Hach EC1000 Instruction Manual page 53

Figure 10 PID pH Process Gain
Figure 11 PID Titration Curve
14
13
12
11
10
9
8
pH
7
6
5
4
3
2
1
10 20
The process gain seen by the controller is the slope of a line between
the setpoint and the pH measurement on the titration curve.
16
15
14
13
12
11
10
9
8
pH
7
6
5
4
3
2
1
0
-1
-2
0 20
3
2
1
Setpoint
30 40 50 60
REAGENT DEMAND %
40 60
REAGENT DEMAND %
53
4
5
70 80 90 100
80 100