Instruction manual MPU analog output 4-20 ma

Transcription

1 Instruction manual MPU analog output 4-20 ma July 2012 Part no Rev. 3 Enraf B.V. P.O. Box AV Delft Netherlands Tel. : Fax : enraf-nl@honeywell.com Website : Instruction manual MPU analog output 4-20 ma Page 1

2 Copyright Enraf B.V. All rights reserved. Reproduction in any form without the prior consent of Enraf B.V. is not allowed. This manual is for information only. The contents, descriptions and specifications are subject to change without notice. Enraf B.V. accepts no responsibility for any errors that may appear in this manual. The warranty terms and conditions applicable in the country of purchase in respect to Enraf B.V. products are available from your supplier. Please retain them with your proof of purchase. Page 2 Instruction manual MPU analog output 4-20 ma

3 Preface Preface This manual is intended for technicians involved with the installation, commissioning and service of the MPU board. A description preceding the technical procedures gives the technical information necessary to understand its functioning. It is recommended to read this description prior to performing any of the procedures. Safety and prevention of damage Safe execution of the procedures in this manual requires technical experience in handling tools, and knowledge of safety regulations in handling electrical installation in hazardous environments. "Warnings", "Cautions", and "Notes" have been used throughout this manual to bring special matters to the immediate attention of the reader. A Warning concerns danger to the safety of the technician or user; A Caution draws attention to an action which may damage the equipment; A Note points out a statement deserving more emphasis than the general text, but does not deserve a "Warning" or a "Caution". The sequence of steps in a procedure may also be important from the point of view of personal safety and prevention of damage; it is therfore advised not to change the sequence of procedural steps or alter a procedure. Legal aspects The information in this manual is copyright property of Enraf B.V., Netherlands. Enraf B.V. disclaims any responsibility for personal injury or damage to equipment caused by: Deviation from any of the prescribed procedures; Execution of activities that are not prescribed; Negligence of the general safety precautions for handling tools, use of electricity and microwave radiation. Instruction manual MPU analog output 4-20 ma Page 3

4 Table of contents Table of contents Preface Introduction General MPU_II analog output Typical connection diagrams Commissioning Settings to be done for analog output operation Calibration of the analog output... 8 Appendix A Layout MPU_II board... 9 Appendix B Specifications Appendix C Overview of analog output items Appendix D ASCII table Index Page 4 Instruction manual MPU analog output 4-20 ma

5 Introduction 1 Introduction 1.1 General Enraf field instruments (854 ATG, 854 XTG, 873 SmartRadar and 877 FDI) can be equipped with a special MPU board. It is a microprocessor controlled board providing an 4-20 ma analog output which represents the level. The 4-20 ma analog output provides the gauge with a digital controlled current sink, and can be used to adapt the Enraf field instruments for control applications or analog readers and/or plotters. The analog output circuitry is completely galvanically isolated from the gauge and may be used in grounded and floating applications. The current sink is of the passive type, hence an external loop supply source must be connected. There are two versions of the MPU board in use: MPU and MPU_II. For the differences see the specifications in appendix B. 1.2 MPU_II analog output The voltage of the loop supply should be at least 12 Vdc, and may not exceed 64 Vdc (measured at the terminals of the gauge). The loop resistance is the total resistance from the loop, and hence includes supply output resistance, total cable resistance (including series resistor) and the input resistance from reader or analog input. Care should be taken that the supply voltage is high enough to prevent voltage starvation of the loop i.e. a minimum of 12 V (loop current 22 ma) should always be present. Voltages exceeding 64 V on the terminals of the MPU can damage the electronic circuitry. To reduce the dissipated power on the MPU_II inside the Enraf field instrument, an extra resistor must be wired in series with the loop in case the loop supply is higher then 36 Vdc (see figure 1.2). Figure 1.2 Supply voltage (Vdc) versus loop resistance (Ω) MPU II board It can be read from figure 1.2 that the maximum loop resistance may be 960 ohm in case the loop supply is 36 Vdc. In case the loop supply is higher then 36 Vdc the minimum extra loop resistance can be calculated with the formula: R min ext = 40 * (V loop - 36) Ω The maximum loop resistance can be calculated with the formula: R max loop = 40 * (V loop - 12) Ω Instruction manual MPU analog output 4-20 ma Page 5

6 Introduction Example: Loop supply is 55 Vdc. R min ext = 40 * (55-36) = 760 Ω R max loop = 40 * (55-12) = 1720 Ω If a resistor of 820 ohm is wired in the loop, the remaining loop resistance may be maximal: = 900 Ω. 1.3 Typical connection diagrams Page 6 Instruction manual MPU analog output 4-20 ma

