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Optimizing Your Process System with the Series 988

1. for ramp multiple 988 s using the remote set point output 3 of the master Or you could use an analog output from a PLC to send set point values to a 988 Match input and output impedances zone 2 zone 4 zone 5 zone 7 Remote Remote Remote Remote output 3 Sample Application An engineer has a machine with eight independent zones of heat He wants to to change set points on all zones without having to adjust each control indi vidually This can be achieved using a 988 with a 0 5VDC retransmit output as the master controller The seven remote 988 s will use the 0 5VDC signal on input 2 as a remote set point When the set point is changed on the master controller the retransmit output changes the set points of the seven remote controllers By enabling the ramp to set point feature in the master 988 all eight zones are ramped up to set point at a user defined rate on power up The retransmit output from the master 988 is set so that OVDC represents 0 F and 5VDC represents 800 F On the remote controllers set the input 2 DIP switch to the position for the 0 5 1 5 0 10VDC process input In the Input menu under the input 2 prompt MEB select 0 5 The remote set point prompt should be set to ON and decimal 2 set to 0 The range low 2 and the range high 2 parameters will establish the scaling for the remote set point input Range low 2 should be set to O and range high 2 should be set to 800 To operate a specific zone ten degr
2. Set the DIP Switches The Series 988 989 User s Manual explains how to set the DIP switches inside the controller chassis You can set DIP switches to lock out the Factory and Setup menus Other DIP switches allow you to select some of the input output and power needs of your application 3 Mount and Wire the Controller The Series 988 989 User s Manual clearly ex plains and illustrates the process of correctly mounting and wiring your controller 4 Configure the Controller for Your Application The next step involves determining settings and values then entering them from the front panel of the 988 Chapter Seven of this book will help you chose the software and parameters to best control your application The Series 988 989 User s Manual will guide you through the menus and prompts you will use to configure the controller s software 5 Startup and System Operation For the final setup step carefully review the previous steps then turn on the system Some parameters such as slidewire feedback can be auto tuned after startup Then system perfor mance and alarms should be thoroughly tested 6 Documentation Once the system is operating corrcctly make photocopies of the menu flow diagrams in the user s manual and document all your settings Optimizing Your Process System with the WATLOW Series 988 Specifications The Series 988 989 User s Manual provides the information you will need to install wire
3. We will be pleased to consult with you regarding a specific application upon request Table of Contents Watlow Mission Introduction Chapter 1 Test Drives Controlling an Extruder Drying Grain Melting Aluminum Mixing Urethane Chapter 2 Basic Control Strategies and Terms Glossary Questions and Answers Control Strategies Chapter 3 General Software Features Auto tune Burst fire Communications Dead band Digital event Heater current Input filter Input linearization Ramp to set point Remote set point Retransmit master remote Slidewire feedback Chapter 4 Enhanced Software Features Cascade Differential Dual PID sets Duplex Ratio h ODAANM iu Optimizing Your Process System with the WATLOW Series 988 Chapter 5 Standard Features Alarms Auto Manual Diagnostics Input errors Lockout Transmitter power supply Chapter 6 Specifications Input Table Output Table Dimensions Displays and Keys Chart Setup Requirements User s Manual Product Specifications Warranty Chapter 7 Select the 988 That Fits Your Application 7 1 Index Watlow Sales Offices Overview Input Output Software Standard Features Hardware Review and Optimize Application Worksheet Series 988 Model Number Worksheet 7 11 Prompts parameters and menus back cover Optimizing Your Process System with the WATLOW Series 988 Test Drives Controlling an Extruder Drying Grain Melting Alumin
4. alarm is a deviation process or rate alarm Selecting process 1 or deviation 1 references the input 1 value against the alarm 2 low and alarm 2 high settings Selecting process 2 or deviation 2 references the input 2 value against the alarm 2 low and alarm 2 high settings Input 2 hardware must be connected and enabled Selecting rate references the rate of change of the input 1 value in degrees per minute defines a negative rate and defines a positive rate of change limit A process alarm sets an absolute process value independent of the set point When the process exceeds that value an alarm occurs The pro cess value is independent of the set point A deviation alarm alerts the operator when the process strays too far from the set point The operator can enter both high and low alarm settings referenced to the set point A change in set point causes a corresponding shift in the deviation alarm Low alarms are set at a nega tive deviation and high alarms are set ata positive deviation 3 Hysteresis This selects the switching hysteresis for the alarm Once an alarm has occurred it will not clear until the process value is above the alarm low setting or below the alarm high settings by a margin equal to the hysteresis Example An alarm starts when the process value reaches the alarm high setting The alarm will not clear until it is below the high setting by an amount equal to or greater than the alarm hysteresis 4 La
5. 32 to 2372 F or O to 1300 C R t c 32 to 3200 F or O to 1760 C S t c 32 to 3200 F or O to 1760 C B t c 1598 to 3300 F or 870 to 1816 C E t c 328 to 1470 F or 200 to 799 C C t c 32 to 4200 F or O to 2316 C D t c 32 to 4200 F or O to 2316 C Pt 2 32 to 2543 F or O to 1395 C 1 RTD JIS 328 to 1166 F or 200 to 630 C 1 RTD DIN 328 to 1472 F or 200 to 800 C 0 1 RTD JIS and DIN 99 9 to 999 9 F or 73 3 to 537 7 C 0 5VDC 999 to 9999 1 5VDC 999 to 9999 0 10VDC 999 to 9999 0 20mA 999 to 9999 4 20mA 999 to 9999 0 50mVDC 999 to 9999 0 100mVDC 999 to 9999 Slidewire 100 to 1200Q Current O to 50mA Potentiometer O to 1200Q Output Options Solid state relay 0 5A 24VAC min 253VAC max opto isolated zero cross switching With or without contact suppression Open collector switched DC signal provides a minimum turn ON voltage of 3VDC into a mini mum 500Q load maximum ON voltage not greater than 32VDC into an infinite load eElectromechanical relay Form C 5A 120 240VAC 6A 28VDC 1 8 hp 120VAC 125VA 120VAC With or without contact suppression Process 0 20mA 4 20mA 0 5VDC 1 5VDC or 0 10VDC eElectromechanical relay Form A B 5A 120 240VAC 6A 28VDC 1 8 hp 120VAC 125VA 120VAC Without contact suppression External transmitter power supply 5V 5 30mA 12V 5 30mA or 20V 5 30mA RS 232 communications or EJA 485 RS 422 com munication
6. The Diagnostics menu is a standard feature on all Series 988 controllers When asking the factory for technical assistance have the information from the above prompts on hand All prompts in this menu are read only Sample Application An engineer needed to figure out why an oven was malfunctioning She used test output to force ON output 1 EME which controlled the heaters A quick check with a meter revealed a burned out heater element Optimizing Your Process System with the WATLOW Series 988 5 5 Standard Features Overview When the 988 receives input information it cannot interpret or finds a problem with one of its internal functions it generates an error code to help identify the problem The control ler switches to manual mode and operates at a fixed power output level depending upon the type of error code and the selections made in the Global menu If an input related error occurs four dashes GEE appear in the upper display and the bottom display indicates the output power level Press the AUTO MAN key once to display the error code in the upper display for five seconds The failure mode prompt determines what the 988 output power level will be when an input error occurs The bumpless transfer selection allows the 988 to switch from auto matic to manual mode at the percent power level the controller was at when the input error occurred However certain conditions must be met the process must have stabilized at
7. a8 PROCESS ne Li L2 L3 L4 DEV DISPLAY OUT AUTO MAN amp controller allows a negative output value only if one of the control outputs is configured for cool If the LED in the corner of the AUTO MAN key is off the controller is in the automatic mode and the bottom display is a set point value in degrees or units If the LED is on the controller is in the manual mode and the bottom display indicates the percent power output To toggle between auto and manual operation press the AUTO MAN key twice When you press the AUTO MAN key once the LED in the lower right hand corner of the AUTO MAN key begins to flash To complete the change press the AUTO MAN key again while the LED is flashing The transition from automatic to manual is a bumpless transfer the control will switch to manual mode maintaining the last power level it used in automatic mode Requirements Automatic manual operation is a standard feature on all units AUTO MAN Key kA Auto Manual LED SERIES 988 Sample Application An engineer has a process that needs to be brought on line at a low power level until a predetermined process value is achieved At this point the controller can be allowed to take control of the output power level Utilizing the automatic manual function the engineer manipulates the power level in manual mode until it is safe to allow the controller to take control At that point he switches the 988
8. e RTD s will provide the most accurate measure ment in a temperature related system e The accuracy of a process sensor for flow level pressure etc will depend strictly on the sensor manufacturers specifications e The Series 988 measures the input and updates the output 10 times per second with one input With 2 inputs each input is measured five times per second What is the wire length required to reach controller page 6 8 e When designing a system using thermocouple or RTD sensors if the lead length is excessive errors may be introduced into the system By using a signal transmitter to convert the thermocouple or RTD signal to a process signal the errors can be avoided Is cost a factor in the sensor selection e Typically a thermocouple costs less than an RTD sensor However it almost never pays to spend less on a sensor which is arguably the most important part of the thermal system e Process sensors can vary widely in cost Other factors such as accuracy response time and durability must be weighed Will this be a grounded or ungrounded applica tion page 5 8 e Although inputs are electrically isolated from outputs in the 988 you must determine if other sources of ground loops in the system may affect the sensor This can occur in the Series 988 if there are two grounded inputs or if an output is tied to an input such as using a transmitter power supply output to power a thermocouple transmit
9. 2 9 PDR control 2 7 2 9 percent power output 5 4 percent power output OUT LED 6 5 personal computer 2 6 Pl control 2 9 PID 2 2 2 3 2 7 2 9 2 10 3 2 4 2 4 3 4 5 PIDA 4 3 4 5 PIDB 4 3 4 5 PID menus 3 5 PLC 3 11 power 6 8 7 7 power supply 5 5 5 8 7 8 pressure switch 4 5 process 2 2 4 5 5 5 process 1 5 2 8 2 Optimizing Your Process System with the WATLOW Series 988 Index process 2 5 2 process 2 prompt 3 7 process alarms 2 6 3 7 5 2 process input 6 2 process retransmit 6 3 process variable 2 9 product specifications 6 8 proportional band 2 4 2 9 3 2 proportional control mode 5 5 proportional derivative control with manual reset 2 9 proportional integral control 2 3 proportional integral derivative PID 2 3 proportioning control 2 2 2 9 2 10 proportioning control with deriva tive 2 9 protocol 3 4 Q QCD 3 3 QPAC 3 3 questions and answers 2 5 R radio frequency interference 1 7 radio frequency noise 3 3 ramp rate 3 10 ramp to set point 1 3 2 7 3 10 ramping function prompt 3 10 range 2 5 range high 2 3 11 3 13 4 3 range high 2 prompt 3 7 range low 2 3 11 3 13 range low 2 prompt 3 7 rate 2 3 2 4 2 10 5 2 rate alarm 3 10 rate band 2 9 ratio control 1 8 1 9 2 7 2 9 4 7 read only 5 7 reference junction 2 10 relative humidity 3 8 remote set point 3 6 3 11 4 4 reset 2 4 2 10 resistance temperature detector RTD 2 5 2 10 6 2 retransmit 2 6 2 10 3 12
10. Also the NEMA 4X rating was certified indepen dently by UL under UL 50X Controller Operation Operation of the Series 988 can be broken down into three concerns setup operation and maintenance The questions you ask yourself should examine each of these areas Does the system have any interactive process variables Chapter 4 e Interactive process variables include ratio differential or cascade control or slidewire feedback of valve position Also heater current measurements can be used to detect system faults Is an event input useful in this application page 3 6 e Before finalizing the design check out this basic option The event input can expand the user friendliness and or security of your system Is ramp to set point required On start up On set point change page 3 10 e Many systems are susceptible to damage if the process changes too rapidly The ramp to set point feature can minimize system stress How should the controller respond to an error page 5 6 e In the event of an error system response is critical Some systems might require that the control output turn full ON to provide cooling Other systems would require that the control outputs be turned OFF The design of some systems might allow the control to continue operating in the manual mode without operator action All of these options are available with the Series 988 Are you shipping products overseas page 2 3 e In some count
11. Basic Control Strategies and Terms annunciator a device that uses pilot lamps to indicate the former or existing condition of a system being monitored ANSI American National Standards Institute burst fire output that switches full AC cycles ON and OFF repeatedly Zero cross burst fire switches only at the zero voltage point of the AC sine wave Variable time base burst fire would switch ON and OFF 30 times a second to achieve a 50 percent power level with a 60 cycle AC power supply Also see zero switch ing calibration offset adjustment to the actual process input and to the process values the Series 988 uses for display and control cascade control algorithm in which the output of an outer control loop is the set point for an inner loop The inner loop in turn determines the control action closed loop control system that uses a sens ing device for process variable feedback cold junction point of connection between thermocouple metals and the electronic instru ment cold junction compensation electronic means to compensate for the effective tempera ture at the cold junction current transformer a transformer designed for measuring electrical current with its primary winding connected in series with a circuit carrying the current to be measured dead band The dead band setting determines the amount of interaction between heat reverse acting and cool direct
12. a measurable predictable voltage that corresponds to its temperature thermocouple break protection fail safe operation that assures output shutdown upon an open thermocouple condition three mode control proportioning control with integral reset and derivative rate Also see PID time proportioning control action that varies the amount of on and off time when close to the set point i e in the proportional band This variance is proportional to the difference between the set point and the actual process In other words the amount of time the output relay is energized depends on the system process value transmitter power supply When Option T is ordered for output 2 3 or 4 the Series 988 can 2 10 supply power to external signal conditioners transducers or transmitters With internal DIP switches the user selects between 5 12 or 20VDC at 30mA ratings zero cross Action that provides output switch ing only at the zero voltage crossing points of the AC sine wave Also see burst fire Optimizing Your Process System with the WATLOW Series 988 Chapter Three General Software Features Auto tune 3 2 Burst fire 3 3 Communications 3 4 Dead band 3 5 Digital event 3 6 Heater current 3 7 Input filter 3 8 Input linearization 3 9 Ramp to set point 3 10 Remote set point 3 11 Retransmit master remote 3 12 Slidewire feedback 3 13 How to use this chapter This chapter de
