Emerson 3081FG Section HART/AMS, Overview, Hart Communicator Signal Line, Connections, Hart/Ams

Model 3081FG

Instruction Manual

IB-106-3081 Rev. 1.5 September 2002

SECTION 4

HART/AMS

4-1 OVERVIEW	The HART Communicator may be interfaced
	with a personal computer (PC) providing special
The HART Communicator is a handheld com-	software has been installed. To connect the
munications interface device. It provides a	HART Communicator to a PC, an interface
common communications link to all microproc-	adapter is required. Refer to the proper HART
essor-based instruments that are HART com-	Communicator documentation regarding the PC
patible. The handheld communicator contains	interface option.
an 8 x 21 character liquid crystal display (LCD)
and 25 keys. A pocket-sized manual, included	4-2 HART COMMUNICATOR SIGNAL LINE
with the HART Communicator, details the spe-
	CONNECTIONS
cific functions of all the keys.
	4

To interface with the Two-Wire In Situ Oxygen Analyzer, the HART Communicator requires a termination point along the 4-20 mA current loop and a minimum load resistance of 250 ohms between the communicator and the power sup- ply. The HART Communicator accomplishes its task using a frequency shift keying (FSK) tech- nique. With the use of FSK, high-frequency digital communication signals are superimposed on the 4-20 mA transmitter current loop. The communicator does not disturb the 4-20 mA signal since no net energy is added to the loop.

The HART Communicator can connect to the Two-Wire In Situ Oxygen Analyzer analog out- put signal line at any wiring termination in the 4- 20 mA current loop. There are two methods of connecting the HART Communicator to the sig- nal line. For applications in which the signal line has a load resistance of 250 ohms or more, re- fer to method 1 and Figure 4-1.For applications in which the signal line load resistance is less than 250 ohms, refer to method 2 and Figure 4-2.

Rosemount Analytical Inc. A Division of Emerson Process Management HART/AMS 4-1