User`s manual

88 Chapter 7 535 User's Manual
Applications
Basic Operating Procedures
A PID set can be selected in one of four 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.
• When using PID trip values, 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
input 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.
L. 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
control parameters, which in turn helps to eliminate overshoot of the Setpoint.
Software Configuration
1. Go to the TUNING menu.
2. Set POWR.BACK parameter to ENABLED.
3. Go to the SELF TUNE menu.
4. For DEAD TIME, set the value (time) that the controller should wait before invoking
an output change. This value is typically the dead time of the process. Or, let Pretune
calculate the dead time, then complete just steps 1 and 2 above.