Emerson Fisher 846 Data Sheet

Product Bulletin

846 Transducer

D102127X012

March 2015

Fisherr 846 Electro-Pneumatic Transducer

62.1:846

The Fisher 846 electro-pneumatic transducer is a
rugged, field-mountable transducer that accepts an
electrical input signal and converts it to a pneumatic
output signal. Typically, the 4 to 20 mA is converted to

0.2 to 1.0 bar (3 to 15 psi). In the most common
application, the transducer converts an electrical
output signal from a controller to a pneumatic signal
necessary to operate a control valve actuator or
pneumatic positioner.

The transducer includes a deflector/nozzle design
(figure 1) that consists of two nozzles positioned so
that the constant air flow exiting the supply nozzle is
directed at the entrance of the receiver nozzle. Each
nozzle has a large bore of 0.41 mm (0.016 inches),
which provides good resistance to plugging. The input
current signal positions a deflector bar within the

nozzle's flow stream. As the input signal changes, the
deflector bar moves to alter the flow stream to the
receiver nozzle, establishing a pilot pressure at the
receiver nozzle. The pilot pressure, in turn, controls the
booster stage and output of the transducer.

An electronic feedback control network constantly
compares the value of the pneumatic output signal
with the input current signal. A solid-state pressure
sensor is part of the electronics package monitoring
the pneumatic output (figure 3). A comparator circuit
in the control network detects input-output deviations
and adjusts the output by moving the deflector in the
pilot stage to a corrected position. Because of this
feedback network, the transducer can correct for
error-producing effects such as variations in supply
pressure and downstream leakage.

X0234

www.Fisher.com

FISHER 846 ELECTRO-

PNEUMATIC TRANSDUCER

W6307-1

846 MOUNTED

ON FISHER 667 ACTUATOR

Product Bulletin

62.1:846
March 2015

Specifications

Input Signal

4-20 mA DC, field adjustable split ranging.

Multirange Performance: 9.7 m

2.5 bar (35 psi) supply pressure

846 Transducer

D102127X012

3

/hr (360 scfh) at

Equivalent Circuit

See figure 4

Output Signal

Standard Performance:

J 0.2 to 1.0 bar (3 to 15 psi).

Rangeability between 0.1 to 1.2 bar (1 and 18 psi)
Multirange Performance:

J 0.4 to 2.0 bar (6 to 30 psi), and J 0 to 2.3 bar (0 to

J 0 to 1.2 bar (0 to 18 psi),

33 psi) nominal ranges. Actual rangeability available
between 0.03 to 2.3 bar (0.5 and 33 psi)
Action:

J Direct (increasing input signal increases

transducer output) (Minimum span, 6 psi) or

J Reverse (increasing input signal decreases

transducer output) (Minimum span, 11 psi)

Supply Pressure

Standard Performance: 1.2 to 1.6 bar
(18 to 24 psi)

Multirange Performance:
Minimum: 0.2 bar (3 psi) [0.14 bar (2 psi) for a 2.3 bar
(33 psi) output] greater than the maximum calibrated
output pressure.
Maximum: 2.4 bar (35 psi)

Supply Pressure Medium

Clean, dry air

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

Maximum Steady-State Air Consumption

(1)

0.3 m3/hr (12 scfh) at 1.4 bar (20 psi) supply pressure.

Output Air Capacity

(1)

Standard Performance: 6.4 m3/hr (240 scfh) at

1.4 bar (20 psi) supply pressure.

- continued -

Temperature Limits

Operating: -40 to 85_C (-40 to 185_F)
Storage: -40 to 93_C (-40 to 200_F).

Humidity Limits

0-100% condensing relative humidity.

Performance

(2)

Linearity, Hysteresis, and Repeatability: $0.3% of
span

Temperature Effect (total effect including zero and
span): $0.07%/_C (0.045%/_F) of span

Vibration Effect: $0.3% of span per g during the

following conditions:

5-15 Hz at 4 mm constant displacement

15-150 Hz at 2 g. 150-2000 Hz at 1 g.
per SAMA Standard PMC 31.1, Sec. 5.3, Condition 3,
Steady State.

Shock Effect: $0.5% of span, when tested per SAMA
Standard PMC 31.1, Sec. 5.4.

Supply Pressure Effect: Negligible

Electromagnetic Interference (EMI): Tested per IEC

61326-1 (Edition 1.1). Meets emission levels for Class
A equipment (industrial locations) and Class B
equipment (domestic locations). Meets immunity
requirements for industrial locations (Table A.1).
Immunity performance is shown in table 1.

Leak Sensitivity: Less than 1.0% of span for up to

3

4.8 m

/hr (180 scfh) downstream leakage.

Overpressure Effect: Less than 0.25% of span for
misapplication of up to 7.0 bar (100 psi) supply
pressure for less than 5 minutes to the input port.

Reverse Polarity Protection: No damage occurs from
reversal of normal supply current (4-20 mA) or from
misapplication of up to 100 mA.

Connections

Supply and Output Pressure: 1/4-18 NPT internal
connection.
Electrical: 1/2-14 NPT internal conduit connection.

2

846 Transducer

D102127X012

Specifications (Continued)

Product Bulletin

62.1:846

March 2015

Adjustments

Zero and Span: Screwdriver adjustments located in
terminal compartment.

