Model: LC5296-AT /LC5248E-AT/LC5296V-AT
masibus
Doc. Ref. no. : - m61C/om/301
Issue no. 13
User’s Manual
Page 28 of 44
7. CONTROL FUNCTION
7.1 ON/OFF Control
ON/OFF Controller is the simplest form of temperature control device. The output from
the device is either on or off, with no middle state. An on-off controller will switch the
output only when the temperature crosses the setpoint. For heating control, the output
is on when the temperature is below the set point, and off above set point.
Since the temperature crosses the set point to change the output stage, the process
temperature will be cycling continually, going from below set point to above, and back
below. In cases where this cycling occurs rapidly, and to prevent contactors and valves
from getting damaged, an on-
off differential, or “hysteresis,” is added to the controller
operations. On-Off hysteresis prevents the output
from “chattering” or making fast,
continual switches if the cycling above and below the set point occurs very rapidly.
Figure 7.1: Typical Relay operation
High type (H-ON):
For High type of set value, once process value reaches up to set point + Hysteresis
value, relay will be ON after few seconds (as per relay delay) and it will be ON until
process value goes down to Set point.
Low type (L-ON):
For Low type of set value, once process value reaches down to set point
–
Hysteresis
value relay will be ON after nearly few seconds (as per relay delay) and it will be ON
until process value goes up toward Set point.
NOTE:-
LC5296-AT/LC5248E-AT /LC5296V-AT has both ON-OFF & PID
Controlling for Relay-1. And Relay-2 is used for Alarm output. If ON-OFF
controlling is required for Relay-1, COP (Control Type) must be selected
as ON-OFF.
When PB,TI,TD term is ‘0’ and auto tune is set ‘no’, and unit is not in
manual mode, then control output will work as on-off controller else it
will work as PID controller.