13. acting control outputs default parameters the parameters or pro grammed instructions permanently stored in the microprocessor software derivative anticipatory action that senses the rate of change of the process and compensates to minimize overshoot and undershoot Also see rate differential control With enhanced software the Series 988 controller can control one process in relation to the difference of a second process A set point is added to the measured value of the second process This sum is used as the set point for the input 1 process value DIN Deutsche Industrial Norms a widely recognized German standard for engineering units droop difference between the set point and stabilized process value duplex control With enhanced software duplex control splits a single process output into two individual outputs For example a 4 20mA output is split into a 4 12mA direct acting cooling output and a 12 20mA reverse acting heating output thus allowing one control output to function as two duty cycle percentage of load ON time relative to total cycle time external transmitter power supply a DC voltage source of power for external devices filter as applied to the Series 988 a low pass filter designed to minimize display or process input fluctuations form A single pole single throw relay that only utilizes the normally open N O and common contacts Thes
14. all of the graphs have illustrated overshoot occurs with any of the previous control meth ods Overshoot may be hazardous to certain processes It is preventable with a control function known as derivative rate Derivative is an anticipatory function in a process control that measures the rate of change of the process and forces the control into a proportioning action on an accelerated basis to slow that change This action prevents a large degree of overshoot on start up and also functions to prevent overshoot when system disturbances would tend to drive the process up or down A proportioning control with integral and derivative PID control provides the type of control required for difficult pro cesses with frequent system disturbances or applications that need precision control Temperature Proportional m Reduced Overshoot Time Profile developed by a proportional plus integral plus derivative PID control Control System Tuning In this phase of making the system work we will focus on the process controller as the primary component of a closed loop system that must be adjusted for optimum perfor mance These adjustments provide a means to compensate for system problems For instance when the sensor cannot be placed in the most desirable location because of physical limita tions a PID controller can compensate for the sensor s resulting thermal lag problem Tuning Methods Process control
15. case 2 7 chart recorder 2 6 3 12 chattering 2 2 closed loop 2 2 2 8 5 4 cold junction 2 8 2 10 communications 2 6 3 4 6 3 Communications menu 3 4 compression molding press 3 7 computer 3 4 configuration error 5 6 configure 6 6 control mode 2 2 6 8 control output action 3 6 control parameter 4 7 control prompt 4 4 control room 5 8 control software revision 5 5 control strategies 2 2 controller environment 2 6 controller operation 2 7 CSA 2 7 6 8 current 3 7 current monitor 2 6 5 5 current retransmit 5 5 current transformer 2 8 D damping 2 4 data bits and parity 3 4 dead band 2 8 3 5 decimal 2 3 11 decrement key 3 11 4 4 5 6 6 5 default parameters 2 8 defects 6 9 derivative 2 3 2 4 2 8 2 10 3 2 derivative 1 5 2 derivative 2 5 2 Deutsche Industrial Norms 2 8 DEV deviation LED 6 5 deviation alarm 1 5 2 6 5 2 5 3 device address 3 4 diagnostics 5 4 5 5 Diagnostics menu 2 7 5 5 differential 2 7 2 8 4 4 digital event 3 6 5 7 6 2 dimensions 2 6 6 4 DIN 2 8 DIP switch 3 11 5 7 6 6 6 7 display 5 5 DISPLAY key 3 7 4 4 6 5 display loop 6 5 displays 6 5 7 8 documentation 6 6 down arrow key see decrement key droop 2 2 2 3 2 4 2 8 drying grain 1 4 dual PID 1 3 4 5 duplex 2 8 4 6 duty cycle 2 8 E EIA 485 422 1 9 2 6 3 4 5 5 6 3 electrically noisy environment 5 8 electromechanical relays 6 3 6 8 enclosure heater 2 7 enhanced software
16. config ure and operate the Series 988 controller in most applications Detailed drawings illustrate DIP switch settings panel mounting and proper wiring of the 988 Easy to use charts and instruc tions explain how to use the menus and prompts to configure the 988 to your application A communications manual and a calibration manual are also available for the Series 988 Optimizing Your Process System with the WATLOW Series 988 6 7 Specifications Product Specifications Control Mode Dual input quad output optional retransmit of set point or process variable Programmable direct and reverse acting control outputs One step auto tuning Operator Interface Local Remote set point capability Dual 4 digit LED displays Upper 0 4 10mm Lower 0 3 8mm Mode Auto Man Display Up and Down keys Input Contact input for software function select Type J K T N C W5 D W3 E R S B Pt 2 thermocouple 100Q platinum 1 or 0 1 RTD or 0 50mV 0 100mV 0 20mA 4 20mA 0 5VDC 1 SVDC 0 10VDC slidewire digital event input or heater current options Sensor break protection de energizes control out put to protect system or selectable bumpless transfer to manual operation Latching or non latching F or C display or process units user selectable Sensor Ranges J t c 32 to 1500 F or O to 816 C K t c 328 to 2500 F or 200 to 1371 C T t c 328 to 750 F or 200 to 399 C N t c
17. control action between the ON and OFF switching points to prevent switching the output device ON and OFF within a span that is too narrow Switch ing repeatedly within such a narrow span will create a condition of intermittent rapid switch ing known as output chattering The process is always controlled about set point dictated by the switching hysterisis of the ON OFF control This form of control action further dictates that there will always be a certain amount of overshoot and undershoot The Temperature Switching Sensitivity Set Point Time Profile produced by ON OFF control degree of overshoot and undershoot will be dependent on the characteristics of the entire system Time Proportioning Time proportioning control provides more precise control of a process A time proportion ing control operates in the same way as an ON OFF control when the process is far enough away from set point to be outside the propor tional band When the process approaches set point and enters the proportional band the output device is switched ON and OFF at the established cycle time At the lower limit of the band the ON time is considerably greater than the off time As the process more closely approaches set point the ratio of ON to OFF time changes the amount of ON time decreases as the OFF time increases This change in effective power to the load provides a throttling back effect resulting in le
18. if shaded Optimizing Your Process System with the WATLOW Series 988 6 3 Specifications 4 03 WATLOW 102mm PROCESS Cse JERN As PROCESS 65 mm en LI L2 L3 L4 102mm a DEV DEV DISPLAY OUT manl OUT MAN SERIES 988 J L3 L4 SERIES 989 2 18 55 mm Adjustable Panel a Mounting Bracket Panel Cutout il CC Maximum Panel Thickness 0 38 9 65mm 3 62 0 03 0 00 92mm 0 8 1 77 0 02 0 00 45mm 0 6 0 68 a mja 4 06 B 17 mm 103 mm Note A minimum of 1 66 inches 42 2 mm spacing between panel cutouts is recommended 6 4 Optimizing Your Process System with the WATLOW Series 988 Specifications Displays and Keys Chart Upper Display Reads actual process value or operating paramenter value or error code red or green DEV Deviation LED Indicates that the lower display now reads a deviation from the set point value OUT percent output LED Indicates that the lower display now reads the percent output value Increment up arrow Key Increases the value or changes the selection in the upper display Decrement down arrow Key N Decreases the value or changes the selection in t
19. in 2 disables MODE and AUTO MAN keys the off position allowing access to the Setup 3 disables all keys except the and Factory menus increment decrement combination The front panel can be locked out via digital Requirements events at input 2 or 3 This lockout function is All 988 Family controllers are equipped with enabled by selecting lock under an event software and hardware lockout features input prompt E or GHB in the Global menu The software lockout functions appear under the Factory prompt in the Panel Lockout menu For each menu one of three lockout You can lockout the Setup and Factory menus with a DIP switch behind the front panel You can lock out the front panel with the digital event input Lockout menus let you DEY fi zone configure access to menus ae and settings SRE Sample Application During the initial configuration and start up an engineer will need access to all the parameters Once the process is configured he will give the operator access to only the process and alarm set points Security is also an issue and he wants only authorized operators to have access to these parameters Li be L3 Ll4 The Panel Lockout menu gives him access to all parameters during the start up Once the process is online all Panel lockout menus except System are set to full lockout GMM The System menu is set to no lockout GEM giving the operator access to the alarm set points Process security is achieved
20. non volatile memory To abort an auto tune set the auto tune prompt to or press the AUTO MAN key twice or cycle the power OFF and ON The previous PID parameters will be restored Requirements The Series 988 can be ordered with two com plete sets of heat cool PID sets This requires the enhanced software option A single set of PID parameters is available with the standard software option auto tune complete temperature gt time gt temperature sensor In this example the oven needs to hold at 350 degrees F To complete the tuning sequence set the set point for 350 degrees and auto tune by setting the auto tune prompt to BEI 3 2 Optimizing Your Process System with the WATLOW Series 988 General Software Features Overview Variable time base burst firing from the 988 Requirements provides a command signal to an SSR or SCR firing card that translates into a burst of AC cycles The output is zero cross fired and always allows at least one AC cycle to pass within the variable time base The fact that we are zero cross switching the power device means we enjoy the benefits of low radio frequency RFI noise Burst firing is the pre ferred mode to control resistive loads The burst fire time base in the 988 varies from a maximum 1 66 second time base 1 percent output down to a 33 3 millisecond time base 50 percent output The examples below show how the time base varies depending on the percent ou
21. retransmit calibrate offset 3 12 retransmit high limit 3 12 retransmit low limit 3 12 retransmit options 3 11 RFI 3 3 RS 232 3 4 5 5 6 3 RS 422 1 9 2 6 3 4 6 3 RTD 2 5 2 10 6 2 S safety limits 2 6 SCR firing card 3 3 security 2 7 5 7 semiconductor oven 3 3 sensor break 5 4 6 8 sensor cost 2 5 sensor fails 5 6 sensor over range error 5 6 sensor ranges 6 8 sensor under range error 5 6 serial communications 3 4 serial number 5 5 serial port 3 4 Series 988 989 User s Manual 6 6 6 7 set point 3 10 4 5 setup 3 4 6 6 Setup menu 5 6 5 7 6 5 6 6 ship date 5 5 shipping overseas 2 7 signal transmitter 2 5 silencing alarm 2 6 5 3 sketch 7 1 7 11 slidewire feedback 1 4 2 7 2 10 3 13 6 2 5 5 slidewire valve actuators 3 13 software features 7 6 software revision 5 5 solid state output 2 6 solid state relay 3 3 6 3 spacing between controllers 2 6 specifications 6 8 square root extraction 3 9 SSR firing card 3 3 standard features 5 1 5 8 7 7 start 3 10 startup 2 7 6 6 switch PID sets 3 6 switched DC 5 5 switching sensitivity 2 10 system cycle time 2 4 system diagram 2 5 System menu 3 11 5 7 system response time 2 4 system stress 2 7 system tuning 2 3 T terminals 6 8 test chamber 3 4 4 5 test output prompt 5 5 thermal lag 2 3 thermal system 2 10 thermocouple 2 10 6 2 thermocouple only 5 5 three mode control 2 10 three way valve 4 6 time proportioning control 2 2 2 10 transm
22. warranty does not apply to damage resulting from transportation alteration misuse or abuse Optimizing Your Process System with the WATLOW Series 988 6 9 Chapter Seven How to Choose the Right 988 to Fit Overview Input Output Software Standard Features Hardware Review and Optimize Faxable System Description Model Number Information How to use this chapter The Watlow 988 family of controllers can be used in an almost infinite variety of applications in part be cause the inputs outputs and many other attributes can be factory config ured to match the requirements of many different processes A control ler s model number contains this factory configuration information This chapter will guide you through the process of optimizing your appli cation with a Series 988 controller and determining the correct model number Make one or more copies of the work sheet on page 7 10 and any other pages you want to write on Then sit down with scratch paper and a pencil and carefully work through the steps to determine the best configuration for your application Use the Helpful References listed in the left column of each page Optimizing Your Process System with the WATLOW Series 988 Your Application 7 2 7 3 7 4 7 5 7 6 7 7 7 8 7 10 7 11 When you finish you will have a completed diagram showing how your application can be controlled by a Series 988 controller and a model number for the proper con
23. 28 2 2 A3 if multiple devices are used with the EJA 485 or RS 422 interface If the full protocol is selected a device address must be selected at the address prompt GEED For RS 232 full or on XON XOFF protocol may be selected Requirements Choose which interface your application will use RS 232 serial communications EJA 485 or RS 422 serial communications The com puter must have a compatible serial port Test Test Test Chamber 4 Chamber 5 output 4 output 4 output 4 A test engineer uses 988 s to control the temperatures of several automated test chambers His computer is linked to the controllers through its RS 422 serial communications port His computer program monitors the tempera tures of the 988 s and initiates automatic test sequences when certain pro gram parameters have been met After completing a sequence the computer loads the next temperature to the controller The computer periodically interrogates each controller for its process temperature set point and alarm status This information is stored on a disk to provide test verification data for the completed products 3 4 Optimizing Your Process System with the WATLOW Series 988 General Software Features Dead band Overview The dead band prompts and GEN located in the PID menus determine the amount of interaction between heat reverse acting and cool direct acting control outputs The dead band directly offsets the target set point o
24. 3 2 4 1 4 7 7 6 environmental chamber 3 5 3 8 error 2 7 error code 5 6 event input 2 7 4 5 event input 1 prompt 3 6 event input 2 5 5 5 7 external transmitter power supply 2 8 extruder 1 2 F factory menu 5 7 6 6 factory prompt 5 5 5 7 failure mode prompt 5 6 field calibration 2 7 filter 2 8 filter time constant 3 8 Optimizing Your Process System with the WATLOW Series 988 8 1 Index fixed power output 5 6 flow transmitter 1 8 3 9 formA relay 2 8 5 2 6 3 form A B relay 5 5 form B relay 2 8 5 2 6 3 form C relay 2 9 5 2 5 5 6 3 four dashes 5 6 front panel 2 7 front panel lockout 3 6 full lockout 5 7 G gas valve 5 6 gas fired furnace 3 13 gaskets 2 7 Global menu 3 6 3 10 44 4 5 4 7 5 6 5 7 ground counts 5 5 ground loops 2 5 H hardware 7 8 heat treat oven 3 12 heater current 1 2 2 7 3 3 3 7 heater current transformer 6 2 horizontal version 989 1 7 7 8 hose down 2 7 hunting 1 5 2 9 3 13 hysteresis 2 2 2 9 5 2 idle set point 3 6 idle temperature 3 6 increment key 3 11 4 4 5 6 6 5 incubator 3 6 input 1 counts 5 5 input 1 linearization 3 9 input 2 counts 5 5 input 2 linearization 3 9 input 2 prompt 3 7 3 11 3 13 input devices 7 4 input errors 5 6 input filter 3 8 input linearization 2 9 3 9 Input menu 3 7 3 11 Input Table 6 2 inputs 2 5 5 5 6 8 integral 2 2 2 4 2 9 2 10 3 2 integration function 2 3 interactive process variables 2 7 inte
25. 8 3 9 General Software Features Ramp To Set Point Overview Ramp to set point enables the 988 to ramp the the process value upon power up and uses set point at a user defined rate This allows the that value as the starting point for the ramp If 988 to start up a system or change between set a set point change initiates the ramp to set points at a rate that will not stress the product point function the 988 looks at the process or system components The ramp rate is value when the change is made and uses that defined in degrees per minute Ramp to set value as the starting point for the ramp If the point can be initiated at start up only or at set point is changed during a ramp the process start up and also on any set point changes value at the time of the change becomes the starting point for the new ramp When a ramp is initiated the starting point for the ramp is the current process value If the Requirements ramp is initiated on start up the 988 looks at This feature is standard on all units s From start up to set point without ramping From start up to set point with 1 min ramping 1200 10004 10004 800 4 800 4 6004 6004 oG eC 400 4 4004 2004 2004 0 0 0 2 4 6 8 hours after startup TUTTE TTT TTT heaters temperature sensor AIENEA I II heaters SERIES 905 Sample Application An engineer needs to control the temperature of a muffle furnace The furnace set point must b
