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 based on proportional flow can be found here.  This article will discuss how you can set up a dosing channel to deliver a fixed quantity of fertilizer each irrigation cycle. An example would be that you want to dose 50 liters of fertilizer each irrigation cycle regardless of how much water is given.

Why would I want to use quantity based dosing?

Quantity based dosing is often used for outside irrigation.  The plants growing outside may need different amounts of water from day to day based on the outside weather.  For instance, if it is raining, the plants do not need any water but if it is dry outside, the plants will need to be irrigated.  The challenge is that regardless of whether it has rained or not, the plants will need fertilizer.  When using quantity based dosing, the grower can adjust the amount of water the plants get while ensuring that they get the required amount of nutrients.

How do I set this up?

To set up a dosing channel for quantity based 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 QUANTITY, the dosing channel will deliver a fixed quantity of fertilizer each irrigation cycle.  You will also need to set the dosing channel capacity so the system knows how much fertilizer is being delivered.  Finally, you need to set the rate at which the fertilier will be dosed. This can be done per recipe in Water Room - >Recipes ->Advanced Settings under the setting use channel with recipe X.  This is normally set to 100% 

How do I set my quantity for each irrigation cycle?

In Water Room - >Settings, you can set the quantity the dosing channel will give for each recipe.   The dosing channel will dose at the rate set in Water Room - >Recipes ->Advanced Settings ->use channel with recipe X until enough fertilizer has been delivered. After that the dosing channel will turn off.    You need to make sure that the irrigation cycle is long enough for the desired quantity of fertilizer to be delivered,