masibus DIGITAL CONTROLLER 5002U Ref No: m55a/om/101 Issue No: 08 Operator s Manual Operator s Manual Page 1 of 20

Transcription

1 Operator s Manual DIGITAL CONTROLLER 5002U Operator s Manual Page 1 of 20

2 CONTENTS 1. TECHNICAL DETAILS 2. SPECIFICATIONS 3. DIMENSIONS & PANEL CUTOUT 4. FRONT FASCIA 5. CONNECTIONS DETAIL 6. USER GUIDE 7. MODE OF OPERATION 8. MODBUS DETAIL (OPTIONAL) 9. COMMUNICATION PARAMETERS 10. TROUBLE SHOOTING Operator s Manual Page 2 of 20

3 1. TECHNICAL DETAILS This is a versatile microprocessor based ON/OFF controller with a very high performance to price ratio. The features offered in this product are better than any other controller available in similar price range. The instrument is made in 96 x 96 x 180 mm³ size with standard cutout of 92 x 92 mm². Front is sealed membrane type to withstand dusty environment. On back plate, PCB soldered terminals are used. The programming and calibration of the instrument is done by a 4-button keypad, equipped with two independent displays for set point and process variable. Set point display is kept 0.3 to differentiate it from process variable display. Status of control/alarm relays and presently displayed set point are displayed by 3 mm red LED. The operation of the instrument is menu- driven with user-friendly prompts. Provision for zero and span setting is made to restrict range of usage and programming. This restricts accidental wrong setting of set-point beyond the range of interest. Outside this range the unit will indicate temperature as 'OVER' for some abnormal condition. This zero and span setting is used for linear inputs for setting the range between to 9999 counts. Also, the unit has an optional provision for isolated linearzed retransmission signal or isolated serial communication using RS-485. Retransmission signal is useful for recorder or secondary display. The output can be 4-20 ma for the programmed range or 1 mv/degree (1-5V) for thermocouple types so that an ordinary DPM can be connected to this signal for remote indication of temperature. The product is made to accept all the Ten standard thermocouple inputs, PT100 RTD, 4-20 Ma, 0-5 VDC and 0-2V inputs. It is available as a single input version or field selectable input version. In case of thermocouple type of instrument, the type of input can be changed in field itself. The calibration of the unit is done without trimpots. The unit can be calibrated in installed condition itself by front panel keys at any given point i.e. user need not feed a fixed signal. All thermocouples and RTD inputs are linearized for 0.1% accuracy through out range. RTD input comes with 0.1 degree indication for entire range. Three set-points with individual Hysteresis are provided with separate relays. The set-points can be programmed as control or alarm type, relay on below or above set-point, as deviation from main set-point and control outside band or control inside band. This entire configuration can be done on-line without opening the unit. Operator s Manual Page 3 of 20

4 2. SPECIFICATIONS DISPLAY 4 digit 0.56" Red LEDs for Process Variable 4 digit 0.3" Red LEDs for Set Point Individual discrete Red LEDs to indicate relay status, set point selection, and serial transmit and receive indication. INPUT Thermo-couple types B,C E, J, G, K, N, R, S & T (ANSI standard) RTD - PT100 3-wire 4-20mA & 0-20mA linear 1-5 V dc & 0-5 V dc linear mv dc linear 0-2V dc linear Input field selectable. Other types on request Cold junction compensation automatic for thermocouples Accuracy: +/- 1 +/- 0.1% of Span Input open protection upscale Input Impedance: >1MΩ (for DC Volt/mV input) Input Impedance : <100 Ω (for DC Current input) RANGE E -200 to 1000 ºC J -200 to 1200 ºC K -200 to 1372 ºC T -200 to 400 ºC B 450 to 1820 ºC R 0 to 1768 ºC S 0 to 1768 ºC N -200 to 1300 ºC G 0 to 2320 ºC C 0 to 2320 ºC PT to ºC 4-20 ma dc to ma dc to V dc to V dc to mv dc to V dc + 0 to 2000 [Configurable Input Voltage Scale] + If Input type is fixed [Factory set] to 0-2V dc then other input type are not applicable. [for O 2 measurement] CONTROL/ALARM OUTPUT Up to three set-points with individual relay output rated for 2A@230V ac; selectable for alarm or control. Setpoint 2 and 3 can be absolute or deviation type. Individual Hysteresis setting: 0 to 99 Relays: configurable to energize or de-energize above set-points Calibration Ambient, Zero and Span adjusted by digital calibration through front panel keys One shot calibration of both input and output CONTROL KEYS AND TERMINALS Set, Increase, Decrease and Enter keys for operation, programming and calibration GENERAL Power supply: 110V/230V ac 50Hz (Internal Jumper selectable), 24V DC (optional) or 24V AC (optional) Ambient Temperature: 0 to 55 C Humidity: 20% to 95% RH non-condensing Power consumption: Less than 10 VA PHYSICAL Case: M.S. powder coated with ABS molded bezel Terminals: PCB type terminal block can accept up to 2.5 mm² wire Bezel size: 96 X 96 mm² Depth behind Panel: 200 mm maximum including Operator s Manual Page 4 of 20