26. D B GEEB which allows for tight control of the energy source at the set point determined by the primary loop During the tuning process the internal percent 4 value is determined by the auto tune set point parameter GQ The default is 90 This generates a set point for the heater equal to the range high times the value The PID A C388 output 1 988 limit sensor Sample Application settings outer loop are then determined by setting the auto tune prompt to PIDA GED During the tuning process the set point is determined by multiplying the value by the set point SP entered via the front panel Once the system is stable the heater will operate at a value greater than the final pro cess value input 1 If this value is significantly different than the set point at which the sec ondary loop was tuned adjust the param eter so that the tuning set point is near the value at which the heater is controlling Requirements Cascade control requires enhanced software Two analog inputs are required to monitor the inner and outer loops At least one control output is required to control the process outer loop thermocouple inner loop thermocouple Lube Oil Tank A Series 988 is used to heat lube oil to 125 F with a screw plug 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 F The 988 is ordered with two thermo
27. Process Systems with the WATLOW Series 988 A reversible motor controls the louver position 2 Outputs The slidewire option requires sitioning motor One output The two electromechanical relay outputs to drive the louver po output closes the louver Open _ y Output 2 The alarm indicates that the temperature has deviated from the set point by more than 3 opens the louver and another not require hanced softwa decided to add a chanical relay alarm Full Closed Full Open The slidewire feature allows the controller to easily learn the resistance at the full open and full closed position 4 Standard Feat Several standard features im pressed Pat She liked the abi ity to calibrate the slide wire input from the front of the trol The anti hunting The silencing feature would keep the alarm from being activated until a new bed of grain warmed up to the set point temperature ew and Optimize The operator chose I O software the alarm silencing feature could and hardware needs for the appli be set to silence the alarm whena tion at 120VAC and the oper the control greatly appreci cation that will provide for all her needs Once the control is in Stalled the system could be fur ther optimized by using the event comparable to the cost of servic input to lockout the front panel or ing the Barber Coleman control lowed the operato Th
28. W A T L O W Optimizing Your Process System with the Series 988 Controller An APPLICATION GUIDE FOR THE WATLOW SERIES 988 FamiLy Watlow Mission Statement To Become the Preferred Source of Industrial Heaters Sensors and Controls by Totally Satisfying Our Customers with Superior Products Quick Delivery on Specials as well as Standards and Intelligent Sales Support Copyright Watlow Winona Inc 1994 with all rights reserved Introduction Welcome to the Watlow Series 988 application guide Optimizing Your Process System with the WATLOW Series 988 This application guide describes all the features of the Series 988 and how they can be applied to your system In addition this guide will walk you through the process of determining the op timal Series 988 for your application Once you have purchased the control ler the Series 988 Users Manual will guide you through installation and setup of the controller Start with Chapter One of this book where test drives show the thought process used for determining the correct Series 988 feature set for a specific application Chapter Two consists of a glossary and a question and answer section that provides more details to help choose the right control Chapters Three through Five describe the features of the controller with a sample appli cation for each feature Chapter Six outlines the controllers specifications Use this chapter to ensure that the contr
29. a power level between 70 percent and 70 percent with no more than plus or minus five percent variation for two minutes prior to the sensor break If these conditions have been met the 988 switches to manual mode at that Series 988 error codes last stable power level If not the 988 transfers to manual mode with no power output Preselect a power level at the failure mode prompt with the increment up arrow and decrement down arrow keys If the unit is configured for heat only the fail power level is adjustable from O off to 100 percent full heat If it controls heat and cool outputs the power level is adjustable from 100 full cool to 100 percent full heat If the error code is related to internal functions of the 988 HZB or EZ the controller remains in auto mode with both control outputs off switches all alarm outputs to the shelf state power OFF lower display is blank and the upper display indicates the error code keys are all inactive The above conditions will occur regardless of which menu is active at the time or what failure mode value was selected If occurs all Setup menu parameters will return to factory default values To clear any one of these errors turn the 988 OFF for a few seconds then turn it back ON If the error remains contact the factory input 1 input 2 A D underflow error input 1 input 2 sensor under range error input 1 input 2 sensor over range error input 1 in
30. all increments allowing the system to settle down stabilize before making additional changes until the system just starts to oscil late Then back the setting off enough to re establish system equilibrium Derivative Rate Rate is the last control parameter adjustment to be made Rate s function is to reduce or eliminate overshoot excursions above or below set point It has a time base measured in minutes that must be tuned to work with the overall system response time system cycle time The initial setting for rate should be at the smallest integer of minutes possible least corrective action Increase the integer in small increment then after each adjustment increase the set point moderately Observe the approach of the actual process to set point If it over shoots continue to increase the rate integer in small increments Then increase the set point moderately until optimum approach to set point is achieved If at some point the system becomes very sluggish or cannot reach the new set point at all too much rate corrective action has been adjusted into the control system To reduce this damping effect decrease the number of minutes of rate Recommended Tuning Reference There are many reference books on the art of tuning electronic controllers to the systems they control If you are not an instrument technician qualified to tune thermal systems we suggest that you become familiar with the following refer
31. band span of the process from the set point within which time proportional control action takes place proportioning control See time proportion ing control rate band a thermal control band that defines where the rate derivative function begins The Series 988 rate band centers on the set point and is twice the width of the proportional band ratio application in which the flow of an uncontrolled stream is measured and used to maintain the flow of a controlled stream at a ratio to the uncontrolled stream Optimizing Your Process System with the WATLOW Series 988 2 9 Basic Control Strategies and Terms reference junction synonymous with cold junction Also see cold junction retransmit an analog signal representing a control variable either the process values or the set point values RTD resistance temperature detector Resistive temperature sensing device that displays a positive temperature coefficient slidewire feedback closed loop valve actuator control using a potentiometer to indicate valve position switching sensitivity in ON OFF control the process value change necessary to change the output from full on to full off thermal system a regulated environment consisting of a heat source heat transfer medium sensing device and a process variable control instrument thermocouple temperature sensing device constructed of two dissimilar metals that generates
32. c chart warranty Step 5 Standard Features A This section lists features that may be important to your application that are built into all of the 988 family of controllers None of this information is needed on your worksheet but you might want to take some time to learn about these features calibration diagnostics factory settings errors input lockout water and corrision resistant front panel display and keys setup isolation user s manual product specifications three year limited warranty Optimizing Your Process System with the WATLOW Series 988 How to Choose the Right 988 to Fit Your Application HELPFUL REFERENCES _ lockout 5 7 L dimensions 6 4 L display amp key chart 6 5 L specifications 6 8 vertical horizontal 100 240 V 988 989 24 28 V 986 987 bs Step 6 Hardware A Would the controller fit your applications panel better in its vertical configuration 986 or 988 or horizontal configuration 987 or 989 Be sure to check all dimensions for fit B Will you connect your controler to a 100 240 volt power supply 988 or 989 or a 24 28 volt power supply 986 or 987 Either configuration works with either AC or DC power C Each of the two displays in the 988 family can be either red R or green G Choose a color for each display D You can lockout access to controller settings with software hardware switches or with an digital event input All of t
33. commands controller compares this to the percent output and takes action to match the two by opening Requirements or closing the valve A slidewire configuration uses at least two inputs and two control outputs Input 2 must Set the hunt parameter to limit valve be a slidewire input Outputs must be compat hunting The value is set for the percent of ible with the slidewire valve actuators output 0 0 to 100 0 When the valve is within Gas fired Furnace Valve Actuator temperature sensor limit B26 8 sensor cy 00000000000000000 PTTL cut off valve valve slidewire input Sample Application The 988 controls the gas valve for a gas fired furnace to heat treat large metal parts First the 988 must be married to the slidewire feedback from the valve actuator To do this first set the input 2 prompt to slidewire GIF Advance to the learn low resistance value prompt GEMM Close the valve manually to the minimum resistance reading from the slidewire Select in the upper display and press the MODE key to advance to the learn high resistance value prompt MAE Manually open the valve maximum slidewire resistance Select in the upper display and press the MODE key At this point both the high and low resistance values have been learned and stored in the range low 2 and range high 2 prompts You can also manually set the range low and range high values From the slidewire specifications determine the low and high resi
34. couple inputs Input 2 the inner loop in the cascade configuration measures the heater sheath Input 1 the outer loop measures the lube oil temperature before it leaves the tank The external set point is 125 By setting range high 2 to 250 the set point for the heater sheath will be limited thus extending the lube oil life Optimizing Your Process System with the WATLOW Series 988 4 3 Enhanced Software Features Differential Overview Differential control allows the Series 988 to point which can be adjusted with the incre control one process at a difference to another ment up arrow and decrement down arrow process Input 2 acts as a remote set point keys input However the displayed set point indi cates the desired difference between input 1 Please note that while in the differential control and input 2 The set point to which input 1 will mode the set point for input 1 cannot be viewed control to is determined by the equation and must be calculated with the equation internal set point input 2 differential set point Requirements Two inputs and the enhanced software option The lower display shows the differential set are required Water Boiler outside 988 temperature FOCT A temperature sensor limit sensor sensor SERIES 908 heating element CEECEE CECE TATE Sample Application The most common application using differential control is to maintain water temperature in a boiler a
35. cteristics 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 The 988 family can be configured to switch between PID A and PID B based on a process value a set point value or the event input 988 output 2 388 output 1 Sample Application status Use the dual PID prompt in the Global menu to select what will cause the switch process GRR set point B or none GP If process is selected at the prompt the PID s will switch based on the crossover process value If set point is selected at GFA the PIDs will switch at the crossover set point value PID A used below the crossover point and PID B above PID crossover can also be selected via event input by selecting EFP at the or prompt PID A is used when the event input switch is open PID B when closed Note One event input is stan dard on all units a second event input is an option Requirements The 988 family controller needs the enhanced software option to use dual PID sets Test Chamber chiller temperature sensor sensor pressure heater TT A test engineer needs to control the temperature in a test chamber that can be operated at normal atmosphere or under vacuum conditions If he tun
36. d allow you to imple ment the Series 988 controller in the most cost effective manner giving you optimal control of your specific system Many of the decisions for system compo nents are limited by factors not associ ated with the Series 988 The strategy presented here is designed to get you thinking of all the different parameters associated with your system and how the Series 988 fits in Optimizing Your Process System with the WATLOW Series 988 2 1 2 2 Basic Control Strategies and Terms Control Strategies Process Control Process controls are of two basic types open loop and closed loop An open loop control device has no self correcting feedback informa tion The closed loop system uses feedback information from a sensor to adjust the system As the process changes the feedback loop provides up to date status information that the controlling device uses to make self correcting adjustments The closed loop control device provides much better process control Control Modes A variety of control modes offer various degrees of controllability The most common modes are on off and PID control The PID control cat egory includes varying degrees of complexity that provide accurate stable control under a variety of conditions ON OFF Control The operation of the ON OFF control as the name implies turns the output device full ON or full OFF Temperature or process sensitivity hysterisis is designed into the
37. d band 3 5 _ digital event 3 6 L_ heater current 3 7 Ll input filter 3 8 Llinput linearization 3 9 Llramp to setpoint 3 10 L remote set point 3 11 _ retransmit 3 12 LI slidewire feedback 3 13 Enhanced Software Features _ cascade 4 2 _ differential 4 4 _ dual PID sets 4 5 L_ duplex 4 6 ratio 4 7 See the filled in worksheets in Chapter 1 Test Drives Step 4 Software A Determine what software features your process will require B Determine the process range or ranges that the software must maintain in the process C Determine what conditioning if any is needed for your input data D Will you use any enhanced software features E Use the information you have just gathered to fill in the software box in your photocopy of the worksheet from page 7 10 Outp WATLOW 988 Key Features Check the software features you will use If you will use any enhanced software features fill in a B otherwise fill in an A Power amp Hardware 98 Display colors 98_ Optimizing Your Process System with the WATLOW Series 988 7 5 How to Choose the Right 988 to Fit Your Application HELPFUL REFERENCES 7 6 calibration diagnostics factory settings errors input lockout moisture resistance displays and keys setup isolation training manual spe
38. e 5 2 Setting to loop error detect enables monitoring and alarm functions and also triggers an error and shuts OFF all outputs if current is present with output 1 OFF or when no current is present and output 1 power is more than zero input 1 9a current transformer Sample Application There are limits associated with this feature eTo obtain a reading the output ON time must be a minimum of 0 3 seconds To calculate this multiply the percent output by the cycle time setting Example With 30 percent output and a 2 0 second cycle time the on time would be 0 30 x 2 0 0 6 seconds This would yield a valid reading If a valid reading is not possible the 988 will display the last valid reading It will not function with burst fire outputs This does not necessarily apply to the loop error detect feature If enabled any current detected with no output triggers an error It will not function when the 988 has a process output for output 1 A known cycle time is required to detect the current There is no cycle time associated with process outputs The maximum signal the input can accept from the current transformer secondary is 50mA So you must calculate the output range of the current transformer before wiring the system Requirements Choose the heater current option for input 2 Output 1 cannot be used as a process output Heater current monitors only output 1 Compression Mo
