Emerson Fisher 4194S User manual

www.Fisher.com
Fisher™4194S Differential Pressure Controllers
Contents
1. Introduction 2...............................
Scope of Manual 2.............................
Description 2.................................
Specifications 5...............................
Educational Services 5.........................
2. Installation 7................................
Actuator Mounting 7..........................
Panel Mounting 7.............................
Wall Mounting 7..............................
Pipestand Mounting 7.........................
Pressure Connections 9........................
Process Pressure 9.............................
Supply Pressure 10............................
Vent 10......................................
Remote Set Up Point Pressure (Option M) 10.......
3. Controller Operation 11.......................
Operating Information 11......................
Adjustments 11...........................
Manual Set Point 11........................
Remote Set Point 11.......................
Proportional Band (Differential Gap) 11.......
Changing Controller Action 11...............
Auto/Manual Switching (Option E) 11.........
Prestartup Checks 12.......................
Startup 13................................
Calibration 14................................
Process Zero and Span Adjustment 14........
Remote Set Point Zero and Span
(Option M) 14..........................
Setting Switching Points 15.................
Direct‐Acting Controllers 15.................
Reverse‐Acting Controllers 17...............
Principle of Operation 17.......................
Overall Operation 17.......................
Remote Set Point 19.......................
Auto/Manual Option 19.....................
4. Maintenance 21..............................
Troubleshooting 22............................
Changing Controller Action 23..................
Replacing Controller Parts 24....................
Process Pressure Scale 24...................
Relay 25..................................
Case and Cover 26.........................
Gauges 26................................
Pressure Control Block 26...................
Figure 1-1. Fisher 4194S Differential Pressure
Controllers
NAMEPLATE
W3613
W5663‐1
Supply Tubing and Positive
Feedback Tubing Assemblies 27...........
Proportional Band Knob, Nozzle
Assembly, and Set Point
Beam Assembly 27......................
Flapper Flexure Pivot Assembly 31............
Positive Feedback Bellows 34................
Links 36..................................
Link Number 1 36.........................
Link Number 2 38.........................
Instruction Manual
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Contents (cont'd)
Link Number 3 39.........................
Link Number 4 39.........................
Link Number 5 40.........................
Long Pivot Assembly 40.....................
Short Pivot Assembly 40....................
Process Drive Flexure 41....................
Process Tubing 41.........................
Capsular Element Assembly 41...............
Maintenance Calibration 42.................
Precalibration Procedures 42................
Aligning the Drive Bracket Assembly 42.......
Setting the Travel Stops 42..................
Aligning Linkage 43........................
Zero and Span Adjustment 43...............
Linearity Adjustment 44....................
Flapper Alignment 44..........................
Remote Set Point (Option M) 45.................
Replacing Parts 45.........................
Pivot Assembly A 46........................
Pivot Assembly B 46........................
Drive Flexure 47...........................
Tubing 47................................
Remote Set Point Capsular Element
Assembly 47...........................
Link A 48.................................
Link B 48.................................
Maintenance Calibration 48.................
Precalibration Procedure 48.................
Setting Travel Stops 49.....................
Aligning Linkage 49........................
Zero and Span Adjustment 49...............
Linearity Adjustment 50....................
Auto/Manual (Option E) 50.....................
Replacing the Auto/Manual Station 51........
Disassembly 51............................
Assembly 51..............................
Replacing the Switch Body Assembly,
Lever O‐Ring, Switch Body O‐Ring,
and Tubing Assembly 51.................
Disassembly 52............................
Assembly 52..............................
Replacing the Loader Range Spring,
Diaphragm Assembly, Ball Seat,
Tubing, and Ball 53......................
Disassembly 53............................
Assembly 53..............................
Replacing the Loader Valve Plug and
Valve Plug Spring 54.....................
5. Parts Ordering 55.............................
Parts Kits 55..................................
Parts List 55..................................
General Controller Parts 55..................
Mounting Parts 57.........................
Pipestand Mounting 57....................
Panel Mounting 57........................
Wall Mounting 57.........................
Actuator Casing Mounting 57...............
Actuator Yoke Mounting 57................
Tubing 57...............................
Fittings 57...............................
Section 1 Introduction1
Scope of Manual
This instruction manual provides installation, operating, calibration, maintenance, and parts ordering information for
the 4194S differential pressure indicating controllers. Portions of this manual apply only to specific configurations in
the 4194S product line. These configurations of the controller are indicated by letter suffixes in the type number that
correspond to the mode and option designated in table 1-2. Refer to table 1-2 for available 4194S configurations. The
type number of the controller is on the nameplate. Refer to figure 1-1 for the location of the nameplate.
Description
The controllers described in this manual provide a differential gap output with the options as shown in table 1-2. The
controller shows process differential pressure and set point on an easy‐to‐read process scale. The controller output is a
pneumatic signal that operates a final control element.
Do not install, operate or maintain a 4194S differential pressure indicating controller without first being fully trained
and qualified in valve, actuator and accessory installation, operation and maintenance. To avoid personal injury or
property damage it is important to carefully read, understand, and follow all of the contents of this manual, including
all safety cautions and warnings. If you have any questions about these instructions, contact your Emerson sales office
or Local Business Partner before proceeding.

