Near Intersection of I-35 & I-90 Southern Mn. | With the Raven 440 family at least, the characteristics of the control valve are determined by the valve cal. The standard starting suggested value is the 2123 number that is on the label for the butterfly type control valves (there are other types of control valves that have other suggested valve cals).
This suggested Valve Cal of 2123 is NOT a complete number. It consists of the 4 separate digits, 2, 1, 2, 3. each of which affects a certain characteristic of the control circuitry. The control circuitry operates is what I think of as "high range" when the applied rate is considerably higher or considerably lower than the desired target rate. The control circuitry operates is what I thing of as "low range: when the applied rate is just somewhat higher or somewhat lower than the desired target rate. The idea is that large "shots of correction" are used to open or close the butterfly when the rate needs a considerable change but change to low "shots of correction" when the applied rate is close to the target rate.
This should help the system to more quickly get close to the target rate but then make minor adjustments so as not to over or under shoot it.
The left most digit (2 in the suggested valve cal) refers to the amount of backlash in the gears in the control valve. This comes into play when the direction of the change is opposite than it had been in the most recent change. Suppose the system commanded the control valve to open up a bit. Later due to a change in ground speed, it needs to close the control valve a bit. Due to the slop in the gear train, the first "hit" should be somewhat larger than subsequent hits in that direction to get the gear train "tight" in the other direction.
The next number (1 in the suggested valve cal) determines how "heavy" the correction "hits" should be when the system is in "high range" correction. The next number (2 again) determines at what point the system changes from "high range" to "low range" correction. The final digit (3 in the suggested valve cal) is the PerCent off target when correction should be attempted (3%). As long as the rate is within 3% high or low the system will make no attempt to change the control valve.
The above may seem confusing and most folks just simply use the suggested 2123 value. If the system seems to work but seems lazy, increasing the second digit will make it respond more rapidly. The danger is that the system might then overreact.
One might think that they want the system to have a tighter tolerance and thus reduce the value to 2122 or 2121 meaning that you wish to be within 2% or even better 1%. Usually this is counterproductive as the system might be working almost constantly and might actually result in poorer control.
You mention that when you tested directly on a battery that the control valve seemed rather slow (8 seconds for full close to full open) that would be correct. In actual use, the control valve should move even slower yet. When you shut off the Master switch, the section valves should close rather quickly but the control valve does not move at all. That way the control valve should be in the approximate correct position when spraying resumes.
When in Rate 1 or Rate 2 the system will move the control valve much slower since the second digit (the 1 in 2123) will give very short shots of electricity to the control valve motor in an attempt to move it just slightly. This is desirable since a very minor change is usually all that is needed when the rate is close.
The system is a closed loop correction arrangement. When the rate is out of tolerance (off by more than the 3%), the system will apply a short shot or a long shot of correction (the 1). It will then compare the new applied rate against the target rate and decide if another shot of correction is needed or the correction was too large. It does this constantly while spraying in Rate 1 or Rate 2. It does this based on the flow indicated by the flow meter and makes no reference to pressure.
Edited by tedbear 5/29/2023 06:01
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Flow issues with a Raven system
