Process Controls
TWO POSITION CONTROL SYSTEMS
TWO POSITION CONTROL SYSTEMS
A two position controller is the simplest type of controller.
EO 1.4
DESCRIBE the characteristics of the following types of
automatic control systems:
a.
Two position control system
Controllers
A controller is a device that
Figure 11 Process Control System Operation
generates an output signal based
on the input signal it receives.
The input signal is actually an
error
signal,
which
is
the
difference between the measured
variable and the desired value, or
setpoint.
This input error signal represents
the amount of deviation between
where the process system is
actually operating and where the
process system is desired to be
operating. The controller provides
an output signal to the final
control element, which adjusts the
process system to reduce this
deviation. The characteristic of
this output signal is dependent on
the type, or mode, of the
controller. This chapter describes
the simplest type of controller,
which is the two position, or ON-
OFF, mode controller.
Rev. 0
Page 17
IC-07