5 terminals Panel cutout: 92 X 92 mm² 3. DIMENSIONS & PANEL CUTOUT Isolated Transmitted Power Supply No of Supply : 1 Voltage Rating : 24 V 20 ma Isolated output Isolation : 500 V dc Isolated Serial Communication (Optional *) Communication standard: RS-485 Communication Protocol: Modbus RTU Distance of Communication: 1200 meter (Twisted pair cable as per EIA 485 standard) Maximum Slaves: 32 without repeaters Isolation: 500 V dc Isolated Retransmission (Optional *) No of Output: 1. Output Type: 4-20 ma Isolated.. O/P**. Load Impedance: 250 ohms max. Accuracy: Isolation: 0.25 % of Full scale. 500 VDC * Note: 5002u digital controller will come with Isolated serial or Isolated retransmission O/P. - ** Note: 5002u digital controller with 0-2V input type only has facility of configurable RX output. User can set zero and span for RX output in configuration mode. Operator s Manual Page 5 of 20

6 4. FRONT FASCIA PV : Process Value SV : Default Set-Point Value RL1,RL2,RL3:Relay Status On/Off Some application RL1 is not used, RL2 is used for Alert Operation & RL3 is used for danger Operation RX,TX: Serial Data Transmit and Receive Status SP1, SP2,SP3:Default Set-points Displayed on SV Window SET: Indexing Parameter in Various Modes ENTER: Saves Desired Parameter in Various Mode INCR: Increments the Selected Parameter Value to Desired Value DECR: Decrements the Selected Parameter Value to Desired Value Note: Here Terminal Nos. are shown (which are not marked on back plate), for the purpose of explanation only. Here some terminals may not be available, if they are not applicable as per Purchase order. 5. CONNECTIONS DETAIL The description of the Back Panel terminals is as follows: No. Description 1 Input IN+ Sensor Input 2 Input IN - ( T/C or RTD or 3 C+(Com of RTD I/P) Linear type ) 4 +24V Output 24V D.C. 5-24V Output TPS o/p 6 + ma output Re-transmission 7 - ma output Output V / Line Mains 9-24V / Neutral Supply 10 Earth 11 Common Relay 1 output 12 Normally Open rated for 230V ac 13 Normally 2A 14 Common Relay 2 output 15 Normally Open rated for 230V ac 16 Normally 2A 17 Common Relay 3 output 18 Normally Open rated for 230V ac 19 Normally 2A 20 TXD Serial Communication 21 RXD RS485 Operator s Manual Page 6 of 20

