Craig Day: Okay, to get this calibration as accurate as possible, I want to weigh the water. To do that, we need to check how accurate our scales are. A very handy reference weight is a one-dollar coin, which weighs nine grams. So, we get a one-dollar coin, pop it on the scales, and confirm it shows nine grams.
Next, we weigh the water from five models, average that out, and multiply it by 40 to determine the total flow for this machine.
We’ve taken our samples for half a minute, and now we’ll weigh them to see the equivalent flow. Since a kilo of water equals a litre, we can check our scales’ accuracy. After taring the measuring cylinder, we record 504 mls in half a minute. That equates to one litre plus 8 mls per minute, so everything aligns with this rig. We write down 504 for that measurement.
We’ve recorded all weights for the four samples: 504, 518, 501, and 509 mls. These are over half a minute, so we double the values to calculate total flow. The total for the four nozzles is 4.064 litres. Dividing 4.064 by four gives 1.016 litres per minute per nozzle. The rate controller shows 40, so multiplying 1.016 by 40 nozzles gives 40.64.
We can now adjust the flow controller’s constant to match this manual calculation. Before doing so, I’d recommend testing more nozzles, up to 20, for a more comprehensive check.
Keep in mind, this calibration is based on water, but actual spraying often involves different solutions with varying densities. This can affect the flow meter. Adjustments might be needed. Additionally, consider how accurate the measuring jug is. For a straight jug test, relying solely on the jug’s markings might introduce errors. To check, I tare the jug, add a kilo of water, and compare it to the 1-litre mark. On this jug, at 960 grams, the marking is above the 1-litre mark. For better accuracy, avoid relying on such measurements alone, especially for brand-new sprayers. |
