Near Intersection of I-35 & I-90 Southern Mn. | If a 50 acre "batch" is actually covering 60-62 acres some thing is wrong. For the system to accurately apply a desired rate, many factors are involved. One early question: How are you determining that the batch is covering 60-62 acres? I'm assuming this is based on your knowledge of the size of your fields.
The system uses a speed sensing device (in your case I believe it to be a radar gun) and a flow sensing device (flow meter), The system uses the speed cal number that you enter to convert the pulses produced by the speed sensing device into useful units such as feet, miles etc. The system uses the meter cal to convert the pulses produced by the flow meter into useful units such as gallons. It also uses the working width to calculate the area being covered.
It uses the results of the flow meter and the area being covered to compute the applied rate. The system will compare what it believes to be the applied rate against the target rate that you have entered and change the applied rate if it is not in close agreement with the target rate. This is if the unit is set in Rate 1 or 2. It does this for a short block of time and then repeats the process over and over again.
For all this to work properly, the sensing systems must be working properly and the correct speed cal, meter cal and width must be entered. First off I would check your various settings for speed cal, meter cal and boom widths. These may have inadvertently got changed and are not correct.
Your problem may be an incorrect speed cal but the results of your observations contradict each other. I suspect your problem is elsewhere.
Concerning the speed cal: The speed cal will be dependent on the speed sensing device. With many radar guns this is dependent on the angle at which they are mounted. You mention that you have been using 612 for a speed cal. This is a common starting number for working with radar guns typically found on many Deere tractors or sprayers. Your book refers to 598. This is the suggested starting number when using a Raven radar gun. The Raven radar is box that is mounted horizontally. The speed (actually distance) shown should be compared to a known ACCURATE distance and the speed cal adjusted to make this agree.
A caution here about using a country mile. Roads which seem to be one mile apart are notoriously inaccurate so a more accurate measurement would be better. If your roads are actually 5280 feet apart and the system reported 5380 feet the speed cal should be reduced. Your computation of changing from 612 to 600 would be correct. The system will then report a somewhat slower ground speed and less acres for a given field. When the system calculates the applied rate it will result in a slightly higher value and the system will reduce the flow accordingly. This would mean that a batch would cover even more acres than before! I'm not saying that 600 is incorrect but changing to it will not help your problem of covering too many acres.
The flow meter cal number is also very important. This number varies from flow meter to flow meter but a common meter cal for a Raven flow meter is 740. This means that when Raven ran 10 gallons of water through that flow meter they observed 740 pulses being produced. The meter cal number that you enter is used to covert the flow meter pulses to gallons. In this example it would divide the number of pulses by 74 to calculate the volume in gallons that has passed through it.
Your problem maybe your flow meter or meter cal. There is a turbine inside the flow meter that turns as liquid passes through it. This turbine has magnets on it that are sensed to produce the pulses that the 440 receives. The flow meter can be tested on a flow meter test stand. When I worked as a tech we did this by putting the test flow meter inline with a known good one. Each flow meter was connected to a display and water was run through them. We would compare the results of the test meter against the known good one and adjust the meter cal on the test meter until they agreed. If the new meter cal was vastly different than what we expected we knew there was some problem.
You can do this yourself with your sprayer. If you set the volume back to zero and spray out a tank, the volume on the Raven should reasonably agree with the tank capacity. Be aware that the tank markings are not very accurate and it is quite common that a tank will hold more than its rated value. If your meter cal is too low, the tank will go further than it should. Increasing the meter cal will result in a lower calculated applied rate so the system will open the control valve a bit more which will result in fewer acres being covered per batch.
Edited by tedbear 9/4/2017 07:29
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Raven 440SCS in Patriot
