Emerson Process Management 3081 pH/ORP manual

Model 3081 pH/ORP Smart T wo-Wire Microprocessor T ransmitter Instruction Manual PN 51-3081pH/rev .D August 2002[...]

ESSENTIAL INSTRUCTIONS READ THIS P AGE BEFORE PROCEEDING! Rosemount Analytical designs, manufactures, and tests it s products to meet many national and international standards. Because these instrument s are sophisticated technical products, you must properly inst all, use, and maintain them to ensure they continue to operate within their normal sp[...]

WHA T YOU NEED T O KNOW BEFORE INST ALLING AND WIRING A ROSEMOUNT ANAL YTICAL SENSOR T O THE MODEL 3081 pH/ORP TRANSMITTER 1. THE MODEL NUMBER OF THE SENSOR • Look on the label. • Also note the model option string. • If the label is missing or unreadable, see the flowcharts on p ages 28 through 30. Write the sensor model number here 2. THE TY[...]

• If the sensor is wired directly to the transmitter , the preamplifier can be in either the sensor or the transmitter . • Look at the wires in the sensor cable. A GREEN wire means the preamplifier is in the sen- sor . An coaxial cable means the preamplifier is in the transmitter . A coaxial cable is an insulated wire surrounded by a braided me[...]

QUICK ST ART GUIDE FOR MODEL 3081pH/ORP Before using this Quick St art Guide, please read “WHA T YOU NEED T O KNOW BEFORE INST ALLING AND WIRING A ROSEMOUNT ANAL YTICAL SENSOR TO THE MODEL 3081 pH/ORP TRANSMITTER” on the preceding p age. Section 1.1 Setup for the Models 381+-52, 385+-04, 396P-02-54, 396P-02-55 and 396R-54 without a junction box[...]

Section 2 Wiring A. Wire sensor Model 381+-55, 385+-03, or 396P-01-55 directly to the transmitter as shown in Figure 3. B. Wire sensor Model 381+-52, 385+-04, 396P-02-55, 396P-02-55, or 396R-54 as shown in Figure 4. C. Wire the 12 - 42.4 Vdc power supply to TB-15 (- 4 - 20 mA) and TB-16 (+ 4 - 20 mA). Section 3 Power up and Calibration A. Apply dc [...]

QUICK REFERENCE GUIDE MODEL 3081PH/ORP Automatic Buffer Calibration Note: A pH measurement is only as good as the calibration, and the calibration is only as good as the buffers used. For best results, calibrate with buf fers having the same temperature as the process. Allow time for the sensor and buffers to reach the same temperature. If the proc[...]

HART Communicator Fast Key Sequences T echnical Support Hotline: For assistance with technical problems, please call the Customer Support Center (CSC). The CSC is staffed from 5:00am to 5:00pm PST . Phone (US only): 800-854-8257 Phone: 949-757-8500 Fax: 949-863-9159 World W ide Web: www .raihome.com PROGRAM CALIBRA TE OutPut GIMP 1000 V Er 81PH.21 [...]

i MODEL 3081 pH/ORP T ABLE OF CONTENTS MODEL 3081 PH/ORP MICROPROCESSOR TRANSMITTER T ABLE OF CONTENTS Section Title Page 1.0 DESCRIPTION AND SPECIFICA TIONS ................................................................ 1 1.1 Features ................................................................................................................[...]

MODEL 3081 pH/ORP T ABLE OF CONTENTS T ABLE OF CONTENTS CONT’D ii 8.0 PROGRAMMING FOR pH MEASUREMENTS ....................................................... 56 8.1 General .................................................................................................................... 56 8.2 Entering and Leaving the Program Menu .............[...]

iii MODEL 3081 pH/ORP T ABLE OF CONTENTS T ABLE OF CONTENTS CONT’D 13.0 pH MEASUREMENTS ............................................................................................. 1 14 13.1 General .................................................................................................................... 11 4 13.2 Measuring Electrode .[...]

iv MODEL 3081 pH/ORP T ABLE OF CONTENTS T ABLE OF CONTENTS CONT’D LIST OF FIGURES Number Title Page 2-1 Model 3081 pH/ORP T ransmitter - Exploded Drawing of Circuit Board S tack ......... 8 2-2 Model 3081 pH/ORP T ransmitter - Analog Board .................................................... 9 2-3 Model 3081 pH/ORP T ransmitter - CPU Board ......[...]

v MODEL 3081 pH/ORP T ABLE OF CONTENTS T ABLE OF CONTENTS - CONT’D LIST OF FIGURES - CONT’D Number Title Page 3-23 Procedure for Removing BNC Connector and Preparing Coaxial Cable for ............ Connection to the Model 3081 pH/ORP Transmitter ................................................ 26 3-24 Preparation of Raw Connecting Cable (PN 9200[...]

vi MODEL 3081 pH/ORP T ABLE OF CONTENTS T ABLE OF CONTENTS CONT’D LIST OF T ABLES Number Title Page 3-1 Wiring Diagrams for Model 399 Sensors .................................................................. 15 3-2 Wiring Diagrams for Model 397 Sensors .................................................................. 15 3-3 Wiring Diagrams for [...]

1 MODEL 3081 pH/ORP SECTION 1.0 DESCRIPTION AND SPECIFICA TIONS SECTION 1.0 DESCRIPTION AND SPECIFICA TIONS 1.1 Features 1.2 Accessories 1.3 Specifications - General for Model 3081 pH/ORP 1.4 Specifications - pH 1.5 Specifications - ORP 1.6 Ordering Information • CHANGING FROM pH T O ORP operation takes only seconds. • REMOTE COMMUNICA TION IS [...]

2 CALIBRA TION: T wo-point, temperature-corrected buffer calibration is standard. T o reduce errors caused by impatient operators, the Model 3081 pH/ORP transmitter does not accept calibration data until programmed st abil- ity limits have been met. If dat a are not acceptable, the transmitter displays an error message and does not update the calib[...]

3 MODEL 3081 pH/ORP SECTION 1.0 DESCRIPTION AND SPECIFICA TIONS minimum voltage and load for HART communication 1.3 SPECIFICA TIONS - GENERAL FOR MODEL 3081 pH/ORP Case: Cast aluminum containing less than 8% magnesium. NEMA 4X (IP65), NEMA 7 (explosion-proof) Epoxy-polyester paint, Neoprene O-ring seals Dimensions: 6.3 in. x 6.9 in. x 6.4 in. (160 [...]

4 MODEL 3081 pH/ORP SECTION 1.0 DESCRIPTION AND SPECIFICA TIONS 1.6 ORDERING INFORMA TION The Model 3081 pH/ORP Smart two-wire microprocessor transmitter is housed in a NEMA 4X case. Communication with the transmitter is through a hand-held infrared remote controller , a Model 275 HART communicator , or any HART com- patible device. Automatic tempe[...]

5 MODEL 3081 pH/ORP SECTION 1.0 DESCRIPTION AND SPECIFICA TIONS MODEL 3081 pH/ORP TRANSMITTER-SENSOR COMP A TIBILITY CHART PREAMPLIFIER LOCA TION Sensor-mounted Remote MODEL pH ORP Sensor junction box junction box T ransmitter 320B x see note 320HP x see note x 330B x 328A x x x 370 x x x x 371 x x x x 381pH x 381pHE x 381 x 381+ x x x x 385 x x x [...]

