Gauge Your Coverage: How to Assemble Your Own Pressure Gauge Tester

By Carly Decker, Ontario Ministry of Agriculture, Food and Rural Affairs

Many farmers have never changed or tested their sprayer pressure gauge(s). This makes assessing sprayer performance and output difficult. Sprayer performance has a direct impact on coverage, efficacy and may affect subsequent yield.

The direct impact of a faulty gauge is that you may be spraying more or less product than you intended. More product means wasted money and less product may mean compromised spray coverage.

A few clear indications that your pressure gauge is near retirement:

  • Opaque or unreadable face,
  • Mineral oil leaking,
  • Needle does not rest on zero pin when sprayer is not under pressure,
  • Needle bounces during operation (this may also indicate the surge suppression chamber on the sprayer is low on air).

Sometimes a gauge is not obviously in need of replacement. Suspecting an issue, some growers will simply go out and buy a new gauge. However, even brand new gauges can be inaccurate right off the shelf. In order to test any gauge you need to apply a known pressure to see if it is reading accurately.

One method is to put two gauges in series on the same sprayer to see if they are in agreement. This is not always possible depending on your make of sprayer.

At a recent sprayer workshop, one grower had a great suggestion for testing gauges. His pressure gauge tester concept is designed to hook up to your farm air compressor (see Figure 1). It allows you to test your suspect gauge against a known working gauge. How do you know if your known gauge is accurate? Buy a few, test them against each other using this tester, keep one that you know to be accurate and return the rest.

Figure 1. The Pressure Gauge Tester

The following is a list of parts that you will need to build the pressure gauge tester.

Parts list (see Figure 2):

Part Price Source
2 x ¼” by 3” Galvanized nipples $2.69 ea TSC
¼” Galvanized 90º elbow $3.19 TSC
¼” Galvanized Tee $3.19 TSC
¼” Ball valve (threaded) $8.19 TSC
*Plug Air Connector (A over ¼”) $2.99 TSC
Teflon pipe tape $0.89 TSC
300 psi liquid-filled gauge $17.80 Hal-nor Tractor Supplies

*Depending on the air connector on your compressor

Test gauge range should match your existing gauge. Sprayer gauges should be twice as much as your typical operating pressure.

Figure 2. Parts required for the tester.

Tools required (see Figure 3):

  • ¼” crescent wrench
  • wire snip pliers
  • locking pliers
  • plumber’s adjustable wrench

Figure 3. Tools used to assemble the tester.

Here are some tips for assembly:

  • Ensure that the tee and elbow line up properly so that the gauges are at the same angle, facing the same way.
  • Ensure there is enough room between the two gauges so they clear each other when you thread them into the tester.
  • Use a crescent wrench to tighten the gauges – DON’T twist the gauge itself by hand. This is a great way to break them.
  • Don’t over-tighten the gauges.

To use the tester, thread the questionable gauge into the elbow, and leave the known gauge in the tee. Close the valve and connect the unit to the compressor line. Bring the compressor up to ½ the scale on the gauge. For example, a 200 psi gauge should come under 100 psi pressure for testing. If your compressor cannot get that high, set it as high as it can safely go.

Slowly open the valve and see if the gauges are in agreement. If the suspect gauge is 10% more or less than the known gauge, get rid of it. A new gauge costs about $20.00 and is well worth the investment.

Special thanks to Mr. Kip Voege, retired owner of Voege vineyards, for the great idea. Further thanks to Mr. Paul Splinter, University of Guelph, Simcoe Campus, for technical assistance.

For more information contact

About Sean Westerveld

Ginseng and Medicinal Herbs Specialist, OMAFRA
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