RC 900 User`s Manual - Environmental Stress Systems
Contents
1. DBA RC 900 Operation Manual 1 2001 23 RC900 Remote Command Summary Name Description Read Value range Write C1 Channel temperature value 2 Input range 2 Channel ft 2 temperature value 2 C2 Input 2 range CAL Lock out calibration menu 2 CAL 0 unlocked 1 read CAL value 2 locked Default 0 CAL Input 1 calibration offset CALI 999 TO 999 CALI value Default 0 CAL2 Input 2 calibration offset 2 CAL2 999 TO 999 CAL2 value Default 0 CF Select temperature units for display CF O F 1 C CF value Default 1 CNTL Control mode used to enable cascade control CNTL O normal 1 cascade software hardware changes also necessary CNTL value Default 0 COM Lockout communication menu COM O unlocked 1 read COM value 2 locked Default 0 CSAC Cascade action use when control function is set to 2 CSAC O direct action cascade CSAC value 1 Default 0 CSP Current profile set point profile mode 2 CSP Input I range Output 1 cycle time for heating PID set 2 0 1 to 999 seconds value Default 1 0 seconds 2 Output 2 cycle time for cooling PID set A 2 2 0 1 to 999 seconds 5 second minimum for electromechanical device CT2A value Default 5 0 seconds 0 2 Output 1 cycle time for heating PID set 2 CTIB 0 3 to 999 seco2. type 328 to 1470 F 200 to 799 Table 3 LOC command values 0 No keypad lockout Lock out SYSTEM PID amp PROGRAM menus 3 Lock out SYSTEM PID PROGRAM menus amp UP amp DOWN arrow keys set point lock out Table 4 POUT command values 0 Continue 1 Hold 2 Abort 3 Idle set point 4 Reset RC 900 Operation Manual 1 2001 28 PID Primer What is PID PID stands for Proportional Integral and Derivative The following explanations describe PID as it applies to the precise control of a process temperature A process is an area or zone that is being controlled at or driven to a precise temperature PID is a control method or mode that has three functions or variables The proportional action dampens process response The integral corrects for droop Droop is the difference in temperature between the process set point and the actual process temperature The set point is the desired process temperature The derivative minimizes overshoot and undershoot Overshoot is the amount in temperature units that the process temperature exceeds the set point before the process stabilizes Process stabilization is achieved when the set point and process temperatures are equal over a defined period of time Undershoot is the amount in temperature units that the process temperature falls below the set point before the process stabilizes Proportional is the control ou
3. PID Reset for output 4 2 cooling PID set A RE2A 0 00 to 9 99 Units represent Repeats per Minute RE2A value Default 0 28 REIB PID Reset for output 2 cooling 0 00 to 9 99 R M Units represent Repeats per Minute REIB value Default 0 28 RE2B PID Reset for output 2 cooling RE2B 0 00 to 9 99 R M Units represent Repeats per Minute RE2B value Default 0 28 RHI Set point span range high limits for input sensor 1 RHI Std 130C Opt 200C Temperature units are in degrees C value Default 130 deg C RC 900 Operation Manual 1 2001 26 2 Set point span range high limits for input sensor 2 RH2 Std 130C Opt 200C Temperature units are in degrees C Note See RH2 value Default 130 deg C section on cascade software special settings Cascade 10 deg C RHS Run Hold status for ramp amp soak profile mode RHS 0 HOLD 1 RUN Set point span range low limits for input sensor tt I Ambient to 99 Temperature units are in degrees C value Default 99 deg RL2 Set point span range low limits for input sensor 2 RL2 Ambient to 99 C Temperature units are in degrees C Note See RL2 value Default 99 deg C section on cascade control software special settings Cascade 10 deg C RP Enable the temperature ramp rate feature RP 0 or 2 0 off 2 on RP value Default 0 RATE Ramp rate in degrees per
4. Table 3 Rate Derivative setting oscillations e e TEMPERATURE Rate too large Decrease Rate value Rate too small Increase Rate value e e TEMPERATURE Rate correct PID settings correct RC 900 Operation Manual 1 2001 39
5. 232 Default 19 PBIA Proportional band width for heating output 1 PID PBIA 0 to 999 set A PBIA value Default 14 PB2A Proportional band width for cooling output 2 PID PB2A 0 to 999 set A PB2A value Default 14 PBIB Proportional band width for heating output 1 PID PBIB 0 to 999 set B PBIB value Default 14 PB2B Proportional band width for cooling output 2 PID PB2B 0 to 999 set B PB2B value Default 14 PIDA Lockout access to PID set A PIDA O unlocked 1 read PIDA value 2 locked Default 0 PIDB Lockout access to PID set B PIDB O unlocked 1 read PIDB value 2 locked Default 0 PWR Percent output power for currently operating output PWR 100 to 100 1 to 100 heating 1 to 100 cooling 0 off RAIA PID Rate for output 1 heating PID set A 0 00 to 9 99 minutes Units represented in minutes RAIA value Default 0 05 2 PID Rate for output 2 cooling PID set A 2 2 0 00 to 9 99 minutes Units represented in minutes RA2A value Default 0 05 RAIB PID Rate for output 1 heating PID set B RAIB 0 00 to 9 99 minutes Units represented in minutes RAIB value Default 0 05 RA2B PID Rate for output 2 cooling PID set B RA2B 0 00 to 9 99 minutes Units represented in minutes RA2B value Default 0 05 REIA PID Reset for output 1 heating PID set A REIA 0 00 to 9 99 R M Units represent Repeats per Minute value Default 0 28
6. RL1 OT2 FAIL DATA 130 NOR NLA ON RH1 CACN ERR PROT 0 OFF NOR 232 CAL AL2 CNTL INTF 0 CC PID FTR1 OT3 AL90 T 1 NO IN2 COFF EI OFF OFF RSP ANUN 75 100 RL2 LOP 130 100 RH2 HIP 0 90 CAL2 ATSP 0 OFF FTR2 RP CONT POUT 2 GSD RC 900 Operation Manual 1 2001 20 RC900 controller default PID settings for MRTP PIDA OPER 30 PB1A 0 10 0 5 RAIA 1 0 CT1A 2 PB2A 0 25 RE2A 0 5 RA2A 5 0 2 0 DBA RC 900 Operation Manual 1 2001 21 RC900 Controller Default Settings for TEMP INPUT OUTPUT GLOBAL COMM SET SET SET SET T HT IG 9600 IN1 OT1 CF BAUD 10 1 8N RL1 OT2 FAIL DATA 130 NOR NLA ON RH1 CACN ERR PROT 0 OFF NOR 232 CAL AL2 CNTL INTF 0 CC PID FTR1 OT3 AL90 T 1 NO IN2 COFF OFF OFF RSP ANUN 10 100 RL2 LOP 130 100 RH2 HIP 0 90 CAL2 ATSP 0 OFF FTR2 RP CONT POUT 2 GSD RC 900 Operation Manual 1 2001 22 RC900 controller default PID settings for TEMP PIDA OPER 1 0 30 0 RAIA 1 0 CT1A 1 PB2A 0 20 RE2A 0 30 RA2A 1 0 CT2A 59
7. if the set point is 100 degrees C and you have set the rL2 and rH2 values to minus 10 10 and plus 10 10 respectively then the controller can force the thermal platform temperature by as much as 10 degrees beyond the set point The platform can be driven to 110 degrees C if necessary to force the device to the 100 degrees C set point This allows the controller to automatically eliminate the thermal error caused by temperature gradients between the platform and the device If the temperature gradient decreases over time the controller will automatically compensate and adjust the thermal platform temperature to hold the device under test at the set point temperature The recommended value for rL2 and rH2 is 10 This number can be raised or lowered slightly if necessary but we have found it to be satisfactory in most cases Note The changing of menu values can be very easily accomplished via the serial or GPIB remote interface Some users find this more convenient than entering menu values from the front panel See the Communications chapter for more details on remote computer interfaces A sample string to set the rL2 and rH2 values is shown below RL2 10 RH2 10 RC 900 Operation Manual 1 2001 10 Communications The RC900 comes standard with EIA 232 serial communications and optional factory or field installable GPIB 488 remote communications The EIA 232 communications uses 3 wire system typical cable diagram is p