6 MODEL 3081 pH/ORP SECTION 1.0 DESCRIPTION AND SPECIFICA TIONS MODEL/PN DESCRIPTION SHIPPING WEIGHT 515 DC loop power supply , see Section 1.2.1 for details 3 lb/1.0 kg 230A T wo alarm module, see Section 1.2.2 for details 3 lb/1.5 kg 275 HART communicator , order from Rosemount Measurement - (800) 999-9307 NA 23572-00 Infrared remote controller ,[...]

2.1 UNP ACKING AND INSPECTION Inspect the shipping container . If it is damaged, cont act the shipper immediately for instructions. Save the box. If there is no apparent damage, remove the transmitter . Be sure all items shown on the p acking list are present. If items are miss- ing, immediately notify Rosemount Analytical. Save the shipping contai[...]

MODEL 3081 pH/ORP SECTION 2.0 INST ALLA TION 8 FIGURE 2-1. Model 3081 pH/ORP T ransmitter - Exploded Drawing of Circuit Board St ack 2.2.4 Preamplifier Location pH sensors produce a high impedance voltage signal that must be preamplified before use. The signal can be preampli- fied before it reaches the transmitter or it can be preamplified in the [...]

9 5. Set the jumpers and the slide switch on the analog board. Refer to Figure 2-2. a. T emperature element jumper . Jumper position T emperature element JP-1 Pt 1000 RTD JP-2 Pt 100 RTD JP-3 3K Balco RTD b. Reference impedance jumper . Jumper position Reference impedance JP-6 low JP-7 high c. Reference impedance jumper JP-5. Jumper position Refere[...]

10 MODEL 3081 pH/ORP SECTION 2.0 INST ALLA TION 6. There are more jumpers on the CPU board. Refer to Figure 2-3. These jumpers are factory set and should NOT need to be moved. This step is for trou- bleshooting purposes only . V erify that jumpers JP-1, JP-3, and JP-4 on the CPU board are in the positions shown in Figure 2-3. For installations wher[...]

11 MODEL 3081 pH/ORP SECTION 2.0 INST ALLA TION FIGURE 2-4. Mounting the Model 3081 pH/ORP T ransmitter on a Flat Surface MILLIMETER INCH 4. Use weathertight cable glands to keep moisture out of the transmitter . 5. If conduit is used, plug and seal the connections at the transmitter housing to prevent moisture from getting inside the transmitter .[...]

12 MODEL 3081 pH/ORP SECTION 2.0 INST ALLA TION FIGURE 2-5. Using the Pipe Mounting Kit to Attach the Model 3081 pH/ORP T ransmitter to a Pipe MILLIMETER INCH 2.4.3 Pipe Mounting. See Figure 2-5. The pipe mounting kit (PN 2002577) accommodates 1-1/2 to 2 in. pipe. DWG . NO. REV . 40308104 G DWG . NO. REV . 40308103 C[...]

13 MODEL 3081 pH/ORP SECTION 2.0 INST ALLA TION 2.5 POWER SUPPL Y/CURRENT LOOP 2.5.1 Power Supply and Load Requirement s. Refer to Figure 2-6. The minimum power supply voltage is 12.5 Vdc and the maximum is 42.4 Vdc. The top line on the graph gives the voltage required to maint ain at least 12.5 Vdc at the transmitter terminals when the output sig-[...]

14 MODEL 3081 pH/ORP SECTION 3.0 WIRING SECTION 3.0 WIRING 3.1 GENERAL INFORMA TION pH and ORP sensors manufactured by Rosemount Analytical can be wired to the Model 3081 pH/ORP transmitter in three ways: 1. directly to the transmitter , 2. to a sensor-mounted junction box and then to the transmitter , 3. to a remote junction box and then from the [...]

MODEL 3081 pH/ORP SECTION 3.0 WIRING 3.2 WIRING DIAGRAMS FOR pH and ORP SENSORS Refer to T ables 3-1 through 3-12 to locate the appropriate wire function and wiring diagram. There is a separate t able for each model. The sensor models having the highest number appear first. If you do not know the model number of the sensor , refer to the flow chart[...]

16 MODEL 3081 pH/ORP SECTION 3.0 WIRING T able 3-4 W iring Diagrams for Model 396P Sensors Sensor Junction Box Preamplifier RTD W ire Function Wiring Diagram 396P-01-55 none in sensor Pt 100 Figure 3-13 Figure 3-14 396P-01-55 remote in sensor Pt 100 Figure 3-13 Figure 3-14 396P-02-50 none in transmitter 3K Balco** Figure 3-10 Figure 3-1 1 396P-02-5[...]

17 MODEL 3081 pH/ORP SECTION 3.0 WIRING T able 3-7 W iring Diagrams for Model 385+ Sensors Sensor Junction Box Preamplifier RTD W ire Functions Wiring Diagram 385+ -02 sensor-mounted in sensor-mounted junction box Pt 100 Figure 3-15 Figure 3-16 385+ -03 none in sensor Pt 100 Figure 3-13 Figure 3-14 385+ -03 remote in sensor Pt 100 Figure 3-13 Figur[...]

18 MODEL 3081 pH/ORP SECTION 3.0 WIRING REMOVE BNC AND TERMINA TE COAXIAL CABLE BEFORE WIRING SENSOR TO TRANSMITTER. SEE FIGURE 3-23. AL TERNA TIVEL Y , USE A BNC ADAPTER (PN 9120531) OR ORDER MODEL OPTION -62 (SENSOR WITH BNC REMOVED AND TER- MINA TIONS COMP A TIBLE WITH 3081 pH/ORP). IF USING A BNC ADAPTER, THE RED WIRE IS MV OR pH IN AND THE BLA[...]

19 MODEL 3081 pH/ORP SECTION 3.0 WIRING REMOVE BNC AND TERMINA TE COAXIAL CABLE BEFORE WIRING SENSOR TO TRANSMITTER. SEE FIGURE 3-23. AL TERNA TIVEL Y , USE A BNC ADAPTER (PN 9120531) OR ORDER MODEL OPTION -62 (SENSOR WITH BNC REMOVED AND TERMINA TIONS COMP A TIBLE WITH 3081 pH/ORP). IF USING A BNC ADAPTER, THE RED WIRE IS MV OR pH IN AND THE BLACK[...]

20 MODEL 3081 pH/ORP SECTION 3.0 WIRING FIGURE 3-10. Wire functions for Models 396R-50, 396R-54, 396R-54-61, 396P-02-50, 396P-02-54, 396P-02-55, 385+ -04, and 385+ -41-52. NOTES: 1. PLACE PREAMPLIFIER SELECTION SWITCH S1 IN "TRANS- MITTER" POSITION (SEE SECTION 2.2). 2. IF SENSOR HAS 3K BALCO RTD, SET JUMPER (SECTION 2.2) AND PROGRAM TRAN[...]

