Emerson Process Management IB106-340 Hart/Ams, Overview, Method 1, For Load Resistance 250 Ohms

Oxymitter 4000

Instruction Manual

IB-106-340 Rev. 2.4 April, 2001

SECTION 5 HART/AMS

5-1 OVERVIEW

The HART Communicator is a handheld com- munications interface device. It provides a common communications link to all microproc- essor-based instruments that are HART com- patible. The handheld communicator contains an 8 ⋅ 21 character liquid crystal display (LCD) and 25 keys. A pocket-sized manual, included with the HART Communicator, details the spe- cific functions of all the keys.

To interface with the Oxymitter 4000, the HART Communicator requires a termination point along the 4-20 mA current loop and a minimum load resistance of 250 ohms between the com- municator and the power supply. The HART Communicator accomplishes its task using a frequency shift keying (FSK) technique. With the use of FSK, high-frequency digital communica- tion signals are superimposed on the 4-20 mA Oxymitter 4000 current loop. The communicator does not disturb the 4-20 mA signal since no net energy is added to the loop.

The HART Communicator may be interfaced with a personal computer (PC), providing spe- cial software has been installed. To connect the HART Communicator to a PC, an interface adapter is required. Refer to the proper HART Communicator documentation in regard to the PC interface option.

5-2 HART COMMUNICATOR SIGNAL LINE CONNECTIONS

The HART Communicator can connect to the Oxymitter 4000 analog output signal line at any wiring termination in the 4-20 mA current loop. There are two methods of connecting the HART Communicator to the signal line. For applica- tions in which the signal line has a load resis- tance of 250 ohms or more, refer to method 1. For applications in which the signal line load resistance is less than 250 ohms, refer to method 2.

a.Method 1, For Load Resistance > 250 Ohms

Refer to Figure 5-1and the following steps to connect the HART Communicator to a signal line 250 ohms or more of load resistance.

Explosions can result in death or seri- ous injury. Do not make connections to the HART Communicator's serial port, 4-20 mV signal line, or NiCad recharger jack in an explosive atmosphere.

Using the supplied lead set, connect the 5

HART Communicator in parallel to the Oxymitter 4000. Use any wiring termination points in the analog output 4-20 mA signal line.

b. Method 2, For Load Resistance < 250 Ohms

Refer to Figure 5-2and the following steps to connect the HART Communicator to a signal line with less than 250 ohms load resistance.

Explosions can result in death or seri- ous injury. Do not make connections to the HART Communicator's serial port, 4-20 mA signal line, or NiCad recharger jack in an explosive atmosphere.

1.At a convenient point, break the analog output 4-20 mA signal line and install the optional 250 ohm load resistor.

2.Plug the load resistor into the loop connectors (located on the rear panel of the HART Communicator).

Rosemount Analytical Inc. A Division of Emerson Process Management HART/AMS 5-1