Lakeshore 325 - Manual Tuning (Closed-Loop PID Control)

Lake Shore Model 325 Temperature Controller User’s Manual
4-16 Operation
Control Setup (Continued)
The Model 325 will display the heater output as either percent of full scale current or percent of full-scale power for the
heater range selected. This parameter affects the heater output display and the scale of the Manual Heater Power (MHP)
output parameter for Loop 1. The MHP Output scale is always the same as the control output display. To change control
output units press the Control Setup key and press Enter until the following display appears.
Select for Loop 1 °®
Heater Out Power
Use the s or t key to toggle between Heater Out Power and Current. Press the Enter key.
4.8 MANUAL TUNING (Closed-Loop PID Control)
In manual PID mode, the controller will accept user-entered Proportional, Integral, and Derivative parameters to provide
three-term PID control. Manual heater power output can be set manually in open loop and closed loop control modes.
For details on PID tuning refer to Section 2.7.
To place the controller in Manual PID tuning mode, press the AutoTune key, and press the s or t key until you see the
following display.
Select for Loop 1 °®
Tune Mode Manual PID
Press the Enter key. The controller is now in Manual PID mode.
4.8.1 Manually Setting Proportional (P)
The proportional parameter (also called gain) is the P part of the PID control equation. It has a range of 0 to 1000 with a
resolution of 0.1. Enter a value greater than zero for P when using closed loop control.
To set Proportional, press the P key. You will see the following display.
Enter for Loop 1
Prop (P) 50.0
The Proportional (gain) limit is entered using the numeric keypad, which includes the numbers 0 – 9, +/–, and decimal
point. Proportional has a range of 0 to 1000 with a default of 50. Press the Enter key to save changes and return to the
normal display.