User's Manual

SET

ACID

FEED

ADJUSTEMENT OF SETPOINTSADJUSTEMENT OF SETPOINTS

ADJUSTEMENT OF SETPOINTS

ACID

ALK

SET

FERT FEED

Make sure that the pH electrode, conductivity/TDS probe and any

ground probe have been properly installed and calibrated (see the

preceding pages).

FOR pH

Simply turn the pH ACID FEED or ALK FEED dial (see

3 - Functional Diagram). The desired value can be

chosen between 4 and 7 pH for HI 9913 and HI

9935, and 5 and 10 pH for HI 9923.

DOSING DIRECTION

The dosing terminals of HI 9935 are activated

when the pH value exceeds the setpoint. HI 9935 will then dose

acidic solutions to reduce the pH until the user-selected setpoint is

reached.

The dosing terminals of HI 9923 instead are activated when the pH

value falls below the setpoint. HI 9923 will then dose alkaline

solutions to increase the pH until the user-selected setpoint is reached.

FOR EC/TDS

HI 9913 provides for an “ALK/ACID” switch (see 4 -

Functional Diagram) so that the operator may select the

direction. If the switch is left on “ACID”, the terminals are

activated when the pH value exceeds the setpoint. HI 9913

will then dose acidic solutions to reduce the pH until the

user-selected setpoint is reached. Inversely, by leaving the switch on

“ALK”, the terminals are activated when the pH value falls below

the setpoint. HI 9913 will then dose oxidants to increase the pH until

the setpoint is reached.