Extech Instruments 48VTR User Manual page 12

Pb setting too narrow
When a Proportional Band is set too
narrow, the PV rises too quickly and
typically overshoots the SV as shown.
0% Output Region
P
R
O
C
Output throttles
E
between 0 and 100%
S
in the Pb region
S
V
PV undershoots SV
A
R
I
A
B
L
E
100% Output Region
TIME
Proportional Band (Pb) set too wide
Pb set correctly
When the Proportional Band is set
correctly, the PV rises to the SV in a
reasonable amount of time with little
undershoot. A slight oscillation of the PV
(within specification) is typical once the
SV is reached.
0% Output Region
P
R
O
C
Output throttles
E
between 0 and 100%
S
in the Pb region
S
V
A
R
I
A
100% Output Region
B
L
E
TIME
Proportional Band (Pb) set too narrow
SV
Pb setting too wide
Pb
When a Proportional Band is set too
Region
wide, the PV rises too slowly and may
never reach the SV.
Desirable slow oscillation of
0% Output Region
P
R
O
C
Output throttles
E
between 0 and 100%
S
in the Pb region
S
V
A
R
I
A
B
L 100% Output Region
E
TIME
Proportional Band (Pb) set correctly
12 Model 48VTR - Version 5.0 – January 2006
PV overshoots SV
SV
Pb
Region
PV around SV
SV
Pb
Region