7 6. USER GUIDE 6.1 INTRODUCTION DTC 5002U is an on-off controller userfriendly key-pad and display for guiding the user with programming and calibration operation. The manual covers all aspects of operation of the instrument. Users are requested to go read the instructions carefully before altering any configuration. 6.2 POWER SUPPLY Before connecting power to the instrument ensure that you are connecting right input voltage to right terminal. The instrument is having terminals for both 110V ac and 230V ac or 24V dc. On application of correct power supply, the instrument will display input type set, for five seconds. Once the input is applied, its value will be displayed in PV window and presently selected set-points will be displayed in the SV display along with appropriate set-point LED. 6.3 KEY BOARD There are four keys for operation of the instrument. SELECT (SET) This key is used for programming set points. Set-points data can be checked and reprogrammed by this key. First press select key, it will display setpoint parameter. By pressing INC/DEC keys value of the set-points and Hysteresis can be changed as desired. Bring the set-point at a desired value and press enter key for storing the value permanently. On pressing of enter key the display shows the parameter prompt. On pressing of set key next parameter in sequence are selected and changed by the same procedure. The parameters in sequence are: Sp1 Setpoint1 Hys1 Hysteresis for first set-point Sp2 Setpoint2 Hys2 Hysteresis for second set-point Sp3 Setpoint3 Hys3 Hysteresis for Third set-point After the last parameter display will go back to normal run mode. If no key is pressed for 20 seconds, the display will fall back to normal run mode. To exit from any mode to normal run mode press select key for 3 seconds. ENTER This key is used for entering into mode (CALb Or ConF) and for entering the value of the selected parameter. After setting the data to proper value, if enter key is pressed, the data will be permanently stored in non-volatile memory. On pressing of enter key, display shows the parameter which you have entered. Now data change is not possible until Enter key pressed once again. On pressing of Enter key decimal point on last digit will glow and allow changing data. INC ( ) This key will increment the selected parameter value by one count in all operating mode. If the key is pressed continuously than the rate of increment will be made five times faster. This facility is called dual speed increment facility to allow faster data change for higher values. This key is also used to move into different mode (calibration and configuration). DEC ( ) This key is used to select the desired operating mode and parameter in various operating modes. On first press of this key in RUN mode for 3 second, it will display PASS in PV (Process value) window. PASS Operator s Manual Page 7 of 20

8 Now, setting correct value of password in SV (set value) window and pressing enter key mode will be displayed. mode By pressing INC/DEC Key, user can view operating modes (CALb Or ConF) in PV (Process value) window and by pressing Enter key unit will enter into that particular operating mode. Conf Calb After Entering into operating mode (CALb Or ConF), first parameter will be displayed in SV window and by Pressing select key subsequent parameter will be displayed. Corresponding parameter values will be displayed in PV window. By pressing INC/DEC Key, user can select desired value and by pressing ENTER Key, user can store selected value. After the last parameter is displayed, pressing of SEL key for 3 second will bring the instrument in Run mode. This key will also decrement the selected parameter value by one count in all operation modes. If the key is pressed continuously than the rate of decrement will be made five times faster. This facility is called dual speed decrement facility to allow faster data change for higher values. This key is also used to move onto different mode (calibration and configuration). 7. MODE OF OPERATION There are five modes of operations. Run mode Password mode Program mode Configuration mode Calibration mode Before looking into various modes of operations, it will be better to understand some fundamentals for various types of set-points and effect of Hysteresis on relay operation. 7.1 SET-POINTS & HYSTERESIS EFFECTS For set-points selection, there are three different options, which can be selected for a particular set-point. On-Above/On-Below Set-point If user selects on above set-point option, the relay will be energized when the process variable is more than set variable. In case of on below set-point operation of relay is reverse. Control/ Alarm Set-point In the case of control set-point the Hysteresis effect is different from alarm type. In case of alarm set-point, the relay can be acknowledged on pressing of ENTER key in run mode. So, this selection should be done carefully according to application. Absolute/ Deviation Set-point Deviation option is applicable only for second and third set-points. In case of deviation set-point, it is added to the first set-point to derive the actual setpoint. This set-point selection can be done by changing the configuration. Refer to section on reconfiguration elsewhere in this manual. Now, let us see an example to illustrate the effect of Hysteresis setting on relay operation. For control set-point and alarm set-point the effect of Hysteresis is little different so we will consider each case separately. Suppose you have selected a set-point of 200 and Hysteresis of 5. Also the setting is for control type and on below set-point. So in this case the Hysteresis effect is applicable while turning ON the relay. The relay will turn off exactly at 200 after being turned on. But it will not turn on once again until temperature falls below = 195. This provides a band of 5 around the set-point. In Operator s Manual Page 8 of 20