7 Commissioning 2 Commissioning 2.1 Settings to be done for analog output operation Refer to appendix C for relevant analog output items. After installing the Enraf field instrument, the analog output option must be set for the level range. Connect the analog loop to the grey terminals marked '1' and '2'. (see section 1.2.2). The positive lead must be connected to terminal 1 and the negative lead to terminal 2. First the proper working of the analog output must be checked: Check the contents of items [A3] and [A4] (the correct factory calibrated values are noted on the safety barrier of the MPU). If necessary refer to section 2.2 'Calibration of the analog output'. Enter protection level 1 (W1=ENRAF1). Set item [AK] to 'O'. The result will be that a current can manually be overwritten via the PET 847 keyboard. Issue item [EX] to exit protection level 1. Set item [PO] to 'J' (PO=J) to show the analog output current on the display of the PET 847. After disconnecting the PET 847 from the Enraf field instrument item [PO] will be reset. ANAL OUT --OENV E+00 ma The '--OENV' indicates an output error because no overwrite value is available. Now an overwrite value can be entered with item [AF], which will result in a current flowing in the output circuit. - Enter a current of 4 ma (AF= E+01) and check reading on the PET display and the contents of item [EA] (content of EA should be 2200). ANAL OUT ----OV E+01 ma Also the voltage on the gauge terminals can be measured: Enter [AV] and wait approximately 20 seconds; set voltage pointer to (VP=10.07). Enter item [VV]: the Enraf field instrument will respond with the voltage on the gauge terminals (must be in range E+02 < VV < E+02). - Enter a current of 22 ma (AF= E+02) and check reading on the PET display and the contents of item [EA] (content of EA should be 2200). ANAL OUT ----OV E+02 ma Also the voltage on the gauge terminals can be measured: Enter [AV] and wait approximately 20 seconds; set voltage pointer to (VP=10.07). Enter item [VV]: the Enraf field instrument will respond with the voltage on the gauge terminals (must be in range E+02 < VV < E+02) Instruction manual MPU analog output 4-20 ma Page 7

8 Commissioning If the analog output functions correct the analog output current can be set for a certain level range as follows: Enter protection level 1 (W1=ENRAF1). Program item [AK] according the mode you want to operate the analog output. See description of item [AK] in appendix C. Program item [AM] with the level which belongs to an analog output current of 4 ma. Program item [AN] with the level which belongs to an analog output current of 20 ma. Issue item [EX] to exit protection level 1. The Enraf field instrument will initialize which activates the new entered parameters. 2.2 Calibration of the analog output Calibration of the analog output current signal can only be done in the workshop. This because an external power supply and a digital ma meter must be connected to the Enraf field instrument. Calibration procedure: Connect a Vdc power supply and a digital current meter to the terminal 1 and 2. The digital current meter should have an accuracy better than 10 ma. Enter protection level 1 (W1=ENRAF1). Issue command item [A5]. A current of approximately 4 ma will flow in the output circuit. Enter the exact reading of the digital current meter in item [A3] (A3=+.xxxxxxxxE+xx). Example: current of 4,02 ma must be entered as A3= E+01. Issue command item [A6]. A current of approximately 18 ma will flow in the output circuit. Enter the exact reading of the digital current meter in item [A4] (A4=+.xxxxxxxxE+xx). Example: current of 17,99 ma must be entered as A4= E+02. Set item [AK] to 'O'. The result will be that a current can be entered manually via the PET 847 keyboard. Issue item [EX] to exit protection level 1. Now an overwrite value can be entered with item [AF], which will result in a current flowing in the output circuit. Check with the digital current meter the accuracy of the loop current at several settings in the range of 4-20 ma. Readings of the current meter and the overwrite setting of the level gauge may not differ more than 12 ma. Write the new values for item [A3] and [A4] on the reserved space on the safety barrier. Page 8 Instruction manual MPU analog output 4-20 ma

9 Appendix A Appendix A Layout MPU_II board MPU_II board for 854 ATG, 873 SmartRadar and 877 FDI MPU_II board for 854 XTG Instruction manual MPU analog output 4-20 ma Page 9

10 Appendix B Appendix B Specifications MPU analog output Valid for the MPU board with number (this number is printed on the board). Type : full galvanic isolated passive 4-20 ma current sink Maximum terminal voltage (no load) : 24 Vdc Minimum terminal voltage (@ 25 ma) : 12.5 Vdc Maximum loop resistance : 575 Ω max. (see figure 1.1) Minimum output current : 3.5 ma Maximum output current : 22 ma current resolution : 6 ma (12 bits) level resolution : 0.1 mm or 1/1000 ft (854 ATG) current un-accuracy : < 0.1% Full Scale (25 ma) Minimum level range : > 0 m Maximum level range : 27 m (854 ATG) Galvanic isolation type : opto-isolator DC isolation (1 min.) : 10 kvdc Surge protection : 350 V Reverse polarity protection : yes Update rate : approx. once per 4 sec. Calibration : electronically (via software) Care should be taken that the supply voltage is high enough to prevent voltage starvation of the loop i.e. a minimum of 12.5 V (loop current 22 ma) should always be present. Voltages exceeding 24 V on the terminals of the MPU can damage the electronic circuitry. Caution The analog output current (level) will not be effected by a power-down of the gauge. Therefore the analog loop supply must be fed by the same mains as used for the Enraf field instrument, and the analog output current signal must be switched with the same switch as used for the mains of the Enraf field instrument. Page 10 Instruction manual MPU analog output 4-20 ma

