Advertisement
Quick Links
Advertisement
Related Manuals for Watlow Controls 988 Series
Summary of Contents for Watlow Controls 988 Series
- Page 1 Series 988 Enhanced Software Features Includes 986, 987, 988 and 989 1/8 DIN Microprocessor-Based Temperature/Process Controller Watlow Controls 1241 Bundy Boulevard, P.O. Box 5580, Winona, Minnesota USA 55987-5580 Phone: (507) 454-5300, Fax: (507) 452-4507 http://www.watlow.com...
-
Page 2: Table Of Contents
We Value Your Feedback Your comments and suggestions on this manual are welcome. Please send them to, Technical Writer, Watlow Controls, P.O. Box 5580, Winona, MN 55987-5580, or call (507) 454-5300, or fax (507) 452-4507. The Series 988 Advanced Software Features manual is copyrighted by Watlow Winona, Inc., ©... -
Page 3: Cascade
Cascade Requirements Cascade control requires enhanced software and two analog inputs, input 1 to monitor the primary, or outer, loop and input 2 to monitor the secondary, or inner, loop. At least one control output is required to control the process. Overview Cascade control can handle a difficult process with minimal overshoot, while reaching the set point quickly. - Page 4 difference between the set point and the process temperature generates an internal percent output value for the second, or inner loop, controller. This value cannot be seen by the operator. This internal percent (% int) output generates the internal set point for the secondary, or inner loop. The secondary loop uses this set point and the value of input 2 (typically attached to the heater sheath) to control the heat source temperature.
- Page 5 The outer loop can be auto-tuned by setting [`AUt] to [PidA]. While auto- tuning, the outer loop will be controlled in an on/off mode at a set point equal to [AtSP] x [`SP1]. In a heating application, make sure the set point is set at a value above ambient temperature.
- Page 6 Figure 9.6 - Lube oil Sample Application tank with cascade A Series 988 controller is used to heat lube oil to 125°F with a screw-plug- control. style heater. To protect the oil from breaking down and maximize its life, it is desirable to limit the maximum heater sheath temperature to 250°...
-
Page 7: Differential
Differential Requirements Two inputs and the enhanced software option are required. Overview Differential control allows the Series 988 to control one process at a difference to another process. Input 2 acts as a remote set point input. However the displayed set point indicates the desired difference between input 1 and input 2. - Page 8 Figure 9.8 - Freezer Sample Application display case with differential control. An application using differential control is to maintain glass temperature of a freezer display case above dew point at a differential to the ambient air temperature. A thermocouple at input 2 senses the outside air temper- ature and adjusts the internal set point to maintain the glass temperature 10 degrees higher.
-
Page 9: Dual Pid
Dual PID Sets 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]. - Page 10 Figure 9.10 - Test Sample Application chamber controlled A test engineer needs to control the temperature in a test chamber that with dual PID sets. can be operated at normal atmosphere or under vacuum conditions. If he tunes the controller for normal atmospheric conditions, when he reaches the portion of his test that requires a vacuum, he must stop the test and enter new PID parameters to maintain stable temperatures.
-
Page 11: Duplex
Duplex Requirements The duplex control feature requires enhanced software and a process out- put. NOTE: Overview Duplex applications Certain systems require that a single process output control both heating require a special and cooling outputs. A Series 988 controller configured with enhanced valve. -
Page 12: Ratio
Ratio Requirements Ratio control requires enhanced software. Two analog inputs are required to monitor the process, and at least one output adjusts the controlled part of the process. Overview This feature allows the Series 988 to control one process as a ratio of another process.