102
Chapter 7
535-PROF User's Manual
Applications
(each PID set will be active when its respective local setpoint is active).
3.
PID TRIP
determines which variable selects the various PID sets: process
variable, setpoint or deviation from setpoint.
4.
TRIP:X
defines the point (in the PV range) at which that set of PID values
become active.
Basic Operating Procedures
A PID set can be selected in one of six ways.
• For
NO. OF PID
= PV NUMBER, the PID set (1 or 2) is selected when PV1
or PV2 is used.
• For
NO. OF PID
= SP NUMBER, the active set of PID values is the same
as the active setpoint. For example, if SP3 is active, then PID set #3 will
be active.
• For
NO. OF PID
= REC. NUMBER, the PID set (1-8) is the same as the
current recipe number which is running (or on hold).
• For
NO. OF PID
= SEG SELECT, the PID set (1-8) is assigned to the current
recipe segment as defined by the
PID SET:##
parameter in the
RECIPE
#
menu.
• When
NO. OF PID
= a number (2-8), a PID set becomes active when the
variable exceeds its trip point.
For example, if
PID TRIP
= SETPOINT, and
TRIP:2
= 500, the second
set of PID values becomes active when the setpoint exceeds 500, and
remains active until the setpoint drops below 500 or exceeds the next
highest trip point. The PID set with the lowest trip point is also active when
the trip variable is less than the trip value. (The user can set the lowest trip
point = the low end of the process variable range, but this is not required.)
• A digital input can be set to trip to the second set of PID upon closure,
which overrides a selection based on trip points.
Using with Adaptive and Pretune
The 535 can be programmed to automatically set the PID values using the
Pretune and Adaptive Tuning functions.For both functions, the tuned set of PID
is that which is active upon initiation of the tuning function.
The controller cannot trip to other PID sets (based on trip point or the digital in-
put contact) until Adaptive Tuning is disabled. However, if the PID set is tied to
the corresponding local setpoint, the active PID set values will change with the
local setpoint.
Each PID set has 5 parameters that control its function—proportional band, reset,
rate, manual reset (or loadline), and trip point. For each set (2 thru 8), these values
have to be manually set.
1. Press
MENU
to access the
TUNING
menu.
2. Set values for parameters 1 thru 20 (these include the first PID set)
3. Press
MENU
to access these parameters for each additional PID set (2
through 8):
PROP. BND, RESET, RATE, MAN. RST.
and
TRIP
.
M. POWERBACK
POWERBACK is a proprietary algorithm which, when invoked by the user,
reduces or eliminates setpoint overshoot at power up or after setpoint changes.
Powerback monitors the process variable to make predictive adjustments to
