Chapter Three: Overview Tuning the 649 Pressure Controller
27
Tuning the 649 Controller
Tuning the 649 controller involves adjusting the Proportional and Integral terms to optimize the
response of the controller in your system. Since every system is different, the optimum settings
for the P term and I term will vary. Also, the response of the system to increasing and decreasing
pressures may vary. Tune the system to provide the best response in the direction of pressure
change that you anticipate.
The following graphs show the response of the 649 controller to changes in the set point. The set
point changed from 4 Torr [533 Pa] (2 Volts) to 6 Torr [800 Pa] (3 Volts), and back again.
Note
The following three graphs were generated on a system consisting of a
649 controller with a 10 Torr [1333Pa] pressure transducer, 1000 sccm
flow of nitrogen gas, 1552 Torr [207 kPa] inlet pressure, and 1 liter
system volume. Tuning with nitrogen may not offer maximum
performance if another gas is used for processing.
The same P and I term values may not create the same effect in your
system.
Controller Response with the Initial Values
The initial values (P = 0; I = 0) yield:
P = 0
I = 0
Settling Time
Settling Time
Set Point
Signal
4
2
6
8
Pressure, (Torr)
Time
Figure 10: Controller Response with Initial P Term and I Term Values
The controller response is slow to reach the set point, however, there is no pressure overshoot and
no oscillation. Increase the P term to create a faster response.
To Next Page
Loading...