8. GLBL Lockout the global menu GLBL O unlocked 1 read GLBL value 2 locked Default 0 GSD Guaranteed soak temperature deviation in degrees GSD 0 to 999 Applied in profile mode GSD value Default 0 HIP Output 1 heating power limit in percentage 2 HIP 0 to 100 HIP value Default 100 HOLD Simulates a HOLD key press profile mode HOLD 0 not in HOLD HOLD value 1 HOLD INI Input 1 thermocouple sensor type INI 1to 5 see table 2 INI value Default 3 IN2 Input 2 thermocouple sensor type 2 IN2 5 see table 2 IN2 value Default 3 INPT Lockout the input menu INPT O unlocked 1 read INPT value 2 locked Default 0 INSP Examine the cascade control platform set point 2 INSP 999 to 999 Used when control action is set to cascade mode Default 10 to 10 LOC Front panel keypad lockout LOC 0 to 3 see table 3 LOC value Default 0 LOP Output 2 cooling power limit in percentage LOP 0 to 100 LOP value Default 100 OTI Output 1 action type OTI O heat 1 cool value Default 0 OT2 Output 2 action type 2 OT2 O heat 1 cool RC 900 Operation Manual 1 2001 25 OT2 value Default 1 OTPT Lockout output menu access OTPT O unlocked 1 read OTPT value 2 locked Default 0 OTY4 Examine serial communication type OTY4 0 19
9. Once stable control of the energy source 15 achieved tune the set to get good control at the device Cascade control checklist sure that the sensor 1 and sensor ft 2 are connected to proper location on the process In normal control sensor 1 is attached to the energy source and sensor 2 is attached to the DUT In normal control sensor 2 acts only as monitoring sensor to indicate DUT temperature It is not a part of the control loop In cascade control sensor is attached to the DUT and sensor 2 is attached to the energy source Both sensors are critical components of the control loop Failure to connect the sensors properly will result in erratic control Be sure that sensor is securely attached to the DUT in a location that best matches the desired temperature monitoring point as outlined in the test procedures e Be sure that sensor 2 is connected to the energy source e Set up the RC900 for cascade under control type and direct under cascade action in the Global menu See RC900 operation manual e Set the high and low range values for input 2 RL2 and RH2 in the Input menu Factory default is 10 for RL2 and 10 for RH2 Tune inner loop energy source PID set B values Tune the outer loop DUT PID set A values RC 900 Operation Manual 1 2001 35 Typical normal control application DUT is low profile and responds quickly to changes in thermal pla
10. advanced features it will be necessary to leave the home display and enter the configuration menus The default settings for the RC900 are stored in several different menus complete menu map with all of the factory default settings 15 located at the end of the manual To set the RC900 up for controlled rate of temperature change it is necessary to enter the GLOBAL menu and enable the RAMP feature WARNING ONLY CHANGE THE MENU SETTINGS THAT YOU ARE INSTRUCTED TO ALTER CHANGING OTHER PARAMETERS MAY CAUSE THE CONTROLLER TO OPERATE IMPROPERLY AND OR MALFUNCTION To enter the GLOBAL menu from the home display press the UP and DOWN arrow keys simultaneously for at least three 3 seconds or until you see the display change Note If no further keypad activity takes place for 60 seconds the display will automatically revert back to home Pressing the VIEW key at any time while in the configuration menus will also return you to the normal operation display The display should show one of the four 4 menus The menus are as follows InPt OtPt 9LbL COM e INPUT Menu The INPUT menu displayed InPt covers all of the sensor input parameters e OUTPUT Menu The OUTPUT menu displayed OtPt covers all of the heating and cooling output parameters e GLOBAL Menu The GLOBAL menu displayed 9LbL covers all of the global setup parameters e COMMUNICATIONS menu The COMMUNICATIONS menu displayed COM covers all of the remote communications setup paramet
11. minute The maximum RATE 0 to 999 degrees min ramp rate is limited by the platform performance RATE value Default 100 SOFT Software version revision SOFT 0to 26 0 A 26 Z SPI Set point for thermal platform temperature SPI to span SPI value No Default SPEE Write set point to EEPROM Set to 0 for remote SPEE O write 1 do not communications Resets to 1 at each power up SPEE value write Default 0 RC 900 Operation Manual 1 2001 27 Tables Table I ER2 command error codes 0 No error 1 Transmit buffer overflow 2 Receive buffer overflow 3 Framing error 4 Overrun error 5 Parity error 6 Talking out of turn 7 Invalid reply error 8 Noise error 20 Command not found 21 Prompt not found 22 Incomplete command line 23 Invalid character 24 Number of characters overflow 25 Input out of limit 26 Read only command 27 Write only command 28 Prompt not active 30 Request to RUN invalid 31 Request to HOLD invalid 32 Command invalid in RUN mode 33 Command invalid in HOLD mode 38 Asterisk not allowed 39 Infinite loop error Table 2 IN1 amp IN2 command values J type t c 32 to 1500 F 0 to 816 C type 328 to 2500 F 200 to 1371 C type 328 to 750 F 200 to 399 N type t c 32 to 2372 F 0 to 1300
12. properly then the outer loop PIDA set must be tuned Tuning the PID Values for Normal Control Normal control refers to single loop control Another section will cover tuning PID values for cascade control PID values are set at the factory and under normal conditions should not need to be changed However if you determine that your process requires adjustment of the PID values or you are using cascade control you may need to enter new PID values There are many good reference books available on PID This section is not meant to be an in depth study of PID but simply to provide basic hands technique for PID tuning There are other viable methods of determining good PID settings but the following method is one that has worked well for us Warning Improperly set PID values can cause erratic process control Do not attempt to change the PID values unless you have read and understand the following sections The effect of changed PID values on process is best observed when large change in process temperature occurs For example if you typically test at 85 degrees then good test of PID values would be to observe their effect on overshoot undershoot and stabilization time on process that begins at 25 degrees and ends at 85 degrees The greater the temperature change the more accurate the evaluation of the PID values will be Proper PID tuning starts by recording the current PID values for Proportional Reset and Rate and t
13. restart the profile RC 900 Operation Manual 1 2001 6 Note If at any time while you are entering values into the RC900 controller and there is no keypad activity for I minute the RC900 will automatically revert back to the home display The table below shows typical ramp and soak profile chart Making chart or graph of the desired profile is very helpful when programming the ramp amp soak profile STEP NUMBER STEP TYPE SET POINT VALUE RAMP RATE 1 SET POINT 100 10 STEP NUMBER STEP TYPE HOURS MINUTES SECONDS 2 SOAK 1 30 0 STEP NUMBER STEP TYPE SET POINT VALUE RAMP RATE 3 SET POINT 50 15 STEP NUMBER STEP TYPE HOURS MINUTES SECONDS 4 SOAK 0 45 0 STEP NUMBER STEP TYPE SET POINT VALUE RAMP RATE 5 SET POINT 20 10 STEP NUMBER STEP TYPE HOURS MINUTES SECONDS 6 SOAK 1 15 0 STEP NUMBER STEP TYPE JUMP TO STEP JUMP COUNT 7 JUMP 1 3 STEP NUMBER STEP TYPE END TYPE 8 END HOLD RC 900 Operation Manual 1 2001 Cascade Control Temperature control applications with long thermal lag times between the heat or cool source and the point where the temperature is being measured cannot be controlled accurately with conventional single loop control methods For this reason the primary temperature sensor is located in the thermal platform as close to the source of hea
