Lakeshore 325 - Manually Setting Integral (I); Manually Setting Derivative (D)

Lake Shore Model 325 Temperature Controller User’s Manual
Operation 4-17
4.8.2 Manually Setting Integral (I)
The integral parameter (also called reset) is the I part of the PID control equation. It has a range of 0 to 1000 with a
resolution of 0.1. Setting I to zero turns the reset function off. The I setting is related to seconds by:
For example, a reset number setting of 20 corresponds to a time constant of 50 seconds. A system will normally take
several time constants to settle into the setpoint. The 50-second time constant, if correct for the system being controlled,
would result in a system that stabilizes at a new setpoint in between 5 and 10 minutes.
To set Integral, press the I key. You will see the following display.
Enter for Loop 1
Integ (I) 20.0
The Integral (reset) is entered using the numeric keypad, which includes the numbers 0 – 9, +/–, and decimal point.
Integral has a range of 0 to 1000 with a default of 20. Press the Enter key to save changes and return to the normal
display.
4.8.3 Manually Setting Derivative (D)
The derivative parameter (sometimes called rate) is the D part of the PID control equation. The rate time constant should
normally be somewhere between 1/4 and 1/8 the integral time in seconds, if used at all. As a convenience to the operator,
the Model 325 Derivative time constant is expressed in percent of ¼ the integral time. The range is between 0 and 200%.
Start with settings of 0%, 50%, or 100%, and determine which setting gives you the type of control you desire. Do not be
surprised if the setting you prefer is 0. Note that by using a percent of integral time, derivative scales automatically with
changes in the integral value and does not have to be revisited frequently.
To set Derivative, press the D key. You will see the following display.
Enter for Loop 1
Deriv (D) 0.0
The Derivative (rate) is entered using the numeric keypad, which includes the numbers 0 – 9, +/–, and decimal point.
Derivative has a range of 0 to 200 percent with a default of 0. Press the Enter key to save changes and return to the
normal display.