11 Appendix B MPU_II analog output Valid for the MPU_II board with number (this number is printed on the board). A watchdog is implemented to check if the MPU_II board with analog output is still alive. If the MPU_II board is not alive it takes about 10 seconds to decrease the output current to about 2 ma. Type : full galvanic isolated passive 4-20 ma current sink Maximum terminal voltage (no load) : 64 Vdc (with additional loop-resistor) see figure 1.2 Minimum terminal voltage (@ 25 ma) : 12 Vdc Maximum loop resistance : 960 Ω max (loop voltage 36 Vdc) see figure 1.2 Minimum output current : 3.5 ma Maximum output current : 22 ma current resolution : 6 ma (12 bits) level resolution : 0.1 mm or 1/1000 ft (854 ATG) current un-accuracy : < 0.1% Full Scale (25 ma) Minimum level range : > 0 m Maximum level range : 27 m (854 ATG) Galvanic isolation type : opto-isolator DC isolation (1 min.) : 10 kvdc (Opto coupler) Surge protection : 300 V (gas arrestor) Reverse polarity protection : yes Update rate : approx. once per second Calibration : electronically (via software) Instruction manual MPU analog output 4-20 ma Page 11

12 Appendix C Appendix C Overview of analog output items For service purposes like calibration and setting the Enraf field instrument can be controlled via the infra-red communication port via the PET 847. All readings, settings and calibrations are done via so called items. All parameters necessary to program the analog output can be done after entering protection level 1. This is done by typing W1=ENRAF1 in which ENRAF1 is the factory programmed default password for level 1. The [EX] command should be given to exit protection level 1. Item summary In this appendix relevant items for the analog output option are mentioned. User items Item AM AN AK Description Level value which corresponds with current 4 ma Level value which corresponds with current 20 ma Operation mode analog output Service items Item A3 A4 A5 A6 AF AO AQ AV EA VP VV Description Analog output current (4 ma) Analog output current (18 ma) Set analog output current to 4 ma Set analog output current to 18 ma Overwrite analog output current Analog output current value Analog output status Analog voltage measurement command Error analog output request Voltage pointer Voltage value Page 12 Instruction manual MPU analog output 4-20 ma

13 Appendix C Analog output item descriptions Item : A3, A4 Analog output calibration value Entry format : 14 ASCII characters Default value : E+00 These items are used to calibrate the analog output of the MPU. The correct value for [A3] is obtained by sending command item [A5] after which the current output (approximately 4 ma) is measured with a digital ma meter. The measured value must be programmed in item [A3]. The correct value for [A4] is obtained by sending command item [A6] after which the current output (approximately 18 ma) is measured with a digital ma meter. The measured value must be programmed in item [A4]. Item : A5, A6 Analog output calibration command Default value : not applicable These command items are used to calibrate the analog output of the MPU. See item description for items [A3] and [A4]. Item : AF Analog output overwrite Entry format : 14 ASCII characters Default value : not applicable With this item the user can manually overwrite the current output. The item [AK] must be set to overwrite mode. See items [AK], [AO] and [AQ]. Instruction manual MPU analog output 4-20 ma Page 13

14 Appendix C Item : AK Analog output mode Entry format : 1 ASCII character Default value : D Via this item is selected under what conditions the analog output current will operate. [AK] [AL] V Valid level I Invalid level F Level fail T Time-out Start-up D Analog output disabled (default setup value) O Io = [AF] (Overwrite mode) Io = 3.5 ma (during start-up) P Io = [AF] (Overwrite mode) Io = 22 ma (during start-up) L Io = [AL] Io = [LV] no [LV]:Io=3.5 ma Io = 3.5 ma M Io = [AL] Io = [LV] no [LV]:Io=22 ma Io = 22 ma A Io = [AL] Io = 3.5 ma B Io = [AL] Io = 22 ma I Io = [AL] Io = 3.5 ma J Io = [AL] Io = 22 ma [AF] = Analog output overwrite value [AL] = Actual level [LV] = Last Valid level Io = Output current Note: 3.5 ma <= Io <= 22 ma Item : AM Analog 4 ma level Entry format : according to item LD Default value : according to item LD This item must be programmed with the level value which corresponds with an output current of 4 ma. Item : AN Analog 20 ma level Entry format : according to item LD Default value : according to item LD This item must be programmed with the level value which corresponds with an output current of 20 ma. Item : AO Actual analog output current Default value : not applicable The level gauge will respond with the actual current value. In this way the actual current can be checked. Refer to item [AQ] for the analog output status bytes. Page 14 Instruction manual MPU analog output 4-20 ma