14. 00 thereby prolonging the useful life of the EEPROM To command the RC900 not to write new set points received form the remote interface to EEPROM send the following string lt space gt SPEE gt space gt 1 lt carriage return or SPEE 1 You can check that the RC900 is not writing new set points to EEPROM by sending the following string space SPEE lt carriage return or SPEE If the RC900 returns a 1 then writing set point to EEPROM has been disabled If it returns 0 then it will write set points to the EEPROM It is only necessary to send the SPEE command at the beginning of a session unless the RC900 is powered down After every power down the RC900 always resets to a state whereby new set points received via the remote interface will be written to non volatile memory Brief Command Summary List Command Description Type Sample C1 Sensor 1 temperature Read only sp Cl lt cr gt C2 Sensor 2 temperature Read only sp C2 lt cr gt RP Enable Ramp Rate Mode Read amp Write lt sp gt RP lt sp gt 2 lt cr gt lt gt lt gt Ramp rate deg C min Read amp Write lt sp gt RATE lt sp gt 15 lt cr gt lt sp gt RATE lt cr gt SP1 Enter New Set Point Read amp Write lt sp gt SP1 lt sp gt 100 lt cr gt lt sp gt SP1 lt cr gt HIP Disable heat output Read amp Write lt sp gt HIP lt sp gt 0 lt cr gt lt sp gt HIP lt cr
15. TURE 3A 70 WAIT 2 80 GOTO 40 90 END Calibration The RC900 is factory calibrated and under normal conditions should not require calibration in the field However if is determined that calibration becomes necessary use the following procedure The RC900 is calibrated from the CAL calibration menu To carry out proper calibration the following equipment is necessary J reference compensator with reference junction at 32 degrees F O degrees or Type J thermocouple calibrator set at 32 degrees F 0 degrees Precision millivolt source 0 50mV minimum range 0 01mV resolution Setup and Calibration 1 With the MRTP powered off remove the cabinet cover and remove the thermocouple wires from terminals 9 amp 10 and 19 amp 20 2 For input 1 connect the millivolt source to terminal 9 and terminal 10 with 20 to 24 gauge copper wire For input 2 connect the millivolt source to terminal 19 and terminal 20 using 20 to 24 gauge copper wire 3 Apply power to the unit and let it warm up for 15 minutes After the warm up period is complete enter the CAL calibration menu by pressing the UP and DOWN arrow keys simultaneously for at least 6 seconds or until you see PLOC in the upper display and FctY in the lower display Press the UP arrow until you see CAL in the upper RC 900 Operation Manual 1 2001 14 display and FctY in the lower display Note Input 1 is referred to as and inp
16. and then it would turn off The cooling output would not turn on again until the process temperature reaches 71 degrees hysteresis of 2 0 degrees Note that the hysteresis is measured from the dead band turn off point and not from the set point As with dead band hysteresis is only factor when in an ON OFF control mode In proportional mode PB greater than zero hysteresis can be set to zero 0 Cycle time is the time required for the controller to complete one on off on cycle do not confuse with ON OFF control Cycle time is the period of time that the process controller can make an adjustment to the output duty cycle based on the error between set point and process temperature Duty cycle is the amount of time that the output remains energized during the cycle time period What this means is that the controller will break up the job of controlling the process temperature into little windows of time The duration of each time period is determined by the cycle time value Proportional control is often based on time and is therefore also referred to as time proportioning control This is how it works If you have a cycle time of 5 seconds and the PID control calls for an output duty cycle of 50 then the output will be on for 2 1 2 seconds and off for 2 1 2 seconds The duty cycle on time plus the off time will equal the cycle time period Likewise if the output duty cycle is 20 then there would be a 1 on time with 4
17. ature control sensor Cascade control is sophisticated approach to process control and requires careful set up to function properly It is recommended that you use it only if your application needs it and you understand completely the proper set up procedure To enable cascade control it is necessary to make hardware and software changes to the RC900 Hardware Configuration for Cascade Control The thermocouple sensors must be switched so that sensor 1 becomes the device sensor and sensor 2 becomes the thermal platform sensor In normal control sensor 1 is attached to the thermal platform and sensor 2 is attached to the device under test For cascade control sensor 1 must be attached to the device under test and sensor 2 must be attached to the thermal platform Sensors 1 and 2 can be re configured for cascade control by unplugging sensor 1 from the input 1 socket and unplugging sensor 2 from the input 2 socket Power down the RC900 before switching sensors to avoid a sensor fail condition that will occur if the sensors are disconnected during operation sensor fail condition self corrects when RC 900 Operation Manual 1 2001 8 the sensors re connected and the RC900 is powered off and then back on again Plug sensor 1 into the input 2 socket and plug sensor 2 into the input 1 socket The RC900 is now hardware configured for cascade control Proceed to the software configuration Warning Sensor connection
18. ayed response results in overshoot and undershoot or oscillations Oscillations as applied to process control refer to state where temperature overshoot and undershoot continue to occur over long period of time without diminishing In other words the error between set point and process temperature cannot be eliminated and stabilization never occurs process with long lag times or thermal gradients cannot be controlled precisely with single loop controller because energy would build up and cause thermal oscillations It may be possible to reduce the oscillations by using PID settings that minimize overshoot but the time it would take for the process to reach set point and stabilize would be unacceptably long Cascade utilizes two loops to provide precise control in long lag time process The two loops are described as the inner loop and the outer loop Each loop has a thermal sensor The sensor on the inner loop is located in close proximity to the energy source energy source is typically heater or coolant supply The sensor on the outer loop is located in close proximity to the DUT The inner loop energy sensor is used to prevent the excessive build up of energy The outer loop DUT sensor is used to provide precise temperature control of the DUT Cascade software in the controller is used to drive the energy output based on the input from the two sensors Cascade requires that temperature range be set for the energy sour
19. basic elements A process to be controlled a temperature sensor a temperature controller and energy source The sensor measures the process temperature compares it to the set point and drives an energy source to eliminate the error The error is the difference between the set point and actual process RC 900 Operation Manual 1 2001 29 temperature The second control loop determines the control action The control action is the response of the control output relative to the error between the process temperature and the set point Cascade is used to control difficult process where minimal overshoot and quick stabilization are desired difficult process is described as process in which there is long thermal lag or unacceptable thermal gradients Thermal lag refers to the time it takes for the process sensor to measure the effect of an increase or decrease in the heating or cooling output Long lag times can be caused by many conditions Poor sensor location and thermally insulated sensor are two possible causes thermal gradient is the difference in temperature between the device under test DUT and the process at stabilization DUT with large volume or mass poor thermal conduction or large and or varying heat dissipation can cause thermal gradients These conditions would require cascade for precise control Thermal lag causes lot of energy to be built up in the process before the sensor can detect a response Del
