User Guide

44
sure falls below setpoint value minus hysteresis.
Such a behavior is suitable to control an acid dosing pump.
A relay enabled as a low setpoint, is energized when the pH
value is below the setpoint and is de-energized when the pH
value is above the sum of setpoint and the hysteresis. This
operational mode may be used to control an alkaline dosing
pump.
P.I.D. CONTROL MODE
PID control is designed to eliminate the cycling associated
with ON/OFF control in a rapid and steady way by means of
the combination of the Proportional, Integral and Derivative
control methods.
With the proportional function, the duration of the activated
control is proportional to the error value (Duty Cycle Control
Mode); as the measurement approaches setpoint, the ON
(relay energized) period diminishes.
ON
OFF
Setpoint
14
Setpoint –
Hysteresis
ON
OFF
14
Setpoint +
Hysteresis
Setpoint