Programmable Ramp / Soak PID Temperature Controller For High Temperature Furnace (20 digit display Model: PRC-312) Model Wise Descriptions: Sr. No Model Product Description 12.5 PRC-312-F 12.6 PRC-312-U Ramp/Soak programmable PID temperature controller with single fixed input and 10 profiles - each of 16 steps. Ramp/Soak programmable PID temperature controller with single universal input and 10 profiles - each of 16 steps. Description: Libratherm offers Microcontroller based multiple Ramp / Soak programmable PID temperature controller Model PRC-312, which is designed to improve reliability, accuracy and control for all processing applications. It features Ramp and Soak functions (the capability to control the temperature and its rate of change over a predetermined time span). One to ten different patterns each of total sixteen (ramp/soak) steps can be programmed into the memory using the front panel membrane keyboard. Separate displays are provided to monitor simultaneously the Process temperature, Set temperature, Program number, step number, safety temperature and remaining time of the profile in progress. Servo start and auto tracking facilities are additional useful features available in this model. Multiple display allows user to view the program status at a glance, without having to press multiple keys. The front panel LED graph shows the status of current step in progress, whether heating ramp, cooling ramp or soaking step. PRC-312 can also be used as single set point control when the profile control is not desired. Inputs can be Thermocouple, IR sensors, RTD Sensors or from transmitters generating voltage or current signal. PRC-312 offers both switching outputs in the form of SSR or triac to drive external load contactor and linear control output in the form of (4-20)mA or (0-5)volt etc., which can be used to control heater power through Thyristor power pack (for electrical heating system) or to control the position of a modulating motor valve (for oil or gas fired heating systems). The analog outputs can be directly connected to Libratherm make single phase / three phase SCR based phase angle control power 1
regulators, which is ideally suitable for both resistive and inductive heating loads. Additional 4 relays are also provided for time or temperature dependent event outputs as per the system requirement. The programmed profile and other parameters are retained in the nonvolatile memory in the event of power failure for automatic resumption from the last point. To monitor the on line temperature profile of the heating system on the computer screen, serial digital interface on RS 485 MODBUS RTU protocol is available. Libratherm provides window based software to view the on line behavior of the heating system in both graphical and tabular format. Features: Accepts standard type of thermocouple or RTD (Pt-100)/2 or 3-wire input. Servo start from the process temperature. Auto tracking and run the program from the desired step User programmable 10 different ramp/soak patterns Retention of programmed parameters in the internal memory Resumption of program from last step in case of power failure Facility of delayed start of heating cycle. Facility to use as analog/time proportional PID or ON / OFF controller. Security lock for unauthorized tampering of the PID and profile values. Applications: Heat Treatment Investment casting in jewellery and automobile industry Metallurgical / Ceramic research Furnace / oven control 2
Technical Specifications: Design Input Range Resolution Indicating Accuracy Display (PRC-312) Tuning Control Algorithm PID values Control mode Set Point Microcontroller based with 12 or 16 bit ADC and 12 bit DAC Thermocouple type J, K, R, S, B or RTD (Pt-100)/2 or 3-wire, ( 4-20)mA, (0-10)VDC. User selectable through keyboard. Subject to the full range of the specified input. 0.1 / 1 o C Subject to the specified input and range. Better than ± 0.1% of the range ( by software linearization of curves) 4 digit 0.5 for Process value, 4 digit 0.5 for set value 2 digit 0.3 for current Program number, 2 digit 0.3 for step number 4 digit 0.3 for safety temperature and 4 digit 0.3 for remaining time of the current step. Auto / Manual tuning of PID values. PID mode for heating control - (reverse action) On/Off mode with programmable hysteresis. Proportional Band (P)= 0.0 to 100.0% of Span, Integral value (I)= 0.00 to 5.00 resets/minute, Derivative value (D) = 0.00 to 5.00 minutes Cycle Time (CYC)= 2 to 100 seconds, On/Off Hysterisis (HYSt)= 0 to 10 o C, Single