39. e allows the Series 988 family to receive commands from and transmit data to a master device usually a computer Any function that can be performed via the front panel can also be accomplished using the serial communications port allowing you to operate the controller from a computer and to store process data on a computer The 988 is available with a choice of serial hardware interfaces An RS 232 interface allows for one master computer and one controller with a maximum network length of 50 feet 15 meters The EIA 485 RS 422 option equips the control ler for a multi drop interface up to 32 total network devices with EIA 485 and up to 10 total network devices with RS 422 Each controller will have its own unique address The total maximum network length is 4 000 feet 1 219 meters These are isolated inter faces Test Test Chamber 1 Chamber 2 Personal Computer with RS 422 port Sample Application Chamber 3 To select between EIA 485 or RS 422 enter the setup prompts by holding the increment up arrow and decrement down arrow keys simultaneously until setup appears in the bottom display Use the decrement key to select the Communications menu Wl The interface prompt selects between 485 or 422 Other parameters that must be configured in the Communications menu are the baud rate ERM data bits and parity EEE protocol GZB and device address EED The protocol prompt must be set to full ANSI X3
40. e contacts close when the relay coil is energized The contacts open when power is removed from the coil form B single pole single throw relay that only utilizes the normally closed N C and common contacts These contacts will open when the relay coil is energized The contacts will close when power is removed from the coil 2 8 Optimizing Your Process System with the WATLOW Series 988 Basic Control Strategies and Terms form C single pole double throw relay that utilizes the normally open N O normally closed N C and common contacts The user has the option of wiring for a form A or form B contact Refer to the form A and form B above for more information hunting oscillation or fluctuation of the process between the set point and process variable hysteresis in ON OFF control the process change necessary to change the output from full on to full off input linearization For thermocouple and RTD inputs the process variable is automati cally linearized Certain flow transmitters generate a non linear signal corresponding to the flow being measured The square root of the signal is calculated to generate a linear signal integral control action that automatically eliminates the offset or droop between the set point and actual process value Also see reset isolation Electrical separation of sensor from high voltage circuitry Allows use of grounded or ungrounded sensing
41. e much smaller Watlow 988 controller replaced the half DIN Barber Coleman and external board greatly reducing the space and wiring requirements 5 Hardware The control required opera The electrician who installed new bed of grain is brought in ata ator chose red upper and temperature much lower than the lower displays to match the set point The system costs were other controls in the panel ated the touch safe terminals on the back of the 988 Optimizing Your Process Systems with the WATLOW Series 988 15 FF JP Type K z thermo Test Drive couples Cascade Control f romeo of an Aluminum Melting Furnace heater face and aluminum Overview _ i ible for an a is responsible Se ibe furnace at Ajax oe a heaters on an alumini chy aa must run at near CaP E periods To maximize heate ce life temperature of the face of the Zero cross fired burst fire reduced radio frequency interference and extended the heater life The cascade feature gives one 988 the ability to do the work of two controllers Inputs Outputs With a melting point of 1080 ightly con thermocouples for measuring Tight control of the heater Fier vara east ee aie aan ere of ser with degrees F and an expected both the heater face and face required burst fire con ee reall heater temperature of 1800 the alumi
42. e ramped up at a defined rate to prevent stressing the muffle and other system components By enabling the ramp to set point function in the 988 the engineer can control the rate at which the set point will rise Ramp to set point is enabled in the Global menu using the ramping function prompt HW To ramp on start up only select start EB To ramp on start up and on any set point changes select set point B The ramp rate is in degrees per minute For further protection of the system output 2 3 or 4 can be configured as a rate alarm monitoring the rate of increase or decrease in the process variable on input 1 The alarm low and alarm high prompts The 2 in these examples refer to output 2 establish the ramp down and ramp up rate set points respec tively in degrees per minute 3 10 Optimizing Your Process System with the WATLOW Series 988 General Software Features Remote Set Point Overview The remote set point feature allows the 988 to Requirements use a thermocouple RTD or process signal at Input 2 must be either a thermocouple or input 2 to establish the set point This feature universal signal conditioner options 1 or 2 gives the 988 the ability to have its set point value manipulated by an external source A If the application uses a master controller common application would use one ramping choose one of the retransmit options M 0 controller with a set point retransmit output to 20 4 20mA or N 0 5 1 5 or 0 10VDC
43. ees hotter than the others increase the range low 2 to 10 and the range high 2 to 810 With remote set point enabled and local selected under the local remote prompt in the System menu the set point is adjusted using the increment up arrow and decrement down arrow keys Selecting remote under the local remote prompt WE disables the increment and decrement keys allowing the set point value to be manipulated via the input 2 signal Optimizing Your Process System with the WATLOW Series 988 3 11 General Software Features Overview The retransmit output can be used to transmit chart recorder or to generate a set point for an analog signal representing the value of other controls in a multi zone application see either input process variable or the target set page 3 11 point variable The retransmit signal is factory configured as either a milliamp or a voltage Requirements signal In choosing the type of retransmit signal Output 3 is used for the retransmit option the operator must take into account the input Choose output type M 0 20 4 20mA or N 0 impedance of the device to be retransmitted to 5 1 5 or O 10VDC depending on the signal and the required signal type either voltage or type Select the output range in the Output milliamps menu Typically applications might use the retransmit Enhanced software is not required for this option to record one of the variables with a feature Heat treat Oven 988 temperature a se
44. element JIS Joint Industrial Standards Also Japanese Industrial Standards Committee JISC Estab lishes standards for equipment and compo nents linearization the extraction of a linear signal from the non linear signal of a flow transmitter Also see input linearization NEMA 4X a front panel rating that certifies the control as washdown capable and corrosion resistant ON OFF control control of a process by turning the output full ON below set point and full off above set point open loop control system without sensory feedback output action in response to difference be tween the set point and process variable overshoot condition in which the process exceeds set point due to initial power up or process changes P control proportioning control PD control proportioning control with deriva tive rate action PDR control proportional derivative control with manual reset is used in fast responding systems where the reset causes instabilities With PDR control an operator can enter a manual reset value that will eliminate any droop in the system The option requires enhanced software PI control proportioning control with integral auto reset action PID control proportioning control with inte gral auto reset and derivative rate action process variable regulated system parameter such as time temperature flow humidity etc proportional
45. en to 100 percent In some cases this type of hanced software and a process output Duplex output is required by the device that the 988 applications require a special valve Fluid Sample Container 388 co hot water 988 eo o o o u temperature transmitter SERIES 980 cold water Sample Application The system outlined below uses a three way valve for heating and cooling a fluid sample Coils surround the container holding the fluid When the tem perature needs to be raised the signal to the valve will be between 12 and 20mA sending hot water through the coils When cooling is required the signal will be between 12 and 4mA sending cold water through the coils 4 6 Optimizing Your Process System with the WATLOW Series 988 Enhanced Software Features Overview This feature allows the 988 to control one level equal to the quantity measured at input 2 process as a ratio of another process This is multiplied by the ratio term set by the user especially useful in applications that mix two Input 1 monitors the controlled part of the materials whether steam paint or food ingredi process ents Requirements Input 2 of the 988 measures the part of the Ratio control requires enhanced software Two process that is either uncontrolled or controlled analog inputs are required to monitor the by another device The part of the process process and at least one output adjusts the controlled by the 988 will be maintained at a contro
46. ence before attempting to tune your system Tuning of Industrial Control Systems by Armando B Corripio Published by the Instrument Society of America ISA Member 48 00 list 60 00 approx Phone 919 549 8411 Optimizing Your Process System with the WATLOW Series 988 Basic Control Strategies and Terms Questions and Answers System Diagram No matter what your application you must start with an accurate system diagram A blueprint of the system wiring is typically not a faxable document When consulting the factory it s helpful to be able to fax a system diagram similar to the hand drawings shown in the Test Drives in Chapter One This diagram should include all inputs outputs the controller the load any alarms and any connections to other systems or equipment This diagram should show the expected signal types and ranges at each interface point to allow you to properly order and set up your 988 controller For the advanced user of the Series 988 this will be second nature For the less experienced opera tor putting together a diagram including all system components will allow a Watlow sales rep or factory applications engineer to review the system for correctness Inputs The 988 controller accepts a wide variety of input signals and ranges covering most tem perature and process applications Ask yourself the following questions about your inputs What accuracy is required for each input page 6 8
47. erature until the next batch is loaded with minimum operator interaction By connecting an external switch to the digital event input he can select either the operating temperature or the idle temperature with the flip of a switch The idle set point prompt is enabled by setting the event input 1 prompt M in the Global menu to the idle set point R The idle set point value is accessed by pressing the MODE key from anywhere in the display loop When the switch closes the lower display will indicate the idle set point and the controller will maintain this new set point 3 6 Optimizing Your Process System with the WATLOW Series 988 General Software Features Heater Current Overview The heater current feature measures and responds to heater current in a system This is an ideal method for detecting heater loss in multiple heater applications The current is measured when output 1 is ON For instance if a system has five 10 amp heaters the heater current input measures 50 amps regardless of the percent output To view the heater current press the DISPLAY key and advance to the process 2 prompt GGA The upper display indicates the last valid current reading The input 2 prompt under the Input menu can be set to current or loop error detect M Current allows you to monitor heater current and set alarm set points based on high and low heater current values Alarms can only be configured as process alarms see Alarms pag
48. es 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 The system characteristics are so very different that one set of PID s will not give satisfactory results under both normal and vacuum conditions The 988 solves this problem with the dual PID option Auto tuning PID A un der normal atmospheric conditions then auto tuning PID B under vacuum conditions establishes PID values for two sets of system characteristics A pressure switch connected to the event input tells the controller when to switch between PID A and PID B eliminating the need to change PID values manually Optimizing Your Process System with the WATLOW Series 988 4 5 Enhanced Software Features Overview Certain systems require that a single process controls such as a three way valve that opens output control both heating and cooling out one way with a 12 to 20mA signal and opens puts A Series 988 controller configured with the other way with a 4 to 12mA signal This enhanced software and a process output can feature reduces the overall system cost by function as two separate outputs With a 4 to using a single output to act as two outputs 20mA output the heating output will operate from 12 to 20mA 0 to 100 percent and the Requirements cooling output will operate from 12 to 4mA 0 The duplex control feature requires the
49. etected This can cause the system to overshoot the set point which could damage the heater product or heat transfer medium such as a heat transfer fluid This graph illustrates a system with a long lag time Curve A represents a single control A set point 7 eeni J time gt system with PID parameters that allow a maximum heat up rate Too much energy is introduced and the set point is overshot In most long lag time systems the process value may never settle out to an acceptable error Curve C represents a single control system tuned to minimize overshoot This results in unacceptable heat up rates with the final value taking hours to reach Curve B shows a cascade system that limits the energy intro duced into the system allowing an optimal heat up rate with minimal overshoot This drawing shows two controllers configured as a cascade system The second controller Two controllers in one Inner loop Controller Outer loop Controller The cascade feature allows the Series 988 to internalize the func tions of two controllers generates the internal set point The Series 988 effectively combines both controllers into a single package The primary controller measures the process in the outer or primary loop with input 1 and compares the value to the desired set point The difference between the set point and the process temperature generates an internal pe
50. f the cool control output With a positive dead band both control out puts will never be on at the same time With the process in a positive dead band the output value is determined by adding the percent heat output to the percent cool output and only applying the result to the correct output cooling action if the sum is negative and heating action if it is positive input 1 388 output 1 e output 2 Sample Application If the dead band is set to a negative value the heat and cool outputs can both be ON at the same time Requirements The dead band feature is standard on any Series 988 controller with two control outputs The dead band prompts will appear if the control outputs are configured for heat cool or cool heat Environmental Chamber chiller temperature sensor sensor heater TT An engineer for an environmental chamber manufacturer who is design ing the heating and cooling system for a new chamber wants to minimize the energy costs of operating the chamber She has chosen the 988 and will configure the heat and cool outputs with a positive dead band When the chamber temperature is near ambient the cooling and heating systems had a tendency to buck one another resulting in inefficient use of energy The engineer started with a dead band of five degrees but in the process of tuning the system for optimal control the setting was reduced to two degrees This made the system more energy efficient and
