Rockwell Automation T6200 Compressor Anti-Surge and Capacity Controller - Manual (Page 116)

Control Primer
7-14
Deadtime is not the same as lag. An example showing the difference is an empty garden hose
connected to a water faucet. When the water faucet is turned on there is a delay before any water
reaches the other end of the hose.
This delay is called the deadtime. Lag is the time the first drop of water reaches the end of the hose
until its reaches maximum flow.
Cascade Control
Cascade control is where the setpoint of a controller is automatically altered by some variable or
controller other than an operator. Controller B in Figure 7-12 is an illustration of a controller used in
a cascade application. The master controller maintains the master variable at its desired level by
adjusting the setpoint of the slave controller.
Deadtime
Non-Interactive
Control Action
Figure 7-10
Figure 7-11