Heavy users should check every few weeks during peak spraying periods, since abrasive products accelerate nozzle wear.

When should I replace a spray nozzle tip?

Industry guidance recommends replacement once a tip's flow rate exceeds that of a new tip by 10 percent. You can only apply this rule accurately by measuring flow rate with a calibrator such as the SpotOn SC-2.

What is the difference between the SpotOn SC-2 and SC-5?

The SC-2 is designed for flow rates below 2.25 GPM (8.52 LPM), suiting most herbicide and insecticide work. The SC-5 covers higher flow rates, up to 5 GPM, and suits liquid fertiliser or higher-output applications.

Does the SpotOn SC-2 need an app or calculations?

No. It automatically displays flow rate, tip wear percentage and, once you enter your speed and nozzle spacing, your application rate in GPA or LPH.