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Table 1-1. Specifications
Available Configurations
See table 1-2
Sensing Element Range (Input Signal)
Lower and Upper Range Limits: As shown in table 1-3
Maximum Allowable Pressure: As shown in table 1-3
Process Scale
Matched to the range of the process differential
pressure as standard. Optional scales available(1)
Process Connections
Standard: 1/4 NPT internal stainless steel (all input
ranges)
Optional: 1/2 NPT internal stainless steel
Output Signal
Differential Gap Range: 0 and 1.4 bar (0 and 20 psig)
or 0 and 2.4 bar (0 and 35 psig)
Action: Field‐reversible between direct (increasing
differential pressure increases output pressure) or
reverse (increasing differential pressure decreases
output pressure).
Supply and Output Connections
1/4 NPT internal
Supply Pressure Requirements
See table 1-4
Supply Pressure Medium
Air or Natural Gas
Supply medium must be clean, dry and non-corrosive
Per ISA Standard 7.0.01
A maximum 40 micrometer particle size in the air
system is acceptable. Further filtration down to 5
micrometer particle size is recommended. Lubricant
content is not to exceed 1 ppm weight (w/w) or
volume (v/v) basis. Condensation in the air supply
should be minimized.
Per ISO 8573-1
Maximum particle density size: Class 7
Oil content: Class 3
Pressure Dew Point: Class 3 or at least 10°C less than
the lowest ambient temperature expected
Remote Set Point Pressures
0.2 to 1.0 bar (3 to 15 psig) or
0.4 to 2.0 bar (6 to 30 psig)
Controller Adjustments
Differential Gap Control: 5 to 100% of process scale
range
Set Point: Continuously adjustable from 0 to 100% of
the scale range
Steady‐State Air Consumption(2)
0 to 1.4 Bar (0 to 20 Psig) Output:
0.08 m3/hr (2.8 scfh)
0 to 2.4 Bar (0 to 35 Psig) Output:
0.07 m3/hr (2.5 scfh)
Operative Ambient Temperature Limits(3)
-40 to 70_C (-40 to 160_F)
Housing
Designed to NEMA 3 (weatherproof) and IEC 529 IP54
specifications
Hazardous Area Classification
4194S differential pressure indicating controllers
comply with the requirements of ATEX Group II
Category 2 Gas and Dust
Mounting
Controller can be mounted on actuator, panel, wall,
or pipestand.
Approximate Weight
4.5 kg (10 pounds)
Declaration of SEP
Fisher Controls International LLC declares this
product to be in compliance with Article 4 paragraph
3 of the PED Directive 2014/68/EU. It was designed
and manufactured in accordance with Sound
Engineering Practice (SEP) and cannot bear the CE
marking related to PED compliance.
However, the product may bear the CE marking to
indicate compliance with other applicable European
Community Directives.
NOTE: Specialized instrument terms are defined in ANSI/ISA Standard 51.1 - Process Instrument Terminology.
1. Consult your Emerson sales office or Local Business Partner for additional information.
2. Normal m3/hour - Normal cubic meters per hour at 0_C and 1.01325 bar, absolute. Scfh - Standard cubic feet per hour at 60_F and 14.7 psia
3. Also for transportation and storage limits.