51. gh dif ferent conditions What happens if conditions ex ceed limits What happens if a device breaks down E Go over your work with a colleague and ora Watlow sales rep to check whether you have over looked anything F If you made any changes on your worksheet revise your model number 7 8 Optimizing Your Process System with the WATLOW Series 988 How to Choose the Right 988 to Fit Your Application Notes Page Optimizing Your Process System with the WATLOW Series 988 7 9 Faxable Series 988 System Description date of pages to from comp dept comp dept phone phone fax fax EEE WATLOW 988 98__ Input 2 98 Power amp Hardware 98__ 98 Display colors digital event standard 98 5 Sketch your application in this space output 1 output 2 j output 3 as i input 3 Ce G2 output 4 wes Make photocopies of this page Do not write on the original Use the informa tion you gathered in the previous pages to fill in the boxes and model number Output 1 7 10 Optimizing Your Process System with the WATLOW Series 988 How to Choose the Right 988 to Fit Your Application Series 988 989 Model Number Information 98__ ah Hardware 6 Vertical mounting 24 28 V 7 Horizontal mounting 24 28 V 8 Ver
52. he upper display Incr Decr Combination Press for three seconds to reach the Setup menu press for three more seconds to reach the Calibration menu Optimizing Your Process System with the WATLOW Series 988 MODE Incr Combination Press to move backwards through prompts in a menu Press and hold the MODE key and use the increment key to move backwards until you reach the top of the menu Lower Display Reads Display Loop information menu or prompt names or alarm codes red or green hardware L1 L2 L3 L4 LEDs Shows the active output s DISPLAY Key Takes the control home to the Display Loop current process values and set point informa tion from any menu location AUTO MAN Key Clears or silences alarms with one press or toggles between Auto and Manual control with two presses AUTO MAN LED Indicates Manual control or when blinking indicates that another press will toggle control state Steps through the menus In Auto control enters data selected less than five seconds previ ously 6 5 Specifications 6 6 Setup Requirements Controllers from the Series 988 family require six steps to set up from system design to system operation 1 Build the Part Number This booklet helps with the first step selecting the features your application will need The features are recorded in a part number which Watlow uses to custom build each controller 2
53. hese are standard features E Fill in the appropriate spaces in your photocopy of the worksheet from page 7 10 You should have all the information you need to fill in the part num ber Use the table to choose and fill in your power and hardware configuration Power amp Hardware 98 Choose the upper and lower display colors RR red upper red lower RG red upper green lower GG green upper green lower GR green upper red lower Display colors 98 Optimizing Your Process System with the WATLOW Series 988 7 7 How to Choose the Right 988 to Fit Your Application HELPFUL REFERENCES Chapter 1 Test Drives provides diagrams and explana tions of several different types of applications Chapter 2 Basic Control Strate gies and Terms explains the basic concepts and vocabulary of control applications Step 7 Review and Optimize A Review the last six steps looking for errors and opportunities to optimize your application s use of the Series 988 controller B If any of the inputs or outputs are not used by your application check whether they could be used to enhance your application perhaps with the addi tion of an alarm or the communications option C How might your needs change in the future It s more efficient and economical to order options now D Make several copies of the worksheet on the next page and test drive your application throu
54. its and parity 3 4 date 5 5 dead band A 3 5 dead band B 3 5 switched dc 5 5 deviation 1 5 2 deviation 2 5 2 decimal 2 3 11 diagnostics 5 5 differential 4 4 8 4 Optimizing Your Process System with the WATLOW Series 988 Index display test 5 5 E error 1 1 5 6 error 1 2 5 6 error 1 3 5 6 error 1 4 5 6 error 2 1 5 6 error 2 2 5 6 error 2 3 5 6 error 2 4 5 6 event input 1 3 6 4 5 5 7 event input 2 4 5 5 5 5 7 error 5 5 6 error 9 5 6 F failure 5 6 factory 5 5 5 7 filter time constant 1 3 8 full 5 7 G ground counts 5 5 H hunt 3 13 hysteresis 5 2 l idle set point 3 6 input 2 3 7 3 11 3 13 input 3 7 communications interface 3 4 current retransmit 5 5 input 1 type 5 5 input 2 type 5 5 L local 3 11 local remote 3 11 latching 2 5 2 linearization 1 3 9 linearization 2 3 9 front panel lockout 3 6 5 7 loop error detect 3 7 learn high resistance 3 13 learn low resistance 3 13 N no module 5 5 5 7 0 open loop 5 5 output 3 12 output 1 type 5 5 output 4 type 5 5 output 1 active 5 5 output 4 active 5 5 P E switch PID sets 3 6 4 5 PID 2 4 5 GED PID A 3 2 4 3 4 5 GED PID B 4 3 4 5 panel lockout 5 5 5 7 process 1 5 2 process 2 3 7 5 2 process value 1 3 12 process 4 5 5 5 protocol 3 4 R remote 3 11 ramp rate 3 10 rate 5 2 ratio 4 7 read 5 7 range high 2 3 7 3 11 3 13 range low 2 3 7 3 11 3 13 4 3 relay A B 5 5 relay C s
55. itter power supply 2 10 6 3 tune 3 2 Tuning of Industrial Control Systems 2 4 tuning reference 2 4 tuning the system 2 4 U UL 1 9 2 7 6 8 UL recognized 1 9 uncontrolled stream 4 7 universal millivolts 5 5 universal off 5 5 universal process types 5 5 6 3 universal RTD 5 5 universal signal conditioner 3 9 6 2 universal tc high gain 5 5 universal tc low gain 5 5 up arrow key see increment key updates 2 5 upper display 6 5 urethane mixing 1 8 user s manual 6 7 V vacuum 4 5 valve oscillations 3 13 variable time base 2 6 2 8 3 3 vertical configuration 7 8 Optimizing Your Process System with the WATLOW Series 988 8 3 Index voltage retransmit 5 5 WwW warranty 6 9 waste water process 3 9 wire length 2 5 wiring 6 6 6 7 Z zero cross fired 1 7 3 3 zero cross switching 3 3 zero switching 2 8 2 10 Prompst parameters and menus RS 232 5 5 EIA 485 422 5 5 A alarm 2 high 3 10 5 2 alarm 2 low 3 10 5 2 retransmit calibrate offset 3 12 ambient counts 5 5 control action output 3 6 address 3 4 alarm 2 energized 5 2 alarm 2 de energized 5 2 algorithm 4 5 alarm reset 3 6 ambient temperature 5 5 analog output 3 12 retransmit high limit 3 12 retransmit low limit 3 12 auto tune set point 3 2 4 3 auto tune 3 2 4 3 E baud rate 3 4 bumpless transfer 5 6 burst fire 3 3 C input 1 counts 5 5 input 2 counts 5 5 control 4 4 4 7 communications 3 4 current 3 7 5 5 D data b
56. lding Press U oo0o0 o0o0 10A heaters temperature sensor sensor The Series 988 controls the lower platen of a compression molding press that contains five 10 ampere heaters A 50A 50mA current transformer is used to monitor heater current Set the input 2 prompt to current WEB the range low 2 prompt to O and the range high 2 prompt to 50 Find the range high 2 value with the following equation maximum CT primary current load current range high a maximum output from CT secondary input x 50mA The application uses a Watlow current transformer CT part 16 0233 which has a maximum input of 50 amperes which corre sponds to a maximum output of 50mA 50Amps BOMA x 50mA range high 2 Solving for rH2 gives you 50 This is the range high 2 setting Optimizing Your Process System with the WATLOW Series 988 3 7 General Software Features Overview In certain applications the process being measured can be unstable which makes it difficult to control and also makes the con stantly changing display difficult to read The Series 988 input filter can solve these problems by smoothing out just the display or the display and the input signal You can set a time constant in seconds fora Display readings with input filter off RH gt time gt becca output 1 _ 960 988 Cr 13 La nev woore DISPLAY AUTO MAN d Sample Application low pass filter tha
57. les cannot provide dependable readings The engineer has installed several Series 988 controllers with power supplies matched to a variety of transducers DIP switch settings configure the output voltages for 5 12 or 20VDC 5 8 Optimizing Your Process System with the WATLOW Series 988 Specifications Input Table 6 2 Output Table 6 3 Dimensions 6 4 Displays and Keys Chart 6 5 Setup Requirements 6 6 User s Manual 6 7 Product Specification 6 8 Warranty 6 9 How to use this chapter This chapter contains charts and lists describing specifications of the Watlow s 988 family of controllers Optimizing Your Process System with the WATLOW Series 988 6 1 Specifications Input Table 988 FAMILY INPUT TYPES 0 none 1 basic signal conditioner type J K T N C D Pt 2 high temperature moderate sensor accuracy and stability low and high range low sensor cost 2 universal signal conditioner process input 0 5VDC 1 5VDC 0 10VDC 0 50mVDC 0 100mVDC 0 20mA 4 20mA non thermal applications sensor determines accuracy and stability long leads of transducer output low and high range best sensor noise immunity moderate to high sensor cost resistance temperature detector RTD 100 ohm platinum type 1 JIS or DIN 0 1 JIS or DIN high sensor accuracy and stability low range moderate sensor cost thermocouple type J K T N R S B C D Pt 2 high temperature moderate sensor accuracy and stabi
58. lity low and high range low sensor cost 3 slidewire feedback 0 to 1200 ohm range determines valve position sensor determines accuracy and stability moderate sensor cost 4 heater current transformer 50mA transformer secondary maximum reads heater current moderate sensor accuracy and stability additional ranges may be available moderate sensor costs 5 digital event 6 2 dry switch or DC volts input 0 3VDC open to 14 36VDC closed input 2 0 3VDC closed to 14 36VDC open input 3 no to low cost Input 1 Input 2 Input 3 option available if shaded Optimizing Your Process System with the WATLOW Series 988 Specifications Output Table 988 FAMILY OUTPUT TYPES Output 1 Output 2 Output 3 Output 4 none A solid state relay good life low cost B 0 5A w RC suppression K 0 5A w o RC suppression open collector best life low cost C switched DC electromechanical relay shortest life high cost w maintenance D form C 5A w RC suppression E form C 5A w o RC suppression electromechanical relay shortest life high cost w maintenance J form A or B 5A w o RC suppression universal process types best life low cost F 0 5VDC 1 5VDC 0 10VDC 0 20mA 4 20mA transmitter power supply T 5 12 20VDC 30mA process retransmit chart recorder or data logging device M 0 20mA 4 20mA N 0 5VDC 1 5VDC 0 10VDC communications with a computer R RS 232 S EIA 485 RS 422 option available
59. lled part of the process output 1 mixed paint PROCESS flow transmitter flow transmitter controlled flow of pigment SERIES 808 uncontrolled flow of unmixed paint motorized valve Sample Application Blue pigment must be added to paint at a ratio of one part per 100 to create a mixed paint of the desired color The uncolored paint flows into the mixer in an uncontrolled stream that is set manually and sensed by input 2 A motorized valve controls the flow of pigment which is moni tored by the flow sensor to input 1 The flow rate of the uncolored paint determines the set point for the motorized valve that controls the pigment flow If an operator needs to change the rate of flow for the uncolored paint the set point will shift accordingly to maintain the correct ratio in the mixing tank The application engineer set up this feature in software by choosing ratio as the control parameter in the Global menu The set point value displayed was then a ratio value He entered 0 01 to maintain an input l input 2 ratio of 1 100 Optimizing Your Process System with the WATLOW Series 988 4 7 Chapter Five Standard Features Alarms 5 2 Auto Manual 5 4 Diagnostics 5 5 Input errors 5 6 Lockout 5 7 Transmitter power supply 5 8 How to use this chapter This chapter describes features that with the exception of transmitter power supply are included in every controller in Watlow s Series 988 fami
60. ly Optimizing Your Process System with the WATLOW Series 988 5 1 Standard Features Overview Outputs 2 3 and 4 can be configured as alarms To configure an alarm the operator makes several decisions First we ll show the difference between a form A B and C relay 5 COM common NO NC normally open Form A Relay COM NC L___4 NO normally closed COM Form C Relay Form B Relay The relays are shown in the shelf state with no power applied Note that the form C option allows the operator to configure it as either a form A or a form B output For the purposes of this discussion we will use the form C version available in outputs 2 and 4 Output 3 is selected via a hardware jumper as either a form A output or a form B output You need to make five decisions to configure an alarm output In the following explanations only output 2 will be configured 1 Output Type First choose the type of alarm either normally energized or normally de energized GME This means that when there is no alarm condi tion the alarm output is energized if normally energized is selected and de energized if normally de energized is selected Example With normally energized se lected for output 2 the output will be energized in the non alarm state Therefore the normally closed NC contact will be open 2 Alarm Type This prompt allows you to select which input variable will trigger the alarm and whether the
61. mocouple 3 slidewire feedback 4 heater current transformer 5 digital event option available if shaded Step 2 Input A List all the input devices in your process sketch Refer to your answer to 1D B List all of the parameters and specifications that apply to each of the above items C Input types must match the appropriate input of the 988 Use the input chart on page 6 2 to assign each input device to one of the 988 s inputs D Use the information on your list to fill out the input boxes in your photocopy of the worksheet from page 7 10 WATLOV 98 Key Features Software 98 Power amp Hardware 98 Display colors digital event standard 98 Fill in input device information and codes from page 6 2 98 Optimizing Your Process System with the WATLOW Series 988 7 3 How to Choose the Right 988 to Fit Your Application HELPFUL REFERENCES Use the complete output table in Chapter 6 Specifications Alarms and transmitter power supply are explained in Chapter 5 Other Features See the filled in worksheets in Chapter 1 Test Drives Outputs 1 12 3 4 A none solid state relay B 0 5A w RC suppression K 0 5A w o RC suppression open collector C switched DC electromechanical relay D form C 5A w RC supp E form C 5A w o RC supp electromechanical relay J form A
62. n three co Outpu Bob a WE eat to determine a p signal from the main flow P met with his e for mixing various The controllers used for resin transmitter to maintain the The resin flow controllers use tional control valve for Using control n aii ratio mixing require a 4 20mA correct mix ratios a 4 20mA output to a propor precise flow control ratio co resins a process input from a flow hanced so The system required transmitter A second input controller does no mixing up to four types of an control so it needs 0 resin at specific ranes ives rtioning valv control of ne Also alow for accurate m down if a tank is level contact automatic shu t of resin in each tank about to run ou connected to i input 3 shuts C ea all four valves SQ H he any oner gt e tanks Is about to run WATLOW g out of resin 988 Flow TRANSMITIER Key Features URE aa eee aE SAL SONAL Finer Paro Contest itina ae E Software STANDARD 9 IF i ih LUATI I ET S i ud a a T j ee ee ET A 4 Standard Feat B C D ENHANCED ATA 6C sa BEST Input 2 A NO NPort winks TRANS ecd fee Power amp Hardware The impedance of the 4 20mA o A inputs in the 988 is only 5 oo _ ee Neen ohms This allows the Input 3 98 transmitter to send a8 all four controller A Low TANW LEVEL B C D No INPUT Di
63. nsor 988 limit vee sensor output 3 heaters ET Chart Recorder Sample Applications The 988 is being used to control the temperature of a heat treat oven The temperature of the process must be recorded on a chart recorder The oven temperature range stays between 600 to 900 degrees F The chart recorder requires a 4 20mA signal In the Output menu set analog output to to tag the input 1 process value as the parameter to be retransmitted Set retransmit low limit to 600 to set the low range for the retransmit signal to 600 Set retransmit high limit to 900 to set the high range for the retransmit signal to 900 Set retransmit calibrate offset to 0 assuming there is no calibration offset required The retransmit output will be 4mA until the oven temperature is greater than 600 degrees F at which point the signal will increase with tempera ture to 20mA at 900 degrees F and will not exceed 20mA 3 12 Optimizing Your Process System with the WATLOW Series 988 General Software Features Slidewire Feedback Overview The 988 can control the position of a valve with this dead band a change in output greater a slidewire feedback position indicator The 988 than half the hunt parameter is required to senses the resistance of the slidewire and trigger action Output 1 responds to close compares it to the range low and range high commands and output 2 responds to open settings to determine the valve position The
