Emerson Fisher 646 Data Sheet

Product Bulletin

646 Transducer

D101374X012

February 2015

Fisherr 646 Electro-Pneumatic Transducer

62.1:646

The Fisher 646 electro-pneumatic transducer uses a
converter module that converts a 4 to 20 milliampere
input signal to a proportional 0.2 to 1.0 bar (3 to
15 psig) pneumatic output signal. The converter
module uses small parts of minimum mass, which are
balanced symmetrically around a pivot point at the
center of the mass. This balanced arrangement results
in a high performance instrument that reduces
sensitivity to vibration.

An integral pneumatic relay provides the high capacity
necessary to drive pneumatic control valve/acutator

assemblies without additional boosters or positioners.
The transducer also provides stable, accurate
operation when its output is transmitted to small
volume chambers, such as a pneumatic positioner or
other pneumatic instrument. Reduced sensitivity to
vibration combined with high capacity and first order
lag characteristics make the 646 transducer ideal for
direct mounting on control valve/actuator
combinations.

Connectors and piping can be installed with each 646
transducer for diagnostic testing.

FISHER 646 ELECTRO-PNEUMATIC TRANSDUCER

WITH FISHER 657 ACTUATOR AND E VALVE

www.Fisher.com

W6783-1

W4908-1

FISHER 646 ELECTRO-PNEUMATIC TRANSDUCER

Product Bulletin

62.1:646
February 2015

Specifications

646 Transducer

D101374X012

Input Signal

4 to 20 mA DC, constant current with 30 VDC
maximum compliance voltage

Equivalent Circuit

The 646 equivalent circuit is a series circuit consisting
of a constant voltage drop (battery) of approximately

2.1 VDC and a total resistance of 143 ohms. Input is
shunted by three 6.8 V zener diodes (see figure 1).

Output Signal

0.2 to 1.0 bar (3 to 15 psig) direct acting only

Supply Pressure

(1)

Recommended: 1.4 bar (20 psig)
Minimum: 1.4 bar (20 psig)

Maximum: 3.4 bar (50 psig)

Average Steady‐State Air Consumption

(2)(3)

0.08 m3/hr (3 scfh) at 1.4 bar (20 psi) supply pressure

Maximum Output Air Capacity

(2)

8.0 m3/hr (300 scfh) at 1.4 bar (20 psig) supply
pressure

Performance

(4)

Reference Accuracy: ±0.5% of full scale output span;
includes combined effects of hysteresis, linearity, and
deadband

Independent Linearity: ±0.5% of full scale output span

Hysteresis: 0.4% of full scale output span
Frequency Response: Gain is attenuated 3 dB at 10 Hz

with transducer output signal piped to a typical
instrument input

Temperature Effect: ±4% of full scale output span per
55_C (100_F) change

Supply Pressure Effect: 0.2% of full scale output span
per psi supply pressure change

Vibration Effect: Less than 1% of full scale output span
when tested to SAMA PMC 31.1, Condition 3

-continued-

Electromagnetic Compatibility:
Meets EN 61326-1 (First Edition)
Immunity—Industrial locations per Table 2 of
the EN 61326-1 standard. Performance is
shown in table 1 below.
Emissions—Class A
ISM equipment rating: Group 1, Class A

Operating Ambient Temperature Limits

(1)

-40 to 71_C (-40 to +160_F)

Electrical Classification

CSA— Intrinsically Safe, Explosion-proof, Type n,
Dust-Ignition proof, Div 2

FM— Intrinsically Safe, Explosion-proof, Type n,
Non-incendive, Dust-Ignition proof

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

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

Housing

CSA— Type 3 Encl.
FM— NEMA 3, IP54
ATEX— IP64
IECEx— IP54

Mount instrument with vent on side or bottom if
weatherproofing is a concern

Other Classifications/Certifications

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

INMETRO— National Institute of Metrology, Quality
and Technology (Brazil)

KGS— Korea Gas Safety Corporation (South Korea)
Contact your Emerson Process Management sales

office for classification/certification specific
information

Construction Materials

Housing, Cap, and Relay Body: Die cast aluminum
with less than 1% copper

2

646 Transducer

D101374X012

Specifications (continued)

Product Bulletin

62.1:646

February 2015

Adjustments

Zero and Span: Trim potentiometers (20 turn) for
zero and span adjustments are located under the
housing cap

Mounting Position

Any position is acceptable for standard pipestand,
panel, or actuator mounting. For weatherproof
housing, mount the transducer to allow the vent to
drain.

Connections

Supply and Output Pressure: 1/4 NPT internal
connection

Vent: 1/4 NPT internal
Electrical:

J Standard 1/2 NPT or, J Optional M20 or

PG13 conduit adapter (see figure 3)
Wire Size: 18 to 22 AWG

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

1. The pressure and temperature limits in this document and any applicable standard or code limitation should not be exceeded.

2. Normal m

3. Average flow rate determined at 12 mA and 0.6 bar (9 psig) output.

4. Performance values are obtained using a transducer with a 4 to 20 mA dc input signal and a 0.2 to 1.0 bar (3 to 15 psig) output signal at an ambient temperature of 24_C (75_F).

3

/hour--Normal cubic meters per hour (0_C and 1.01325 bar, absolute). Scfh--Standard cubic feet per hour (60_F and 14.7 psig).

Approximate Weight (Transducer Only)

1.6 kg (3.5 pounds)

Options

Output pressure gauge

Table 1. EMC Summary Results—Immunity

Port Phenomenon Basic Standard Test Level Performance Criteria

Electrostatic discharge (ESD) IEC 61000-4-2

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 61000-4-6 150 kHz to 80 MHz at 3 Vrms A

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 1 kHz AM at 80%
2000 to 2700 MHz @ 1V/m with 1 kHz AM at 80%

(1)

A

A

Figure 1. Equivalent Circuit

4 - 20 mA

+

6.8V 6.8V 6.8V

-

A6013

0.7V

0.7V

0.7V

60 Ohms

60 Ohms

23 Ohms

3