Page 1: Table Of Contents
846 Current-to-Pressure Transducer ™ Contents Figure 1. Fisher 846 Current‐to‐Pressure Transducer Introduction Scope of Manual ......
Page 2: Scope Of Manual
The 846 is an electronic I/P transducer. It has a single electronic circuit board, as shown in figure 2. The circuit contains a solid‐state pressure sensor that monitors output pressure and is part of an electronic feedback network. The self‐correcting ability provided by the sensor/circuit combination allows the transducer to produce a very stable and...
Page 3 0.4 bar (30 to 6 psi), and 1.7 to 0.3 bar (25 to 5 psi) Performance Rangeability between 2.3 and 0.03 bar (33 and 0.5 psi) Note: The performance of all 846 I/Ps is verified using computer automated manufacturing systems Supply Pressure to ensure that every unit shipped meets its performance specifications.
Page 4 O‐Rings: Nitrile, except silicone for sensor O‐rings. Required Operating Voltage with Remote pressure Options Reading Off Fisher 67CFR filter regulator, supply and output Min. 6.0 V (at 4 mA) gauges or tire valve remote pressure reading, module Max. 7.2 V (at 20 mA) cover with multiple stroke ports, stainless steel housing, or stainless steel mounting bracket.
Page 5: Educational Services
1. A = No degradation during testing. B = Temporary degradation during testing, but is self‐recovering. Educational Services For information on available courses for the 846 current‐to‐pressure transducer, as well as a variety of other products, contact: Emerson Automation Solutions...
Page 6: Installation
MODULE FINAL ASSEMBLY NOTE: THE 846 IS NOT A CONSTANT RESISTOR IN SERIES WITH AN INDUCTOR. IT IS BETTER MODELED IN THE LOOP AS A 50 OHM RESISTOR IN SERIES WITH A 6‐VOLT DC VOLTAGE DROP WITH NEGLIGIBLE INDUCTANCE. A6325...
Page 7: Hazardous Area Classifications And Special Instructions For Safe-Use And Installation In Hazardous Locations
When a control valve is ordered with an 846 transducer specified to be mounted on the actuator, the factory‐mounted transducer is connected to the actuator with the necessary tubing and calibrated to the specifications on the order.
Page 8: Mounting
Instruction Manual 846 Transducer June 2017 D102005X012 Mounting WARNING This unit will vent to the atmosphere through the stroke port in the module cover and the exhaust port, located under the nameplate. Do not remote vent this unit. The transducer is designed for mounting on a control valve, 51 mm (2‐inch) diameter pipestand, wall, or panel. Figures 5, 6, 7, and 8 show recommended mounting configurations.
Page 9 Instruction Manual 846 Transducer D102005X012 June 2017 Figure 4. Typical Dimensions and Connection Locations (Aluminum Construction Shown) CONDUIT CONNECTION 1/2 ‐ 14 NPT OUTPUT PORT 1/4 ‐ 18 NPT (5.07) (4.68) NAMEPLATE EXHAUST PORT UNDERNEATH NAMEPLATE (1.38) MODULE COVER WITH...
Page 10: Supply Pressure
The air supply line can be connected to the 1/4‐18 NPT supply port, or to the supply port of a filter‐regulator mounted directly to the transducer. Figures 5, 6, 7, and 8 show the installation options. Figure 5. Typical Dimensions with Fisher 67CFR Filter/Regulator and Gauges FOR PROPER MOISTURE DRAINAGE THIS END MUST BE UP (8.48)
Page 11 Instruction Manual 846 Transducer D102005X012 June 2017 Figure 6. Typical Transducer Mounting with Universal Mounting Bracket ADDITIONAL ADAPTER PLATE MOUNTING BRACKET PART NUMBER 03311‐0318‐0001 (SEE DETAIL “A”) REQUIRED FOR I/P WITH FOR PROPER MOISTURE FOR PROPER MOISTURE STAINLESS STEEL HOUSING...