64. num F e purst fire control to interface with a Watlow QPAC SCR power control degrees Andy chose K type equipped with a DC input firing card trol This dictates the use of a solid state power device An open collector output was gle Seri quires the e option Once it ured for cascade co oe Set Point Andy configured the controller to trigger both a low tem perature and a high temperature alarm Standard Feature He configured two alarm out puts one to indicate over te perature on the heater fa one to warn of low a temperature It is_ maintain alumi ePID control of both heater and aluminum e dual inputs for measuring heater and aluminum low e alarms for both ae high temperatures Bugs ER OPEN Couto B Input 1 ALUMINUM Pe v megno Coude WATLOW 988 Key Features UUMINUM FURNACE with Buger Fige AND 2 THELMOWNE are Chec REQuizeES ENHANCER SorTWwAge Re SopPRESK O 38 _B __ see ae a O Power amp Hardware HorizonTAL ConTRale pesos st 00 240 VAc 96 Mele ee Display colors Rem UPPER And Lowe 98 ee Low TEMP ALARM PELAY SA wmout Input 2 We AVE FACE Pe K THERMO Output 3 HiGH TEMP ALARM RELAY 5A witout RE GUPPRESSION Input 3 None digi
65. oller interfaces correctly with other system components Finally Chapter Seven walks you through the feature set selection for your specific application Once you have used the guide a few times you will be able to skip to Chapter Seven and use the previous chapters for reference The purpose of this technical guide is to assist you in the system design pro cess The final responsibility for the system design must remain with the sys tem design engineer Watlow manufactures heaters sensors and controls We can provide a com plete thermal system For more information concerning the Series 988 con tact your local sales representative listed on the back cover Literature on the Series 988 includes e Series 988 989 Users Manual e Calibrating Watlow Process Controls How to Use Data Communications with the Watlow Series 988 989 or How to Use Data Communications with the Watlow Process Controls Disclaimer of Warranty The information presented here is of a general nature Because of the diver sity of conditions and hazards under which control products may be applied and because of the differences in components and methods of installation no representation or warranty of any kind express or implied is hereby made that the applications discussed herein will be effective in any particular appli cation or set of circumstances or that additional or different precautions will not be reasonably necessary for a particular application
66. one month 30 second cycle time 24 hours per day The mechanical relay option is only warranted for 100 000 cycles e With a solid state output a variable time base burst fire option can provide the tightest load control Make sure the power control is com patible with the burst fire output page 3 3 What actuator interfaces are required page 6 8 e Typically the output of the Series 988 does not directly control the load Instead it acts as a pilot duty output interfacing with another device that actually controls the load If this is the case in your application make sure that the output of the Series 988 is compatible with the input of the external device What alarm or annunciation outputs are required page 5 1 e The alarm options in the Series 988 can be used to alert an operator to a system malfunc tion These outputs should not be used as safety limits to protect system components or personnel A separate safety limit device should be used in any system where damage or injury could occur due to a system component failure How should the alarms operate page 5 1 e The alarm options can be field configured to function in any fashion A process alarm can be used to warn the operator of impending equipment damage A deviation alarm can be used to warn that the system is operating outside of the desired specifications Each alarm can be set for latching or non latching silencing and reverse or normal logic Sh
67. or B 5A w o RC spp universal process types F 0 5VDC 1 5VDC 0 10VDC 0 20mA 4 20mA transmitter power supply T 5 12 20VDC 30 mA process retransmit M 0 20mA 4 20mA N 0 5VDC 1 5VDC 0 10VDC communications R RS 232 S EIA485 RS 422 options available if shaded Step 3 Output A List all the output devices in your process sketch Refer to your answer to 1F B List all of the parameters and specifications that apply to each of the above items C Output types must match the appropriate output of the 988 Use the Output Chart on page 6 3 to assign each output device to one of the 988 s out puts D Use the information on your list to fill in the output boxes in your photocopy of the worksheet from page 7 10 E Make a sketch of your application on your photo copy of the worksheet Make sure the appropriate devices are connected to the appropriate inputs and outputs WATLOW 988 Key Features Software 98 Power amp Hardware 98 Display colors 98 Fill in output devices and codes from page 6 3 7 4 Optimizing Your Process System with the WATLOW Series 988 How to Choose the Right 988 to Fit Your Application HELPFUL REFERENCES General Software Features L_ auto tune 32 L burst fire 3 3 L communications 3 4 L_ dea
68. or Inputs 1 and 2 no module thermocouple only current detect EF slidewire fia universal OFF faa Universal RTD universal tc high gain HIJA universal tc low gain GRA universal millivolts universal process Si event input 2 Types for Outputs 1 through 4 no module 0 5A SSR 0 5A SSR w suppression 2 0A SSR switched DC form C relay form C relay w suppression form A B Relay process voltage retransmit current retransmit power supply RS 232 communications EJA 485 422 communications Display tests each display and LED If any display or LED is absent contact the factory The test output prompt can be used to activate the available outputs on the unit with the exception of process outputs transmitter power supply or communications output To select an output use the increment or decre ment key to advance from OFF to the desired output output 1 active through output 4 active MMD After three seconds the corresponding load LED will light and the output will be energized This output will remain energized until you select another output or off or exit the Diagnostic menu The open loop prompt enables the open loop error function The error message open loop flashes in the lower display when ON is selected and a heat or cool output is full on and no temperature change has oc curred over a period of time based on system characteristics This prompt only functions in the proportional control mode Requirements
69. or it The machine continues run ning but results in a slow start up and inconsistent product Chris decided to attach a J thermocouple and a current detector to inputs 1 and 2 a solid state relay to control the heaters allowing short trol Solid state relays were chosen for the secondary cooling output to control a The engineer decided to use cycle times and optimal con Chris needed a control that could alert the operator if a heater burned out solenoid valve for cooling water Two mechanical relay alarms were added one tagged to the heater current input to alert the operator of a heater burn out and the sec ond to alert the operator if the process deviated too far from the set point Using the 988 improved Chris productivity by eas ing the setup and opera tion of the system and by minimizing down time through the heater moni toring feature Aooooo gt ai 400 Tempurature After reviewing the applica tion Chris decided to use the event input to shut down the process if the extruder screw jammed The conscientious Time minutes Chris programmed a 5 per min heat up rate on start up to bring the process up to set point over a 1 hour period 45 60 75 90 Tempurature Ch of PID p the control toe select between t based on the set po Chris wanted a control that was easy to set up
70. ould you monitor the load current page 3 7 e While this option is available as an input it is important to note that this feature in the Series 988 is not currently available when using a process output 4 20mA 0 5VDC etc Also it limits the minimum on time of the output Does the process require a retransmit output page 3 12 e Output 3 can be used as either a 4 20 or 0 20mA output or as a 0 5 1 5 or 0 10VDC output to retransmit the process value of either of the inputs or the set point value It allows the controller to function as a master controller in a master remote application or to retransmit a process value to a chart recorder What types of monitoring of the outputs is required page 3 4 e The retransmit option is one way to monitor the system status e A serial communications option can be used to monitor and or change all the parameters in the controller With the EIA 485 option up to 32 controllers can be monitored from a single communications port on a personal computer over distances of 4000 feet The RS 422 option can address up to 10 controllers over 4000 feet and the RS 232 option can address a single control over a distance of 50 feet Make sure the computer or other monitoring device is equipped with the correct serial communica tions card and that the baud rate and other capabilities are compatable Controller Environment There are several factors to consider concern ing the environment
71. ppression K Solid state relay Form A 0 5A without RC suppression M Retransmit 0 20mA 4 20mA N Retransmit 1 5VDC 0 10VDC 0 5VDC T External signal conditioner power supply 5 12 or 20VDC 30mA 4 Output A None B Solid state relay Form A 0 5A with RC suppression C Switched DC open collector isolated D Electromechanical relay Form C 5A with RC suppression E Electromechanical relay Form C 5A without RC suppression K Solid state relay Form A 0 5A without RC suppression R Isolated RS 232 communications S Isolated EIA 485 RS 422 communications T External signal conditioner power supply 5 12 or 20VDC 30mA Display Color Upper Lower GG Green Green GR Green Red Electromechanical relays are not recom RG Red Green mended for PID control They are warranted RR Red Red for only 100 000 contact closures 100Q platinum Sensor Ranges J t c 32 0 K t c 328 200 T t c 328 200 N t c 32 0 R t c 32 0 S t c 32 0 B t c 1598 870 E t c 328 200 C t c 32 0 D t c 32 0 Pt 2 32 0 4 RTD JIS 328 200 1 RTD DIN 328 200 0 1 RTD JIS and DIN 99 9 L 73 3 0 5VDC 999 1 5VDC 999 0 10VDC 999 0 20mA 999 4 20mA 999 0 50mVDC 999 0 100mVDC 999 Slidewire 100 Current 0 Potentiometer 0 Optimizing Your Process System with the WATLOW Series 988 to to to to to to to to to to to to to to to to to to
72. put 2 A D overflow error non volatile checksum error configuration error Sample Application An engineer has many applications throughout his plant requiring con trollers He wants to know what the controller will do if the sensor fails In some of his processes for instance a gas valve the outputs must go full OFF 0 percent others such as a valve controlling water to a cooling jacket should go to full open 100 percent while others need the outputs to go to an intermediate power level With the 988 the user can determine what the output will do if a sensor fails 5 6 Optimizing Your Process System with the WATLOW Series 988 Standard Features Overview An array of hardware and software lockout levels can be selected Full lockout does features gives you tremendous flexibility in not allow the selected menu to be viewed or configuring various levels of user access The altered Read only allows a menu to be Factory and Setup menus can be viewed but not altered No lockout allows locked out by setting a DIP switch behind the the selected menu to be viewed and changed panel Four levels of lockout can be set from the front panel A simple switch or a keylock The lock prompt allows the operator to switch can be connected to a digital event input select several levels of front panel lockout to lock or unlock access to the front panel 0 enables all keys 1 disables the MODE key The 988 leaves the factory with DIP switch 2
73. r Kansas City Tulsa Region 14 Minneapolis Region 15 Portland San Francisco Seattle Region 16 Los Angeles Phoenix San Diego 214 422 4988 713 440 3074 303 440 9345 913 897 3973 918 496 2826 612 431 5700 206 253 5855 408 980 9355 206 546 6817 714 935 2999 602 258 9206 619 728 9188 B vas LOW oe Watlow St Louis 12001 Lackland Road Watlow Products and Technical Support Delivered Worldwide Asian Sales Offices Korea 5777 Singapore Taiwan 9586 European Sales Offices France 2425 Germany 94000 Italy 5161 Watlow maintains a worldwide network of stocking distributors e FAX 314 878 6814 82 2 563 65 777 5488 886 7 371 33 1 3073 49 7253 39 2 5518 Your Authorized Watlow Distributor is D Printed on Recycled Paper 10 Postconsumer Waste W988 AGV2 9444
74. rcent output value for the second controller This value cannot be seen by the operator This internal percent 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 heater tem perature Algorithm The following formulas show how the primary control sends a set point based on input 2 range high and range low values to the sec ondary control The secondary control uses this set point SP to generate a percent output to the heater 1 PID Set A in1 SP 2 SP rH2 rL2 rL2 3 PID Set B In2 SP The critical parameters are the range settings for input 2 of the second controller The range high value rH2 is the maximum allowed set point for the secondary loop The range low value rL2 is the minimum allowed set point 4 2 Optimizing Your Process System with the WATLOW Series 988 Enhanced Software Features In a system controlling a heater this would be the maximum and minimum desired sheath temperatures of the heater Typically the range low term is set below the ambient temperature Otherwise the system could never fully cool down Setup The PID parameters for the two PID sets PID A and PID B are determined with the auto tune function First the PID B settings inner loop are determined by setting the auto tune prompt to PI
75. reduced wear on the refrigeration system Optimizing Your Process System with the WATLOW Series 988 3 5 General Software Features Digital Event Overview The digital event input options on the Series 988 controller allow the operator to select one of several software functions with the close of a customer supplied switch or by a change in DC voltage The list below outlines the functions that can be controlled with the digital event input Idle set point lets the operator select with the close of a switch a second idle set point Turn control outputs OFF allows a closed input to inhibit the control outputs Alarm reset resets alarms from a remote output 1 event input 1 Sample Application location with a momentary closed input Switch PID sets HGF selects between PID set A or B requires enhanced software Remote set point switches between local and remote set points Front panel lockout locks out the front panel keys to prevent tampering Control output action switches the control action of Output 1 from heating to cooling or vise versa Requirements A single digital event input is standard on all controls A second digital input is available as an option for Input 2 Incubator temperature sensor sensor heater TRUUINUQUUAALUUALON TIN ATIT ATA A manufacturing engineer is building an application that needs to switch to an idle temperature at the end of a batch and maintain that temp
76. rface prompt 3 4 internal percent 4 3 internal set point 4 2 4 4 isolation 2 9 J JIS 2 9 Joint Industrial Standards 2 9 K keylock switch 5 7 keys 6 5 L latching alarm 2 6 5 2 learn high resistance value 3 13 learn low resistance value 3 13 LED 5 4 5 5 6 5 limits 1 7 2 5 2 6 linearization 2 9 local 3 11 local remote prompt 3 11 lockout 3 6 5 7 long lag times 4 2 long sensor lead 5 8 loop error detect 3 7 louver 1 4 1 5 low level contact 1 9 low pass filter 3 8 lower display 6 5 manual mode 5 4 5 6 manual tuning 2 3 master remote 2 6 3 11 mechanical relays 2 6 MODE key 3 6 3 13 5 5 5 7 6 5 model number 7 1 motorized valve 4 7 mounting 6 4 6 6 6 7 muffle furnace 3 10 multi zone application 3 12 N natural oscillation 2 4 NEMA 4X 2 7 2 9 6 8 no lockout 5 7 no module 5 5 noise immunity 2 5 non latching alarm 2 6 5 2 non volatile checksum error 5 6 normally de energized 5 2 normally energized 5 2 O offset 2 4 ON OFF control 2 2 2 9 open collector 3 3 6 3 open loop 2 2 2 9 5 4 open loop prompt 5 5 operating environment 6 8 operator interface 6 8 optimize 7 9 output 1 active 5 5 output 4 active 5 5 output devices 7 5 Output menu 3 12 5 3 Output Table 6 3 outputs 2 5 2 9 5 5 6 8 outputs turn off 3 6 overshoot 2 3 2 4 2 9 P P control 2 9 paint 4 7 panel cutouts 6 4 Panel Lockout menu 5 7 panel lockout prompt 5 5 part number 6 6 PD control
77. ries and in certain markets in the U S the default units may be either degrees C or degrees F and the PID parameters might use proportional in percent of span integral and derivative or proportional in degrees reset and rate The 988 can switch between these default sets to suit the user s preference What level of operator security do you need page 5 7 e The Series 988 provides numerous levels of both software and hardware lockout Refer to page 4 5 for more information on lockout What do you do if a system component fails page 5 5 e When investigating a system failure the Series 988 s Diagnostics menu can be used to monitor inputs and selectively activate outputs The menu also shows the software revision and the I O types What about field calibration e All Watlow microprocessor based controls can be field calibrated with the right equipment The calibration manual for the Series 988 family of controllers is available upon request Putting It All Together You should now have a good idea of what types of questions to ask when designing your system with the Series 988 We suggest that you read through the rest of this chapter and Chapters Three through Seven for more detailed informa tion on the features available in the Series 988 If you are already familiar with the 988 skip to Chapter Seven to select the 988 that fits your application Optimizing Your Process System with the WATLOW Series 988 2 7
