Watlow Electric 988 用户手册

WATLOW Series 988 User’s Manual

Enhanced Software Features, Chapter 9

Enhanced Software

Requirements
The Series 988 controller needs the enhanced software option to use dual
PID sets.

Overview
Standard software units have a single set of PID parameters. Units with
enhanced software can use two independent sets of heat/cool PID para-
meters, PID A [PidA] and PID B [Pidb]. To enable dual PID, enter the
Global Menu and set the algorithm prompt [ALgO] to dual PID [Pid2].
This second set of PID parameters enables the controller to switch
between two sets of PIDs, to compensate for changes in the system char-
acteristics. This need can arise from a variety of circumstances, such as
significant set point changes (controlling at 250, then controlling at 750),
operating a furnace with half a load versus a full load of steel, changing
the speed of a conveyor through a curing oven or using different materials
in an extruder.

Series 988 controllers can be configured to switch between PID A and PID B
based on a process value, a set point value or the event input status.

•  At [Pid2] PID 2 Crossover Selection (Global Menu) select what will

cause the switch: 

•  [Proc] Crossover Process Value, (input 1), PIDs will switch 

based on the crossover process value;

•  [StPt] Crossover Set Point (1) Value, PIDs will switch at the 

crossover set point value, PID A used below the crossover 
point and PID B above;

•  [``no] no crossover.

•  At [`Ei1] Event Input 1 or [`Ei2] Event Input 2 select [`Pid]:

•  PID A is used when the event input switch is open;
•  PID B when the event input switch is closed. 

(Note: One event input is standard on all units, a second event input is an
option.)