Delta AH500 Manual page 133

Ch a pt er 5 Tem per at ur e M eas ur em ent Mo d u l e A H 04 PT / AH 0 8 PT G
Control diagram:
T he instruction PID is inside the dotted line.
+
-
The PID algorithm is as follows.
t
( )
∫
= +
MV K E t K E ) (
P I
0
( )
E t
Forward action:
( )
E t
Reverse action:
b. Control mode
Cyclic control mode: Users set a cycle according to a controlled environment. (If the ambient
The width of a pulse is defined below.
 Pulse width=Output value (MV)/(Maximal output value–Minimal output value)×Cycle
Users can set the width of a pulse and a cycle (sampling time) by means of the instruction
GPWM.
Example:
The cycle is 2000 ms, the maximal output value is 100, and the minimal output value is 0. After
the PID algorithm is performed, the output value gotten is 50.
 Width of a pulse=50/(100-0)×2000 ms=1000 ms
Therefore, the pulse width used in the instruction GPWM is 1000 ms, and the cycle used in the
instruction GPWM is 2000 ms.
1/K
1/S
I
+
K
S
D
dE ) ( t
+
t dt K *
D
dt
( ) ( )
=
PV t - SV t
( ) ( )
=
SV t - PV t
air temperature changes slowly, the cycle can be longer.)
+
1/K
G(s)
P
+
5 - 11