9 case of on above set-point type, the operation will be reverse. Now suppose you have kept same setpoint of 200 and Hysteresis of 5. Setpoint type is alarm and on below setpoint. In this case the Hysteresis effect will be applicable while turning OFF the relay. The relay will turn ON when the process value goes below 200. But it will not turn OFF until the temperature goes beyond = 205. This provides a band of 5 around the set-point. In case of on above set-point type, the operation will be reverse. Band Set-point In case of band set point main set point is taken as a reference and band set point is distributed both side of main set point equally. If either of the key is kept pressed continuously for more than 10 counts change in setting, it will start incrementing or decrementing the data at a five time faster rate. Bring the setpoint at a desired value and press enter key for storing the value permanently. On pressing of enter key the display shows the parameter prompt. On pressing of select key other parameter in sequence are selected and changed by the same procedure. The parameters in sequence are: Sp1 Setpoint1 Hys1 Hysteresis for first set-point Sp2 Setpoint2 Hys2 Hysteresis for second set-point Sp3 Setpoint3 Hys3 Hysteresis for Third set-point 7.2 RUN MODE This is normal mode of display. From other modes of operations, display falls back to this mode if no key is pressed for 20 seconds. In this mode PV display will show value of input signal and SV display will show the selected set-point for normal display. 7.3 PASSWORD MODE In Run mode on first press of DEC key for 3 second, it shows password mode. By setting correct password in SV(Set value) window and pressing enter key display will show menu mode. but if password is wrong than it comes back to the run mode. 7.4 PROGRAM MODE This mode is used for programming setpoints. In this mode set-points data can be checked and reprogrammed. For entering this mode press select key, It will display first set-point parameter. By pressing INC/DEC keys value of the set-points and Hysteresis can be changed as desired. After the last parameter display will go back to normal run mode. If no key is pressed for 20 seconds, the display will fall back to normal run mode. 7.5 CONFIGURATION MODE This mode is useful for changing the basic configuration of the unit. No hardware changes are necessary for changing input type. It can be changed by just using front keys. For entering this mode press DEC key for 3 seconds, PASS will be displayed, now enter correct password and press enter key to enter in menu mode. Now press INC ( ) and DEC ( ) for selecting Configuration mode Conf. Now if Enter key is pressed the unit will enter in the configuration mode and will display input Inpt as first configuration mode. These parameters can be changed by increment, decrement and enter keys as described earlier. User can select parameter to be programmed by SET key. The parameters which can be changed by this mode are described below in sequence in which they are displayed. Operator s Manual Page 9 of 20

10 First we will see the meaning of various prompts displayed. Inpt zero SpaN NOSP Tsp1 Tsp2 Tsp3 D SP dp OPSE PASS init SLOt Byps Input type Zero setting Span setting Number of set-point Type of first set-point Type of second set-point Type of third set-point Default Display set-point Decimal point position Open sensor Password Initialization Slot configuration Bypass selection[used to bypass 3 rd Relay and RL3 LED Indication in front] srno Serial No baud Baud Rate rt-z RX zero setting [ Applicable for 0-2V input and Retransmission Option ] rt-s RX span setting [ Applicable for 0-2V input and Retransmission Option ] 7.6 Input Type Type of input is displayed as code for input type. The type of inputs available is E, J, K, T, B, R, S, N, G,C, RTD, 4-20 ma DC, 0-20 ma DC and 0-5 Volt DC, 1-5 Volt DC, mv DC, 0-2 Volt DC with display prompt shown below. Input type can be selected by INC key or DEC key. Input type and each type of input are displayed by prompt as follows. Inpt E-tc input -200 to J-tc input -200 to 1200 K-tc input 200 To T-tc input -200 to 400 B-tc input 450 to R-tc input 0 to 1768 S-tc input 0 to 1768 N-tc input -200 to G-tc input 0 to C-tc input 0 to Rtd input 0.1 deg. Resolution to ma input to ma input to V input to V input to mv input to V input 0 to For changing of input type, no internal hardware changes are required. When an input type is selected its corresponding zero and span range is automatically adjusted as per its table. However if user wants to change zero and span as required he can move to the zero or span prompt and can change. With this facility if the same input is selected (i.e. ENTER key is pressed on the same input), its zero and span range is kept as it is. For setting the range as per the table one has to change the input type only. Refer corresponding range as per the inputs. ZERO & SPAN These settings are for specifying minimum and maximum range of operation. Although full sensor input range is supported, user can select his range of operation. The set-point cannot be set below zero setting and above the span setting. The reading will display over when the input is below zero setting by 5% or above span setting by 5%. This 5% is calculated for the difference of zero and span settings. Extreme limits for thermocouple and RTD types for the setting are sensor limits. zero span Zero and span setting are used for selecting range for all inputs. This allows selecting any value between to 9999 for the range of the all. Operator s Manual Page 10 of 20

