HI 9913 is a 2-in-1 pH and conductivity controller engineered for dosage of fertilizer solutions in hydroponics.

HI 9913 measures pH from 0 to 14 and EC from 0 to 10 mS/cm. Two separate set points can be user-adjusted from 4 to 7 pH and 0 to 6 mS/cm. The relays are activated when pH exceeds the set point or conductivity falls below the desired value. Two pumps or electro-valves can be wired directly to the controller and be powered through the terminal. The operator can adjust two independent proportional settings for pH and conductivity. The time cycle is adjustable from 0 to 90 seconds, while the proportional band is 0 to 2 for both pH and EC. A ground probe can be connected to the appropriate terminals to eliminate interference and prolong the pH electrode's life.

HI 9913 provides for an alarm relay which is activated in several circumstances. These include when the pH is below the set point by the operator-adjustable threshold of 0.5 to 2.5 pH, or EC exceeds the set point by a value in the 0.5 to 2.5 mS/cm range. The alarm goes off if the pH and/or conductivity are not corrected within the operator-determined time frame of 1 to 10 minutes. The alarm can be turned off during maintenance. The fertilization status can be ascertained from a distance through dosage and alarm LED's.

HI 9913 accepts pH electrodes with a BNC and a conductivity probe with a DIN connector. HI 9913 compensates for the temperature effect on conductivity measurements automatically.