Page 12 Instruction Manual 846 Transducer June 2017 D102005X012 Figure 6. Typical Transducer Mounting with Universal Mounting Bracket (continued) FOR STAINLESS STEEL HOUSING, 4 X 10 (0.375) ALIGN 4 HOLES WITH I/P HOUSING (3.50) (.89) (1.18) (3.50) (1.13) 5 X 10 (0.375) (1.16)
Page 13 Instruction Manual 846 Transducer D102005X012 June 2017 Figure 7. Typical Transducer Dimensions with Gauges SUPPLY (3.2) GAGE OUTPUT GAGE FILTER‐ REGULATOR 67CFR (1.92) 14‐18 NPT 1/4‐18 NPT SUPPLY CONN OUTLET CONN (2.83) PLUGGED WHEN (0.36) GAUGE NOT 14B7332‐D E0776 FURNISHED (INCH) Figure 8.
Page 14: Output Pressure
Excessive current can damage the transducer. Do not connect an input current of more than 100 mA to the transducer. Note For North American explosion‐proof applications, 846 transducers have been designed so that a conduit seal is not required. For all other applications install the product per local, regional, or national code, rules, and regulations.
Page 15: Venting Ports
Instruction Manual 846 Transducer D102005X012 June 2017 Connect the positive signal lead to the positive terminal, marked +. Connect the negative signal lead to the negative terminal, marked -. Note Units with the Remote Pressure Reading (RPR) option may cause interference with the analog output signal from some instrumentation systems.
Page 16: Calibration
Also refer to the WARNING at the beginning of the Maintenance section. Calibration of the 846 requires either an accurate current generator or an accurate voltage generator with a precision 250‐ohm, 1/2‐watt resistor. Figure 9 shows how to connect either device.
Page 17 The input range is selected by changing the position of a jumper located on the electronic circuit board. Refer to Electronic Circuit Board in the Maintenance section, and figure 18 for the location and instruction on placement. Table 3. Fisher 846 I/P Rangeability Matrix Output Pressure Range (psi) (Performance Code) Common Ranges Misc.
Page 18: Standard Performance: Full Range Input, Direct Action
Instruction Manual 846 Transducer June 2017 D102005X012 Standard Performance: Full Range Input, Direct Action WARNING Refer to the WARNING at the beginning of the Maintenance section. Use the following procedure to achieve a standard 0.2 to 1.0 bar (3 to 15 psi) output span for a 4 to 20 mA input signal: 1.
Page 19: Standard Performance: Split Range Input, Direct Action
Instruction Manual 846 Transducer D102005X012 June 2017 Use the following procedure with a multirange performance unit to achieve the desired direct action output span for a 4 to 20 mA input signal: 1. Perform steps 1 through 9 of the calibration procedure for Standard Performance: Full Range Input, Direct Action.
Page 20: Standard Performance: Full Range Input, Reverse Action
Instruction Manual 846 Transducer June 2017 D102005X012 6. Repeat steps 4 and 5 to verify and complete the calibration. 7. Turn off the air supply. Remove the module final assembly from the housing. Place the range jumper in the Lo position for Low Range, as indicated in figure 18.
Page 21: Standard Performance: Split Range Input, Reverse Action
Instruction Manual 846 Transducer D102005X012 June 2017 3. Apply an input of 20.0 mA (Vm = 5.0 V), and adjust the span screw to achieve the desired lower limit of the output range. The span must be at least 0.7 bar (11.0 psi). The lower limit of the 20.0 mA setting is 0.03 bar (0.5 psi). The output increases with clockwise rotation of the span screw.
Page 22: Transporting The Module Final Assembly
Ensure that the span and zero potentiometers are not moved from their calibrated positions. Principle of Operation The following paragraphs describe the functional parts of the 846. Figure 10 shows the block diagram. Figure 10. Functional Parts Block Diagram...
Page 23: Magnetic Actuator
Instruction Manual 846 Transducer D102005X012 June 2017 The sensor's pressure signal is fed to a simple internal control circuit. By using this technique, the transducer's performance is set by the sensor/circuit combination. Changes in output load (leaks), variations in supply pressure, or even component wear are sensed and corrected by the sensor/circuit combination.