11 This range can be changed any time, to make instrument usable for any type of 4-20 ma output transmitters or such other instrument. Number of Set-points Number of set-points is normally fixed at factory to 1, 2 or 3 depending upon specifications given while ordering. However, user can reduce no. of setpoints from actual if all of them are not used. The programmed no. of setpoint is displayed in program modes. Type of Set-point The type of set-point is independently programmable for each set-point. So, in configuration mode you get three different settings. This selection is programmed by a code among 0 to 11. For first set-point code available is 0 to 3 only as codes 4 to 11 are applicable for deviation & band type. The table for selection of set-point type is given below: 0 -Absolute, control, on- above set-point 1 -Absolute, control, on- below set-point 2 -Absolute, alarm, on-above set-point 3 -Absolute, alarm, on-below set-point 4 -Deviation, control, on-above set-point 5 -Deviation, control, on-below set-point 6 -Deviation, alarm, on-above set-point 7 -Deviation, alarm, on-below set-point 8- Band, control, normal (On outside band) set-point 9- Band, control, fail safe (On within band) set-point 10-Band, alarm, normal (On outside band) set-point 11-Band, alarm, fail safe (On within band) set-point For more details refer the below figures. Operator s Manual Page 11 of 20

12 pressing enter key again it goes to initialization mode after initialization instrument resets and all parameters will be initialized. Slot configuration This parameter is used to select the auxiliary output card and its parameters. This parameter is configured for three types of outputs. Type of relay action for set-points can be configured any time depending upon application. Be careful in selecting proper type as this decides final relay action. Also refer description of Hysteresis effect in section 7.1 described earlier for various set-point types. Default Display Set-point This option decides the set-point to be displayed in normal run mode display. User can select any of the set-point for display. Normally first set-point is considered main set-point and that is displayed as default. Decimal Point Position This decides the decimal point position for linear inputs (4-20 ma and voltage inputs). For other input types it is not having any effect on display. Decimal point position can be programmed from 0 to 3. Position of 0 means no decimal point. Any non-zero number puts decimal point after that digit. For example if decimal point position is set to 2 and input reading is 1000, it will be displayed as Make sure to put correct decimal point for linear inputs. Password Password parameter can be set in the range of 0 to 9999 this mode. Initialization This parameter is used for initialization of all the parameters. By setting default password for initialization and pressing enter key it will display yes and by Retransmission o/p rtrc Serial communication COMC NO output none Serial Number This parameter is basically used for Modbus communication, to identify the unit. Modbus communication is master and slave communication, in which master will send query and slave will give response. If there are multiple slaves connected, so to synchronies communication, slave has its identification no (serial no) and it responds to only those query, which have its serial no. Range of serial no is from 1 to 99. Srno 0 to 99 This parameter is required while using the Serial Communication facility. It represents the serial number or the ID number of the Unit. It can be configured between 1 and 99 by using INC/DEC keys. Baud Rate bd k Operator s Manual Page 12 of 20

13 This parameter is used to set the BAUD RATE for serial communication. Different baud rates can be selected by using INC/DEC keys. In Asynchronous communication, master and slave has its separate clock source, for synchronizing, they must have same baud rate. Baud rate can be set from 9600 and 19.2KB. Cals Cala rtrz rtrs -Span Calibration -Ambient Calibration. - Retransmission zero Calibration [ Applicable for Retransmission Option ] -Retransmission span Calibration [ Applicable. for Retransmission Option] RX ZERO & SPAN These setting are provided only for input type 0-2V and retransmission card is seleted. These settings are for specifying minimum and maximum range of RX operation. Although full sensor input range is supported, user can select his range of RX operation. Rt-z Rt-s This allows selecting any value between 0 to This range can be changed any time, to make instrument usable for any type of 4-20 ma output transmitters or such other instrument. CALIBRATION MODE The instrument is factory calibrated for the specified range, but due to long term drift of components, recalibration may be necessary in some cases. For calibrating the instrument a reliable source is required. This source should be at least ten times accurate compared to the range of the instrument. The unit can be calibrated without opening it and without trimpots. For entering this mode press select key, PASS will be displayed, now enter correct password and press enter key to enter in menu mode and then INCR/DECR to choose Calibration mode and then press Enter key. It will display first calibration parameter. Now the subsequent calibration parameter can be viewed by pressing the select key. The parameters in sequence are as below. Calz - Zero Calibration Calibration procedure for ANALOG INPUT. [A] For T/C type 1. Short the input terminals. 2. Press the SET Key and then press INC/DEC Key to select CALb (Calibration mode) and press ENTER key. Now press SET key twice SV window will indicate CALA. Now set the current ambient temperature with the help of INC or DEC keys and press ENTER key to calibrate Ambient. 3. Feed the mv (Amb. subtracted except for B type) according to the T/C chart (For TC type) for ZERO value. 4. Again go to Calibration mode by Pressing the SET Key and then press INC/DEC Key to select CALb (Calibration mode) and press ENTER key. SV window will indicate CALZ. Now set the ZERO (lower limit of range) with the help of INC or DEC keys and press ENTER key to calibrate ZERO value. 5. Feed the mv (Amb. subtracted except for B type) according to the T/C chart (For TC type) for SPAN value. 6. Press the SET Key once. More, SV window will indicate CALS. Now set the SPAN (higher limit of range) by INC or DEC keys and press ENTER key to calibrate SPAN (value is according to requirement & TC type). Now check the linearity for the whole range. [B] For RTD type Operator s Manual Page 13 of 20

