Omron NJ501-1500

2 Instruction Descriptions
2-400
NJ-series Instructions Reference Manual (W502)
z Proportional Action (P)
The proportional action increases the absolute value of the manipulated variable in proportion to the
deviation between the process value and the set point. The process value of the controlled system
changes as shown below.
The proportional band is one of the settings that are used for the proportional action. The propor-
tional band is the range of the process value to which the proportional action is applied. If the pro-
cess value is not in the proportional band, the manipulated variable is set to 100% or 0%.
The proportional band is expressed as the percentage of the input range in which to perform the
proportional action (% FS). The following diagram shows the proportional band set to 10% FS.
Another parameter for the proportional action is the manual reset value. The manual reset value is
the manipulated variable that is used when the deviation is 0. The manual reset value determines
the position of the proportional action range in the process value−manipulated variable graph. The
relationship between the manual reset value and the proportional action region is shown below.
The position of the proportional action range is determined so that the manipulated variable when
the process value and the set point are the same equals the manual reset value.
Time
A large deviation produces a large MV,
which produces a large change in the process value.
A small deviation produces a small MV,
which produces a small change in the process value.
Process value
Set point
100%
0%
Manipulated
variable
Process value
Proportional band
at 10% FS
Lower limit of input range
100% FS input range
Upper limit of input range
100%
0%
Proportional action region
when the manual reset value is a.
Proportional action region
when the manual reset value is b.
Manipulated
variable
a
b
Process value
Set point
The position of the proportional action
range is determined so that the
manipulated variable when the process
value and the set point are the same
equals the manual reset value.