21 MODEL 3081 pH/ORP SECTION 3.0 WIRING FIGURE 3-13. Wire functions for Models 396P-01-55, 385+ -03, 381+ -40-55, and 381+ -43-55. NOTES: 1. PLACE PREAMPLIFIER SELECTION SWITCH S1 IN "SENSOR/JUNCTION BOX" POSITION (SEE SECTION 2.2). 2. TO EXTEND CABLE LENGTH, USE JUNCTION BOX PN 23550- 00 WITH EXTENSION CABLE PN 23646-01 (FINISHED) OR PN [...]

22 MODEL 3081 pH/ORP SECTION 3.0 WIRING FIGURE 3-15. Wire functions for Model 385+ -02. NOTES: 1. PLACE PREAMPLIFIER SELECTION SWITCH S1 IN "SENSOR/JUNCTION BOX" POSITION (SEE SECTION 2.2). 2. SEE FIGURE 3-24 FOR TERMINA TION OF RAW INTERCONNECTING CABLE (PN 9200273). 3. JUMPER SUPPLIED BY CUSTOMER. 4. DO NOT CONNECT BLUE WIRE. INSULA TE [...]

23 MODEL 3081 pH/ORP SECTION 3.0 WIRING NOTE: MODEL 328A-08 HAS UNDRESSED COAXIAL CABLE. SEE SENSOR INSTRUCTION SHEET FOR CABLE PREP ARA TION PROCEDURE. FIGURE 3-17. Wire functions for Model 328A-07. NOTES: 1. PLACE PREAMPLIFIER SELECTION SWITCH S1 IN "TRANS- MITTER" POSITION (SEE SECTION 2.2). 2. JUMPERS SUPPLIED BY CUSTOMER. 3. MODEL 32[...]

24 MODEL 3081 pH/ORP SECTION 3.0 WIRING NOTES: 1. PLACE PREAMPLIFIER SELECTION SWITCH S1 IN "TRANS- MITTER" POSITION (SEE SECTION 2.2). 2. TERMINALS IN JUNCTION BOX ARE NOT NUMBERED. COUNT POSITION FROM LEFT TO RIGHT AS SHOWN IN DRA WING . 3. JUMPERS SUPPLIED BY CUSTOMER. 4. CUSTOMER MUST INST ALL AND WIRE pH ELECTRODE AND TEMPERA TURE SE[...]

25 MODEL 3081 pH/ORP SECTION 3.0 WIRING FIGURE 3-21. Wire Functions for Model 399-33 FIGURE 3-22. Wiring Diagram for Model 399-33[...]

26 MODEL 3081 pH/ORP SECTION 3.0 WIRING FIGURE 3-23. Procedure for Removing BNC Connector and Preparing Coaxial Cable[...]

27 MODEL 3081 pH/ORP SECTION 3.0 WIRING FIGURE 3-24. Preparation of Raw Connecting Cable (PN 9200273).[...]

28 MODEL 3081 pH/ORP SECTION 3.0 WIRING SENSOR FLOW CHART (continued on page 29)[...]

29 MODEL 3081 pH/ORP SECTION 3.0 WIRING SENSOR FLOW CHART (continued on page 30)[...]

30 MODEL 3081 pH/ORP SECTION 3.0 WIRING SENSOR FLOW CHART[...]

31 4.1 INTRINSICALL Y SAFE INST ALLA TIONS The installation wiring, operating p arameters, or agency tags for intrinsically safe operation are given in Figures 4-1, 4-2, and 4-3. 4.2 EXPLOSION PROOF INST ALLA TIONS The installation wiring and operating p arameters for explosion proof operation are given in Figure 4-4. MODEL 3081 pH/ORP SECTION 4.0 [...]

32 FIGURE 4-2. FMRC Inst allation for Model 3081 pH/ORP T ransmitter[...]

33[...]

FIGURE 4-3. CSA Installation for Model 3081 pH/ORP T ransmitter 34[...]

35[...]

FIGURE 4-4. Explosion-Proof Inst allation for Model 3081 pH/ORP T ransmitter 36[...]

37 MODEL 3081 pH/ORP SECTION 5.0 OPERA TION WITH REMOTE CONTROLLER SECTION 5.0 OPERA TION WITH REMOTE CONTROLLER CALIBRA TE PROGRAM DIAGNOSE CALIbrAtE EXIT NEXT ENTER 7.00 pH MV F A U L T H O L D ♥ Appears when transmitter is in hold (see Section 8.3.2) Appears when a disabling condition has occurred (see Section 8.3.2) Appears during HART and AM[...]

38 MODEL 3081 pH/ORP SECTION 5.0 OPERA TION WITH REMOTE CONTROLLER 5.2 INFRARED REMOTE CONTROLLER (IRC) - KEY FUNCTIONS The infrared remote controller is used to calibrate and program the transmitter and to read diagnostic messages. See Figure 5-3 for a description of the function of the keys. Hold the IRC within 6 feet of the transmitter , and not[...]

39 MODEL 3081 pH/ORP SECTION 5.0 OPERA TION WITH REMOTE CONTROLLER PROGRAM CALIBRA TE OutPut GIMP 1000 V Er 81PH.21 tEMP 25 C InPut 58.9 ShoW FLt nonE rIMP 10 dIAGnOStIC tEMP bUFFEr dISPLA Y ISOPOtntAL SIM OUtPUt CALIbrAtE Std tEMP AdJ tEMP 25.0 4 MA 00.00 20MA 14.00 HoLd 21.00 F AULt 22.00 dPn 0.00 tAUtO On tMAn 25.0 tC 100-3 tYPE PH tEMP C OUtPUt[...]

40 5.5 MENU TREE - ORP The Model 3081 ORP transmitter has three menus: CALIBRA TE, PROGRAM, and DIAGNOSE. Under the Calibrate and Program menus are several sub-menus. For example, under CALIBRA TE, the sub-menus are St d (standard) and tEMP AdJ (temperature adjust). Under each sub-menu are prompts. For example, the Std sub-menu cont ains the single[...]

41 5.7 SECURITY 5.7.1 General. Use the programmable security code to protect program and calibration settings from accidentally being changed. The transmitter is shipped with the security fea- ture disabled. T o program a security code, refer to Section 8.6, Display Units. 5.7.2 Entering the Security Code. 1. If calibration and program settings are[...]

42 6.1 Note on Model 275 HART Communicator The Model 275 HART Communicator is a product of Rosemount Measurement. This section contains selected information on using the Model 275 with the Rosemount Analytical Model 3081 pH/ORP T ransmitter . For complete information on the Model 275 Communicator , see the Model 275 instruction manual. For technica[...]

43 MODEL 3081 pH/ORP SECTION 6.0 OPERA TION WITH MODEL 275 6.3 Operation 6.3.1 Off-line and On-line Operation The Model 275 Communicator features off-line and on-line communications. On-line means the communicator is connected to the transmitter in the usual fashion. While the communicator is on line, the operator can view meas- urement data, chang[...]

44 MODEL 3081 pH/ORP SECTION 6.0 OPERA TION WITH MODEL 275 FIGURE 6-2a. pH Menu T ree (HART) (Figure 6-2 is continued on page 41)[...]