14 1. Set the input resistance at ohm, get CALZ Prompt on the display and set it to 00.0 C by INC or DEC keys and press ENTER key to calibrate ZERO. 2. Now set the input resistance at ohm. Get CALS Prompt on the display and set by INC or DEC keys and press ENTER key to calibrate SPAN. Now check the linearity for the whole range [C] For Linear type 1. Set the input at ma, get CALZ Prompt on the display and set it to Actual ZERO by INC or DEC keys and press ENTER key to calibrate ZERO. 2. Now set the input at ma. Get CALS Prompt on the display and set it to Actual SPAN by INC or DEC keys and press ENTER key to calibrate SPAN. Now check the linearity for the whole range. ISOLATED SIGNAL RETRANSMISSION This is an optional feature. This output can be either 4-20 ma or voltage output up to 5 volts. This output is proportional to the zero and span setting for input type. For example, if you set zero and span at 0 deg. and 1200 deg. for K type thermocouple input, it will output 4 ma for 0 deg. and 20 ma for 1200 Deg. Calibration procedure for ANALOG OUTPUT. 1. Enter into calibration mode as explained in the above paragraph. 2. Now SV window will display rtrz and PV window will display (4 ma). With help of INC or DEC keys set this ma value exactly same as at Ampere-meter reading connected at output. Now Press ENTER key to calibrate O/P for 4 ma. 3. Now on pressing SET key SV window will display rtrs (calibrate span) and PV will display and 2.. (20 ma). With help of INC or DEC keys set this ma value exactly same as on Amperemeter reading connected at output. Press ENT key to calibrate O/P for 20 ma. Note: For input type 0-2V: rt-z parameter must be set to 0 and rt-s parameter must be set to 2000 to calibrate the unit for analog output. After calibration user can set rt-z and rt-s parameter as per requirement. Now check the linearity for the whole range. 7.7 SPECIAL NOTE This controller is storing all data programmed by user and calibration in EEPROM. There are lots of software and hardware protections added for safeguarding against data corruptions. There can be a very rare possibility of data getting disturbed. The controller is having unique algorithm to store data at multiple places. So, even if the data in one place gets disturbed, it is automatically over-ridden by other correct data values. It is also having software protections against accidental writing to EEPROM also. Even after all this, if the data gets corrupted by heavy transients on power line or noise on power line (for which protections are already given in hardware), the unit will display data Err message on the display and will stop control action, keeping all relays in OFF condition as safety. In this event, programming mode will still continue working. User can go to program mode and check the data, which has changed. Re-program the data if it is changed and still it shows data error message, select Operator s Manual Page 14 of 20

