8. OPERATION VIA HART COMMUNICATOR

8.1 Conditions of Communication Line

8.1.1Interconnectwion between AXFA11 and HART Communicator

I +

I -

AXFA11

The HART Communicator can interface with the AXFA11 from the control room, the AXFA11 site, or any other wiring termination point in the loop, provided there is a minimum load resistance of 230  between the connection and the receiving instrument. To communi- cate, it must be connected in parallel with the AXFA11, and the connections must be non- polarized. Figure 8.1.1 illustrates the wiring connections for a direct interface at the AXFA11 site. The HART Communicator can be used for remote access from any terminal strip as well.

 

 

 

Control room

 

4 to 20 mA DC signal line

Terminal board

 

 

 

 

Relaying

 

 

 

 

 

 

 

 

 

 

 

 

terminals

 

 

 

 

 

Receiving instrument

 

 

 

load resistance:

 

 

 

230 to 600

 

 

HART

HART

 

HART

Communicator

Communicator

 

Model 275

Model 275

Communicator

 

 

Model 275

F0802.EPS

Figure 8.1.1 Interconnection Diagram

8.1.2Communication Line Requirements

Specifications for Communication Line:

 

 

Load resistance:

230 to 600  (including cable resistance)

Minimum cable size: 24 AWG, (0.51 mm diameter)

Cable type:

Single pair shielded or multiple pair with overall shield

Maximum twisted-pair length:

6,500 ft (2,000 m)

Maximum multiple twisted-pair length: 3,200 ft (1,000 m)

Use the following formula to determine cable length for a specific application:

L =

65106

(Cf+10,000)

 

(RC)

 

C

 

 

where:

L = length in feet or meters

 

 

 

 

R = resistance in ohms, current sense resistance

 

 

 

 

C = cable capacitance in pF/ft or pF/m

 

 

 

 

Cf = 50,000 pF

8-2

IM 01E20C01-01E

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APC AXFA11G user manual Conditions of Communication Line, Interconnectwion between AXFA11 and Hart Communicator