45 MODEL 3081 pH/ORP SECTION 6.0 OPERA TION WITH MODEL 275 FIGURE 6-2b. pH Menu T ree (HART)[...]

46 MODEL 3081 pH/ORP SECTION 6.0 OPERA TION WITH MODEL 275 FIGURE 6-3a. ORP Menu T ree (HART) (Figure 6-3 is continued on page 43)[...]

47 MODEL 3081 pH/ORP SECTION 6.0 OPERA TION WITH MODEL 275 FIGURE 6-3b. ORP Menu T ree (HART)[...]

48 MODEL 3081 pH/ORP SECTION 7.0 CALIBRA TION OF pH MEASUREMENTS SECTION 7.0 CALIBRA TION OF pH MEASUREMENTS 7.1 General 7.2 Entering and Leaving the Calibrate Menu 7.3 Using the Hold Function 7.4 T emperature Calibration 7.5 Auto Calibration 7.6 Manual Calibration 7.7 Making the T ransmitter Reading Match a Second pH Meter (St andardization) 7.1 G[...]

49 CALIBRA TE tEMP A A d J EXIT NEXT ENTER CALIBRA TE tEMP EXIT ENTER 0 25.0 MODEL 3081 pH/ORP SECTION 7.0 CALIBRA TION OF pH MEASUREMENTS 7.4 TEMPERA TURE CALIBRA TION 7.4.1 Purpose 1. As discussed in Section 13.6, Glass Electrode Slope, measuring tempera- ture is an important p art of measuring pH. The accuracy of a new sensor and transmitter loo[...]

50 7.5 AUTO CALIBRA TION 7.5.1 Purpose 1. New sensors must be calibrated before use. Regular recalibration is also necessary . 2. The use of auto calibration instead of manual calibration is strongly recommended. Auto calibra- tion avoids common pitfalls and reduces errors. 3. For more information about calibration in pH measurements and the use of[...]

7.5.4 Procedure 1. Refer to Section 8.7, Buffer Calibration Parameters. V erify that auto calibration is activated. Identify the buffers being used and set the st ability limits. 2. Enter the CALIBRA TE menu by pressing CAL on the IRC. The CALIbrAtE sub-menu appears (pic- tured above left). 3. At the CALIbrAtE sub-menu, press ENTER . The CAL bF1 pr[...]

52 MODEL 3081 pH/ORP SECTION 7.0 CALIBRA TION OF pH MEASUREMENTS 7.6.1 Purpose 1. New sensors must be calibrated before use. Regular recalibration is also necessary . 2. Manual calibration is an alternative to auto calibration. Because auto calibration eliminates many common calibration errors, it is strongly recommended. 3. In auto calibration, th[...]

53 7.6.3 Procedure 1. Before starting, refer to Section 8.7, Buffer Calibration Parameters, to deactivate auto cali- bration. 2. Enter the CALIBRA TE menu by pressing CAL on the IRC. The CALIbrAtE sub-menu appears (pictured above left). 3. At the CALIbrAtE sub-menu, press ENTER . The CAL bF1 prompt appears. 4. Rinse the sensor with deionized water [...]

54 MODEL 3081 pH/ORP SECTION 7.0 CALIBRA TION OF pH MEASUREMENTS 7.7 MAKING THE TRANSMITTER READING MA TCH A SECOND pH METER (ST ANDARDIZA TION). 7.7.1 Purpose 1. This section describes how to make the transmitter reading match the reading from a second pH meter . The measurement made with the second meter is called the st andard pH (pH std ). The [...]

55 MODEL 3081 pH/ORP SECTION 7.0 CALIBRA TION OF pH MEASUREMENTS CALIBRA TE Std EXIT NEXT ENTER CALIBRA TE SLOPE EXIT NEXT ENTER CALIBRA TE Std EXIT NEXT ENTER 08 .00 5 9.00 7.7.3 Procedure 1. Enter the CALIBRA TE menu by pressing CAL on the IRC. The CALibrAtE sub-menu appears (pictured above left). 2. At the CALibrAtE sub-menu, press NEXT . The St[...]

56 MODEL 3081 pH/ORP SECTION 8.0 PROGRAMMING FOR pH MEASUREMENTS SECTION 8.0 PROGRAMMING FOR pH MEASUREMENTS 8.1 General 8.2 Entering and Leaving the Program Menu 8.3 Output Ranging 8.4 Diagnostic Parameters 8.5 T emperature Related Settings 8.6 Display Unit s 8.7 Buffer Calibration Parameters 8.8 Isopotential Parameters 8.9 Generating a T est Curr[...]

57 ITEM MNEMONIC DISPLA Y LIMITS F ACTOR Y SETTINGS USER SETTINGS PROGRAM LEVEL (Sections 8.0 - 8.9). A. Output Range (Section 8.3) OutPut 1. 4 mA Output 0 - 14 pH 0.00 pH _______ 2. 20 mA Output: 0 - 14 pH 14.00 pH _______ 3. Hold HOLd 3.80 to 22.00 mA 21.00mA _______ 4. Dampening dPn 0 to 255 seconds 0 seconds _______ 5. Fault Current Output Sett[...]

58 MODEL 3081 pH/ORP SECTION 8.0 PROGRAMMING FOR pH MEASUREMENTS 8.3 OUTPUT RANGING 8.3.1 Purpose This section describes how to do the following: 1. assign pH values to the 4 and 20 mA outputs, 2. set the output current generated by the transmitter during hold, 3. set the output current generated by the transmitter when a fault is detected, 4. cont[...]

59 8.3.3 Procedure 1. Enter the Program menu by pressing PROG on the IRC. The OutPut sub-menu appears. 2. Press ENTER . The screen displays the 4 MA prompt. Use the editing keys to change the displayed number to the desired pH. The allowed range is 0.00 to 14.00. Press ENTER to save. 3. The screen displays the 20 MA prompt. Use the editing keys to [...]

60 8.4 DIAGNOSTIC P ARAMETERS 8.4.1 Purpose This section describes how to do the following: 1. change the standardization or reference of fset, 2. enable and disable sensor diagnostics, 3. enable and disable glass impedance temperature compensation, 4. set the high and low warning and failure limits for the glass electrode. 5. set the high and low [...]

61 4. REFERENCE IMPEDANCE. The majori- ty of reference electrodes used in indus- try are low impedance silver-silver chlo- ride electrodes. Every pH and ORP sen- sor manufactured by Rosemount Analytical has a low impedance refer- ence. However , there are applications that call for either a high impedance sodi- um or pH glass reference electrode. B[...]

62 8.4.3 Procedure 1. Press PROG on the infrared remote controller (IRC). 2. Press NEXT until the diAGnOStIC sub-menu appear . Press ENTER . 3. The screen displays the rOFFSt prompt. Use the editing keys to change the flashing display to the desired standardization (reference) of fset (in millivolts). The range is 0 to 1000 mV . Press ENTER to save[...]

63 12. The rFH prompt appears. Use the editing keys to change the display to the desired ref- erence electrode high impedance fault value. The allowed ranges are T ype of reference electrode Allowed range Low impedance ( LO in step 1 1) 0 - 2000 kilohms High impedance ( HI in step 1 1) 0 - 2000 megohms Entering 0000 disables the feature. When the r[...]

