Near Intersection of I-35 & I-90 Southern Mn. | Here's a rough description of a process that could be used to determine a reasonable starting meter cal number for a dry product. Setup the spreader with a gate setting that you plan on using in the field. Enter in a self-test speed, anticipated width and target rate. Choose an arbitrary cal number such as 100 and enter it into the controller. Zero out the total volume .
Put actual product in the spreader and weigh it. Run the spreader with the spinners off so the product falls on a pad to be reclaimed. Run for a while. Stop and reweigh the spreader.
Subtract the ending weight from the starting weight. This is how much material was dispensed. Compare that value with the volume shown on the controller. If they agree fairly closely (unlikely) then the arbitrary cal number you chose is a good starting point. More than likely the value shown on the controller will not agree with the weight removed. Refine the cal number and repeat the process. If the value shown on the controller is less than the scale indication then decrease the cal number. After a few trials you should get a ballpark figure for the cal number for that product under those conditions.
Check under actual conditions to compare what the controller feels it is applying against the known amount. Refine the meter cal as necessary. Ag Leader controllers have a Wizard that guides you through the above steps. They refer to the first part as Static calibration since you are not moving. They propose a second refining step which is called Dynamic calibration since it refines or fine tunes the cal number based on actual application. This refining step might be done with a complete fill and empty of the spreader. The Wizard compares the actual weight you have entered against what it obtained using the old cal. It then refines the cal number slightly. This is really the same process that I describe above but the Wizard guides you through the steps and does the math for you.
Checking the weights for a total field might be the only practical way to handle this unless you have a scale. This is about the best that can be done.
A problem with VR and dry products is that the method above assumes that the applied rate is directly related to the speed of a shaft sensor usually driven by the bed. This is true within a limited range. It is far from an exact science. Calibrating a flow meter for use with a liquid product is much more predictable over a wider range.
As an example, doubling the speed of the conveyor may NOT double the output. This means the meter cal for a dry product is very dependent on the conditions. The meter cal can be fairly close as long as those conditions do not change. Changes in rate, ground speed, product density, flowability etc. all play a big part.
Long story short - finding a good calibration number for a wide range of dry application situations can be difficult.
This brings up the question of even attempting VR. I hope so since I pay extra for having the local elevator VR my dry fertilizer. I realize that it is not necessarily exact but hopefully still worth the effort. Soil tests are taken every couple of years. The results of the soil tests seem to indicate that having them apply the dry fertilizer at different rates in different areas has tended to bring up the levels in certain areas that were lacking.
Edited by tedbear 12/28/2024 14:03
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Calibrate dry spreader for vari-rate