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Table 1-2. Available Configurations for Fisher 4194S Controllers
CONTROLLER(1) OPTIONS
Internal Auto/Manual Station, Option E Remote Set Point, Option M
4194S
4194SE
4194SM
4194SME
X
X
X
X
1. Reverse‐acting constructions are designated by an R added to the type number
Table 1-3. Process Sensor (Capsular Element) Pressure Ratings and Materials
UNITS CAPSULAR
STANDARD RANGES
DIFFERENTIAL SPAN
UNITS
STATIC PRESSURE
OPERATING RANGE OPERATING
LIMIT(3)
STANDARD
MATERIAL
Minimum(1) Maximum(2)
Minimum
Inches of
Mercury (bar)
Maximum
Bar
0 to 4.0
0 to 0.7
0 to 1.4
0 to 2.0
0.2
0.4
0.7
1.0
0.4
0.7
1.4
2.0
Bar
-0.4
-.07
-1.0
-1.0
0.4
0.7
1.4
2.0
0.5
1.0
2.1
3.1 N09902
Psid
0 to 5
0 to 10
0 to 20
0 to 30
2.5
5.0
10.0
15.0
5
10
15
20
Psig
-10
-20
-30
-30
5
10
20
30
7.5
15.0
30.0
45.0
1. Span is adjustable between minimum shown and maximum of the capsular element operating range and can be positioned anywhere within this range. For example, if a 0 to 2.0 bar (0 to 30
psid) capsular element is used and the minimum span of 1.0 bar (15 psid), 1.0 to 2.0 bar (15 to 30 psid), or any value between minimum and maximum value of the operating range.
2. Maximum difference between the two input supply pressures.
3. Capsular element may be pressured to this value (after reaching travel stop at upper range limit) without permanent zero shift or structural damage to controller components.
Table 1-4. Supply Pressure Data
OUTPUT SIGNAL RANGE NORMAL OPERATING SUPPLY PRESSURE(1) MAXIMUM PRESSURE TO PREVENT INTERNAL DAMAGE(2)
Bar 0 & 1.4 1.4 2.8
0 & 2.4 2.4 2.8
Psig 0 & 20 20 40
0 & 35 35 40
1. If this pressure is exceeded, control stability may be impaired.
2. If this pressure is exceeded, damage to the controller may result.

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Specifications
WARNING
This product is intended for a specific current range, temperature range and other application specifications. Applying
different current, temperature and other service conditions could result in malfunction of the product, property damage or
personal injury.
Specifications for 4194S controllers are listed in table 1-1.
Educational Services
For information on available courses for 4194S controllers, as well as a variety of other products, contact:
Emerson Automation Solutions
Educational Services - Registration
Phone: [phone] or 1-800-338-8158
E-mail: [email protected]
emerson.com/fishervalvetraining

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Section 2 Installation22-2-
The controllers should be mounted with the housing vertical (as shown in figure 2-1) so that the vent points down.
WARNING
To avoid personal injury or property damage from sudden release of process pressure:
D Always wear protective clothing, gloves, and eyewear when performing installation and maintenance procedures.
D Personal injury or property damage may result from fire or explosion if natural gas is used as the supply medium and
preventive measures are not taken. Preventive measures may include, but are not limited to, one or more of the
following: Remote venting of the unit, re‐evaluating the hazardous area classification, ensuring adequate ventilation,
and the removal of any ignition sources. For information on remote venting of this controller, refer to page 10.
D Check with your process or safety engineer for any additional measures that must be taken to protect against process
media.
D If installing into an existing application, also refer to the WARNING at the beginning of the Maintenance section in this
instruction manual.
CAUTION
Do not use sealing tape on pneumatic connections. This instrument contains small passages that may become obstructed
by detached sealing tape. Thread sealant paste should be used to seal and lubricate pneumatic threaded connections.
Actuator Mounting
Refer to figure 2-1. Controllers specified for mounting on a control valve actuator will be mounted at the factory. If the
controller is ordered separately for installation on a control valve actuator, mount the unit as described in this section.
Mounting parts vary for different actuator types.
Attach the mounting bracket to the actuator yoke with cap screws, lock washers, and spacer spools. Attach the
controller to the bracket with cap screws, lock washers, and spacer spools. On some designs, the mounting bracket is
attached to the actuator casing rather than to the yoke.
Panel Mounting
Refer to figure 2-2. Cut a hole in the panel surface using the dimensions shown in figure 2-2. Slide the controller into
the hole and attach the bracket (key 68) to the rear of the controller using three cap screws (key 66) and lock washers
(key 67). Tighten the screws (key 70) to draw the case snugly and evenly to the panel surface.
Wall Mounting
Refer to figure 2-3. Drill holes in the wall (using the dimensions in figure 2-3) to align with the four holes in the bracket
(key 68). If the process tubing is to run through the wall, drill a hole in the wall large enough to accept the tubing.
Mount the controller to the bracket using three cap screws (key 66) and lock washers (key 67). Attach the bracket to
the wall, using suitable screws or bolts.
Pipestand Mounting
Refer to figure 2-4. Pipestand mounting parts are provided to mount the controller to an NPS 2 (nominal) pipe. Attach
a bracket (key 68) to the controller with cap screws (key 66) and lock washers (key 67). Attach two clamps (key 69) to
the bracket, and fasten the controller to the pipe.