64 MODEL 3081 pH/ORP SECTION 8.0 PROGRAMMING FOR pH MEASUREMENTS 8.5 TEMPERA TURE RELA TED SETTINGS 8.5.1 Purpose This section describes how to do the following: 1. activate and deactivate automatic temperature compensation, 2. set a manual temperature compensation value, 3. match the transmitter to the type of temperature element in the pH sensor [...]

65 8.5.3 Procedure 1. Press PROG on the infrared remote controller (IRC). 2. Press NEXT until the tEMP sub-menu appears in the display . Press ENTER . 3. The screen displays the tAUTO prompt. Press Ï or Ð to enable ( On ) or disable ( OFF ) automatic temperature compensation. Press ENTER to save. 4. The tMAN prompt appears. Use the editing keys t[...]

66 8.6 DISPLA Y UNITS 8.6.1 Purpose This section describes how to do the following: 1. switch the process display units between pH and ORP (millivolts), 2. select °C or °F for the temperature display , 3. select percent of full scale or milliamps for the output display , 4. program a security code. 8.6.2 Definitions 1. DISPLA Y UNITS. Select pH i[...]

67 8.7 BUFFER CALIBRA TION P ARAMETERS 8.7.1 Purpose This section describes how to do the following: 1. activate or deactivate auto calibration, 2. identify which buffers will be used during auto calibration, 3. set the stability criteria for auto calibration. 8.7.2 Definitions 1. AUTO CALIBRA TION. In auto calibration, screen prompts direct the us[...]

68 3. ST ABILITY CRITERIA. For the Model 3081 pH/ORP transmitter to accept calibration data, the pH must remain within a specified range for a specified period of time. The default values are 0.02 pH units and 10 seconds. In other words, at the default setting, calibration data will be accepted as soon as the pH reading is const ant to within 0.02 [...]

69 MODEL 3081 pH/ORP SECTION 8.0 PROGRAMMING FOR pH MEASUREMENTS 8.8 ISOPOTENTIAL P ARAMETERS 8.8.1 Purpose This section describes how to do the following: 1. convert the pH at the measurement temperature to the pH at a reference temperature by entering a solution temperature coefficient, 2. change the transmitter isopotential pH. NOTE Do NOT chang[...]

70 8.8.3 Procedure 1. Press PROG on the infrared remote controller (IRC). 2. Press NEXT until the ISOPOtntAL sub-menu appears. Press ENTER . 3. The screen displays the tCOEFF prompt. Use the editing keys to change the display to the desired solution temperature coefficient. The allowed values are -0.044 to +0.028 pH/°C. T o enter a negative coeffi[...]

71 PROGRAM tESt EXIT ENTER 1 2.00 PROGRAM SIM O O UtPUt EXIT NEXT ENTER MODEL 3081 pH/ORP SECTION 8.0 PROGRAMMING FOR pH MEASUREMENTS 8.9 GENERA TING A TEST CURRENT 8.9.1 Purpose This section describes how to generate output currents for testing recorders and dat a han- dling systems. 8.9.2 What happens while the transmitter is generating a test cu[...]

72 MODEL 3081 pH/ORP SECTION 9.0 CALIBRA TION OF ORP MEASUREMENTS SECTION 9.0 CALIBRA TION OF ORP MEASUREMENTS 9.1 General 9.2 Entering and Leaving the Calibrate Menu 9.3 Using the Hold Function 9.4 T emperature Calibration 9.5 St andardization 9.1 GENERAL The Calibrate menu allows the user to calibrate the ORP and temperature response of the senso[...]

73 CALIBRA TE tEMP A A d J EXIT NEXT ENTER CALIBRA TE tEMP EXIT ENTER 0 25.0 MODEL 3081 pH/ORP SECTION 9.0 CALIBRA TION OF ORP MEASUREMENTS 9.4 TEMPERA TURE CALIBRA TION 9.4.1 Purpose 1. As discussed in Section 14.6 (ORP , Concentration, and pH), ORP is a function of temperature. The accuracy of a new sensor/transmitter loop is about ±1°C, which [...]

74 9.5.3 Procedure 1. Place the transmitter in ORP mode. See Section 10.6.3, steps 1 - 3. Af ter selecting and saving OrP , press EXIT twice to return to the main display . 2. Enter the CALIBRA TE menu by pressing CAL on the IRC. The St d sub- menu appears. 3. Rinse the sensor with deionized water and place it in the ORP standard along with a therm[...]

75 10.1 GENERAL This section describes how to do the following: 1. assign ORP values to the 4 and 20 mA outputs, 2. set the current generated by the transmitter during hold, 3. set the current generated by the transmitter when a fault is detected, 4. change sensor diagnostic limits, 5. change the units of the displayed variables, 6. program a secur[...]

76 MODEL 3081 pH/ORP SECTION 10.0 PROGRAMMING FOR ORP MEASUREMENTS ITEM MNEMONIC DISPLA Y F ACTOR Y USER LIMITS SETTINGS SETTINGS PROGRAM LEVEL A. Output Range (Section 10.3) OutPut 1. 4 mA Output -1400 to 1400 mV -1400 mV _______ 2. 20 mA Output: -1400 to 1400 mV 1400 mV _______ 3. Hold HoLd 3.80 to 22.00 mA 21.00mA _______ 4. Dampening dPn 0 to 2[...]

77 MODEL 3081 pH/ORP SECTION 10.0 PROGRAMMING FOR ORP MEASUREMENTS 10.3 OUTPUT RANGING 10.3.1 Purpose This section describes how to do the following: 1. assign ORP values to the 4 and 20 mA outputs, 2. set the output current generated by the transmitter during hold, 3. set the output current generated by the transmitter when a fault is detected, 4.[...]

78 MODEL 3081 pH/ORP SECTION 10.0 PROGRAMMING FOR ORP MEASUREMENTS 10.3.3 Procedure 1. Enter the Program menu by pressing PROG on the IRC. The OutPut sub-menu appears. 2 . Press ENTER. The screen displays the 4 MA prompt. Use the editing keys to change the displayed number to the desired ORP . The allowed range is -1400 to 1400. T o change the disp[...]

79 MODEL 3081 pH/ORP SECTION 10.0 PROGRAMMING FOR ORP MEASUREMENTS 10.4 DIAGNOSTIC P ARAMETERS 10.4.1 Purpose This section describes how to do the following: 1. change the standardization (reference) of fset, 2. enable and disable sensor diagnostics, 3. enable and disable glass impedance temperature compensation for a glass reference electrode, 4. [...]

80 MODEL 3081 pH/ORP SECTION 10.0 PROGRAMMING FOR ORP MEASUREMENTS PROGRAM rEF EXIT ENTER L O PROGRAM IMPtC EXIT NEXT ENTER O N PROGRAM rOFFSt EXIT ENTER PROGRAM dIAGnOSTIC EXIT NEXT ENTER 0 6 0 PROGRAM dIAG EXIT ENTER OFF 10.4.3 Procedure 1. Press PROG on the infrared remote controller (IRC). 2. Press NEXT until the diAGnOStIC sub-menu appears. Pr[...]

