Function Blocks
3/99 Function Block Reference Guide 85
2.29 LDLG Function Block
Description
The
LDLG
label stands for
Lead/Lag
.
This block is part of the
Auxiliary
category. It looks like this
graphically on the Control Builder.
Function
Modifies an analog input value (X) to include LEAD (T2) and LAG (Tl ) time constants of from 0 to 99
minutes, when a digital input (EN) is ON.
• If EN = ON, then:
OUT = 1 + sT2 x X
1 + sT1
s = Laplace operator
If T1 = 0, then:
OUT = last X + T2 (X - last X)
t
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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