Typically dosing channels are used to control EC or pH levels. However, it is also possible to set up a dosing channel to dose based on other conditions. An article on dosing to deliver a fixed quantity of fertilizer can be found here. This article will discuss how you can set up a dosing channel to deliver fertilizer at a rate that is proportional to the amount of water that is given. An example would be that you want to dose fertilizer at a 100:1 ratio.
What is proportional flow?
With proportional flow, the amount of solution is adjusted based on the volume of water that passes through the water system rather than dosing based on the desired EC or pH levels.
Proportional flow controls are based on the measured flow at the flow sensor. You need to have a flow sensor as part of your water system in you want to use proportional control. You will also need to know the capacity of your dosing channel.
How do I set this up?
To set up a dosing channel for proportional flow, you need to go to the configuration of the dosing channels This is found in Water Room ->Recipes. In the dosing channel configuration, you can set the solution. If you set this to FLOW, the dosing channel will use proportional control based on flow. You will also need to set the capacity
How do I set the ratio I want?
You will need to do a little math to figure out how to calibrate the dosing channel. There are a couple of steps that you need to do.
First, in the Configuration of the water system, there is a variable called 100% flow for dosing reference. In here you enter the capacity of the water unit.
Next, in the settings of the recipe, you can set the variable called “use channel for recipe X”. This is normally set at 100% if you want to use the dosing channel or 0% if you do not use the dosing channel. But for flow, you will need to set it at something else. The best way to explain this is by example.
Assume you have a Nutrijet 300 with a capacity of 12 m3/hour. Enter 12.0 in the 100% flow for dosing reference setting. If you want to dose at a proportional ratio of 100:1, your dosing channel needs to dose at a rate of 0.12 m3/h or 120 liters an hour (L/h) when the Nutrijet is running at it's full capacity of 12 m3/hour.
If your dosing channel is rated at 300 L/h, you will need to dose at 40% (120 L/h divided by 300 L/h) when the Nutrijet is running at full capacity. Enter 40 in the use channel for recipe X of the recipe that you want to use.
Once this has been set up, you can test it with water. Fill your tank that will feed the dosing channel with water. Run an irrigation cycle. At the end of the irrigation cycle, go to the Water system ->Status screen and check how much water was used in the irrigation cycle. Then check how much water remains in tank. If the proper amount of water was drawn from the tank based on how much water was given to the plants,, you know everything is set up properly.