Page 24: Booster Stage
Instruction Manual 846 Transducer June 2017 D102005X012 To vary the pilot output pressure, the high‐velocity stream is diverted away from the receiver nozzle by the deflector, which is a cylindrical, aerodynamic body located between the two nozzles. In response to a change in actuator coil current, the deflector is repositioned between the nozzles. There is a linear relationship between the coil current and the pilot stage output pressure.
Page 25: Troubleshooting
June 2017 Troubleshooting The modular design and unitized subassemblies of the 846 allows for quick and easy troubleshooting and repair. This section presents information on the diagnostic features and procedures for troubleshooting both models in service or in the shop.
Page 26: In-Service Troubleshooting
Instruction Manual 846 Transducer June 2017 D102005X012 Equations (1) P = m(p) + b P = pressure Example p = frequency = 3 psig = 6000 Hz = 15 psig = 9000 Hz (2) m = 15 - 3 Procedure...
Page 27 Instruction Manual 846 Transducer D102005X012 June 2017 Figure 14. Field Troubleshooting Flowchart TROUBLESHOOTING TROUBLESHOOTING FROM THE CONTROL ROOM IN THE FIELD NOTE: AFTER FINAL CORRECTIVE ACTION, CHECK LOOP OPERATION. IF NOT OK, RESTART TROUBLESHOOTING PROCEDURE. 1 REFER TO REPLACING THE MODULE FINAL ASSEMBLY IN SECTION 6.
Page 28 Instruction Manual 846 Transducer June 2017 D102005X012 WARNING Personal injury or property damage could result from an uncontrolled process. Before removing the module cover, ensure the process is properly controlled and the supply air to the transducer is turned off and vented. Unscrewing the module cover removes power from the electronics and opens the supply and output air passages to atmosphere resulting in an output signal of 0.0 psi.
Page 29: Troubleshooting In The Shop
If the entire transducer is brought to the shop for troubleshooting, then the preceding sequence applies. If only the module final assembly has been brought to the shop, then use another 846 housing as a test fixture. Insert the module into the test fixture.
Page 30 Instruction Manual 846 Transducer June 2017 D102005X012 b. Make sure the O‐rings are lightly lubricated with silicone grease and properly seated. c. Reassemble and check operation. d. If after cleaning, the transducer does not function, replace the pilot/actuator assembly with a new one.
Page 31: Maintenance
The presence of Emerson Automation Solutions personnel and approval agency personnel may be required if you service (other than normal, routine maintenance, such as calibration) or replace components on an 846 transducer that carries a third‐party approval. When replacing components, use only components specified by the factory. Substitution with other components may void the third‐party approval and result in personal injury or property damage.
Page 32: Module Final Assembly
Instruction Manual 846 Transducer June 2017 D102005X012 Module Final Assembly WARNING Refer to the Maintenance WARNINGS at the beginning of this section. The active mechanical and electrical components of the transducer are incorporated into a single, field‐replaceable module called the module final assembly, as shown in figure 15. Electrical connection between the terminal compartment and module final assembly is made by electrical feedthroughs that extend into the module compartment.
Page 33 Instruction Manual 846 Transducer D102005X012 June 2017 ELECTRONIC CIRCUIT BOARD SCREWS Figure 15. Fisher 846 Exploded View ELECTRONIC CIRCUIT BOARD MODULE SUBASSEMBLY ELECTRONIC PILOT/ACTUATOR CIRCUIT BOARD O‐RINGS ASSEMBLY MODULE O‐RINGS TERMINAL COVER MODULE HOUSING PILOT/ACTUATOR V‐GROOVE ASSEMBLY O‐RINGS ALIGNMENT MARK...
Page 34: Removing The Module Final Assembly
Instruction Manual 846 Transducer June 2017 D102005X012 Removing the Module Final Assembly The module final assembly is attached to the module cover. Removing the module cover automatically removes the module final assembly from the housing. When the module cover is unscrewed, the electrical feedthroughs and span and zero adjustments automatically disengage.