15 all entries of configuration and program modes and press ENTER key once for all parameters. This is required because the data displayed may be correct, but the same data at other positions might be disturbed. Even after this the data error message is not removed, calibration data would have got disturbed. Re-calibrate the unit as per the procedure stated earlier. Even after all efforts to re-program data, the error remains, the EEPROM might have got damaged permanently. The unit needs to be repaired in this case. When messages are transmitted on standard Modbus serial networks, each character or byte is sent in this order (left to right): Least Significant Bit (LSB)...Most Significant Bit (MSB) with RTU character framing, the bit sequence is: i.e., 1 start bit, 2 stop bit and No parity MESSAGE QUERY 8. MODBUS DETAIL 8.1 INTRODUCTION The Digital controller 5002u can be connected in RS-485 communication data link either in multi drop or repeat mode. Each Digital controller 5002u must have unique Serial Number. No two Digital controllers 5002u have the same address. Entire range of addresses (1 to 99) may be used. Before starting any communication, choose a baud rate and protocol compatible to the host computer. Only two-pass protocol is available on Digital controller 5002u and hence when using the Digital controller 5002u, only twopass protocol is assumed. This speeds up the total throughput. 8.2 COMMUNICATION PROTOCOL The communication protocol is a HEX protocol. The host computer issues the commands to the Digital controller 5002u that in turn respond to each command. The entire protocol is based on the command/answer protocol SERIAL TRANSMISSION RTU FRAMING START DELAY AND ADDRESS Always contains the start of message with 3.5 null char delay followed by the address of the Digital controller 5002u to be addressed. The address is represented by a HEX character ranges from 00 to FUNCTION Operator s Manual Page 15 of 20

16 When a message is sent from a master to a slave device the function code field tells the slave what kind of action to perform. In Digital controller 5002u the functions implemented are 01 READ COIL STATUS (REFERENCE - 0x) 03 READHOLDING REGISTERS (REFERENCE- 4x) 06 PRESET SINGLE REGISTER (REFERENCE - 4x) Here Same Reference Functions are used for Reading and writing a parameter, so only one Variable Tag is required for reading and writing a parameter DATA FIELD Read The query message specifies the starting register and quantity of registers to be read. Registers are addressed starting at zero- registers are addressed as Write The query message specifies the register address and the data to be written in that register. Registers are addressed starting at zero- register 1 is addressed as CHECKSUM COMPUTATION The error checking field contains a 16-bit value implemented as two eight-bit bytes. The error check value is the result of a Cyclical Redundancy Check (CRC) calculation performed on the message contents. CRC to the message. The receiving device recalculates a CRC during receipt of the message, and compares the calculated value to the actual value it received in the CRC field. If the two values are not equal, an error is encountered. The CRC is started by first pre loading a 16-bit register to all 1's. Then a process begins of applying successive eight-bit bytes of the message to the current contents of the register. Only the eight bits of data in each character are used for generating the CRC. Start and stop bits, and the parity bit, do not apply to the CRC. During generation of the CRC, each eight-bit character is exclusive ORed with the register contents. Then the result is shifted in the direction of the least significant bit (LSB), with a zero filled into the most significant bit (MSB) position. The LSB is extracted and examined. If the LSB was a 1, the register is then exclusive ORed with a preset, fixed value. If the LSB was a 0, no exclusive OR takes place. This process is repeated until eight shifts have been performed. After the last (eighth) shift, the next eight-bit byte is exclusive ORed with the register's current value, and the process repeats for eight more shifts as described above. The final content of the register, after all the bytes of the message have been applied, is the CRC value. When the CRC is appended to the message, the low-order byte is appended first, followed by the highorder byte MESSAGE RESPONSE CRC CALCULATION The CRC field checks the contents of the entire message. It is applied regardless of any parity check method used for the individual characters of the message. The CRC value is calculated by the transmitting device, which appends the Operator s Manual Page 16 of 20

17 For a normal response, the Digital controller 5002u Indicator simply echoes the original function code. For an exception response, the Digital controller 5002u Indicator returns a code that is equivalent to the original function code with its most significant bit set to logic Data Field If no error occurs, the data field of a response from a Digital controller 5002u Indicator to a master contains the data requested. The char will be the byte count of data requested. For the command the response will be an echo of the query. If an error occurs, the field contains an exception code that the master application can use to determine the next action to be taken. 9.4 CHECKSUM COMPUTATION CRC of the message is calculated same way as explained earlier and appended to message. 9. COMMUNICATION PROTOCOL 9.1 DELAY AND ADDRESS Always contains the start of message with 3.5 null char delay followed by the address of the Digital controller 5002u to be addressed. The address is represented by a HEX character ranges from 00 to FUNCTION When the Digital controller 5002u Indicator responds to the master, it uses the function code field to indicate either a normal (error-free) response or that some kind of error occurred (called an exception response). 9.5 EXCEPTION RESPONSE The table explains the meaning of error codes, if Digital controller 5002u Indicator transmits error message. COD E MEANING 1 Function code Invalid. It must be 01, 05, 03 or Illegal data starting address. The range is specified for different functions in the Table below. 3 Illegal data value. The range is specified for different Functions in the table below. 4 Check sum (CRC) error. Garbled message. Operator s Manual Page 17 of 20

