Function Blocks
LDLG Lead/Lag Function Block
Revision 11 HC900 Hybrid Control Designer Function Block Reference Guide 179
2/07
LDLG Lead/Lag Function Block
Description
The LDLG label stands for Lead/Lag.
This block is part of the
Auxiliary category.
Function
Modifies an analog input value (X) to include LEAD (T2) and LAG (T1) time constants of from 0 to 99
minutes, when a digital input (EN) is ON.
• If EN = ON, then:
OUT =
1 + sT2
1 + sT1
x X
s = Laplace operator
If T1 = 0, then:
OUT = last X +
T2
t
(X - last X)
last X = Input value from execution cycle.
t = Duration of previous cycle time in minutes.
If T2 = 0, then the block functions as a digital lag filter.
• If EN = OFF, or initial start, then: OUT = X.
Inputs
X
= Analog value (Primary Input)
EN = Digital signal (Enable)
Output
OUT
= Analog value as modified
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