Delta AH500 - Page 207

Chapter 6 Temperature Measurement Module AH04TC/AH08TC
6-11
Control diagram:
G(s)
S
1/S
1/K
I
K
D
+
+
+
-
The instruction PID is inside the dotted line.
P
+
1/K
The PID algorithm is as follows.
( )
dt
tdE
KdttEKtEKMV
D
t
IP
)(
*)(
0
++=
∫
Forward action:
( ) ( ) ( )
tSV-tPVtE =
Reverse action:
( ) ( ) ( )
tPV-tSVtE =
b. Control mode
Cyclic control mode: Users set a cycle according to a controlled environment. (If the ambient
air temperature changes slowly, the cycle can be longer.)
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.