20. ce temperature range is the amount in degrees that the inner loop temperature energy source can exceed the set point in an effort to bring the DUT to the set point with minimal overshoot and the shortest stabilization time The range is a relative value based on the current set point There is high setting for the heat energy source and low setting for the cooling source The range high setting is positive number and the range low setting is negative number The range high and low settings are usually based on the maximum temperature gradient that you want to eliminate that occurs between the DUT and process when stabilization first occurs For example if a set point of 100 is selected there may be a RC 900 Operation Manual 1 2001 30 difference of several degrees between DUT temperature the process temperature The range setting allows the process to heat up beyond the set point to drive the device to 100 degrees The inner and outer loop each have their own set of PID variables to provide precise control loop must have the correct PID values in order for the cascade to function properly The inner loop energy source is assigned PID set B PIDB and the outer loop DUT is assigned PID set PIDA The inner loop PIDB set is tuned first Tuning is the process of entering PID variables and watching the effect on the process until satisfactory control and stabilization result Once the inner loop PIDB is set
21. different address can be set remotely via the GPIB interface For example to set new GPIB address of 720 do so in the following manner SYST COMM GPIB ADDR 20 Note Provide a 0 1 second delay after sending the new address before querying the new address setting To query the new address setting use the following command SYST COMM GPIB ADDR The GPIB port on the RC900 should respond with 20 If the RC900 responds with the correct new address then it should be saved to non volatile memory Do so with the following command SAV lt sp gt 0 Sample HP Basic program to change the GPIB address from 704 to 720 10 OUTPUT 704 SYST COMM GPIB ADDR 20 20 WAIT 0 1 30 OUTPUT 720 SYST COMM GPIB ADDR 40 ENTER 720 A 50 DISP A 60 WAIT 3 70 OUTPUT 720 SAV 0 80 END RC 900 Operation Manual 1 2001 13 The command strings used by the GPIB interface are identical to the ones used for the EIA 232 interface See the previous section on EIA 232 communications for details about command strings simple HP Basic sample program showing some typical command strings is shown below 10 OUTPUT 704 SPEE 1 set point changes not saved to EEPROM 20 OUTPUT 704 SP1 85 sends new set point of 85 degrees 30 OUTPUT 704 RATE 15 sets rate of change to 15 degrees C minute 40 OUTPUT 704 C1 queries channel 1 temperature 50 ENTER 704 A 60 DISP SENSOR 1 TEMPERA
22. ers NOTE Typically when you enter the menus the InPt INPUT menu is the first one displayed However if one of the other three 3 menus is displayed scroll through the menus by pressing the UP or DOWN arrow key until you see 9LbL GLOBAL shown in upper display and SEt SET shown in lower display Now press the MENU key to display the first parameter in the GLOBAL menu Continue to press the MENU key to scroll through the different parameters in the menu until you see OFF OFF shown in the upper display and rP RAMP shown in the lower display Using the UP and DOWN RC 900 Operation Manual 1 2001 4 arrow keys change the upper display to read StPt SETPOINT Press the MENU key again to set the rate of change You should see the factory default setting of 100 or a previously entered rate value shown the upper display and rAtE RATE shown in the lower display Press the DOWN arrow to set the desired maximum rate of temperature change in degrees C per minute Press the VIEW key to return to the home display You have now programmed the RC900 to change the thermal platform temperature at a rate of 10 degrees per minute This rate of change will be used every time new set point is entered unless you enter new rate value or set the rate control to OFF in the GLOBAL menu PROFILES The RC900 is capable of programming and running three 3 temperature and three 3 soak period profile The profile can be repeated up to 255 t
23. et Output I cycle time set PB2B Output 2 proportional band set B RE2B Output 2 reset set B RA2B Output 2 rate set B CT2B Output 2 cycle time set B DBB Dead band set B Tuning the PID Values for Cascade Control Tuning the PID values for cascade control mode is similar to normal control tuning The main difference is that there are two sets of PID values corresponding to the two sensor feedback loops The order is also critical In cascade mode you always tune the B set of PID values first The B set of PID values is assigned to the inner loop energy source After the set is tuned proceed to the set The set is assigned to the outer loop DUT The B set has a discreet set of values for output I and output 2 respectively The set has single set of PID values Cascade control enables difficult process to be controlled with minimal overshoot and rapid stabilization long lag time process cannot be precisely controlled with single loop approach because lot of energy can build up before response can be detected by the process sensor Built up energy causes overshoot and oscillations RC 900 Operation Manual 1 2001 34 aware that the Rate variable for set outer loop RA1A introduce instability into the process even more so that usual Use value of zero 0 if possible Using the charts provided tune the PID B set to achieve stable control as outlined in the charts
24. gt Enable heat output Read amp Write lt sp gt HIP lt sp gt 100 lt cr gt 2 lt gt lt gt Disable cool output Read amp Write lt sp gt LOP lt sp gt 0 lt cr gt lt sp gt LOP lt cr gt Enable cool output Read amp Write lt sp gt LOP lt sp gt 100 lt cr gt 2 lt sp gt LOP lt cr gt SPEE Set point not to EEPROM Read amp Write lt sp gt SPEE lt sp gt 1 lt cr gt sp SPEE cr RC 900 Operation Manual 1 2001 12 Note The HIP amp commands used to temporarily turn off and and or examine the current state of the heat and cool outputs The ability to turn off outputs is helpful when precise measurements need to be made and passive not heating or cooling thermal platform is desirable while taking measurements Note that to re enable the heat output positive 100 HIP value is needed and to re enable the cool output minus 100 100 LOP value must be entered GPIB 488 remote communications The RC900 can be fitted with factory or field installable GPIB IEEE 488 remote communications When the GPIB communications option is installed the EIA 232 communications interface remains usable However only one communication interface be used time switch on the rear of the cabinet next to the remote computer interface connectors must be set to either EIA 232 or GPIB communications The default address for the GPIB interface is set to 704
25. he desired set point and current thermal platform temperature in the lower display The DELTA T LED will light The next press will display the output duty cycle in percentage in the lower display The OUT LED will light The next press will show the temperature selected units in C or Celsius in the lower display A final press will return the display to the normal operation mode The VIEW key is also used to return to the normal operation display from within any of the configuration menu displays e MENU key The MENU key is used only when changing factory default parameters This will be covered in later chapters START STOP key This key is only used to start and stop ramp and soak profiles Profiles will be covered in a later chapter If the START STOP key is accidentally pressed an LED next to the START STOP key will flash and the display will change Press the START STOP key twice to return to the normal operation display If you have not already done so turn the controller on using the POWER switch on the front of the instrument chassis red STOP lamp should be lighted Take few minutes to familiarize yourself with the display Press the VIEW key to scroll through the various displays Use the UP and DOWN arrow keys to raise and lower the set point Using the VIEW key make sure that you are in the normal operation display the upper display should show the thermal platform temperature and the lower display shows the current
