A multiple-variable digital control uses a reaction vessel for which binary inputs of level, temperature, and pressure drive binary outputs to the input valve and the output valve.
A digital HIGH opens a valve. The following conditions must be satisfied:
|
Pressure
|
Temperature
|
Level
|
Input Valve
|
Output Valve
|
|
H
|
H
|
H
|
L
|
H
|
|
L
|
H
|
H
|
L
|
H
|
|
L
|
H
|
L
|
L
|
L
|
|
L
|
L
|
L
|
H
|
L
|
|
H
|
L
|
L
|
H
|
H
|
|
H
|
L
|
H
|
L
|
L
|