15 Appendix C Item : AQ Actual analog output status Default value : not applicable This item reflects the status of the analog output. The reply of the level gauge consists out of one ASCII character which must be decoded into bits (see appendix D: ASCII table). Bit b4 represents the analog output value status: Analog output value status (bit b4) Output status (bit b3 upto b0) b6 b5 b4 b3 b2 b1 b0 1 0 vs os3 os2 os1 os0 [AQ] b4 Analog output value 0 Output current in 4 to 20 ma range P,Q..._ 1 Output current out of 4 to 20 ma range Level control: General output fail: Analog output disable: Overwrite mode: Calibration mode: [AQ] b3,b2,b1,b0 Analog output status 0000 Valid product level used L,M,A,B,I,J A,Q 0001 Last valid product level used L,M B,R 0010 Invalid level used A,B C,S 0011 No valid product level available I,J D,T 0100 No last valid product level available L,M E,U 0101 No level available A,B F,V 0110 Level time-out L,M,A,B,I,J G,W 0111 Invalid level I,J H,X 1000 Level failure A,B,I,J [AQ] b3,b2,b1,b0 Analog output status [AK] I,Y 1001 Analog output general failure not set [AQ] b3,b2,b1,b0 Analog output status [AK] J,Z 1010 Analog output disabled D [AQ] b3,b2,b1,b0 Analog output status [AK] K,[ 1011 Overwrite value used O,P L,\ 1100 No overwrite value available O,P [AQ] b3,b2,b1,b0 Analog output status [AK] M,] 1101 Calibration mode entered L,M,A,B,I,J [AQ] b3,b2,b1,b0 N,^ 1110 not used O,_ 1111 not used Instruction manual MPU analog output 4-20 ma Page 15

16 Appendix C Item : AV Measure analog voltage command Default value : not applicable This item gives a command to the MPU to measure several analog test voltages. The measured voltages can be read via items [VP] and [VV]. Item : EA Analog output error request Default value : 2200 As reply to this item the most recent encountered error by the MPU will be echoed. Possible errors EA Error description 2200 No error, value at initialisation 2210 Vdac error /2 Vdac - offset error 2212 Vdac - offset error 2213 Vloop error (Vloop not in the range Vdc) 2215 Analog output not calibrated ([A3] and/or [A4] are zero, MPU analog output not operational Item : VP Voltage pointer Entry format : 5 ASCII characters Default value : Via this item a voltage pointer is set. The measured voltage (item [AV]) of this pointer can be read via requesting item [VV]. VP Selected voltage pointer Vdac /2 Vdac - offset Vdac - offset Vloop (must be in the range 11,5 to 28 Vdc) Note: A certain delay between loading the voltage pointer (item [VP]) and the value request (item [VV]) should be kept. This to allow the FPU to do the necessary calculations. Item : VV Voltage value Default value : Via this item the voltage value can be requested of the voltage pointer set with item [VP]. Note: A certain delay between loading the voltage pointer (item [VP]) and the value request (item [VV]) should be kept. This to allow the FPU to do the necessary calculations. Page 16 Instruction manual MPU analog output 4-20 ma

17 Appendix D Appendix D ASCII table HEX MSB BIT LSB NUL DLE SP P p SOH DC1! 1 A Q a q STX DC2 2 B R b r ETX DC3 # 3 C S c s EOT DC4 $ 4 D T d t ENQ NAK % 5 E U e u ACK SYN & 6 F V f v BEL ETB 7 G W g w BS CAN ( 8 H X h x HT EM ) 9 I Y i y A LF SUB * : J Z j z B VT ESC + ; K [ k { C FF FS < L \ l l D CR GS - = M ] m } E SO RS. > N ^ n ~ F SI US /? O - o DEL Instruction manual MPU analog output 4-20 ma Page 17

18 Index Index 847 PET... 7, 12 Calibration... 8 Caution... 3 Commissioning... 7 Connection diagrams... 6 Item A A A A AF AK AM AN AO AQ AV EA VV Loop resistance... 5, 10 MPU analog output MPU_II analog output... 5, 11 Note... 3 Protection level , 8, 12 Service items Specifications Supply voltage... 5, 10 User items Warning... 3 Page 18 Instruction manual MPU analog output 4-20 ma

19 Notes Instruction manual MPU analog output 4-20 ma Page 19

20 Notes Page 20 Instruction manual MPU analog output 4-20 ma