Dose times and interval are set by trial and error. The smaller the reservoir the smaller the dose times need to be. The strength or concentration of your stock solutions will also affect the dose time setting. Obviously, the stronger the stock solution, the shorter the time the pump runs. If you are using a small reservoir tank you must ensure that your stock solutions are very dilute. 

Ideally, you are trying to achieve a dose time such that the EC(TDS) goes up by about 0.1EC (50 ppm) for each dose. If you need to set the dose time to a very small number to achieve this then you need to dilute the stock solution. The minimum time that any pump should run for is 1 second, so, if at any stage you have a ratio for one of the nutrient parts set for, say 20%, then the minimum dose time has got to be at least 100/20 = 5 seconds. This is because 5 seconds corresponds to a 100% dose and 20% is only 1/5th of this so the pump for this nutrient part will only run for 1 second. The process is similar for pH dosing where you are trying to achieve a change of, about, 0.1pH for each dose.

The dose interval is set to allow time for a dose to fully mix in before the controller makes the decision as to whether another dose is required. Normally set to 1 minute for a small tank and up to 10 minutes for very large systems.

If the dose interval is set to zero then the valves will open continuously while the measured EC and pH are below the set point and close as soon as they exceed the setpoint. This feature can be used as a simple in-line injection system in which irrigation water is rapidly taken from a small tank and fresh water is added simultaneously such that rapid dosing is required to maintain the EC and pH.

Irrigation intervals and durations for day and night are also set here as is the water ON time for each addition of water. This should be set so that each time it adds water it dilutes the nutrient by about 0.1EC (1CF or 50ppm).

Did this answer your question?