set point or Ramp/Soak profile mode user selectable Programmable throughout the range. In single set point control mode, the set point can be changed. Soft Start (rt) and Power Limit (PL) Built in power on soft start (rt) for analog output = 1 to 100 seconds. Power Limit to restrict the analog control output = 1 to 100 %. Auto/Manual /Standbye mode Auto to Manual and Manual to Auto mode (Bump less transfer of control output) Control Outputs a) 10V DC pulses to drive external SSR and b) (4-20) ma, RL max = 300 Ohms. or c) (0-5)VDC, RL min = 10K ohms. Remote Set point (optional) External 4-20mA can be accepted to change the set point as desired. Digital Input (optional) External 2 nos. of DC pulse/contact can be used as desired. Retransmission Output (optional) Analog 4-20mA or 0-10VDC linearized and proportional to process temperature. Ramp/Soak Steps 1 to 16 Steps. (no restrictions in programming a ramp can be followed by a ramp and a soak can be followed by a soak). Set Temperature Programmable for each steps in the full range of the specified input Time per each Ramp/Soak Step Profile Link facility (optional) Program Hold Facility Run from desired step number (rfsn) 1 to 999 mins. (16 Hrs. per step) Or 1 minute to 100 hours (Two or more steps can be combined for longer time duration). (Two or more profiles can be linked for longer time duration max. 16000 hours or 666 days). Manual Hold or Auto Hold (Hold back feature for guaranteed Ramp/Soak facility). This rfsn facility allows user to skip the ramp/soak steps and run the profile from the desired step number. With servo start facility (to start 3
Memory Backup Alarm Outputs Serial Communication (Optional) Supply Size Panel cut out Enclosure the step from the current furnace temperature) the rate of heating/cooling can be kept same. Retention of PID and set values in the non-volatile memory in the event of power failure. Configurable Alarms for High or Low, End of Profile Alarm Relay (contacts rated for 5A @ 230VAC). Optically isolated RS485 on Modbus RTU protocol. (in Slave mode with programmable slave ID). 230 VAC ± 10% ( approx. 5VA), 50/60Hz. 192 x 96 x 160 mm 186 x 92 mm +/- 0.5 mm Metal Powder coated with ABS bazzel and polycarbonate front. Input and Range Selection Table: Code Input Range A0 User selectable J,K,R,S,B,Pt-100 and 4-20mA As below A1 J type : Fe/Con thermocouple 0 to 760 o C A2 K type : Cr/Al thermocouple 0 to 1372 o C A3 R type : Pt/PtRh13% thermocouple 0 to 1768 o C A4 S type : Pt/PtRh10% - thermocouple 0 to 1768 o C A5 B type : Pt30%Rh/Pt6%Rh thermocouple 200 to 1820 o C A6 C type : W5%Re/W26%Re thermocouple 0 to 2200 o C A7 D type : W3%Re/W25%Re thermocouple 0 to 2200 o C A8 Pt-100 (Alpha = 0.00385) DIN 43760 0.0 to 400.0 o C A9 Oxygen probe 0 to 1200mV A10 4-20mA Infrared pyrometer (scalable range ) 0 to 3000 o C Ordering Information: Model A- Input B- Retransmission C- Control o/p D- Relay-1 / 2 (OUT1 / OUT2) E- Relay-3/4 (OUT3 / OUT4) F- Serial Communication PRC-312-F PRC-312-U A0 User selectable Single Fixed Input (any one of A1 to A10 ) B1- (4-20)mA B2-(0-5)V B3-(0-10)V 00 - None C1- (DC pulse) C2- (0-5) V C3- (4-20) ma C4- (DC pulse + 4-20mA) C5 -- (DC pulse + 0-5V) D1- (High Alarm) D2- (Low Alarm) 00- (None) Any one relay can be used E1- (High Alarm) E2- (Low Alarm) E3- (End of Profile) 00- (None) Any one relay can be used F1 - RS485 00 None Example: Model A- Single Input B- Retrans. C- Control o/p D- Relay-1/2 E- Relay-3/4 F- Serial Communication PRC-312-F A2 00 C1 D1 E3 00 PRC-312-U A0 00 C2 D1 E3 F1 4
Closed Loop Control Schematic: EPRC-312 software features - Libratherm provides customized window based computer software on a single CD, Which is very useful to log real time furnace temperature. The software can be loaded on the computer hard disk and controller PRC-312 can be interfaced to the same computer using RS485 to 232 or USB convertor. The software allows user to operate the controller through PC to program the PID values, Ramp/Soak profile and also allows user to monitor the online behavior of heating system either in the graphical format or in the tabular format. The special features allows user to feed the information related to the heating cycle such as operator name, batch name, heat number, co.name etc, so that the information is visible on the computer screen and the same can be taken on the print format. The historical trends can be searched using these field as well as by giving the desired date and time information. The software is user friendly and easy to operate. 5