81 8. The rWH prompt appears. In the display , W appears as wj . Use the editing keys to change the display to the desired reference electrode high impedance warn- ing value. The allowed ranges are T ype of reference electrode Allowed range Low impedance ( LO in step 6) 0 - 2000 kilohms High impedance ( HI in step 6) 0 - 2000 megohms Entering 0000 [...]

82 MODEL 3081 pH/ORP SECTION 10.0 PROGRAMMING FOR ORP MEASUREMENTS 10.5 TEMPERA TURE ELEMENT 10.5.1 Purpose This section describes how to match the transmitter to the type of temperature element in the ORP sensor . 10.5.2 Definition TEMPERA TURE ELEMENT : ORP sensors use a variety of temperature ele- ments. The Model 3081 ORP transmitter recognizes[...]

83 MODEL 3081 pH/ORP SECTION 10.0 PROGRAMMING FOR ORP MEASUREMENTS PROGRAM OUtPUt EXIT ENTER CUR PROGRAM CODE EXIT ENTER 0 0 0 PROGRAM tYPE EXIT ENTER P H PROGRAM tEMP EXIT ENTER C PROGRAM dISPLAY EXIT NEXT ENTER 10.6 DISPLA Y UNITS 10.6.1 Purpose This section describes how to do the following: 1. switch the process display units between pH and ORP[...]

84 MODEL 3081 pH/ORP SECTION 10.0 PROGRAMMING FOR ORP MEASUREMENTS PROGRAM tESt EXIT ENTER 1 2 . 0 0 PROGRAM SIM O O UtPUt EXIT NEXT ENTER 10.7 GENERA TING A TEST CURRENT 10.7.1 Purpose This section describes how to generate output currents for testing recorders and data handling systems. 10.7.2 What happens while the transmitter is generating a te[...]

85 MODEL 3081 pH/ORP SECTION 1 1.0 MAINTENANCE SECTION 1 1.0 MAINTENANCE 1 1.1 OVERVIEW This section gives general procedures for routine maintenance of the 3081 pH/ORP transmitter and pH and ORP sensors. The transmitter needs almost no routine maintenance. Sensors require periodic inspection and cleaning. The calibration of the transmitter-sensor [...]

86 MODEL 3081 pH/ORP SECTION 1 1.0 MAINTENANCE T ABLE 1 1-1. Replacement Parts for Model 3081 pH/ORP T ransmitter PROBLEM CLEANING SUGGESTIONS Loose scale or debris Use a stream of water from a wash bottle to rinse away solids from the tip of the sensor . If water does not work, gently wipe the glass bulb and liquid junction with a soft cloth, tiss[...]

87 When using acid or alkaline solvents, be careful to keep the solvent away from the liquid junction. If the cleaning sol- vent contact s the junction, hydrogen ions (acid solvent) or hydroxide ions (alkaline solvent) will diffuse into the junc- tion. Because hydrogen and hydroxide ions have much greater mobility than other ions, they produce a la[...]

88 1 1.4 ORP SENSOR MAINTENANCE 1 1.4.1 Frequency of Cleaning The frequency at which an ORP sensor should be inspected and cleaned can be determined only by experience. If the process liquid coats or fouls the sensor , frequent cleaning may be necessary . If the process does not contain a high level of suspended solids, the need for regular cleanin[...]

89 MODEL 3081 pH/ORP SECTION 12.0 TROUBLESHOOTING SECTION 12.0 TROUBLESHOOTING 12.1 W ARNING AND F AUL T MESSAGES 12.2 CALIBRA TION ERRORS 12.3 TROUBLESHOOTING - GENERAL 12.4 TROUBLESHOOTING WHEN A DIAGNOSTIC MESSAGE IS SHOWING 12.5 TROUBLESHOOTING WHEN NO DIAGNOSTIC MESSAGE IS SHOWING 12.6 SYSTEMA TIC TROUBLESHOOTING 12.7 DISPLA YING DIAGNOSTIC V [...]

90 12.2 CALIBRA TION ERRORS If an error occurs during calibration, an error message appears in the main display , and the transmitter does not update the calibration. The calibration errors are S td Err , SLOPE Err LO , and SLOPE Err HI . See Section 12.4 for an explana- tion of the error messages and suggested ways of correcting the problem. 12.3 [...]

91 MODEL 3081 pH/ORP SECTION 12.0 TROUBLESHOOTING 12.4.1 GLASSF AIL GLASSF AIL is an electrode fault message. It means the glass impedance is outside the programmed Glass Fault High ( GFH ) or Glass Fault Low ( GFL ) limit. Glass Fault High suggests the electrode is aging or the electrode is not immersed in the process liquid. Glass Fault Low impli[...]

92 MODEL 3081 pH/ORP SECTION 12.0 TROUBLESHOOTING b. If the sensor was wired with the blue solution ground wire unattached and a jumper between terminals TB-8 and TB-7, remove the jumper and reatt ach the blue solution ground wire to TB-8. Keep the gray reference in wire attached to TB-7. c. For Rosemount Analytical PLUS (+) and TUpH sensors that d[...]

93 MODEL 3081 pH/ORP SECTION 12.0 TROUBLESHOOTING SLOPE ST A TUS OF SENSOR 54-60 mV/unit pH Sensor is in good condition. 48-50 mV/unit pH Sensor is nearing the end of its life. Once the slope drops below 48 mV/unit pH, the sensor can no longer be calibrated. b. The Glass Fail High ( GFH ) limit is probably set too low for the sensor . Set the GFH l[...]

94 MODEL 3081 pH/ORP SECTION 12.0 TROUBLESHOOTING T roubleshooting Flowchart - rEF F AIL A. Be sure the sensor is completely immersed in the process liquid. If the diagnostic message disappears, the sensor is in good condition. If the diagnostic message remains, go to step B. B. Check that the sensor is properly wired to the transmitter . See the a[...]

95 MODEL 3081 pH/ORP SECTION 12.0 TROUBLESHOOTING 12.4.4 rEFW Arn rEF W Arn is an electrode fault message. It means the reference electrode impedance exceeds the programmed Reference W arning High ( RW H ) limit. Ideally , when the measurement system exceeds the warning limits, the user will have adequate time to diagnose and correct problems befor[...]

96 MODEL 3081 pH/ORP SECTION 12.0 TROUBLESHOOTING B. Check the sensor . Refer to the wiring diagrams in Section 3.0 to identify the RTD leads. Disconnect the R TD leads and measure the resistances shown in Figure 12-3. The measured resistance should agree with the value in T able 12-1 to within about 1%. If the measured resistance is appreciably di[...]

97 MODEL 3081 pH/ORP SECTION 12.0 TROUBLESHOOTING C. Check the transmitter . 1. Disconnect the RTD sensor leads and wire the circuit shown in Figure 12-4. Set the resist ance to the value for 25°C shown in T able 12-1. The measured temperature should equal 25°C to within ±1°C. If the measured temperature is correct, the transmitter is working p[...]