Other Classifications/Certifications

CUTR— Customs Union Technical Regulations
(Russian, Kazakhstan, and Belarus)

INMETRO—National Institute of Metrology, Quality,

Remote Pressure Reading (optional)

ON or OFF; jumper selectable

Frequency Range: 0-10,000 Hz
Amplitude: 0.4-1.0 V

p-p

and Technology (Brazil)

KGS—Korea Gas Safety Corporation (South Korea)
NEPSI— National Supervision and Inspection Centre

for Explosion Protection and Safety of
Instrumentation (China)

Required Operating Voltage

Min. 6.0 V (at 4 mA)
Max. 7.2 V (at 20 mA)

Contact your Emerson Process Management

sales office for classification/certification

specific information

with Remote Pressure Reading ON

Min. 6.4 V (at 4 mA)
Max. 8.2 V (at 20 mA)

Electrical Classification

Hazardous Area

(3)

Construction Materials

Housing: J Low-copper aluminum with polyurethane
paint, or

J CF8M

O-Rings: Nitrile, except silicone for sensor O-rings.

(see Bulletin 9.2:001, D103222X012)

CSA C/US—Intrinsically Safe, Explosion-proof,

Mounting

Non-Incendive
FM—Intrinsically Safe, Explosion-proof,

J Actuator, J pipestand, or J surface

Non-Incendive

ATEX—Intrinsically Safe, Flameproof, Type n
IECEx—Intrinsically Safe, Flameproof

Electrical Housing

Weight

Aluminum: 2.9 kg (6.5 lb) excluding options
Stainless Steel: 6.7 kg (14.8 lb) excluding options

Tropicalization (Fungus test per MIL-STD-810)

CSA C/US—Type 4X
FM—Type 4X
ATEX—IP66
IECEx—IP66

NOTE: Specialized instrument terms are defined in ANSI/ISA Standard 51.1 - Process Instrument Terminology

1. Normal m

2. Performance values are obtained using a transducer with a 4 to 20 mA dc input signal, a 3 to 15 psig output, and 20 psig supply pressure.

3. Refer to tables 2, 3, 4, and 5 for additional information.

4. ATEX and IECEx Flameproof — IP66 per CSA Letter of Attestation.

(4)

(4)

3

/hr: normal cubic meters per hour (m3/hr, 0_C and 1.01325 bar, absolute). Scfm: standard cubic feet per minute (ft3/min, 60_F and 14.7 psig).

Options

J Fisher 67CFR filter regulator, J supply and output

gauges,

J remote pressure reading, or J stainless

steel mounting bracket

Table 1. EMC Immunity Performance Criteria

Port Phenomenon Basic Standard Test Level Performance Criteria

Electrostatic discharge
(ESD)

Enclosure

I/O signal/control

Specification limit = ±1% of span

1. A = No degradation during testing. B = Temporary degradation during testing, but is self-recovering.

Radiated EM field IEC 61000-4-3

Burst (fast transients) IEC 61000-4-4 1 kV A
Surge IEC 61000-4-5 1 kV (line to ground only, each) B

Conducted RF IEC 61000-4-6

IEC 61000-4-2

4 kV contact
8 kV air

80 to 1000 MHz @ 10V/m with 1 kHz AM at 80%
1400 to 2000 MHz @ 3V/m with 1kHz AM at 80%
2000 to 2700 MHz @ 1V/m with 1kHz AM at 80%

150 kHz to 8 MHz at 3 Vrms B
8 MHz to 80 MHz at 3 Vrms A

(1)

A

A

3

Product Bulletin

62.1:846
March 2015

846 Transducer

D102127X012

Features

n Vibration Resistant—The low-mass pilot stage,

mechanically damped deflector bar, and rugged
construction provide stable performance in
vibration.

n Large Diameter Nozzles—Large diameter nozzles,

free-flow pilot stage design, and large internal
pneumatic supply passages provide excellent
tolerance to reducing the effects of contaminant
buildup and erosion.

n Increased Accuracy, Reduced Sensitivity to Supply

Pressure Variations and Downstream Leakage—The

electronic feedback control network monitors the
pneumatic output signal, detects any input-output
deviations and corrects them. This provides very
high accuracy and allows the transducer to sense
changes in the final element condition and rapidly
optimize its air delivery.

n Easy Maintenance—Major mechanical and electrical

components are incorporated into a single
field-replaceable “master module” (figure 2). The
transducer does not have to be removed from its
mounting to facilitate troubleshooting or service. A
separate field wiring compartment eases
installation and maintenance.

Figure 1.

W6287

Detail of Deflector/Nozzle Pilot Stage

Installation

The transducer may be actuator, wall, panel, or
pipestand mounted. Dimensions are shown in
figures 6, 7, and 8.

n Quick Diagnostic Checks and Remote Performance

Monitoring—With Stroke Port, a constant bleed from

the pilot stage vents through a hole in the module
cover. Covering the hole increases the transducer
output to confirm the proper operation of the pilot
and booster stages and stroke the actuator. With
optional Remote Pressure Reading, a frequency
directly proportional to the output pressure is
superimposed on the input signal wires.

Using a frequency counter, an operator can monitor
the 846 output pressure.

4

Ordering Information

To determine what ordering information is required,
refer to the specification table. Carefully review the
description of each specification. Specify the desired
choice whenever there is a selection available.

When ordering mounting parts, specify actuator,
surface, or pipestand mounting. For actuator
mounting, specify the actuator type, size, travel, and
diaphragm pressure range. For all 657 and 667
actuators except size 80, specify whether actuator
yoke or actuator casing mounting is desired (yoke
mounting only is available on size 80 actuators).