26. hen setting the three PID variables Proportional Reset and Rate to value of zero 0 There couple of other system values that need mentioning although they are not a part of the PID tuning procedure When setting up process there are some other terms that you should be aware of Dead Band or DB refers to the temperature band around the set point that determines when the output will shut off DB is only used in ON OFF control ON OFF control describes process that does not use proportional control such as home heating and air conditioning system If PB is set to zero 0 then value other than zero 0 must be entered for DB Without DB an ON OFF process could rapid RC 900 Operation Manual 1 2001 31 as soon as it hit set point Since all of our systems utilize proportional control the DB value is not important and should be set to zero 0 Hysteresis is the amount of change in the process temperature that is required to re energize the control output after it has shut off This is the temperature in an ON OFF process where the output will turn back on again after it has turned off For example in an ON OFF process when in cooling mode with dead band of 1 0 degrees and hysteresis of 2 0 degrees you would have the following action If the process is at 80 degrees and you enter new set point for 70 degrees the cooling output would turn on until the process reaches 69 DB of 1 0 degrees
27. ictured below RC900 9 pin connector IBM compatible 9 pin connector Pin 2 Pin 2 Pin 3 Pin 3 Pin 5 Pin 5 RC900 9 pin connector IBM compatible 25 pin connector Pin 2 Pin 3 Pin 3 Pin 2 Pin 5 Pin 7 The RC900 uses the following EIA 232 serial communications parameters Baud rate 9600 Data bits 8 Start bits 1 Stop bits 1 Parity None Protocol Xon Xoff Communications is carried out using ASCII characters in either upper or lower case Command Structure Returns the value of a specific command from the RC900 Sets a specific prompt in the RC900 to a specific value Information bracketed by lt gt indicates a description so lt space gt or lt sp gt indicates an ASCII character hex 20 a space made by the space bar For example if you want to send a new set point of 100 to the RC900 the ASCII string would look like the following lt space gt SP1 lt space gt 100 lt carriage return gt RC 900 Operation Manual 1 2001 or SP1 100 11 To read the current temperature of sensor use the following string space Cl1 carriage return or C1 Programming Note The RC900 writes all new set point commands from the remote interface to non volatile EEPROM memory The EEPROM is good for 10 000 writes When sending a new setpoint using the remote communications it is a good practice to disable the non volatile feature of the RC9
28. imes typical profile might have the thermal platform start at room temperature ramp at specific rate of temperature change to a high temperature soak at the high temperature for a given period of time ramp to low temperature soak at the low temperature for given period of time and return to room temperature the end of ramp and soak profile you can program the RC900 to either hold the final set point temperature or to turn the heating and cooling outputs off after the last soak period ends The Profile is made up of a maximum of eight 8 STEPS Each STEP is assigned type and then any data particular to the type of STEP selected For example a STEP that is defined as a StPt set point type initiates a ramp to a new set point and must contain the new set point value and the ramp rate Likewise a STEP defined as a SoAH soak type must contain a value that defines the length of time of the soak period at temperature in Hours Minutes and Seconds The second to last or seventh 7 step is always used to choose the number of profile repeats or loops You can repeat the profile from 0 to 255 times The last STEP or eighth 8 is always defined as an End end type and can be set to HoLd hold or OFF off If the End STEP is set to HoLd then RC900 will hold the thermal platform at the last set point temperature If set to OFF then the RC900 will turn off the heat and cool outputs and show OFF in the lower dis
29. n have your ramp and soak profile return to any step you want from step 1 to 6 This is selected in at the JStP JUMP to STEP prompt However in almost every case you will want to return to step 1 every time you repeat a ramp amp soak profile The last step step 8 is always an End END type step However you can choose to set the END type to be either HoLd HOLD or OFF OFF type A HOLD type will hold the thermal platform at the last set point of the profile typically step 5 indefinitely If OFF is selected for the END type then the RC900 will turn of the heat and cool outputs once the soak period for the last set point has ended OFF will be shown in the lower display when the profile has finished running When you finished programming all eight 8 steps of the ramp and soak profile press the VIEW key to return to the home display To run a ramp and soak profile press the START STOP key once You will see the start stop LED begin to flash This indicates that the RC900 is in standby mode ready to run the profile You will see StEP STEP in the lower display and 1 in the upper display Pressing the START STOP key again will initiate the ramp amp soak profile The start stop LED will be lighted continuously and the controller will begin driving the thermal platform to the first set point temperature During a profile pressing the START STOP key once will temporarily hold the profile Pressing the START STOP key again twice will
30. nds CTI value Default 1 0 seconds CT2B Output 2 cycle time for cooling PID set CT2B 0 2 to 999 seconds 5 second minimum for electromechanical device CT2B value Default 5 0 seconds DATE Factory test date DATE XX week YY year DBA Dead band PID set A do not use with proportional DBA 999 to 999 control enabled DBA value Default 0 DBB Dead band PID set B do not use with proportional 2 DBB 999 to 999 control enabled DBB value Default 0 RC 900 Operation Manual 1 2001 24 DEV Temperature deviation between set point amp thermal DEV Delta between SP and platform temperature platform temperature DIAG Lockout diagnostics menu DIAG O unlocked 1 read DIAG value 2 locked Default 0 EJC Elapsed repeat jump count cycles profile mode EJC 0 to 255 ER2 Communications error codes ER2 0 to 39 see table 1 FAIL Bumpless output action if sensor fails 1 100 FAIL 100 to 100 heats 1 to 100 cools FAIL value Default 1 cool FTRI Input I signal filter to smooth rapidly changing FTRI 60 to 60 seconds display typically not needed with thermocouples Default 0 2 Input 2 signal filter to smooth rapidly changing 2 60 to 60 seconds display typically not needed with thermocouples Default 0
31. ness OPERATION MANUAL FOR 900 Controller TABLE OF CONTENTS GETTING STARTED Ress Rosana DR 2 RATE CONTROL esenvarennnnanennnnannnnnnanennnnsnnnnansnennnnsnnnnunsnnnnnnsnnvnnnsnnnnnnsnnnnnnnnnnnnnnnnnnn 4 Ha 5 CASCADE 0000 8 GALIBRATION cese caves ere ave Fera ave ce us 14 RC 900 SOFTWARE 16 RC900 CONTROLLER DEFAULT 65 18 RC900 REMOTE COMMAND SUMMARY 22 24 TABLES 28 PID PRIMER ananavnnnanannnnanennnnansnnnnanannnnansnnnnansnnvnansnnnnnnsnnnnnnsnnnnnnennvnnnsennnnnnnennnnnnen 29 TUNING THE PID VALUES FOR NORMAL 31 Environmental Stress Systems Inc 21089 Longeway Road Sonora CA USA 95370 Tel 209 588 1993 Fax 209 588 1997 support essproducts com RC 900 Controller Getting Started If you are like most people you probably want to begin using your RC900 controller right away Before you begin please read this manual carefully to familiarize yourself with the proper operation of the RC900 Begin by getting aquainted with the display and functions of the keys The controller has been completely configured and tested at the factory and there is no need to modify any parameters before use ESS sonora USA Take a moment to familia
