Input Signal(1)

4 to 20 mA dc, constant current with 30 Vdc maximum compliance voltage

Equivalent Circuit

The Type 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 2).

Output Signal(1)

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

Supply Pressure(1,4)

Recommended: 1.4 bar (20 psig)
Minimum: 1.4 bar (20 psig)
Maximum: 3.4 bar (50 psig)

Maximum Steady-State Air Consumption(1)(2)

Air consumption is proportional to output pressure. Maximum consumption at 1.0 bar (15 psig) output is 0.20 normal m3/hr (0.13 scfm).

Maximum Output Air Capacity(2)

8.0 normal m3/hr (5.0 scfm) at 1.4 bar (20 psig) supply pressure

Performance(3)

Reference Accuracy: ±0.5% of full scale output span; includes combined effects of hysteresis, linearity, and deadband
Independent Linearity (1): ±0.5% of full scale output span
Hysteresis (1): 0.4% of full scale output span
Frequency Response (1): 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 100°F (55°C) 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
Electromagnetic Interference (EMI)(1): Tested per IEC 61326-1 (Edition 1.1). Conforms to the European EMC Directive. Meets emission limits for class A equipment (industrial locations) and class B equipment (domestic locations). Meets immunity requirements for industrial locations (Table A.1 in the IEC specification document). Immunity performance is shown in table 1.

Operating Ambient Temperature Limits(4)

-40 to 71°C (-40 to +160°F)

Housing

NEMA 3; IEC 529 IP54 weatherproof. Mount instrument with vent on side or bottom if weatherproofing is a concern.

Electrical Classification

Explosion proof, Dust-Ignition proof, DIV 2, Intrinsically Safe

Explosion proof, Non-incendive, Dust-Ignition proof, Intrinsically Safe

Intrinsically Safe and Type n
Refer to the Hazardous Area Classification bulletins 9.2:001 series and 9.2:002 for additional information and/or approvals.

Construction Materials

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

Adjustments

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

Connections

Supply and Output Pressure: 1/4-inch NPT female connection
Vent: 1/4-inch NPT female
Electrical: ■Standard 1/2-inch NPT or, ■Optional M20 or PG13 conduit adapter (see figure 4)
Wire Size: 18 to 22 AWG

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.

Approximate Weight (Transducer Only)

1.6 kg (3.5 pounds)

Options

Output pressure gauge

• Small Size—The small size and light-weight design of the transducer facilitate mounting and provide improved space utilization.
• Vibration Resistance—The transducer, used in a standard valve/actuator mounted application, exhibits an output shift of less than 1 percent of span when tested to SAMA Standard PMC 31.1, Condition 3.
• High Output Capability—The output volume of the transducer is adequate to drive valve/actuator combinations without requiring a positioner or volume booster.
• Low Air Consumption—The transducer has low air consumption which cuts operating costs.
• Easy Maintenance—Modular design of the converter allows easy replacement in the field for reduced maintenance costs.
• Superior Performance—The accuracy, linearity, and frequency response coupled with minimal hysteresis far exceed the requirements of most control systems.
• Mounting Position Insensitivity—The Type 646 will operate in any orientation.

Note: Fisher does not assume responsibility for the selection, use, or maintenance of any product. Responsibility for the selection, use, or maintenance of any Fisher product remains solely with the purchase and end-user.

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. Also, specify options that are applicable to the application.