Model: LC5296-AT /LC5248E-AT/LC5296V-AT
masibus
Doc. Ref. no. : - m61C/om/301
Issue no. 13
User’s Manual
Page 30 of 44
Derivative Time:
Derivative action is used to restore the change in the processing temperature according
to the rate of change. It reduces the amplitude of overshoot and undershoots width. If
the derivative time is shortened, restoring value becomes small, and if the derivative
time is made longer, an excessive returning phenomenon may occur and the control
system may be oscillated.
Manual Reset:
Virtually no process requires precisely 50% output on single output controls or 0%
output on two output controls. Because of this many older control designs incorporated
an adjustment called manual reset (also called offset on some controls). This adjustment
allows the user to redefine the output requirement at the set point. A proportioning
control without manual reset or Integral time (defined above) will settle out somewhere
within the proportioning band but likely not on the set point.
Some controls use manual reset (as a digital user programmable value), this allows the
user to preprogram the approximate output requirement at the set point to allow for
quicker settling at set point when Automatic reset (Integral time) set to zero. Range for
the manual reset is -50.0% to +50.0% of proportional band for LC5296-AT.
Cycle Time:
The Cycle time for output is the time where the output is on for percentage of that time
and off for a percentage of that time, creating a portioning effect. The cycle time is only
used where PI, PD or PID control action is used. The shorter the cycle time, the higher
the proportionate resolution is, and better is the control.
For Relay output: Set to 10 to 300 seconds or more
For SSR output: Set to 1 to 60 seconds or more
BASIC PID TUNING PROCEDURE:
ADJUSTMENT
SEQUENCE
SYMPTOM
SOLUTION
Proportional Band
Slow Response
Decrease PB
Overshoot or Oscillation
Increase PB
Integral Time
Slow Response
Decrease TI
Instability orOscillation
Increase TI
Derivative Time
Slow Response or Oscillation
Decrease TD
High Overshoot orInstability
Increase TD