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Figure 2-1. Typical Actuator Mounting
MOUNTING
BRACKET
W5661
SPACER
SPOOLS
CAP SCREWS AND
LOCKWASHERS
Figure 2-2. Panel Mounting
REAR VIEW
TOP VIEW
DIMENSIONS OF
PANEL CUTOUT
mm
(INCH)
36A9780‐A
A2757‐4
308
(12.06)
14
(0.56)R
236
(9.31)
Figure 2-3. Wall Mounting
36A9761‐A
A2759‐4 mm
(INCH)
TOP VIEW
REAR VIEW
280
(10.25)
152
(6.00)
13
(0.50)
Figure 2-4. Pipestand Mounting
36A9758‐A
A2869‐1
SIDE VIEW
HORIZONTAL PIPE
VERTICAL PIPE

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Pressure Connections
WARNING
Overpressuring any system component, including the capsular sensing element, could result in personal injury or property
damage due to fire and explosion caused by venting or leakage of a hazardous supply pressure medium or process medium.
To avoid such injury or damage, provide suitable pressure‐ relieving or pressure‐limiting devices if supply pressure or
process pressure is capable of exceeding the maximum allowable pressures in tables 1-3 and 1-4.
CAUTION
Do not use sealing tape on pneumatic connections. This instrument contains small passages that may become obstructed
by detached sealing tape. Thread sealant paste should be used to seal and lubricate pneumatic threaded connections.
Refer to figure 2-5. Supply, output, and vent connections are 1/4 NPT. Process pressure connections are 1/4 or 1/2 NPT
(optional).
Figure 2-5. Location of Connections
46A9765‐A
A3001
REMOTE SET POINT
CONNECTION
SUPPLY PRESSURE
CONTROLLER OUTPUT
PRESSURE
LOW
PRESSURE (A)
HIGH
PRESSURE (B)
VENT
TOP VIEW
BOTTOM VIEW
Process Pressure
Process pressure is piped to the connection marked A and B on the bottom of the case (see figure 2-5). The high
pressure line is piped to connection B, and the low pressure line connects to A.
When installing process piping, follow accepted practices to ensure accurate transmission of the process pressure to
the controller. Install shutoff valves, vents, drains, or seal systems as needed in the process pressure lines.
If the instrument is located such that the adjacent process pressure line will be approximately horizontal, the line
should slope downward to the instrument for liquid‐filled lines and upward toward the instrument for gas‐filled lines.
This will minimize the possibility of air becoming trapped in the sensor with liquid‐filled lines or of condensate
becoming trapped with gas‐filled lines. The recommended slope is 80 millimeters per meter (1 inch per foot).

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Supply Pressure
WARNING
Severe personal injury or property damage may occur if the instrument air supply is not clean, dry and oil‐free, or
noncorrosive gas. While use and regular maintenance of a filter that removes particles larger than 40 micrometers in
diameter will suffice in most applications, check with an Emerson Automation Solutions field office and industry
instrument air quality standards for use with corrosive gas or if you are unsure about the proper amount or method of air
filtration or filter maintenance.
Supply pressure medium must be clean, dry, and noncorrosive and meet the requirements of ISA Standard 7.0.01 or
ISO 8573-1. A maximum 40 micrometer particle size in the air system is acceptable. Further filtration down to 5
micrometer particle size is recommended. Lubricant content is not to exceed 1 ppm weight (w/w) or volume (v/v)
basis. Condensation in the supply medium should be minimized.
Use a suitable supply pressure regulator to reduce the supply pressure source to 1.4 bar (20 psig) for an output signal
range of 0 and 1.4 bar (0 and 20 psig) and to 2.4 bar (35 psig) for an output signal range of 0 and 2.4 bar (0 and 35
psig).
Remote Set Point Pressure (Option M)
If the controller has the remote set point option, connect the remote set point pressure to the top of the controller
case at the location shown in figure 2-5. Use a clean dry air supply.
Vent
WARNING
Personal injury or property damage could result from fire or explosion of accumulated gas, or from contact with hazardous
gas, if a flammable or hazardous gas is used as the supply pressure medium. Because the controller case and cover
assembly do not form a gas‐tight seal when the assembly is enclosed, a remote vent line, adequate ventilation, and
necessary safety measures should be used to prevent the accumulation of flammable or hazardous gas. However, a remote
vent pipe alone cannot be relied upon to remove all flammable or hazardous gas. Vent line piping should comply with local
and regional codes and should be as short as possible with adequate inside diameter and few bends to reduce case pressure
buildup.
CAUTION
When installing a remote vent pipe, take care not to overtighten the pipe in the vent connection. Excessive torque will
damage the threads in the connection.
If a remote vent is required, the vent line must be as short possible with a minimum number of bends and elbows. Vent
line piping should have a minimum inside diameter of 19 mm (3/4 inches) for runs up to 6.1 m (20 feet) and a
minimum inside diameter of 25 mm (1 inch) for runs from 6.1 to 30.5 m (20 to 100 feet).
If a remote vent is not required, the vent opening (figure 2-5) must be protected against the entrance of any foreign
material that could plug it. Check the vent periodically to be certain it is not plugged.

