ON/OFF CONTROL
Single Output
The controller operates in
ON/OFF Control when the
Proportional Band is set to 0.0%. In
this control, the process will
constantly oscillate about the
setpoint value. The amount of
ON/OFF Control Hysteresis
(CHYS) in Output Parameter
Module (2-OP), together with the
process characteristics determines
the period and amplitude of the
oscillations. Larger values of
hysteresis increase both the
amplitude and period of
oscillations but also reduce the
number of output switching cycles.
The Control Action (OPAC) in
Output Parameter Module (2-OP)
can be set to reverse (rEv) for
heating (output on when below the
setpoint) or direct (drct) for cooling
(output on when above the setpoint)
applications.
In controllers with operating
system software revision earlier
than V4.x, the ON/OFF Control
Hysteresis value is not balanced
around the setpoint value. In these
controllers, the Hysteresis is totally
added to the setpoint in reverse
action and totally subtracted from
the setpoint in direct action. The
revision number of the controller’s
operating system software is shown
in the secondary (bottom) display
during controller power up.
-48-
Figure 22, Output 1 (O1) ON/OFF Control
Software Revision V4.0 or Later
Figure 23, Output 1 (O1) ON/OFF Control
Software Revision V3.x or Earlier
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