Chapter 10 Built-in PID Functions
10 - 5
10.3.5 PID control
As shown by (10.3.1) ~ (10.3.5), PID control reduces vibration during PI control by adding the derivative effect to
PI control. The derivative effect operates only when the system state changes, regardless of the system error
value. When the PV measurement signal at the system sensor is not clean or mixed with noise, however, an
undesired derivative effect is created and causes an unstable operation of the heater or pump. To be sure that the
derivative effect is not caused by such trivial changes as noise in the system, it is required to install a filter at the
sensor input and set the derivative coefficient to a low value: in case of an actual system, it is common to set the
derivative coefficient between 0.001 ~ 0.1.
0.0
10.0
20.0
30.0
40.0
50.0
60.0
0
2
4
6
8
10
12
14
16
T
e
mp
eratu
re
Second