32. o arrow keys simultaneously for 6 seconds to reach the 3 FACTORY Fcty menus and use the arrows to select a menu FRONT PANEL LOCKOUT PLOC Press the MENU key to enter and navigate Lockout LOC Values see table 3 Diagnostic diA9 Calibration CAL RC 900 Operation Manual 1 2001 17 RC900 Controller Default Settings for LN2 or LCO2 Plates INPUT OUTPUT GLOBAL COMM SET SET SET SET T HT C 9600 IN1 OT1 CF BAUD 99 CL 1 8N RL1 OT2 FAIL DATA 130 NOR NLA ON RH1 CACN ERR PROT 0 OFF NOR 232 CAL AL2 CNTL INTF 0 OFF PID FTR1 OT3 AL90 T 1 NO IN2 COFF EI OFF OFF RSP ANUN 99 100 RL2 LOP 130 100 RH2 HIP 0 90 CAL2 ATSP 0 OFF FTR2 RP CONT POUT 2 GSD RC 900 Operation Manual 1 2001 18 RC900 controller default settings for LN2 LCO2 Plates PIDA OPER 15 PB1A 0 05 0 01 RAIA 1 0 CT1A 15 PB2A 0 05 RE2A 0 5 RA2A 5 0 2 0 DBA RC 900 Operation Manual 1 2001 RC900 Controller Default Settings for MRTP INPUT OUTPUT GLOBAL COMM SET SET SET SET T HT C 9600 IN1 OT1 CF BAUD 75 1 8N
33. play when the last soak period has ended Profile Programming It is very simple to program a ramp and soak profile from the front panel of the RC900 From the home display current set point in lower display and platform temperature in upper display press the MENU key once You should see OPEr OPERATION shown in the lower display and SYS shown in the upper display Press the UP or DOWN arrows until Pro9 PROGRAM is shown in the upper display Press the MENU key again you should see StEP STEP shown in the lower display and 1 the number 1 in the upper display If a 1 is not shown in the upper display press the DOWN arrow until it is To view the STEP type for STEP 1 press the MENU key once You should see StPt SET POINT in the upper display and StYP STEP TYPE in the lower display The RC 900 Operation Manual 1 2001 5 default type for Step 1 is always StPt set point Press the MENU key again to see the first set point SP will be in the lower display with value in the upper display denoting the first set point temperature Use the UP or DOWN arrow keys to raise or lower the value for the first set point Press the MENU key again to display the ramp rate rAtE RATE will be shown in the lower display with a value in the upper display denoting the rate of change Use the UP or DOWN arrow keys to raise or lower the ramp rate value Press the MENU key again to return to the StEP step display You are now ready to ente
34. r values for step 2 Using the UP arrow key change the number in the upper display to 2 Press the MENU key to show the step type screen Step 2 is usually a soak type step SoAH SOAK should be shown in the upper display If it isn t use the UP or DOWN arrow key to set Step 2 type to SoAH Press the MENU key to advance to the Hour hours display Using the UP or DOWN arrow keys set the number of hours for the soak If the soak is to be less than 1 hour then enter a zero 0 for hours Press the MENU key to advance to the Min minutes screen Repeat the process until you have set minutes and seconds for the step 2 soak period You have now successfully entered all of the values for the first ramp and soak segment Repeat the above process to enter new set points ramp rates and soak times for the remaining two 2 ramp and soak segments This will use the first six 6 of the available eight 8 steps The second to last step step 7 is used to enter the number of profile repeats and the step number to return to at each repeat In most cases you will want to return to step 1 at each repeat You can repeat a ramp amp soak profile from 0 up to 255 times The step type for step 7 is always JMP JUMP Press the MENU key to advance to JStP JUMP TO STEP display You should see JStP in the lower display and 1 in the upper display In most cases you will want the profile to return to the first step step 1 each time it repeats You ca
35. rize yourself with the front panel of the controller It is composed of the following components Upper Display Indicates the actual temperature of the thermal platform Lower Display Indicates the set point or desired temperature e Delta T LED If lighted indicates in the lower display the difference in degrees between the set point and actual temperature Output LEDs The four output LEDs indicate which output if any is energized Output LED 1 indicates heat Output LED 2 indicates cool Output LED 3 indicates the refrigeration compressor is operating Output 4 LED indicates remote communications is occurring OUT LED The percentage output LED when lighted indicates in the lower display the duty cycle of the currently energized output in percentage The duty cycle only applies to outputs utilizing proportional control Typically output 1 heat and output 2 cool RC 900 Operation Manual 1 2001 2 View Key The VIEW key is used to change what values are currently displayed Normally the typical view is thermal platform temperature in the upper display and set point or desired temperature in the lower display Pressing the view key will scroll through additional displays The first press of the VIEW key changes the display to show sensor 2 or user device probe temperature in the upper display This is indicated by Pr 2 probe 2 in the lower display The next press will display the difference in degrees between t
36. s in is necessary to enter the SYS system menu Press the MENU key once and you should see SYS in the lower display and OPEr OPERATION in the upper display Press the UP arrow until you see PidA PIDA in the upper display Press the MENU key and set the following PIDA parameters using the UP and DOWN arrows to change values and the MENU key to advance between menu items PIDA PB1A 20 RE1A 0 1 RA1A 0 5 After the last PID setting press the MENU key until you see the PidA in the upper display Press the UP arrow key to advance to PidB in the upper display Press the MENU key again and set the following PIDB parameters using the technique outlined above RC 900 Operation Manual 1 2001 9 PIDB PB1B 30 RE1B 0 10 RA1B 0 5 CT1B 1 0 PB2B 2 RE2B 0 25 RA2B 0 5 CT2B 5 0 DBB 0 Note The above values are recommended starting settings Your specific application may require adjustment of these values Consult the factory if you need help in setting cascade PID values Press the VIEW key to return to the home display The final values that must be entered are the rL2 range low input sensor 2 and rH2 range high input sensor 2 These values can be found in the InPt INPUT menu The values for rL2 and rH2 represent the high and low platform temperature limits beyond the set point that the thermal platform be driven to in order to eliminate temperature gradient between the set point and the actual device temperature In other words
37. s should only be reversed when using cascade control For normal control make sure sensors 1 is connected to input 1 and sensor 2 is connected to input 2 Software Configuration for Cascade Control To enable cascade control in software it is necessary to enter the GLOBAL menu See the above chapter Rate Control for details on how to enter and navigate menus In the GLOBAL menu scroll down until you see CntL CONTROL in the lower display and nor NORMAL in the upper display Use the UP or DOWN arrow key to change the upper display to CSCd CASCADE Press the MENU key again and verify that CSAC CASCADE ACTION is set to dir DIRECT If it isn t use the UP or DOWN arrow key to set it to dir Press the MENU key to enter the change Press the VIEW key to return to the home display Cascade control is now enabled Be sure the second device probe now sensor input 1 is connected to the device under test at a point where accurate temperature measurement is desired The device probe should be positively secured to the device under test by mechanical means such as a screw and washer assembly Remember that the second device probe is now a part of the closed loop temperature control system Failure to connect the second device probe or a poor thermal connection will cause unstable control or thermal runaway It is now necessary to change the Proportional Integral and Derivative PID variables for proper cascade control To change the PID setting