18 The table show Digital data to be transmitted and its sequence. Sr No Typ e Add Digital Paramete r Type of Acces s 1 RELAY 1 Read Bit RELAY 2 Read Bit RELAY 3 Read Bit The table show Analog data to be transmitted and its sequence. Sr No Analog Paramete r Access Type Typ e Add 1 Process Read Int Value 2 Set-point 1 Read/ Int Set-point 2 Read/ Int Set-point 3 Read/ Int Set-point 1 Hysteresis 6 Set-point 2 Hysteresis 7 Set-point 3 Hysteresis Read/ Read/ Read/ 8 Input Type Read/ 9 No. of set points Read/ 10 Act_zero Read/ 11 Act_span Read/ 12 Type of Set-point 1 13 Type of Set-point 2 14 Type of Set-point 3 15 No. of Slot configuration 16 Decimal Point Read/ Read/ Read/ Read/ Read/ Int Int Int Int Int Int Int Int Int Int Int Int Open Sensor Read/ 18 RX Zero Read/ 19 RX Span Read/ Note: Int Int Int Display on Digital controller 5002u will show over when process value is higher then 5 % of individual span, at that time Digital controller 5002u will send process value fed to it to PC. 2. Same way when process value is lower then 5 % of individual zero Digital controllers 5002u will show under on its display but it will send process value fed to it to PC. 3. If Digital controller 5002u process value is out of limit for particular I/P type then Digital controller 5002u will show Open on display but it will send to PC 4. The serial no of Digital controller 5002u Indicators must be within 00 to Before starting the communication, match the Baud rate and Sr. no. of Master and Slave devices. 6. Analog Parameter RX Zero and RX Span are writable only when input type 0-2V and Retransmission card is selected. 10. TROUBLE SHOOTING 1 Indicator does not Switch ON. Check the Mains Cord. I/P power may not be present. Check power supply voltage is it proper as per order Check fuse, if blown off replace it 2 Calibration of the unit is doubted to have drifted. Check the O/P of sensor is as per the chart supplied to you by sensor manufacturer. Operator s Manual Page 18 of 20

19 Measure it with instrument with better then 0.1% accuracy. Standard multimeter with 3½ digit display may have poor accuracy then Indicator. For temperature measurements check position of the sensor and check for the problem related to sensor first. Calibrate the unit as explained in the manual. Select the proper method according to your Indicator input type. 3 In linear type input the unit shows false reading or OVER or UNDER. Check for the polarity of the I/P connections. Check the current I/P coming from the field, it may be below 4 or over 20 ma. Check for the proper range programmed in that channel. 4 In thermocouple type input the reading indicated has got some error. Check for the proper I/p type selected. Ensure that the compensating cables used are of proper type and connected in proper direction Positive and negative. Check the calibration of the unit. Check that proper zero-span range is programmed or not. 5 Reading indicated by Indicator is unstable, wrong or open. Check the process input and also check their connections are as per the back-plate supplied. Ensure the perfect EARTHING to the unit & also check that neutral should not be floating. Shielded cables should used for input. Shield should be EARTHED near the unit only. Check any of the sensor is not getting EARTHED or having weak insulation with respect to earth. If so, remove that sensor and check the cabling. Check the lead resistance of all the three arms of RTD s. All the three leads should have same lead resistance. If no, change the cables. Check that Input cables are properly tighten Take separate earth wires for separate instruments, avoid looping of earth wires. Check for AC voltage pick up at the signal at Indicator side All low-level input and output such as T/C, Rtd, Linear I/P and control signal wires must be kept separate from supply and relay output cabling. 6 Communication Problem between the Unit and Host PC/Operator Terminal Check the cabling. Check the serial No. and baud rate settings at PC side and Indicator side. Check the RS-485 to RS232 converter for 485 communication. Check RS 232 RS 485 connection at PC and Indicator side. 7 Relay O/P Action problem Check power to the contactor operated by relay from Indicator. If relay burnt out frequently check for the rating of the relay or rating of contactor driven by relay. This is an electronics instrument it may have problem not listed above, in case of such fault while reporting to factory (Masibus area office or head office), mention exact nature of fault with sequence of events. Operator s Manual Page 19 of 20

20 Operator s Manual Page 20 of 20