Page 35: Replacing The Module Final Assembly
Instruction Manual 846 Transducer D102005X012 June 2017 3. Remove the module final assembly from the module cover. To accomplish this, hold the cover steady, and push the module final assembly in the direction of the module cover indicating boss. At the same time, lift the opposite foot of the module final assembly out of the cover slot, as shown in figure 17.
Page 36: Electronic Circuit Board
Instruction Manual 846 Transducer June 2017 D102005X012 9. Hand tighten the module cover as much as possible. Use a wrench or long screwdriver shaft to tighten the module cover an additional 1/4 to 1/2 turn [24 to 27 NSm (18 to 20 lbfSft)]. For units with ATEX/IECEx Flameproof approvals, make sure the cover lock and screw are securely re‐installed.
Page 37: Range Jumper
Pressure Reading (RPR) in the Troubleshooting section. Note When operating 846 transducers in series, only one unit may be configured for Remote Pressure Reading. Activating the RPR feature in two units will result in an unusable RPR signal. Range Jumper The range jumper is positioned according to the calibration specified.
Page 38: Replacing The Electronic Circuit Board
Instruction Manual 846 Transducer June 2017 D102005X012 Replacing the Electronic Circuit Board 1. Verify that the circuit board is green for assembly into a direct action unit, or blue for assembly into a reverse action unit. 2. Ensure that the two O‐rings are in the proper position. The small O‐ring is positioned in the beveled O‐ring gland of the module subassembly.
Page 39: Removing The Pilot/Actuator Assembly
Instruction Manual 846 Transducer D102005X012 June 2017 Removing the Pilot/Actuator Assembly To remove the pilot/actuator assembly, disengage the four mounting screws, and gently pull the assembly out of the module subassembly. To aid removal, the pilot/actuator framework may be gently gripped with a pair of pliers.
Page 40: Module Subassembly
Instruction Manual 846 Transducer June 2017 D102005X012 2. Inspect the pilot/actuator assembly cavity in the module final assembly to ensure that it is clean. 3. Lightly lubricate the two O‐rings with silicone grease, and place them in the beveled O‐ring glands. O‐rings between the pilot/actuator assembly and the module should be installed justified to the lower portion of the O‐ring gland.
Page 41: Exhaust And Stroke Port Screens
Instruction Manual 846 Transducer D102005X012 June 2017 Figure 21. Terminal Compartment Exploded View TEST PINS TERMINAL BLOCK CONNECTION BOARD TERMINAL BLOCK ZERO AND SPAN SCREWS ELECTRICAL FEEDTHROUGHS GROUNDING LUG A6656 Separate test points are provided that have a 10‐ohm resistor in series with the signal negative (-) terminal. The test points allow the input current to be determined with a voltmeter without disconnecting a signal lead.
Page 42: Parts
Use only genuine Fisher replacement parts. Components that are not supplied by Emerson Automation Solutions should not, under any circumstances, be used in any Fisher instrument. Use of components not supplied by Emerson Automation Solutions may void your warranty, might adversely affect the performance of the instrument, and could cause personal injury and property damage.
Page 43 Instruction Manual 846 Transducer D102005X012 June 2017 Figure 22. Supply Gauge Figure 23. Output Gauge 1/4 NPT 14 sq (0.55) 14 sq (0.55) 1/4 NPT (INCH) (INCH) Figure 24. Exploded Parts Drawing (also see table 5) GE89695 NOTE: 1 THREE O‐RINGS ARE REQUIRED FOR THE MODULE SUBASSEMBLY.
Page 44 Responsibility for proper selection, use, and maintenance of any product remains solely with the purchaser and end user. Fisher is a mark owned by one of the companies in the Emerson Automation Solutions business unit of Emerson Electric Co. Emerson Automation Solutions, Emerson, and the Emerson logo are trademarks and service marks of Emerson Electric Co.

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