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Section 3 Controller Operation33-3-
Operating Information
This section includes descriptions of adjustments and procedures for prostrate and startup procedures. Location of
adjustments are shown in figures 3-1 and 3-2. To better understand the adjustments and overall operation of the
controller, refer to the Principle of Operation section and the schematic diagrams, figures 3-4 and 3-5.
Adjustments
Manual Set Point
To adjust the set point, open the controller cover and move the set point adjustment until the pointer indicates the
desired value of pressure on the process pressure scale. Move the adjustment to the right to increase the set point, and
to the left to decrease it. Adjusting the set point does not affect the differential gap setting.
Remote Set Point (Option M)
CAUTION
Do not move the set point adjustment manually on controllers with remote set point. Doing so could damage the
controller.
If the controller is equipped with the remote set point option (see figure 3-2), vary the remote set point pressure to
change the set point. Increase the pressure to increase the set point, and decrease the pressure to decrease the set
point.
Proportional Band (Differential Gap)
The proportional band knob adjusts the width of the gap between switching points. Rotate the proportional band
knob until the desired setting is opposite the line on the proportional band indicator cover.
Changing Controller Action
Controller action can be switched from direct to reverse or vice versa by simply loosening the screws on the
proportional band indicator cover and moving the cover out so the proportional band knob can be rotated to the
desired action. The white portion of the adjustment enables direct controller action; the black portion enables reverse
controller action.
Auto/Manual Switching (Option E)
Refer to figure 5-4 if the controller has the auto/manual option. Two balance methods are available to equalize the
manual output with the controller pressure. To switch from automatic to manual mode, carefully adjust the loader
knob until the metal ball inside the plastic tube moves into the switching zone. Then move the automatic/manual
switch to MANUAL. Turn the loader knob clockwise to increase the controller output or counter‐clockwise to decrease
it. To switch from manual to automatic mode, adjust the set point manually or with remote set point pressure to move
the ball into the switching zone. Turn the switch to AUTOMATIC, and move the set point adjustment to control the
output.

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When the automatic/manual switch is in AUTOMATIC, adjusting the loader knob has no effect on the controller
output. When the automatic/manual switch is in MANUAL, changing the set point adjustment has no effect on the
controller output.
Note
Switching the controller between automatic and manual mode without balancing can disturb the process and cause controller
cycling.
Prestartup Checks
When performing the checks, open loop conditions must exist. Refer to figure 3-1 for location of adjustments.
Note
If the controller has the auto/manual option (option E), be sure the controller is in the automatic mode prior to performing
prestartup checks.
Figure 3-1. Location of Controller Parts and Adjustments
C0541
38A1731‐B
38A3819‐A
HIGH PRESSURE
CAPSULAR UNIT
INDICATING
ASSEMBLY
LOW PRESSURE
CAPSULAR UNIT
SET POINT
INDICATOR
PROCESS
INDICATOR
PROPORTIONAL
BAND
INDICATOR
COVER
PROPORTIONAL
BAND INDICATOR
LOW
PRESSURE
INPUT
DRIVE LINKAGE
CONNECTING
LINK
SUPPLY
GAUGE
HIGH PRESSURE
INPUT
PROCESS POINTER
SPAN ADJUSTMENT
POINTER ZERO
ADJUSTMENT
OUTPUT
PRESSURE GAUGE
GUIDE
FLEXURE
DRIVE
FLEXURE
LONG
PIVOT
SHORT
PIVOT
LINKS
LINK 1
LINK 2
LINEARITY
ADJUSTMENT
SENSING ELEMENT
FRONT VIEW