38. second off time The controller is constantly monitoring the error and will adjust the output duty cycle as necessary for each cycle time period The shorter the cycle time the more precise the control However very short cycle times can cause electromechanical devices to wear out prematurely good rule of thumb is to use minimum of 5 second cycle time for any output that utilizes an electromechanical device such as solenoid valve Devices such as resistive elements heaters can use as short a cycle time as desired because there are no moving parts to wear Cycle time for non electromechanical devices can be 1 second or less Burst or zero cross firing is term used to describe type of control method that can yield more precise control and longer energy source life It can only be used with devices that have no moving parts such as heater elements Burst firing repeatedly turns on and off full AC cycles It is also called zero cross firing because it switches close to the zero voltage point of the AC sine wave Burst firing selectively holds or transits AC cycles to achieve the desire output power level Burst firing offers much more precise method of RC 900 Operation Manual 1 2001 32 control with maximum of 1 66 second time base to minimum 33 3 millisecond time base Element life is also prolonged In a typical heat cool system there 15 separate set of PID values for the heat output and the cool output Output I is
39. set point Using the UP or DOWN arrow keys raise or lower the set point to the desired temperature When you are ready for the thermal platform to begin heating or cooling press the START switch on the front of the instrument chassis for moment then release it The START switch enables the thermal failsafe system If for any reason the thermal platform heats up beyond a safe operating point the failsafe thermostat attached to the thermal platform will disable the heating circuit Anytime that the heating circuit is disabled the red STOP lamp on the front of the instrument chassis will be lighted Momentarily pressing the START switch will enable the heating circuit The thermal platform should begin heating or cooling depending on whether the new set point is above or below the current thermal platform temperature The RC900 utilizes proportional control of the outputs to minimize overshoot and provide precise and stable temperature control RC 900 Operation Manual 1 2001 3 Rate Control The RC900 is capable of controlling the rate of change of the thermal platform For most users this is probably not an issue However if your device can be damaged by rapid changes in temperature most thermal platforms have 10 to 30 degree per minute maximum rate of change then you may want to take advantage of this feature Up till now we have explained how to operate the controller from the main or home display In order to activate the
40. tform temperature controller sensor 2 DUT sensor sensor 1 DUT Sensor thermal platform energy source Typical cascade control application DUT is high profile and responds slowly to changes in thermal platform temperature Normal control would allow unacceptable thermal gradients Moving single loop sensor to DUT would allow energy build up that would result in oscillations and instability sensor 1 DUT sensor sensor 2 enegy source sensor controller gy thermal platform energy source RC 900 Operation Manual 1 2001 36 Table 1 Proportional band setting overshoot 100 undershoot error T oscillations gt LLI Proportional band too small Increase PB 25 TIME undershoot 100 E lt 07 large droop error a gt Proportional band too large Decrease PB 25 TIME minimal overshoot 100 5 minimal droop lt a gt LLI Hr Proportional band correct Proceed to set Reset value 25 TIME RC 900 Operation Manual 1 2001 37 Table 2 Reset Integral setting e TEMPERATURE Reset too small Increase Reset value oscillations e TEMPERATURE Reset too large Decrease Reset value di e e TEMPERATURE Reset correct Proceed to set Rate value RC 900 Operation Manual 1 2001 38
41. ting and cooling as possible This approach works well for precise temperature control of the thermal platform with minimal overshoot However some components due to their size shape heat dissipation or physical construction can experience an unacceptable difference in temperature from that of the thermal platform Simply moving the sensor from the thermal platform to the device under test cannot eliminate this error Doing so will introduce thermal lag and cause the temperature control to become unstable simple but labor intensive way to eliminate the temperature error is to manually adjust the set point of the thermal platform until the desired device temperature is reached This can be effective if you are testing the identical type of device repetitively Unfortunately if the device changes in mass and or heat dissipation then additional manual adjustment of the set point will be required to eliminate varying thermal errors Cascade control eliminates the need for manual set point adjustment by adding an additional sensor attached to the device and using software to automatically eliminate thermal error while still maintaining precise control with minimal overshoot The RC900 is equipped with second device sensor and the necessary software to provide cascade control The second sensor is always active as read only device sensor input but the cascade software must be enabled and the hardware configured before it can be used as a temper
42. tion 98 COMMUNICATIONS COM Press the MENU key to enter and navigate Baud Rate Values 300 600 1200 2400 4800 9600 bits s Data dAtA Protocol Prot Choices Xon Xoff on Modbus Mod Full FULL Instrument IntF Choices EIA 232 232 EIA 485 485 RC 900 Operation Manual 1 2001 16 Press the MENU key once to reach the OPERATION OPEr menu and twice to reach the AUTO TUNE AUt menu OPERATION OPEr Use the arrow keys to navigate and the MENU key to enter SYSTEM SyS IF SOFTWARE CONTROL IS IN NORMAL MODE PID PidA Proportional Band 1 heating Pb1A Reset or Integral 1 heating rE1A Rate or Derivative 1 heating rA1A Cycle Time 1 heating Ct1A Proportional Band 2 cooling Pb2A Reset or Integral 2 cooling rE2A Rate or Derivative 2 cooling rA2A Cycle Time 2 cooling Ct2A Dead Band A db A PID B Pidb not accessible IF SOFTWARE CONTROL IS IN CASCADE MODE PID A PidA Proportional Band 1 cascade Pb1A Reset or Integral 1 cascade rE1A Rate or Derivative 1 cascade rA1A PID B Pidb Proportional Band 1 heating Pb1b Reset or Integral 1 heating rE1b Rate or Derivative 1 heating rA1b Cycle Time 2 heating Ct1b Proportional Band 2 cooling Pb2b Reset or Integral 2 cooling rE2b Rate or Derivative 2 cooling rA2b Cycle Time 2 cooling Ct2b Dead Band B db b PROGRAM Pro9 SEE PROFILE SECTION OF THE MANUAL AUTO TUNE AUt Value OFF Press the tw