98 MODEL 3081 pH/ORP SECTION 12.0 TROUBLESHOOTING B. The RTD sense or the R TD return wire inside the sensor cable may be broken. Keep the sensor wires attached and jumper TB-3 and TB-4. If the diagnostic message disappears, either the RTD return or R TD sense wire is broken. T o verify a broken wire, disconnect the leads and measure the resistance[...]

99 MODEL 3081 pH/ORP SECTION 12.0 TROUBLESHOOTING 12.4.9 SLOPE Err LO SLOPE Err LO means that a two-point buffer calibration attempt has failed. The slope is too low (<40 mV/pH) for a good measurement. T roubleshooting Flowchart-SLOPE Err LO A. Repeat the calibration. 1. Inaccurate buffers can cause a low slope. Repeat the calibration using fres[...]

100 MODEL 3081 pH/ORP SECTION 12.0 TROUBLESHOOTING 12.4.10 SLOPE Err HI SLOPE Err HI means that a two-point buffer calibration attempt has failed. The slope is too high (>62 mV/pH) for a good measurement. T roubleshooting Flowchart-SLOPE Err HI A. Repeat the calibration. 1. Inaccurate buffers can cause a low slope. Repeat the calibration using f[...]

101 MODEL 3081 pH/ORP SECTION 12.0 TROUBLESHOOTING If the sensor is not rebuildable... T ry the reference electrode rejuvenation procedure described in Section 1 1.3.4. If the rejuvenated sensor can be calibrated, the problem has been corrected. If the sensor cannot be calibrated, replace the sensor . 12.4.12 rOM F AIL or CPU F AIL rOM F AIL or CPU[...]

102 MODEL 3081 pH/ORP SECTION 12.0 TROUBLESHOOTING SYMPTOM SECTION Id 000 appears in display when trying to program or calibrate transmitter 12.5.1 Error message flashing in display 12.4 T ransmitter does not respond to remote controller 12.5.2 Calibration Problems: SLOPE Err HI or SLOPE Err LO appears after calibration attempt 12.5.3 bF1 or bF2 co[...]

103 MODEL 3081 pH/ORP SECTION 12.0 TROUBLESHOOTING 12.5.1 Id 000 in Display A security code has been programmed into the transmitter . The correct code must be entered before the transmitter can be programmed or calibrated. T o retrieve a lost security code see Section 5.7. T o change the security code, see Section 8.6. 12.5.2 T ransmitter Does Not[...]

104 MODEL 3081 pH/ORP SECTION 12.0 TROUBLESHOOTING 12.5.5 pH Reading in Buffer Drif ts During Manual Calibration A. Allow adequate time for the temperature of the sensor to reach the temperature of the buffer . If the sensor was in a process substantially hotter or colder than the buf fer , allow at least 20 minutes for readings in the buffer to st[...]

105 MODEL 3081 pH/ORP SECTION 12.0 TROUBLESHOOTING 12.5.8 Buffer Calibration Is Acceptable; Process pH is Grossly Different from Expected V alue. The symptoms suggest a ground loop (measurement system connected to earth ground at more than one point), a float- ing system (no earth ground), or noise being induced into the transmitter by sensor cabli[...]

106 MODEL 3081 pH/ORP SECTION 12.0 TROUBLESHOOTING 4. Occasionally , noise can travel into the transmitter housing from the met al it is mounted on. The noise is then radiated into the transmitter electronics. If isolating the transmitter from its met al mounting eliminates the symptoms, move the transmitter to a different location or mount it with[...]

107 MODEL 3081 pH/ORP SECTION 12.0 TROUBLESHOOTING 12. 5.13 T ransmitter Locks Up A. T urn the dc power off, then turn it back on. B. If the problem persists, replace the electronic board stack (PN 23574-02). 12. 5.14 T ransmitter Periodically Rest arts It self A. The problem is usually related to improperly wired RTD input terminals. 1. The RTD re[...]

108 MODEL 3081 pH/ORP SECTION 12.0 TROUBLESHOOTING Process pH measurement problem Perform buffer calibration (outside of the process) Refer to Section 7.5 Buffer calibration OK? Preamplifier and trans- mitter test OK? Put transmitter preamplifier switch (S-1) into junction box position. Likely Process Problem or Ground Loop: 1. Measure pH of a grab[...]

109 MODEL 3081 pH/ORP SECTION 12.0 TROUBLESHOOTING Perform buffer calibration (outside of the process) Refer to Section 7.5 Buffer calibration OK? Analyzer test OK? Place transmitter internal pream- plifier switch in proper position. Likely Process Problem or Ground Loop: 1. Measure pH of a grab sample in a beaker . If pH is correct, then the proce[...]

MODEL 3081 pH/ORP SECTION 12.0 TROUBLESHOOTING 12.7 DISPLA YING DIAGNOSTIC V ARIABLES 12.7.1 Purpose This section describes how to display the diagnostic variables listed below: DIAGNOSTIC MEASUREMENTS DIAGNOSTIC MESSAGES 1. Sensor voltage in mV ( InPut ) 1. Software version ( VEr ) 2. Glass impedance in megohms ( GIMP ) 2. Display last three fault[...]

111 MODEL 3081 pH/ORP SECTION 12.0 TROUBLESHOOTING 12.8.2 pH Simulation When the Preamplifier Is Located in the T ransmitter . 1. V erify that switch S-1 is set to "transmitter". See Section 2.2. 2. T urn off sensor diagnostics. See Section 8.4. 3. T urn off automatic temperature compensation. Set manual temperature compensation to 25°C.[...]

112 MODEL 3081 pH/ORP SECTION 12.0 TROUBLESHOOTING FIGURE 12-9. Simulate pH through Model 381+ Sensor Preamplifier DWG . NO. REV . 40381+05 A 12.8.4 pH Simulation with the Model 381+ Sensor 1. V erify that switch S-1 is set to "sensor or junction box". See Section 2.2. 2. T urn off sensor diagnostics. See Section 8.4. 3. T urn off automat[...]

113 MODEL 3081 pH/ORP SECTION 12.0 TROUBLESHOOTING 10. T ouch the other end of the second jumper to the center pin of the BNC connector on the preamplifier . DO NOT LET THE WIRE T OUCH THE OUTSIDE OF THE BNC CONNECT OR. 1 1. Measure the voltage. The measured voltage should be 0 mV , and the pH should be approximately 7. Because the calibration data[...]

114 SECTION 13.0 pH MEASUREMENTS 13.1 General 13.2 Measuring Electrode 13.3 Reference Electrode 13.4 Liquid Junction Potential 13.5 Converting V oltage to pH 13.6 Glass Electrode Slope 13.7 Buffers and Calibration 13.8 Isopotential pH 13.9 Junction Potential Mismatch 13.10 Sensor Diagnostics 13.1 1 Shields, Insulation, and Preamplifiers 13.1 GENERA[...]

115 MODEL 3081 pH/ORP SECTION 13.0 pH MEASUREMENTS designed, the liquid junction potential is usually small and rel- atively constant. All three potentials depend on temperature. As discussed in Sections 13.5 and 13.6, the factor relating the cell voltage to pH is also a function of temperature. The construction of each electrode and the electrical[...]