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Figure 3-1. Location of Controller Parts and Adjustments (continued)
C0541
35A7374‐B
49A0771‐A
PROCESS SPAN
ADJUSTMENT REMOTE SET POINT
SPAN ADJUSTMENT
SCREW 1
SCREW 3
SCREW 2
SIDE VIEW OF
SET POINT/PROCESS
INDICATOR ASSEMBLY SIDE VIEW OF CONTROLLER
SHOWING FLAPPER LEVELING SCREWS
1. Connect supply pressure to the supply pressure regulator, and be sure it is delivering the proper supply pressure to
the controller. Provide a means of measuring the controller output pressure.
2. For controllers with remote set point (option M), connect regulated pressure of 0.2 to 1.0 bar (3 to 15 psig) or 0.4 to
2.1 bar (6 to 30 psig) to the remote set point connection at the top of the controller case.
3. Loosen two screws (key 6), lift off the proportional band cover (key 36), and set the proportional band knob
between DIRECT and REVERSE.
The process indicator should indicate the process differential pressure. For example, with the process differential
pressure at 50 percent of the input span, the process pointer should be at 50 ±1.0 percent of its span. Slight
adjustment of the indicator zero screw may be necessary. See figure 3-1 for zero adjustment and locking screw
location.
4. If desired, the accuracy can be verified at other points on the scale. If the indicator appears to be out of calibration,
refer to the process zero and span adjustment portion of the calibration procedure.
Startup
It is recommended that the controller switching points be set as described in the calibration procedures.
Slowly open the upstream and downstream manual control valves in the pipeline and close the manual bypass valve if
they are used.

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Calibration
WARNING
To avoid personal injury or property damage resulting from the sudden release of pressure, do not exceed the operating
limits given in this manual.
If the prestartup checks revealed faulty adjustment of the process indicator, perform the calibration procedures. These
procedures are valid for either shop or field calibration, provided that open process loop conditions exist.
Note
If the controller has the auto/manual option, be sure the controller is in the automatic mode prior to performing the calibration
procedure.
Process Zero and Span Adjustment
Note
Any adjustment of the pointer span adjustment screw will require readjustment of the pointer zero adjustment screw.
1. Refer to figure 3-1 for location of adjustments.
2. Remove the two screws (key 6) and lift off the proportional band indicator cover (key 36).
3. Set the proportional band between DIRECT and REVERSE.
4. Adjust the process differential pressure to the low limit of the input range.
5. Adjust the process pointer to the lowest limit of the input scale by loosening the zero adjustment locking screw and
turning the zero adjustment screw.
6. Adjust the process differential pressure to the upper limit of the input span. Note whether the pointer indication is
above or below the upper limit of the process scale.
7. Adjust the span screw as follows: Clockwise to increase span for a low indication; counterclockwise to decrease span
for a high indication. Adjust the span screw to correct one‐half the error.
8. Repeat steps 4 through 7 until the error is eliminated.
9. Turn the proportional band indicator knob to 400 percent in the desired controller action (either DIRECT or
REVERSE).
10. Install the proportional band indicator cover (key 36) and tighten the two screws (key 6).
Remote Set Point Zero and Span Adjustment (Option M)
Note
Any adjustment of the pointer span adjustment screw will require readjustment of the pointer zero adjustment screw.

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1. Refer to figures 3-1 and 3-2 for location of adjustments.
2. Remove the two screws (key 6) and lift off the proportional band indicator cover (key 36).
3. Set the proportional band between DIRECT and REVERSE.
4. Adjust the set point pressure to the low limit of the input range.
5. Adjust the set point indicator to the lowest limit of the input scale by loosening the zero adjustment locking screw
and turning the zero adjustment screw.
6. Adjust the set point pressure to the upper limit of the input span. Note whether the pointer indication is above or
below the upper limit of the process scale.
7. Adjust the span screw as follows: clockwise to increase span for a low indication; counterclockwise to decrease span
for a high indication. Adjust the span screw to correct one‐half the error.
8. Repeat steps 4 through 7 until the error is eliminated.
9. Replace the proportional band indicator cover (key 36), and tighten the two screws (key 6).
Figure 3-2. Location of Controller Parts and Adjustments (Remote Set Point Option)
36A9751‐C
B1668‐1
ZERO ADJUSTMENT
LOW PRESSURE
STOP
DRIVE FLEXURE
GUIDE
FLEXURE
MOUNTING
SCREW
ADJUSTMENT
SCREW
LINK B
LINK A
FRONT VIEW SIDE VIEW
MOUNTING
SCREW
HIGH PRESSURE
STOP
PIVOT
ASSEMBLY B
ZERO ADJUSTMENT LOCKING SCREW
LINEARITY
ADJUSTMENT
CAPSULES
TIE BAR
PIVOT
ASSEMBLY A
Setting Switching Points
Direct‐Acting Controllers
The controller output signal will switch from zero pressure to full supply pressure when increasing process pressure
passes the upper switching point.