78. s opto isolated Accuracy Calibration accuracy amp sensor conformity 0 1 of span 1 LSD 77 F 5 F 25 C 3 C ambient amp rated line voltage 10 eAccuracy span 1000 F 540 C minimum Temperature stability 0 2 F F 0 1 C C change in ambient Voltage stability 0 01 of span of rated line voltage Agency Approvals UL873 and UL508 File E43684 CSA pending NEMA 4X Terminals 6 compression universal head screws accepts 20 14 gauge wire Power 100 240VAC 10 15 50 60Hz 5 16VA maximum Data retention upon power failure via non volatile memory Operating Environment 32 to 149 F 0 to 65 C O to 90 relative humid ity non condensing Electromechanical relays are not recommended for PID control They are warranted for only 100 000 contact closures 6 8 Optimizing Your Process System with the WATLOW Series 988 Specifications The Watlow Series 988 family of controllers is warranted to be free of defects in material and workmanship for 36 months after delivery to the first purchaser for use providing that the units have not been misapplied Since Watlow has no control over their use and sometimes misuse we cannot guarantee against failure Watlow s obligations hereunder at Watlow s option are limited to replacement repair or refund of pur chase price and parts which upon examination prove to be defective within the warranty period specified This
79. s are tuned manually or auto matically Manual tuning requires manually setting each of the controller s operating pa rameters Automatic tuning or auto tuning is accomplished by the 988 s digital microproces sor based electronic circuitry The controller uses a program inside its memory that will calculate the correct setting for each of the controller parameters For more information on auto tuning with the Series 988 refer to page 3 2 Manual Tuning The following steps are generally applicable to most manually set process controllers Please take note of a few precautions e Take your time in tuning the control system If you do it right it will work a long time without further attention e Do not change more than one control adjust ment at a time allowing the system to settle Optimizing Your Process System with the WATLOW Series 988 2 3 2 4 Basic Control Strategies and Terms down to a state of equilibrium before making another change e Remember that the time you need to spend tuning the electronic controller system is relative to the precision of control you need Proportional Band The proportional band adjustment is the means of selecting the response speed gain or sensi tivity of a proportioned controller to achieve stability in the system The proportional band whether measured in degrees percent of range or other units must be wider than the natural oscillations of the system and yet not
80. scribes the software features that are available in Watlow Series 988 controllers Enhanced soft ware options provide additional features that are described in Chapter Four Optimizing Your Process System with the WATLOW Series 988 3 1 General Software Features Overview The auto tune feature allows the controller to manipulate the process and calculate PID values based on the process response This relieves the operator from the tedious task of manually tuning the PID parameters to match the characteristics of the thermal system The point at which the auto tune takes place is determined by the auto tune set point parameter It is adjustable from 50 percent to 150 percent of the current set point with 90 percent being the factory default setting If the auto tune set point is 90 and the current setpoint is 300 degrees the control goes into ON OFF mode of control at 270 degrees 300 deg x 0 9 The displayed setpoint is un changed and the bottom display information alternates with tune at a one second rate until the auto tune is completed Any changes to the set point during an auto tune will cause the auto tune sequence to start over based on the new set point hynin output 1 a88 a Sample Application During an auto tune the controller monitors how fast the process increases and decreases and from this information calculates propor tional band reset and rate values and auto matically enters them into
81. splay colors z RED TP eD Borom os ____ _ WMA A v aeBA 2oFA AARP Bcd 9h2EB 22FK AARP digital event standard WATLOW ae oon gt Joo Low Lever PROCESS CONTACT i TANK y iras gt With the communi a a cation feature Bob DEV oispLay ia Y Fon can easily monitor S A l the mixing process AUTO Lox 4 rs by aii sy fe pl fe Gun UL recognized BN AAUTER ae Lo a b D 9 H coreo 6 Review and Optimize 5 Hardware l L x eR In the final review of the appli personal computer so he The panel containing the four thanks to the UL recognition cation design prior to purchas added the RS 422 EIA 485 controllers was built by a of the Series 988 controller ing the 988s Bob decided that communications option to the third party vendor The re under UL 873 and more im in the future he wants to moni controller part number quirements for a UL recog portantly UL 508 tor the four controllers with a nized panel were easily met 1 8 Optimizing Your Process Systems with the WATLOW Series 988 Optimizing Your Process Systems with the WATLOW Series 988 1 9 Basic Control Strategies and Terms Control Strategies 2 2 Questions and Answers 2 5 Glossary 2 8 How to use this chapter This chapter explains control terms and strategies especially as they apply to the Watlow Series 988 family of controllers It will help you identify issues specific to your application an
82. ss overshoot The ON and OFF cyclic action continues until a stable relationship is achieved At that time the system will be stabilized such that the A Overshoot Temperature Proportional Band Set Pon Eor a a a a a A k Time Profile developed by proportioning control process is controlled at a point below set point The process stabilizes with a resultant droop This condition will remain providing there are no work load changes in the system Integral If the droop cannot be tolerated there are ways to compensate for it Integral automatic reset is an automatic adjustment to compensate for Optimizing Your Process System with the WATLOW Series 988 Basic Control Strategies and Terms a droop condition before it exists An integra tion function takes place that automatically compensates for the difference between set point and the actual process This integration automatically drives the process toward set point Integration action is prevented until the process enters the proportional band If it was 4 Temperature Proportional po Overshoot Set Point _ _Z X ERAR Time Profile developed by a proportional plus integral control allowed to take place at any point it would cause a condition of extreme overshoot This function of eliminating the integration outside of the proportional band is referred to as anti reset windup Derivative As
83. ss the S au with a Pat needed to directly replace slidewire feedback input as ture of the grain w wire RTD the Barber Coleman control input 2 The universal input 400 platinum three and contacted the factory for accepts a 1009 RTD and a cross reference The factory the slidewire impedance recommended a Series 988 was 1000 ohms within the with a universal input as the specifications of the 988 s primary input input 1 and a slidewire input She was especially concerned tors apout four factors air versus e the cost of bac the Series 988 en 8 ae the actual louver position e and manual control of tga e simplifying the apen making it easter to mal e system setup time Output 1 CLOSE Louver RELAY SA Wk Rc SUPPRESSION os__ __B _ ____ WATLOW 988 Key Features G2AIN DRYER WITH Supewite eD BAcw AND TEMP ALARM Software SuUDEWw IRE FEEPBAGL STANDARD gs _ AJ ___ Power amp Hardware Output 2 OPEN LOUVE RELAY SA wrth Input 2 ADEWE INPUT Output 3 VeencaL Procese ALARM n 00 7240 VAC BELAY SA WmouT Ro SUPPRESSION s m Output 4 TI E Display colors Zed ToP Ren Borom See Nor Use Nor ose digital event standard eG A 22DDd EE Ale output 2 input 3 SuPewige Feepeacy INTC ALES Leuven Posmon e 3 wee KO 1 4 Optimizing Your
84. stance values and enter these at the range low and range high prompts Once the control is operating adjust the hunt parameter to minimize valve oscillations The hunt parameter sets up a dead band on both sides of the current valve position The desired valve position is then compared to the actual position If the difference is greater than the one half of the hunt value the 988 repositions the valve to achieve the temperature set point Once repo sitioning is complete the dead band is recalculated for the new valve position Optimizing Your Process System with the WATLOW Series 988 3 13 Chapter Four Enhanced Software Features Cascade Differential Dual PID sets Duplex Ratio How to use this chapter This chapter describes the software features that are available in the 988 family of Watlow controllers equipped with the enhanced software option Optimizing Your Process System with the WATLOW Series 988 4 2 4 4 4 5 4 6 4 7 4 1 Enhanced Software Features Overview Cascade control can handle a difficult process with minimal overshoot while reaching the set point quickly This minimizes damage to system components and allows for oversizing heaters for optimal heat up rates Systems with long lag times between the energy source heater steam etc and the measured process value cannot be controlled accurately or efficiently with a single control loop because a lot of energy can build up before a response is d
85. t a differential to the outside air temperature A thermocouple at input 2 senses the outside air temperature and adjusts the internal set point to maintain the boiler water temperature 120 degree higher Substituting values we have boiler temperature outside temperature 120 In this application the system uses two type J thermocouples one to sense boiler water temperature input 1 and one to sense the outside air tempera ture input 2 To configure the controller first enable input 2 set to J To enable the differential control algorithm set the control prompt in the Global menu to differential EMA Press the DISPLAY key The lower display will read 0 indicating no differential between input 1 and input 2 Adjust the set point to 120 The internal set point for input 1 is now equal to the input 2 value plus 120 which will maintain the boiler water temperature 120 degrees higher than the outside air temperature 4 4 Optimizing Your Process System with the WATLOW Series 988 Enhanced Software Features 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 parameters PID A GIFfj and PID B BEB To enable dual PID enter the Global menu and set the algorithm prompt to dual PID GEB This second set of PID parameters enables the controller to switch between two sets of PIDs to compensate for changes in the system chara
86. t will affect the display only or you can configure the option to filter the input signal itself Use this feature with cau tion because a large time constant could hide system upsets Requirements This feature is standard on all Series 988 controllers Display readings with input filter on RH gt time gt Humidity Chamber temperature sensor sensor humidity transmitter m Heater A Series 988 controls the humidity in an environmental chamber The relative humidity RH sensor provides a 4 20mA signal over a 0 100 RH range The sensor is very sensitive to changes caused by air flow in the chamber The turbulence in the chamber has the 988 display jumping two to three percent To remove this display dithering the filter time constant for input 1 is set to 2 seconds This will smooth the display and provide a more realistic reading 3 8 Optimizing Your Process System with the WATLOW Series 988 General Software Features Input Linearization Overview In many flow applications the output signal from a flow transmitter represents a squared value of the actual flow The square root must be extracted from the signal to make it useful to the operator Many flow transmitters offer this feature in the transmitter itself but this Requirements The square root extraction feature is standard on any Series 988 controller with universal signal conditioner inputs The linearization prompt
87. tal event standard Use WRZONTAL 999 B 1 1 cDd 3 NE SIoN ALA Andy choose the horizontal version of the controller because it fit the If a system component fails control panel well Wi TEMP ALARM the limit shuts the system down Review and Optimize Hardware Accident prevention is a age 85 264VAC option for paramount concern in sucha contactor to function as a limit of the controller fit nicely into power and picked a red upper critical system So the system if the aluminum reaches a the control panel The opera and red lower display was designed with a Watlow dangerous temperature tor also chose the high volt Series 92 DIN rail mounted Optimizing Your Process Systems with the WATLOW Series 988 limit control and an external The horizontal version 989 1 6 Optimizing Your Process Systems with the WATLOW Series 988 1 7 A B C D 1 5 2 1 If the flow from tank A changes the controllers will adjust the flow from the other three tanks to maintain the correct ratio i The controllers can make precise adjustments to each valve a B C and D 2 Tank A naD z follow the flow from wo o ra A 2 Tank B JSE s Tank C Controllers a Rae eee a Overview Minutes tank A iai n h ntrollers uses the 2 Outputs of stributor salesma 1 Inputs o
88. tching Alarms can be latching or non latching When the alarm condition is removed a non latching alarm automatically clears the alarm output and alarm message if one is present You must manually clear a latched alarm by pressing the AUTO MAN key once 5 2 Optimizing Your Process System with the WATLOW Series 988 Standard Features 5 Silencing Alarm silencing overrides the alarm at power up and it allows the operator to silence an alarm with the system still in an alarm condi tion The silencing is active until the process has entered the safe region located between the E output 1 output 2 form C relay low and high alarm settings Any future devia tion outside the safe region triggers an alarm If the alarm occurs at this point the output can be silenced by pressing the AUTO MAN key once but the alarm message is still displayed Oven temperature sensor limit sensor heaters ETN The temperature is within the normal range Output 2 is inactive form C relay temperature sensor limit sensor heaters ETN An over temperature condition activates output 2 which turns the alarm on Sample Application An operator is using a deviation alarm to keep a process within 5 F of the set point Output 2 is set up as a deviation alarm that activates a buzzer However when the process powers up in the morning the process temperature is below the low deviation alarm set point ca
89. ter Is the process relatively fixed or widely vary ing what is the range page 6 8 e Make sure you check and re check the ranges of the input options available in the 988 Although the 988 can operate outside the ANSI ranges for specific thermocouples and RTD s it is not recommended and will shorten the life of the sensor Are there concerns over electrical noise immunity e Although the Series 988 is thoroughly tested for electrical noise immunity it is paramount that you follow good engineering practices when designing the placement of the sensor and power wires Refer to the Series 988 Users Manual and the Watlow Catalog Outputs The outputs command the system to heat cool turn ON and OFF and also trigger other actions in this system or related systems It is very important that you maintain total control over the process External limits or other devices to disable the outputs can protect system components and provide an added layer of safety Consider the following How frequently will the output need to cycle to control the process page 6 8 Optimizing Your Process System with the WATLOW Series 988 2 5 Basic Control Strategies and Terms e What is frequent In order to tightly control a process the more frequent the better Unless absolutely necessary mechanical relays should not be used as the control output A typical mechanical relay application cycles ON and OFF 86 400 times over a period of
