Near Intersection of I-35 & I-90 Southern Mn. | The meter cal on the Raven tag is assuming you want to set your target rate in Pounds of Actual "N" per acre. When doing a comparison for checking against the suppliers scale, remember the supplier will generally be talking about pounds of NH3, so you will need to take 82% of their weight to determine how accurate the Raven system has been.
Since a flow meter measures volume, the meter cal for liquids (water, spray, liquid fertilizer etc.) is pretty straight forward. Basically enter the suggested meter cal from the tag, enter your desired target rate as Gallons per Acre and the displayed rate and volume totals will be in gallons.
When a Raven system was first used with NH3, you still entered that same meter cal but needed to set your target rate in terms of Gallons of Actual "N" desired. You consulted a chart to determine what target rate in terms of Gallons per Acre you desired.
In an effort to avoid the need to consult that chart, Raven decided to print a suggested meter cal for the product on the meter cal tag. Generally 1 gallon of liquid NH3 would contain 4.22 pounds of Actual "N". If you take the meter cal on a flow meter for gallons of liquid and divide by 4.22 you will get the meter cal to use if you wish to work in pounds of Actual "N".
This value is the meter cal for Pounds of Actual "N" you desire. This is generally how most farmers and agronomists express the rate. In other words when asked what rate I desire, I might reply "Oh, 160 I guess". When I say 160, I'm meaning 160 pounds of Actual "N".
You may wonder why I continually use the word Actual. I have found by adding the word Actual and not just saying "N" that it helps distinguish between "N" and NH3.
Here's how it works here. When I pick up a tank of NH3, the supplier has weighed it. When I return the tank, they weigh it again and subtract to determine the pounds of NH3 to charge me for. I take 82% of that weight to determine the number of pounds of Actual "N" that was applied from that tank. I divide that value by the number of acres that the Raven has indicated were covered. This gives me the applied rate in Pounds of Actual "N". Generally this agrees quite closely with what I had in mind. This value will vary somewhat depending on temperature etc.
When using controllers other than Raven controllers with a Raven Accu-flow system, the meter cal may be different. Some setups such as Ag Leader have you enter the meter cal for liquid divided by 10. The Ag Leader system makes the conversion internally since you have indicated you are working with Anhydrous Ammonia. This is correct but can lead to confusion.
If you should enter the suggested meter cal that you would use with a Raven, the conversion gets involved again and you only apply about 1/4 of what you had in mind. I did exactly that with my first tank after I switched to an Ag Leader. I noticed my manifold pressure was lower than I expected and checking the float level in the tank and found I hadn't used much. It was then that I realized that I should have read the Ag Leader screen more closely. I changed the meter cal to the correct value and redid that strip at 3/4 rate.
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raven 440 nh3 units