43. to get the desired results Note A strip chart recorder or other data recorder such as a data logger is very helpful in determining the effect that a change in a PID setting has on the overall process In the absence of automated data recording equipment a watch with a second counter and a pad of notepaper can be used Record temperatures in as short of intervals as is practical for the most accurate results You can create your own charts similar to the ones at the end of the section using a connect the dot technique Once the PB value has been set correctly you should have minimal overshoot minimal droop and minimal oscillations Proceed to setting the Reset Integral value Carefully increase the Reset value until the droop is eliminated A good starting point would be a value of about 0 20 A Reset setting that is too high will re introduce oscillations into the process A Reset value that is to low will either not eliminate the droop or eliminate it over a very long period of time Once the Reset has been set correctly you should observe a single minimal overshoot followed by a single minimal undershoot with a droop that is eliminated in a short period of time followed by a stable process temperature with very little error At this point you can proceed to setting the Rate Derivative value The Rate or Derivative value can have a large and undesirable effect on the process if it is set too high Very carefully increase the Rate val
44. tput effort in proportion to the error from set point A control output is a signal action delivered in response to the difference between set point and process temperature An output usually controls a heating or cooling action The proportional range is referred to as a band and is usually measured in temperature units If a proportional band of 20 degrees is applied to a process that is 10 degrees below set point the heat output would be 50 percent The lower the proportional band the higher the gain Gain is the amount of amplification used in an electrical circuit Proportional band is sometimes referred to as gain The proportional band or PB is a range in which the proportioning function of the controller is active The PB units are usually expressed in degrees Integral is a control action that automatically eliminates droop or offset Offset is the same as droop and is the difference in temperature between the process temperature and the set point Droop or offset is a typical result when using proportional control Integral is also known as Reset Derivative is the rate of change in a process temperature Large values prevent overshoot but can cause sluggishness It is also known as Rate What is Cascade Cascade as it applies to the precise control of a process temperature is a control algorithm in which the output of one control loop provides the set point for another loop A control loop is a closed system comprised of four
45. typically the heat output and output 2 is typically the cool output PB1 would be the proportional band for output 1 and PB2 would be proportional band for output 2 In cascade control where you have two sets of PID values for each output you would have and PBIB is proportional band output 1 set A PB1B would be proportional band output 1 set B A chart later in this section will show all of the abbreviations with their explanations Tuning PID variables always starts with setting the proportional band for the output you are tuning with the Reset and Rate values set to 0 Since the different PID values are related it is best to work with one value at a time Once one value has been set properly the next value can be adjusted observing the effect it has on the process If you are tuning the heat output then you will be setting proportional band 1 first Start with the process at room temperature Enter a starting PB value of 10 and enter a set point of the highest temperature your process will typically be run at such as 100 degrees Watch the process heat up and observe the overshoot undershoot and if the oscillations decrease over time or stay the same It will be necessary to cool the process back down to room temperature when you change the PB value and to send the process back to 100 degrees to accurately observe the effect of the change on the process Study the charts below and adjust the PB value as necessary
46. ue to eliminate the initial minimal overshoot and undershoot If at any time oscillations are re introduced into the process then reduce the Rate value A good starting Rate value would be 0 05 In some cases it is best to leave the Rate value set to 0 If after RC 900 Operation Manual 1 2001 33 setting the PB and Reset correctly you observe oscillations when Rate value is added return the Rate value to 0 general rule any time there are unacceptable oscillations observed in process then one of the PID values is set incorrectly The advantage of setting one value time in the exact order outlined above is that it is easy to identify which PID value is introducing the undesirable oscillations and to make the necessary adjustment Once the PID values have been correctly set for output 1 proceed to set the output 2 values in the same manner as outlined above Keep in mind that the graphs provided would be inverted when you are tuning for process temperatures below ambient PID abbreviations table Output 1 proportional band set REIA Output I reset set A RAIA Output rate set A CTIA Output 1 cycle time set A PB2A Output 2 proportional band set A RE2A Output 2 reset set A RA2A Output 2 rate set A CT2A Output 2 cycle time set A DBA Dead band set A PBIB Output 1 proportional band set REIB Output reset set B Output I rate s
47. ut 2 is referred to as Always calibrate input 1 or first followed by input 2 4 Press the MENU key to enter the calibration menu At the 50 prompt or the B 50 prompt and with the 50 millivolt source connected to the proper terminals wait 10 seconds for stabilization and then press the UP arrow key to enter YES in the upper display Disregard all other prompts Press the MENU key to save the new data and to advance to the next prompt 5 Atthe 00 prompt or the 00 prompt enter 0 00mV from the millivolt source to the proper terminals Allow 10 seconds to stabilize Press the UP arrow key to enter YES in the UPPER display Disregard all other prompts Press the MENU key 6 At the te prompt disconnect the millivolt source and connect the reference compensator or thermocouple calibrator to terminal 9 and terminal 10 If using a compensator turn it on and short the input wires When using a J type calibrator set it to simulate 32 degree F O degrees C Allow 10 seconds for stabilization Press the UP arrow key to change the UPPER display to YES Disregard all other prompts To conclude the calibration process press the VIEW key to return to the home display Restore Calibration If you make a mistake while calibrating your RC900 the rSt restore prompt near the end of the calibration menu can be used to restore the original factory calibration settings At the rSt prompt press the UP arrow key to sho
48. w a YES in the UPPER display Press the MENU key and the original factory values are restored RC 900 Operation Manual 1 2001 15 RC 900 Software Press the two arrow keys simultaneously for 3 seconds to reach the 4 SET SEt menus and use the arrows to select menu INPUT InPt Press the MENU key to enter and navigate Input 1 In1 Values see table 2 Range Low 1 rL1 Range High 1 rH1 Calibration 1 Input Filtering 1 Ftr1 Input 2 In2 Values see table 2 Range Low 2 rL2 Range High 2 rH2 Calibration 2 CAL2 Filter 2 Ftr2 OUTPUT OtPt Press the MENU key to enter and navigate Output 1 Ot1 Value Heat Ht Output 2 Ot2 Value Cool CL Cooling Action CACn Alarm 2 AL2 Outpout 3 Ot3 Interval Time Int Value in minutes Compressor OFF Time CoFF Value in minutes GLOBAL 9LbL Press the MENU key to enter and navigate Temperature units C_F Values Celsius C or Fahrenheit F Sensor Failure Output Function FAIL Error Latching Enable Err Software Control CntL Values normal nor or cascade CSCd Cascade action CSAC Algorithm AL9O Event Input 1 Function Fil Alarm Annunciation Anun Power limit percentage for Output 2 cooling LoP Value 100 Power limit percentage for Output 1 heating HiP Value 100 Auto tune Set Point Ramping initiation rP if not off then RATE appears Power Outage Pout Values see table 4 Guaranteed Soak Devia
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