90. that the Series 988 con troller operates in What are the physical dimensions of the enclosure page 6 4 e The Series 988 family of controls has a behind panel depth of 4 06 inches allowing the control to fit an enclosure with a depth of 6 0 inches When mounting more than one controller in a panel we recommend a minimum spacing of 1 66 inches between controllers What is the ambient temperature inside the enclosure page 6 8 e The Series 988 can operate in ambient tem peratures as low as 32 F 0 C and as high as 150 F 65 C The enclosure requires a non 2 6 Optimizing Your Process System with the WATLOW Series 988 Basic Control Strategies and Terms condensing atmosphere because the vented case is susceptible to dripping water If neces sary include an enclosure heater in your system to maintain the proper environment Is the front panel subject to spray or hose down conditions page 6 8 e The Series 988 has a NEMA 4X rated front panel This rating allows the controller to be hosed down directly without damaging the controller Two gaskets protect the controller one seals the bezel of the control while the other seals the controller face plate and the panel cutout When installing the controller be sure that these gaskets are not twisted What are the agency requirements for the controller and the system page 6 8 e The Series 988 has a UL 873 and UL 508 recognition CSA recognition is pending
91. tical mounting 100 240 V 9 Horizontal mounting 100 240 V Software Standard B Enhanced with cascade ratio dual PID differential 1 Input 1 Basic thermocouple signal conditioner excluding Type R S and B Universal signal conditioner 2 Input 0 None 1 Basic thermocouple signal conditioner excluding Type R S and B 2 Universal signal conditioner 3 Slidewire feedback 4 Current transformer 5 Second digital event one digital event is standard on all units 1 Output B Solid state relay Form A 0 5A with RC suppression C Switched DC open collector isolated D Electromechanical relay Form C 5A with RC supression E Electromechanical relay Form C 5A without RC suppression F Universal process 0 5VDC 1 5VDC 0 10VDC 0 20mA 4 20mA K Solid state relay Form A 0 5A without RC suppression 2 Output A None B Solid state relay Form A 0 5A with RC suppression C Switched DC open collector isolated D Electromechanical relay Form C 5A with RC suppression E Electromechanical relay Form C 5A without RC suppression F Universal process 0 5VDC 1 5VDC 0 10VDC 0 20mA 4 20mA K Solid state relay Form A 0 5A without RC suppression T External signal conditioner power supply 5 12 or 20VDC 30mA 3 Output A None B Solid state relay Form A 0 5A with RC suppression C Switched DC open collector isolated J Electromechanical relay Form A or B 5A without RC su
92. to to to to to to to to to to to to to to to to to to to to 1500 F 816 C 2500 F 1371 C 750 F 399 C 2372 F 1300 C 3200 F 1760 C 3200 F 1760 C 3300 F 1816 C 1470 F 799 C 4200 F 2316 C 4200 F 2316 C 2543 F 1395 C 1166 F 630 C 1472 F 800 C 999 9 F 537 7 C 9999 9999 9999 9999 9999 9999 9999 1200Q 50mA 1200Q 7 11 A A D overflow error 5 6 A D underflow error 5 6 accuracy 6 8 actuator interfaces 2 6 address prompt 3 4 agency approvals 6 8 alarm 2 high 5 2 alarm 2 low 5 2 alarm high 3 10 alarm low 3 10 alarm reset 3 6 alarm silencing 1 5 1 7 alarms 2 6 5 2 6 6 algorithm prompt 4 5 aluminum melting furnace 1 6 ambient counts 5 5 ambient temperature 2 6 5 5 analog output 3 12 annunciation output 2 6 annunciator 2 8 auto mode 5 6 auto reset 2 4 auto tune 1 3 2 3 3 2 4 3 4 5 6 6 auto tune prompt 3 2 4 3 auto tune set point 3 2 auto tune set point parameter 4 3 auto tuning 2 3 4 5 AUTO MAN key 3 2 5 2 5 3 5 4 5 6 5 7 6 5 AUTO MAN LED 6 5 auto manual 5 4 automatic mode 5 4 automatic reset 2 2 2 4 automatic tuning 2 3 Barber Coleman 560 1 4 basic signal conditioner 6 2 baud rate 2 6 3 4 boiler 4 4 break protection 2 10 bumpless transfer 5 4 5 6 burst fire 2 6 2 8 3 3 3 7 buzzer 5 3 C calibration manual 2 7 Calibration menu 6 5 calibration offset 2 8 cascade 1 6 1 7 2 7 2 8 4 2
93. to the automatic mode letting the controller maintain the output power level 5 4 Optimizing Your Process System with the WATLOW Series 988 Standard Features Overview The Series 988 Diagnostics menu allows you to read the software revision ship date hardware configuration and ambient temperature without removing power from the control To access the Diagnostics menu press the increment up arrow and decrement down arrow keys simultaneously for six seconds The factory prompt appears in the lower display and panel lockout prompt in the upper display Press the increment key until diagnosis EMB appears in the upper display Then press the MODE key The list below explains the menu prompts Date provides the date of the final control test The first two numbers indicate the week 01 through 52 and the last two show the year Soft signifies the control software revision The serial number follows Sn in the upper GEES display The six digit number begins with the last two digits in the upper display and wraps around to the lower display Ambient temperature indicates the tem perature at the input 1 terminals in degrees F Ambient counts is for factory use only Ground counts is for factory use only Input 1 counts is for factory use only Input 2 counts is for factory use only Depending on the modules installed and the DIP switch settings some of the following input and output type displays will appear Types f
94. tput 100 Output 10 ON 0 OFF 10 Output 1 ON 9 OFF 988 output 1 Sample Application The 988 family has built in zero cross detection circuitry Therefore special firing circuitry is normally not required for triggering SCR s To enable burst fire the 988 must have an open collector or solid state relay output The feature is enabled by selecting burst fire at the cycle time prompt for the appropriate output You should note that the short time bases used by burst fire makes it incompatible with the heater current feature see page 3 7 The heater current option requires a minimum of 300 msec ON time to get a reading Only the 988 and 989 can use the burst fire feature The low voltage units 986 and 987 cannot use burst firing 50 Output 1 ON 1 OFF 66 Output 2 ON 1 OFF Semiconductor Oven temperature sensor limit sensor heated platen The 988 is being used to control a heated platen in a semiconductor oven Previously it required a power control requiring a 4 20mA signal to implement burst fire control We have replaced the power control with a Watlow Loyola QPAC with a QCD card that accepts a signal directly from an open collector output of the 988 This gives smooth control at a lower overall system cost Optimizing Your Process System with the WATLOW Series 988 3 3 General Software Features Communications Overview The serial communications featur
95. troller configuration Experts who are familiar with the Series 988 controller may want to go directly to the Faxable System De scription on page 7 10 7 1 How to Choose the Right 988 to Fit Your Application HELPFUL REFERENCES Chapter 1 Test Drives provides diagrams and explana tions of several different types of applications Chapter 2 Basic Control Strate gies and Terms explains the basic concepts and vocabulary of control applications input 1 output 1 output 2 input 2 a output 3 input 3 output 4 Step 1 Overview A Describe the process that the 988 will control B What raw materials go into the process C What product does the process create D List the sensors switches and controls used in the process E List the heaters motors valves and other devices used in the process F List ambient conditions performance require ments and safety concerns involving the process G Make a rough sketch of the process including all of the elements listed above Be sure to label all of the parts 7 2 Optimizing Your Process System with the WATLOW Series 988 How to Choose the Right 988 to Fit Your Application HELPFUL REFERENCES Use the complete input table in Chapter 6 Specifications See the filled in worksheets in Chapter 1 Test Drives Inputs 11213 0 none 1 basic signal conditioner 2 universal signal conditioner process input resistance temp detector ther
96. um Mixing Urethane _ _ _ h h oo RD How to use this chapter This chapter describes four actual appli cations in which processes are optimized by using Watlow Series 988 controllers Optimizing Your Process System with the WATLOW Series 988 1 1 r Overview Chris an engineer for Acme awe studied the products of severa The heater current input can detect the failure of a heater or the power control device vendors to find a control for severa ould extruders that e detect heater burnout to ee down time and improve qu e i teria av run a variety of ma a scant An different tuning paramete e prevent machine eS from changing parameters e maintain tight control of process quality ebe automatically upe to minimize set up time Inputs Detecting a burned out heater required an input that moni tors heater current and turns ON an alarm if a heater fails In extruders it is not always apparent that a heater has failed because adjacent WATLOW 988 Key Features EXTRUDER HEATER CopgenT Input 1 3I THEAMOCVPLE eS S Software ENHANCED Dur PID s_B ____ Power amp Hardware Veena gt 00 240VAc HEATER CURENT Display colors RED WP oe GREEN BolT al 1 2 Optimizing Your Process Systems with the WATLOW Series 988 Outputs zones may make up f
97. urppress 5 5 relay C 5 5 root extraction 3 9 ramping 3 10 remote set point 3 6 3 11 S setup 3 4 4 5 5 7 EA silencing 2 5 3 HEA slidewire 3 13 5 5 serial number upper 5 5 GEE serial number lower 5 5 GEB error output 5 6 software 5 5 power supply 5 5 solid state 0 5A surppress 5 5 solid state 0 5A 5 5 solid state 2A 5 5 set point 3 10 4 5 start 3 10 T thermocouple only 5 5 test output 5 5 tune 3 2 U universal millivolts 5 5 universal OFF 5 5 universal process 5 5 voltage retransmit 5 5 universal RTD 5 5 universal tc high 5 5 universal tc low 5 5 Optimizing Your Process System with the WATLOW Series 988 8 5 e St Louis MO 63146 USA e Phone 314 878 4600 North American Sales Offices Region 1 Boston Region 2 New York Upstate Region 3 New York New Jersey Region 4 Philadelphia Region 5 Atlanta Greenville Charlotte Columbia Nashville Orlando Winston Salem Region 6 Baltimore vidni Region 7 Cincinnati Region 8 Cleveland Pittsburgh Region 9 Detroit Region 10 Chicago Indianapolis Milwaukee Region 11 St Louis Made in the USA 508 655 2225 716 438 0454 908 549 0060 215 345 8130 404 908 9164 704 847 4000 615 833 2636 407 351 0737 910 945 5957 410 788 6400 804 589 5611 513 398 5500 216 838 5522 412 322 5004 810 651 0500 708 490 3900 317 575 8932 414 255 7725 314 878 4600 Region 12 Dallas Houston Region 13 Denve
98. using the buzzer to sound until the process reaches the low alarm set point Selecting ON at the silencing prompt in the Output menu disables the alarm output controlling the buzzer until the process gets within the deviation alarm set points It also allows the operator to silence the buzzer by pressing the AUTO MAN key once if an alarm does occur Optimizing Your Process System with the WATLOW Series 988 5 3 Standard Features Auto Manual Overview When it operates automatically the controller uses an input signal from a thermocouple RTD transmitter etc to determine how best to adjust the output power level to match a set point This constant monitoring of process variables and the corresponding adjustments in the output power level is referred to as closed loop control This is the normal mode of operation for most applications Manual operation does not use feedback from the input signal to determine a power level The power level must be adjusted manually by the operator The controller may or may not be monitoring the process variable This open loop control is used for applications in which closed loop control is not desired for instance as a diagnostic tool or when the controller detects a sensor break see Input Errors page 5 6 Manual operation provides open loop control of the outputs from a range of 100 percent to 100 percent power 100 percent for full cool 100 percent for full heat The Series 988
99. wide enough to dampen the system response The time proportioning output must be set to switch faster than the natural oscillation of the system sometimes called system cycle time The tuning procedure is very simple if you can use a recorder to monitor the actual process variable If a recorder is not available observe the process response and record readings over a defined time period If the system oscillates when the proportional band is at its narrowest setting not zero the adjustment of the proportional band should be increased in small increments until the oscilla tion stops Because the proportional band has been tuned adjusted to have the controller seek stability of the system very often an offset droop from the set point occurs At this point in tuning the system the process variable should be in a state of equilibrium but not right on the desired set point Integral Reset The reset adjustment is tuned at this point to correct for the droop caused by the propor tional output While it does automatically correct for offset errors automatic reset has to be tuned to each system Each system has its own characteristic response time system cycle time thus the auto reset time constant repeats per minute must be tuned to match the overall system response time Initially auto reset should be set at the lowest number of repeats per minute least corrective action Increase the repeats per minute in sm
100. will appear if a process input is se lected via the universal signal conditioner DIP can add significantly to the cost Using the switches square root extraction option in the Series 988 controller can save the operator money The feature is enabled simply by setting input 1 linearization or input 2 linearization to square root extraction GEEB 144 linearized signal Flow in gallons e per minute 44 non linearized signal 4 20mA input signal 188 output 1 488 es Li 12 13 14 DEV e oispLay OUT e flow transmitter Water Treatment Pond Sample Application A waste water process engineer needs to control the flow of a solution to be mixed with waste water for treatment of the water The transmitter provides a 4 20mA output without square root extraction The engineer used the Series 988 with a universal signal conditioner input and a 4 20mA process output to control the flow The input signal was linearized using the square root extrac tion feature of the 988 The above system has a flow range of 0 to 16 gallons per minute The range low and range high parameters for input 1 would be set to O and 16 respec tively The input 1 linearization prompt would then be set to square root extraction GHB You can see from the above graph that without square root extraction to linearize the signal it would not be useful for controlling the process Optimizing Your Process System with the WATLOW Series 98
101. with a keylock switch connected to event input 2 Event input 2 in the Global menu is set to lock WEB Without a key nothing is accessible from the front panel With a key process and alarm set points are accessible Optimizing Your Process System with the WATLOW Series 988 5 7 Standard Features Transmitter Power Supply Overview In an electrically noisy environment or when its outputs The factory sets the power supply you have to use a long sensor lead you may voltage to 2OVDC but you can use DIP need to use a transmitter to convert the sensor switches to change it to 5 or 12VDC as well signal to a 4 20mA signal Normally you would have to buy and install a separate power Requirements supply for the transmitter or for other signal A transmitter power supply can be ordered for conditioning devices but you can order a output 2 3 or 4 Series 988 with a 30mA power supply as one of Control Room Pump Controller Evaporator Controller Heater Controller WATLOW 288 988 heater RTD transmitter power fa RTD transmitter evaporator humidity transmitter pwr Psi humidity transmitter a process flow transmitter power my process flow transmitter i Sample Application An engineer at a food processing plant needs to control several processes from a central control room which is more than 100 feet away from some of the machines being controlled Because of the distance and the noisy electrical environment thermocoup
102. yet couldn t be tampered with Standard Featu The standard auto tune fe ture allowed the operata quickly set up the he cool parameters Red displays are typically used to depict the process while green is used to indicate the set point Review and Optimize engineer also added the ramp to set point feature to reduce stress on the machine as it heats up Hardware Chris chose the vertical con trol with the high voltage 100 264V option and picked a red upper display and a Optimizing Your Process Systems with the WATLOW Series 988 Time Chris ran the extruder at different temperatures requir ing separate PID parameters The dual PID option al lows the selection to be made automatically green lower display to make it easier for operators to visual ize the process 1 3 Ua fi a es Close 3 Output 1 Test Drive in s Drying G Overview a Pat an engineer for eel ae com 3 z E n considering papery and an external A three wire RTD was chosen for accuracy at near Coleman 560 i he board used for slidewire control T ambient conditions Also due to the long lead length ulated air temperature a three wire RTD was used to prevent inaccuracies control aa e by adjusting the yt due to lead wire resistance ina grain edback of a lar tion via slidewire fe f air a jouver that controlled the amount O 1 Inputs n The tempera flowing acro

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