2.5.4 Example of Process PID Control
is an example of a process PID control used
in a ventilation system:
Temper
atur
e
Fan speed
Temperature
transmitter
Hea
t
Heat
generating
process
Cold air
130BA218.10
100kW
n °C
W
Illustration 2.26 Process PID Control in a Ventilation System
In a ventilation system, the temperature can be set from -5
to 35
°
C with a potentiometer of 0–10 V. Use the process
control to keep the set temperature constant.
The control is inverse, which means that when the
temperature increases, the ventilation speed is increased as
well, to generate more air. When the temperature drops,
the speed is reduced. The transmitter used is a
temperature sensor with a working range of -10 to 40
°
C,
4–20 mA. minimum/maximum speed 300/1500 RPM.
Transmitter
96 97
99
98
91 92 93 95
50
12
L1 L2
L1
PE
L3
W PE
V
U
F1
L2
L3
N
PE
130BD373.10
18
53
27
55
54
M
3
Illustration 2.27 2-wire Transmitter
1.
Start/Stop via the switch connected to terminal
18.
2.
Temperature reference via potentiometer (-5 to
35
°
C, 0–10 V DC) connected to terminal 53.
3.
Temperature feedback via transmitter (-10 to 40
°
C, 4–20 mA) connected to terminal 54.
Product Overview
Design Guide
34
Danfoss A/S © 09/2014 All rights reserved.
MG06B402
2
2