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The controller output signal will not return to zero pressure until decreasing process pressure passes the lower
switching point. When making adjustments as described in the following steps, keep in mind that:
D Changing the set point adjustment will move both switching points equally in the direction of adjustment.
D Changing the proportional band adjustment will widen or narrow the differential gap between the two switching
points by moving the position of the lower switching point.
Figure 3-3 shows the relationship between the percent of sensor range between switching points and the proportional
band setting on the controller. The following example illustrates how to use figure 3-3.
Example: The sensing element has a range of 30 psi. The lower switching point is to be set at 10 psi and the upper
switching point is to be set at 25 psi.
Proceed as follows:
D Divide the differential gap (the difference between the upper and lower switching points) by the sensing element
range. Multiply the result by 100 as shown in the following equation:
Differential Gap
Sensing Element Range
x 100 = 15 psi
30 psi
x 100 = 50%
D Locate the 50 percent line on figure 3-3. Move along this line until you intersect the curve. Read the proportional
band setting on the left hand axis. For this example, the setting is approximately 35 percent.
Figure 3-3. Curve for Determining Proportional Band Setting
A2853‐1
% SENSOR RANGE BETWEEN SWITCHING POINTS
PROPORTIONAL BAND SETTING
1. Using the curve in figure 3-3, determine the correct proportional band setting for the desired gap (expressed as a
percent of the input span) between the switching points.
2. Set the proportional band knob to the desired setting determined in step 1.
3. Adjust the set point to the desired upper switching point.
4. Increase the process differential pressure until the controller output signal switches from zero pressure to full
supply pressure.
5. Decrease the process differential pressure to the desired switching point at which the controller output signal
switches from full supply pressure to zero pressure.

Instruction Manual
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4194S Controllers
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6. Narrow the proportional band slowly until the output signal switches from zero pressure to full supply pressure.
7. Repeat steps 4 through 6 until the controller output switches at the desired points.
8. Observe the process pointer when the output switches at the upper switching point. The process pointer indication
should be within ±2 percent of the set point indication. If the output does not snap within ±2 percent of set point,
refer to the calibration procedures.
Reverse‐Acting Controllers
The controller output signal will switch from zero pressure to full supply pressure when decreasing process pressure
passes the lower switching point.
The controller output signal will not return to zero pressure until increasing process pressure passes the upper
switching point. When making adjustments as described in the following steps, keep in mind that:
D Changing the set point adjustment will move both switching points equally in the direction of adjustment.
D Changing the proportional band adjustment will widen or narrow the differential gap between the two switching
points by moving the position of the upper switching point.
Figure 3-3 shows the relationship between the percent of sensor range between switching points and the proportional
band setting on the controller. The following example illustrates how to use figure 3-3.
Example: The sensing element has a range of 30 psi. The lower switching point is to be set at 10 psi and the upper
switching point is to be set at 25 psi.
Proceed as follows:
D Divide the differential gap (the difference between the upper and lower switching points) by the sensing element
range. Multiply the result by 100 as shown in the following equation.
Differential Gap
Sensing Element Range
x 100 = 15 psi
30 psi
x 100 = 50%
D Locate the 50 percent line on figure 3-3. Move along this line until you intersect the curve. Read the proportional
band setting on the left hand axis. For this example, the setting is approximately 35 percent.
1. Using the curve in figure 3-3, determine the correct proportional band setting for the desired gap (expressed as a
percent of the maximum input element span) between the switching points.
2. Set the proportional band knob to the desired setting determined in step 1.
3. Adjust the set point to the desired lower switching point.
4. Carefully adjust the process differential pressure to 100 percent of scale range. Then, decrease the process
differential pressure until the controller output signal switches from zero pressure to full supply pressure.
5. Increase the process differential pressure to the desired switching point at which the controller output signal
switches from full supply pressure to zero pressure.
6. Widen the proportional band slowly until the output signal switches from zero pressure to full supply pressure.
7. Repeat steps 4 through 6 until the controller output switches at desired points.
8. Observe the process pointer when the output switches at the lower switching points. The process pointer indication
should be within ±2 percent of the set point indication. If the output does not snap within ±2 percent of set point,
refer to the calibration procedures.
Principle of Operation
Overall Operation
Refer to the schematic diagram in figure 3-4.