116 MODEL 3081 pH/ORP SECTION 13.0 pH MEASUREMENTS FIGURE 13-5. The Origin of Liquid Junction Potentials. The figure shows a thin section through a pore in the junction plug. The junction separates a solution of pot assium chloride on the left from a solution of hydrochloric acid on the right. The solutions have equal molar concentration. Driven by[...]

117 MODEL 3081 pH/ORP SECTION 13.0 pH MEASUREMENTS 4. the liquid junction potential. The second term, 0.1984 T pH, is the potential (in mV) at the outside surface of the pH glass. This potential depends on temperature and on the pH of the sample. Assuming temperature remains constant, any change in cell volt age is caused solely by a change in the [...]

118 MODEL 3081 pH/ORP SECTION 13.0 pH MEASUREMENTS pH 7.00 and pH 10.00. When the electrodes are placed in pH 7 buffer the cell volt age is V 7 , and when the electrodes are placed in pH 10 buffer , the cell volt age is V 10 . Note that V 7 is not 0 mV as would be expected in an ideal sensor , but is slightly different. The microprocessor calculate[...]

119 MODEL 3081 pH/ORP SECTION 13.0 pH MEASUREMENTS junction potentials in the buffers are assumed to be equal and are exaggerated for clarity . If the liquid junction potential in the sample differs from the buffers, a measurement error result s. Figure 13-8 illus- trates how the error comes about. Assume the true pH of the sample is pH s and the c[...]

120 MODEL 3081 pH/ORP SECTION 14.0 ORP MEASUREMENTS SECTION 14.0 ORP MEASUREMENTS 14.1 General 14.2 Measuring Electrode 14.3 Reference Electrode 14.4 Liquid Junction Potential 14.5 Relating Cell V oltage to ORP 14.6 ORP , Concentration, and pH 14.7 Interpreting ORP Measurement s 14.8 Calibration 14.1 GENERAL Figure 14-1 shows a simplified diagram o[...]

121 14.2 MEASURING ELECTRODE Figure 14-2 shows a typical ORP measuring elec- trode. The electrode consist s of a band or disc of platinum attached to the base of a sealed glass tube. A platinum wire welded to the band connects it to the lead wire. For a noble metal electrode to develop a st able potential, a redox couple must be present. A redox co[...]

122 Liquid junction potentials exist whenever dissimilar elec- trolyte solutions come into contact. The magnitude of the potential depends on the difference between the mobility of the ions. Although liquid junction potentials cannot be elim- inated, they can be made small and relatively constant. A small liquid junction potential exists when the i[...]

123 is described by the following equation, called the Nernst equation: E = E° - (2) In the Nernst equation, E is the electrode potential and E° is the standard electrode potential, both in millivolt s, t is temperature in °C, n is the number of electrons transferred (n = 1 in the present case), and [Fe +2 ] and [Fe +3 ] are the concentrations o[...]

124 The Nernst equation for reaction 3 is: E = E°- (4) Note that the hydrogen ion factor in the concentration ratio is raised to the fourteenth power . The t able shows the expected effect of changing pH on the measured ORP at 25°C. pH changes ORP changes by from 2.0 to 2.2 7 mV from 2.0 to 2.4 35 mV from 2.0 to 1.8 47 mV from 2.0 to 1.6 75 mV Th[...]

125 MODEL 3081 pH/ORP SECTION 14.0 ORP MEASUREMENTS The ORP of the iron (II) - iron (III) standard when meas- ured with a platinum electrode against a saturated sil- ver-silver chloride reference is 476 ± 20 mV at 25°C. The range of values is caused primarily by the high and variable liquid junction potential generated in solutions containing hig[...]

126 15.1 OVERVIEW OF HART COMMUNICA TION HART (highway addressable remote transducer) is a digital communication system in which two frequencies are superimposed on the 4 to 20 mA output signal from the transmitter . A 1200 Hz sine wave represents the digit 1, and a 2400 Hz sine wave represents the digit 0. Because the average value of a sine wave [...]

127 MODEL 3081 pH/ORP SECTION 15.0 THEOR Y - REMOTE COMMUNICA TIONS If your communicator does not recognize the Model 3081 pH/ORP transmitter , the device description library may need updating. Call the manufacturer of your HART communication device for updates. 15.3 ASSET MANAGEMENT SOLUTIONS Asset Management Solutions (AMS) is software that help [...]

128 TERM DEFINITION Acid When dissolved in water acids increase the hydrogen ion concentration. Pure water at 25°C contains 1 x 10 -7 moles per liter of hydrogen ions (H + ) and an equal concentration of hydroxide ions (OH - ). An acid increases the hydrogen ion con- centration above the value found in pure water and decreases the hydroxide ion co[...]

129 MODEL 3081 pH/ORP SECTION 16.0 GLOSSAR Y Combination electrode In a combination electrode, the measuring electrode and reference electrode are combined in a single body . Of ten the temperature element is included in the body as well. Common A point in a circuit against which voltages are measured. Diagnostics Diagnostics, also called advanced [...]

130 MODEL 3081 pH/ORP SECTION 16.0 GLOSSAR Y Fault A fault is a system disabling condition. Measurement data displayed during a fault condition are probably in error and should be regarded with great suspicion. The Model 3081 pH/ORP transmitter displays fault messages to aid in trouble-shooting. Filling solution The electrolyte solution inside an e[...]

131 MODEL 3081 pH/ORP SECTION 16.0 GLOSSAR Y Hold function During hold the Model 3081 pH/ORP transmitter generates a pre-programmed output current or remains at the last value. Placing the transmitter in hold avoids false alarms and unwanted operation of chemical dosing pumps while the sensor is being calibrated or cleaned. Intrinsically safe An en[...]

132 MODEL 3081 pH/ORP SECTION 16.0 GLOSSAR Y pH Although pH is often defined as the negative common logarithm of the hydrogen ion activity , pH is best defined by describing how it is measured. The measure- ment requires three steps. Assemble an electrochemical cell consisting of a glass electrode, a reference electrode, and the solution. Calibrate[...]

133 MODEL 3081 pH/ORP SECTION 16.0 GLOSSAR Y Solution ground A solution ground is a metal post or ring incorporated into the sensor body and mak- ing contact with the process stream. Glass and reference impedances are meas- ured by applying a voltage pulse between the electrode and the solution ground. Solution temperature The pH of many solutions,[...]

134 MODEL 3081 pH/ORP SECTION 17.0 RETURN OF MA TERIAL SECTION 17.0 RETURN OF MA TERIAL 17.1 GENERAL. T o expedite the repair and return of instrument s, proper communication between the customer and the factory is important. Call 1-949-757-8500 for a Return Materials Authorization (RMA) number . 17.2 W ARRANTY REP AIR. The following is the procedu[...]

W ARRANTY Goods and part(s) (excluding consumables) manufactured by Seller are warranted to be free from defect s in workman- ship and material under normal use and service for a period of twelve (12) months from the date of shipment by Seller . Consumables, pH electrodes, membranes, liquid junctions, electrolyte, O-rings, etc. are warranted to be [...]

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