Instruction Manual
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4194S Controllers
July 2018
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Figure 3-4. Schematic of Operation for Fisher 4195S Controllers
SET POINT
INDICATOR
PROCESS POINTER
REMOTE SET POINT
CONNECTED HERE
INPUT ELEMENT
CONNECTED HERE
CONNECTING
LINK
FLAPPER
NOZZLE
PROPORTIONAL
BELLOWS
(VENTED)
POSITIVE FEEDBACK
BELLOWS
PROPORTIONAL
BAND ADJUSTMENT
SUPPLY
PRESSURE
RELAY
OUTPUT PRESSURE
TO FINAL CONTROL
ELEMENT
REVERSE ACTION
QUADRANT
FLAPPER
PIVOT
FEEDBACK
LINK
FEEDBACK
MOTION
DIRECT ACTION
QUADRANT INPUT MOTION
FLAPPER DETAIL
SUPPLY PRESSURE
OUTPUT PRESSURE
NOZZLE PRESSURE
POSITIVE FEEDBACK PRESSURE
B1546‐2
The input element is connected to the process pointer and to the flapper by connecting links. As the process pressure
increases (in a direct‐acting controller), the flapper moves toward the nozzle, restricting flow through the nozzle and
increasing nozzle pressure. When this occurs, relay action increases the output pressure (delivery) of the controller.
Output pressure is fed back to the positive feedback bellows. The action of this bellows is a positive feedback action
that moves the flapper closer to the nozzle, increasing nozzle pressure, which in turn, increases the relay output.
Output pressure to the final control element switches to full supply pressure.
As the process differential pressure decreases, approaching the lower switching point, the flapper moves away from
the nozzle (in a direct‐acting controller) reducing nozzle pressure. Through relay action, pressure to the positive
feedback bellows is reduced, moving the flapper further away from the nozzle, and further reducing nozzle pressure.
Output pressure to the final control element switches to zero.
The set point adjustment changes the proximity of the nozzle and flapper as does a change in process pressure except
that, when the set point is changed, the nozzle moves with respect to the flapper. The set point adjustment moves
both the upper and lower switching points.
The proportional band knob positions the nozzle on the flapper. Increasing (widening) the proportional band moves
the nozzle away from the input connection. When the proportional band adjustment moves the nozzle across the
feedback connection, the controller action changes between direct and reverse. On a direct‐acting controller,
changing the proportional band adjustment will widen or narrow the differential gap between the two switching
points. This is accomplished by changing the position of the lower switching point. On a reverse‐acting controller,
changing the proportional band adjustment will widen or narrow the differential gap between the two switching
points. This is accomplished by changing the position of the upper switching point.

Instruction Manual
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Remote Set Point Option
The capability to adjust the controller set point from a remote location is available with all 4194S controllers. This
option is designated by the letter M in the type number.
Auto/Manual Option
Controllers with the auto/manual option (designated by the letter E in the type number) have piping on the output
side of the relay as shown in figure 3-5. Supply pressure to the relay is also applied to the manual loader. The manual
loader, functioning as a regulator, applies pressure to one side of the plastic tube and to the auto/manual switch.
Output pressure from the relay registers on the other side of the plastic tube as well as in the auto/manual switch.
When the auto/manual switch is in the MANUAL position, the output of the manual loader is channeled through the
auto/manual switch and becomes the output of the controller. When the auto/manual switch is in the AUTO position,
the output of the relay is channeled through the switch to become the output of the controller.
Before the auto/manual switch is operated, the output of the relay must equal the manual loader output to avoid
bumping the process. Adjusting the set point varies the pressure on the left‐hand side of the plastic tube. Adjusting
the manual loader knob varies the pressure on the right‐hand side. When the pressures are equal, the metal ball is
centered in the tube. Pressure imbalance forces the ball to one end of the tube where it forms a seal, blocking air flow
through the tube.
Figure 3-5. Schematic of Auto/Manual Option
AUTOMATIC
POSITION
OUTPUT PRESSURE
TO FINAL CONTROL
ELEMENT
SUPPLY
PRESSURE
RELAY
AUTO/MANUAL
SWITCH
MANUAL LOADER
MANUAL
LOADER
KNOB
MANUAL
POSITION
AUTO/MANUAL
SWITCH
OUTPUT PRESSURE
TO FINAL CONTROL
ELEMENT
PLASTIC TUBE
METAL BALL
RELAY OUTPUT PRESSURE
SUPPLY PRESSURE
MANUAL LOADER OUTPUT PRESSURE
48A5230‐A
A2999‐1

Instruction Manual
D200158X012
4194S Controllers
July 2018
20